Advances in Hydraulics and Water Engineering

The following sections are included:

• PREFACE

• ORGANIZING COMMITTEE

• TABLE OF CONTENTS

The research on open-channel turbulence has been carried out intensively since only the 1970's, thanks to the fortunate development of a hot-film anemometer, a laser Doppler anemometer (LDA) and a particle-image velocimetry (PIV). Almost all hydrodynamic characteristics of various kinds of open-channel turbulence are now available in fundamental sense, and are compared with those of the other wall turbulence such as boundary layers and duct flows. The present keynote lecture highlights a historical review on velocity distribution, wall shear stress, secondary currents and turbulence in two-dimensional (2-D) and three-dimensional (3-D) open-channel flows. Recent challenging research topics will be also reviewed on the basis of the author's experiences.

Turbulence measurements in unsteady open-channel flows over a smooth bed were conducted with a two-component laser Doppler anemometer (LDA). It was confirmed that the peaks of the water-surface slope, the bulk mean velocity, water discharge and finally the flow depth appear in these turn in flooded flows and this tendency becomes more remarkable with an increase of the unsteadiness. This is because the effects of the acceleration term in the momentum equation become stronger with an increase of the unsteadiness. FFT analysis was carried out then. The spectrum of turbulent fluctuations seems to obey the Kolmogoroff's -5/3 power law even in unsteady open-channel flow. The normalized distributions of the turbulent generation and its dissipation in weak unsteady flow are similar to those in steady flow.

Laboratory experiments were conducted using two-components electromagnetic current meter and particle image velocimetry (PIV) to clarify the interaction between main flow and flexible artificial vegetation zone, which was attached to the central bottom and sidewall of an open channel. Experimental results showed that in the main flow region under equilibrium horizontal components of secondary currents pointed in the direction toward the vegetation zone near the bottom, and in vegetation zone vertical components directed the upward. Furthermore, horizontal periodical components of velocity variations activated the momentum transport from main flow region to vegetation zone.

This paper describes an experimental study on mutual turbulent interactions across air-water interface in wind-induced water waves by using two sets of synchronous laser Doppler anemometers (SLDA) in air-water layers simultaneously. The purpose of this study is to clarify turbulent structures in a wind-driven shear layer of each phase (air and water), and to evaluate the turbulent momentum transport phenomena across the air-water interface, and also the transport from air-water interface to the water inertial flow.

Turbulence measurements in and around side-cavity open-channel flows were conducted with a particle-image velocimetry (PIV). The aspect ratio (the stream wise length of the side cavity / the lateral length of the side cavity) was set to 2. Two kinds of experiments were carried out. One is a rigid smooth bed condition. The other is a movable sand bed condition. In the movable case, experiments were conducted after development of the equilibrium sand waves. It was found that a large scour is generated around the edge of the spur dikes. This is because the flow velocity increases there. In contrast, a deposition is generated just behind the sand wave in the main-channel. The vector patterns of time-averaged flow velocities in the movable and rigid cases are quite different from each other. In the rigid case, a large horizontal vortex is generated by the shear instability between the main channel and the side cavity. On the other hand, the vortex in the side cavity is reduced by the mound effect of the main flow in the movable case.

Turbulence measurements in side-cavity open-channel flows were conducted in laboratory flume with a particle image velocimetry (PIV). Such flows are called "Wando" in river engineering. Five types of side cavities were built by using a transparent plate in the wando flow. The mass exchange rate is greatly affected by its shapes. It was found that a vortex, which is located in the side cavity, is stable when the junction mouth between the side-cavity and main channel is narrow. In contrast, large-scale unstable vortices are generated semi-periodically when the junction mouth is wide. The trajectories of the imaginably particles were calculated on the basis of the velocity data measured with PIV. It was suggested that the momentum exchange becomes large when the open moulh is wide.

An unsteady depth-varying open-channel flow is one of the most important flows in hydraulic engineering and therefore these hydrodynamic characteristics should to be investigated in detail. Recently, several highly-accurate turbulence measurements have been conducted in unsteady two-dimensional(2-D) open-channel flows with a two-component laser Doppler anemometer (LDA), and they offer a very valuable database of the observed turbulent structures that is needed to develop numerical simulations.

However, as for three-dimensional (3-D) structures of unsteady open-channel flows that are the most important compound rivers in flood, no accurate database is available as yet. So, in this study, 3D turbulence measurements with LDA were conducted in unsteady compound depth-varying open-channel flows and these results.

In is paper, reaches are done on the image process and rebuilding of flow vector-graph in DPTV (digital particle tracking velocimetry) for big area flow. Image pattern recognition and computer graphics are combined with the continuity of flow field. In this way, measurement for big area flow field can be realized.

The turbulent characteristics in submerged turbulent jet interacting with surface water wave were studied experimentally by the measurement with Laser Doppler Velocimeter (LDV). For this experiment, standing wave is generated in a water tank to form node and anti-node where the vertical jet was positioned. The results of jet wave interaction indicate that the motion of the surface standing wave significantly increases the turbulence levels and the turbulent shear stress, and the horizontal oscillations at the node have stronger effect than the vertical oscillations at the antinode.

The computation of boundary shear stress in smooth prismatic channels is presented in the light of the concept of energy transport through a minimum relative distance developed by Yang (1991). The boundary shear stress distributions are presented in trapezoidal, triangular, rectangular, circular and compound channels. Furthermore, 2^nd order solution of Reynolds equations is also presented. The velocity and Reynolds shear stress and boundary shear stress in rectangular open channels are obtained. The results obtained using 1^st and 2^nd order solutions have compared with experimental data in a good agreement. The methods are extended to 3-D flows in unsteady and non-uniform channel flows. The conclusions can be drawn that the solutions yield better agreement with measured data than other available empirical methods.

The boundary shear stress in smooth rectangular open-channels is determined from the continuity and momentum equations for steady uniform flows. It consists of three components: the primary contribution due to gravity, the effect of secondary currents, and the fluid shear stresses due to velocity gradients. A first approximation for the boundary shear stress is obtained after neglecting secondary currents and assuming a constant eddy viscosity. The analysis considers that the last component vanishes in the direction normal to the isovels. Analytical expressions for the boundary shear stress are obtained using the Schwarz-Christoffel transformation. The first approximation agrees well with the average bed shear stress measurements. After introducing two correction factors for secondary currents and the simplification of eddy viscosity, a second approximation agrees very well with the experimental measurements of both the average bed and side-wall shear stresses for all width-depth ratios. Secondary currents increase the side-wall shear stress at large value of the width-depth ratios. Finally, a side-wall correction procedure based on the second approximation is recommended.

A modified log-wake law is proposed to describe turbulent velocity profiles in smooth rectangular open-channels. The new law consists of three components: a log term, a wake term, and a free surface term. The log term reflects the channel bed effect and predominates in terms of velocity magnitude; the wake term expresses the sidewall effect and can be neglected near the channel bed; and the free surface term satisfies the free surface boundary conditions. The modified log-wake law contains six parameters: (1) the von Karman constant κ ≈ 0.42; (2) the wake strength Π = κ; (3) the bed shear velocity u_*b; (4) the sidewall shear velocity u_*w; (5) the maximum velocity u_max or the integration constant A; and (6) the velocity gradient at the upper boundary. The analysis clearly shows that the wake function results from sidewall effects. The modified log-wake law can replicate the velocity dip phenomenon in narrow channels at width-depth ratios less than 5. When the width-depth ratio exceeds 5, the maximum velocity occurs at the free surface. Finally, the modified log-wake law compares very well with Coleman's, Lyn's and Muste and Patel's experimental data.

Spur dikes have been used as hydraulic structures to suppress bank erosion by flood flow, waves generated by ship and to maintain flow depth as a navigation channel. Recently, it's noticed that they have functions to produce diversified attractive environments in river. In this study, experiments were executed to clarify water and momentum exchange between main flow and non-submerged spur-dikes regions. The results showed that prominent water surface oscillations happened in an arrangement of spur-dikes and the variations obviously correlated with velocity fluctuations, enhanced the water exchange, but did not influence on Reynolds shear stress.

This paper describes the local hydraulic characteristics of flows around the vegetative groins, which is made use of vegetations as a part of river training works. The hydraulic experiment on the basis of the flow visualization and the turbulence measurement was conducted by changing the groin span, the groin angle and the vegetative compactness, and the numerical analysis as well.

The experimental results say that the present vegetative groins have the basic function as the groin work on reducing the velocity inside the groin region and on splashing water toward the main flow region. The numerical results show that we can control the flow velocity inside the vegetative groin region by changing the compactness of vegetation.

This paper deals with spectral analysis of pressure fluctuations at the bottom of hydraulic jumps. Power Spectral as well as Dominant Frequency and some other statistical characteristics of fluctuating pressure beneath hydraulic jumps are obtained. The effect of upstream and inflow condition on the power spectral and dominant frequency of fluctuations have been considered. Pressure data were recorded for different Froude numbers from 6 to 10 and upstream chute slopes from 0° to 35°. A sampling frequency of 100 Hz was selected for each 60 Sec of test runs. The measurements were made in the bed of glass walled laboratory flume by means of pressure transducers and data acquisition systems. Variations of dominant frequency of fluctuations for different points through the jump were also obtained. Validity and adequacy of selected sampling frequency (100 Hz) was checked and as a result of all, useful information on basic criteria of the pressure data recording and experimental investigation of fluctuating pressure field on the floor slabs of stilling basins are reported.

The results of the theory analysis and experimental test indicated that both the average water depth of the circulating current and the momentum correction factor at the tail-water section could affect the sequent depth ration of A-jump. A simple modified formula for the sequent depth ration of A-jump has been proposed.

The choking flow phenomenon caused by local lateral contraction in open channels is studied in this paper. An equation for the determination of limit opening ratio is derived from the principles of conservation of energy and water continuity. The proposed equation takes into account for energy losses associated with local contraction and can accurately predict the limit opening ratios for choking.

When a bridge is constructed in a channel, an increase in depth of flow occurs immediately upstream of structure, which is generally termed as afflux.

In order to study the effect of shape of bridge pier and other important parameters on the amount of afflux, experiments were conducted. Results of experiments on different shapes of piers are reported in this paper. It was found that, under same approach flow condition, rectangular pier produces maximum afflux, while circular pier produces minimum afflux. The afflux due to other shapes of pier will be somewhere in between the afflux due to rectangular and circular piers. New equation for estimation of afflux is introduced.

The following paper is intended to evaluate the hydraulic characteristics at 1 km downstream to 12 km upstream from the Meghna Bridge in the Upper Meghna River. To see the hydraulic changes in the study reach, water level data were collected from existing automatic water level gauges and velocity and sediment concentration measurements were carried out for 12 hours tidal cycle along the pre-specified cross-section of the study reach. Data had been analyzed to see the extent of tidal range with time; variation of water level and water surface slope; changes in velocity and sediment concentration with time, distance, and depth. Flow field together with sediment concentration pattern had been evaluated. Discharge and sediment load had been computed and a correlation between them had been established.

Energy dissipaters in hydraulic structures have attracted the attention of many investigators. In these structures the cinematic energy converted into potential, during which a large amount of energy is also dissipated. This process is associated with high intensity pressure fluctuations. In this work experimental investigations of pressure fluctuations within hydraulic jumps on negative slopes are presented here. The results showed that, the slope of the basin will directly affects the intensity of pressure fluctuations. Previous studies also had shown that a negative slope reduces the length of the basin and thus, the cost of the structure. Therefore, it is believed that the present results will provide information useful in the design of such structures.

When the torrential flow impacts on the baffles in steep channel, water wings will be formed. This paper mainly studies the condition of water wings which is produced, developed and disappears, the main influential factors of the height of water wing and the estimation of the height of water wing. The study results indicate that the main influential factors of the height of water wing have the angle between the surface facing water and bottom plate of steep channel, the relative water depth, Froude number of section in front of baffles and the distance between two baffles.

The following paper concerns the experimental investigation of hydrodynamic forces on a so-called "HYDROMATRD^®-Module" during different underflow conditions. This mobile module is shifted in place of the stoplog slots in a tainter gate bay of an existing run-of-river project – which only currently serve water level control for navigation - to generate electrical energy. Apart from this use, the module also has to fulfill the functions of stoplogs in emergency situations. For this purpose it must be able to sink into the bay flowed through by flood. In order to determine the downpull forces on this module during flood conditions, a hydraulic model was built to a scale of 1:12.5. For this case a short section of the module was modelled in plexiglass which consists of 3 bulb turbine-axes in breadth and 2 turbine-axes in height, The investigation shows different underflow conditions in dependency of the position of the downstream level which influence the development of the hydrodynamic forces essentially, The results of the experiments were depicted in a diagram depending on downstream level, total lift forces and different steady lowering position of the module. Maximum downpull forces can also be easily determined for every gap of the throughflow opening of the module by these diagrams. Influences of different underflow conditions will also be described and evaluated.

The Gorai River off-taking from the Ganges River, is the main source of fresh water supply to the Southwest Region of Bangladesh. It is observed that, since 1989 the off-take of the Gorai fully dries up during the critical dry periods (January – May) and completely cuts off the supply of fresh water. This has caused a serious socio-ecological problem with negative environmental impact on the Southwest Region. Several past attempts of excavating the Gorai mouth have failed to produce hardly any benefit due to lack of adequate knowledge of the off-take mechanism.

For the first time a mathematical model aided three-year pilot dredging programme has been carried out for providing data and experience in devising a long-term sustainable dredging design and strategy. During the dredging, decision on the long-section, cross-section, and alignments of dredging were supported by several scenario simulations by numerical modelling of the hydraulic performance in terms of flow diversion from the Ganges, backfilling rate and erosion processes. Results with hydraulic interpretation of the corresponding simulations have been assessed to minimise the dredging effort by keeping track of the cut-off date for the dredging ensuring required flow diversion from the Ganges and to take decisions on a sustainable approach towards deciding on dredging strategy.

With the basic functions of anti-seepage, filtration, drainage, separation, reinforcement, protection, etc., geo-textiles have been widely used in hydraulic engineering, water resource management and waterway engineering. Through many years' laboratory tests and field practices, a series of design methods and construction of the geo-textiles for different engineering have been presented. However, there are few researches on construction technology for submerged dams consisted of geo-textile sandbags. In this paper through flume experiments, some hydraulic characteristics are studied, i.e., settling style, settling distance and initiation condition. The results are useful to design, construction and maintenance of submerged dams.

To improve the volumetric concentration of sand in the discharge slurry of jet dredger, a model test was conducted. Two kinds of sand, the coarse one and the fine one, were adopted. The speed and the movement direction of jet dredger, working water pressure of scouring nozzles and their layout, working pressure of jet slurry pump and the distance between bottom of suction pipe and sand surface were taken into consideration in the experiment. The key factors affecting the discharge volumetric concentration were figured out and their suitable values were proposed.

This paper introduces a new concept of the design of the two storey intake, two level hanged-plate intake. In such a way, the upper stream is got into channel and the bottom stream becomes the pressure flow. By using this arrangement, more clear water including less sediment are deflected into irrigation channel in addition to increasing the transport sediment ratio. In this paper, flow patterns, velocity profile, pressure distribution, and diversion ratio are studied experimentally for two different headers of hanged-plate such as P-weir and L-weir. The main characteristics of flow through hanged-plate is also investigated and compared with each other.

The following sections are included:

• Introduction

• Empirical Equation to Predict Vortex Formation

• Description of Test Procedure

• The Analysis of Tests Results

• The Compartment between Tests Results and Calculation

• Conclusion

• References

The formula for calculation the critical shear stress of non-uniform grain with in bed surface has been established, while considered the relative expose degree of grain size and the additional force acting on a grain. Coefficients that in the formulas have been obtained by using the monitored data. The value of minimum dimensionless shear stress θ_c0 is 0.23. The value of relative expose degree coefficient ξ is not a constant but located in 0 ~ 1 and varies with the expose of grain lying on bed river. The value of critical shear stress for uniform is in 0.23-0.46 according to the value of ξ = 0 ~ 1. The formula has been verified with factual data. The computed results can reflect the characteristics of incipient motion of sediment. The formula for calculation the bed load transport rate of sediment has been obtained in the text, it's value also located in a region. The value of coefficient θ_c is in 0.23 ~ 0.46 to uniform sediment and also varies with the relative expose degree of grain with in bed.

Based on the differences of transport mechanism between the uniform and non-uniform sediment, the additional force acted on non-uniform sediment has been divided into two parts in this paper. One is caused by the force-arm acted on non-uniform sediment. The other is caused by the influence of the non-uniform sediment to the flow structure near river-bed with non-uniform bed material. A formula used to compute the threshold velocity of the non-uniform sediment is established. Based on the experiment and filed data the coefficients in this formula are determined. The results fully reflect the characteristics of threshold motion of non-uniform sediment.

Based on the cusp-catastrophe theory of nonlinear science, the Shields number was regarded as the state variable, and Reynolds number of sediment and dimensionless constant md_m/d₀ were regarded as the bound variable in cusp-catastrophe model. Based on the standard equation of the cusp-catastrophe, the relation formula between Shields number and Reynolds number of sediment has been derived by using coordinate transform. A cusp-catastrophe formula used to calculation the critical shear stress of incipient motion for non-uniform sediment has been built. Water flume experiment data were applied to verify this formula that the results calculated from the cusp-catastrophe formula agreed well with the water flume experiment data. This indicates that the cusp-catastrophe formula is reasonable, and the results fully reflect the characteristics of threshold motion of non-uniform sediment. The purpose of this paper is to explore the incipient motion laws of non-uniform sediment from the viewpoint of nonlinear science.

Since river bed is composed of graded bed materials, the most recent work on the sediments incipient motion and transport rate have concentrated on non-uniform sediments using many methods. One way is base on the mechanics theory, and the other is based on the random mathematics theory. Along with the development of nonlinear science, the nonlinear science is applied the studies the sediment incipient motion in recent studies. The catastrophe theory of nonlinear science was adopted to study the incipient motion of mud flow by Cui peng (1993). The incipient motion of bed load had been proved that it belonged to catastrophe motion (Wang Xiekang, 1999).

Based on the prior studies, the state variable and the bound variable in cusp-catastrophe model were analyzed in this paper. According to the standard equation of cusp-catastrophe model, the sediment incipient motion formula had been derived from the coordinate transport. The catastrophe model was built, and a new way for studying the incipient motion of bed load will be discussed.

Formation of natural dams is a common in gorges of flow route of relatively steep gradient mountain rivers. These natural dams obstruct the regular flow and cause the water detaining in upstream of dam. Further, the accumulated water submerges a great extent of area. Ultimately, the natural dam becomes unable to hold the huge amount of amassed water any more and destruction of dam begins. The initiation mechanism of destruction differs with the characteristics of dam forming materials and variation of inflow discharges. It may be sudden or progressive in nature. But, even if it starts in a progressive way eventually it turns into sudden collapse once dam section becomes small to resist the water pressure behind it. Finally, it causes debris flow disaster onto the downstream areas, creating a great havoc.

In this observational study, observations have been made on the influential factors that affect the initiation mechanism of destruction and collapse advancement of artificially built dam in a steep-slope experimental flume.

Present study has been made to discuss how the sizes of bed material and discharge variations affect the initiation mechanism of debris flows. Sizes of dam forming materials and discharges have been considered as parameters and slope of experimental channel has been set constant. Experiments have been conducted using almost uniform-sized gravel.

Initiation mechanism of collapse and its progress in upstream direction shows that these kinds of dams collapse in a progressive fashion, starting from downstream and advancing to upstream. Many other parameters, which govern the destruction procedure of dam, need to consider in further research work.

High accuracy in calculating the transport rate of bed load in natural channels is required for design purposes. This can be achieved through good sampling and reliable data sets. However, measurements of bed load transport can be a difficult task for rivers with flow depths exceeding one meter owing to the methods of measurements that uses either a cableway or an AFrame. Therefore this study is confined to rivers with flow depths less than one meter only. Method of measurements employed is wading technique using Helley-Smith bed load sampler that is the most superior to other methods.

Study has been conducted on two rivers namely Sungai Lui and Sungai Semenyih with cross-section spanning between 14 m to 15 m. Sampling was done at every meter through out the river cross-section. The main aim of this paper is to make comparisons on the amount of bed load transport taken at every meter with the bed load transport taken at every two meter points at each observation. Results are tabulated and presented in graphical forms showing the percentage errors ntroduced between the two procedures. A qualitative and quantitative discussion on the improved accuracy of the former sampling method are presented.

A formula in computing the actual bed load has been established to make possible the estimation of bed load if less number of samples were taken at each traverse.

In natural rivers, sand particles are transported by water flow near the bed. Mean flow properties and turbulent characteristics in open-channel flows are affected by the bed load motions. In this study, interactions between fluid characteristics and the behavior of sediments were investigated experimentally. Behaviors of fluid and sand particles were measured with a laser Doppler anemometer(LDA). We could separate fluid data and sand particle data by using an amplitude of a Doppler-burst voltage and a transit time of scattering particles. Five cases of experiments for movable sand beds and fixed sand beds were conducted, respectively. It was found that the Reynolds stress of sand particles increases with an increase of the bed-load transport in the bed-load layer and the high momentum is transported downward by the dropping particles.

Extended Irreversible Thermodynamics is used to describe the behaviour of suspensions of solid rigid particles in a moving Newtonian fluid. In Extended Thermodynamics, the main idea is to elevate the dissipative fluxes as the flux of matter, the heat flux and the momentum flux to the rank of independent variables with the same status as the classical variables like mass, momentum and temperature. The flux variables are obeying evolution equations which generalize the classical equations of transport of Fick, Newton and Fourier. For the sake of simplicity, it is assumed that the heat and momentum fluxes relax much faster than the flux of matter. The main results which are obtained are the following. First, we have derived an evolution equation for the diffusion flux in terms of the basic variables, namely total density, mass concentration, momentum and temperature. Second, we were able to formulate constitutive equations for the usual stress tensor and the stress tensor associated to the motion of the solid particles. Third, as particular cases, we recover the classical Soret and Fick laws.

A new and user-friendly general formula for the computation of total bed material load in alluvial channels under equilibrium transport condition has been developed based on the stream power concept. Its application is extended to coastal waters. The main advantages of this formula are its accuracy, the ease of computation and the wide range of applications. Only one coefficient is involved in the new formula and it is found that a universal value of 12. 5 is acceptable for all cases.

For the flow in channel with rigid vegetation, the bed-load transport rate is obviously lower than that of the non-vegetated flow. The drag due to existence of vegetation elements causes a reduction of the effective tractive force. Furthermore, the critical tarctive force is higher than that of the non-vegetated flow. In the paper, the flow structure and the bed-load transport are investigated in a laboratory flume, and the applicability of the previous conventional bed-load formulas to the flow in vegetated channel is examined.

A very simple but effective approximation for the gamma function and the psi function is presented. The application of the psi function in Einstein sediment transport theory extremely simplifies the estimation procedure of sediment discharge in river and coastal engineering.

The paper deals with the density current in a rectangular settling tank. A special attention is paid to the behavior of density current under the developing stage of the bottom boundary layer. To simulate the density current a mathematical model is developed using a k-ε turbulence model. After verifying the model by laboratory experiments, the effect of sediment concentration and of sediment fall velocity on the density current was demonstrated. If F_dc < 0.5 the density current becomes predominant, while F_dc > 1 the effect of density current is negligibly small, where F_dc is the densimetric Froude number. The density current promoted the settling of sediment near inlet zone, while it showed the negative influence on the settling of finer particles due to enhanced eddy diffusivity.

Using floodwater in arid and semi arid areas of Iran is important especially in the recent years. Using lateral intake is a method of floodwater diverting. In arid and semi-arid areas, floodwater has large amount of sediment that will be carried into the intakes and decreases the channel conveyance. There are several methods of sediment control in lateral intakes. Most of these methods are used in permanent river and irrigation canals. In this investigation using sill for sediment control in lateral intakes has been studied. Also the amount of sediment inclusion into the intake and pattern of sedimentation has been analyzed.

Experiments have been conducted for a 60 degree intake channel. Slope and width of main channel, width of lateral channel and bed material of main channel are constant in all experiments. For the selected bed material, there is only bed load sediment transport. Experiments have been done for three discharges and three depths for each discharge. The volume of sediment entered into the lateral channel and the volume of sediment transported in main channel have been measured. The pattern of sedimentation has been determined using bed topography. It was found that the volume of sediment transported into the lateral channel and the width of sedimentation area decrease with using sill.

In mountainous river, the bed material has wide particle size distribution in which the largest diameter often becomes over 1000 times of the smallest diameter. The size distribution strongly affects the phenomena related with sediment transportation. We propose a new model in order to evaluate the bed evolution and sediment transportation on the mixture bed. In the model, the extent of the grain size is divided into several ranges, and the continuity equation for each grade's particle in flow and erosion / deposition velocity equations are used in predicting the bed variation and the grain size distributions in flow as well as in the bed surface layer. The erosion / deposition velocity formulae are given as a function of the difference between the actual sediment concentration in flow and the equilibrium concentration determined by the competence of flow. The larger the difference, the larger the velocity becomes. Some flume experiments verified the formulae. The one-dimensional comparatively intensive erosion processes of the mixture bed in an experimental flume were well reproduced by the numerical simulation using the present model.

In this paper the distribution of sediments to the branch channels formed by the sand bar has been studied. The water discharge has been measured and sediment discharge has been estimated in the main channel as well as in the branch channels. The sediment transport ratio of the downstream branches of a sand bar has been compared with the nodal point relation developed in the laboratory condition.

The authors conducted a set of survey on suspended sediment load transportation in the Kataniwa River, during the flood on June 22nd-23rd '97, and analyzed the concentration of suspended sediment. The following relationships are found out through the analysis;

1) the shape of suspended load flux hydrograph is corresponding to the discharge hydrograph,

2) on the other hand, the one of wash load is not corresponding to the discharge hydrograph, but to the hyetograph.

These relationships lead to the hypothesis that the suspended load yields at the riverbed and is transported with the flood flow, and that the wash load yields at the surface of the basin and pours into the channel rapidly.

To investigate a mechanism of these relationships, a numerical model which evaluates concentration of suspended sediment load on a tributary basin, was newly developed. Two types of the sediment yield model were demonstrated in accordance with grain size. The larger coarser grain size was produced at the riverbed, and the smaller finer size like wash load was produced on the surface of the basin. The results of the simulation of suspended load show fairly good agreement with the observed data.

This study contemplates on the sediment extraction capability through a vortex tube by analytical means. The current analysis makes use of the mathematical and numerical methods to predict important parameters like discharge, pressure, velocity, shear velocity and effective length of extraction occurring along the tube. The analysis will focus on the reproduction of experimental data conducted by previous researchers. Accordingly, it was discovered that the prediction by numerical method was slightly better than the mathematical one. This is due to the fact that numerical analysis solved the differential equations without involving too much assumptions. Nevertheless, the mathematical analysis, which solved the differential equations in terms of harmonic motion and reduced these into simpler form gave a slightly bigger margin especially for slit ratio more than 1:15. The overall results indicate that both analytical methods could be used to design vortex tube under uniform as well as scattered slits.

Effect of sediment sorting on temporal variation characteristics of braided channels is studied by means of numerical simulations. The results obtained in this study are summarized below.

Sediment particles are exchanged to fine ones in dry bed regions and coarse in streams, respectively. This is because fine particles are included more than coarse particles are present in transported sediment and the deposited sediment includes more fine sediment. Furthermore, sediment is sorted in dry bed regions. Sediment particles are exchanged to fine ones in the downstream region and coarse in the upstream regions of dry beds, respectively.

Streams are bifurcated again and again and produce much smaller streams. Therefore, streams show both self-similar and fractal characteristics. Such river features are expected to promote the restoration of natural riverine ecosystems, because they diversify the physical environment of plants and animals inhabiting rivers. In addition, sediment sorting suppresses formation of small dry bed regions and enhances that of large dry bed regions on non-uniform sediment bed with narrow flood plain width. On the other hand, sediment sorting suppresses formation of large dry bed regions on non-uniform sediment bed with wide flood plain width because sediment material in downstream regions of dry bed areas contains much fine sediment.

A constriction is a reach of sudden reduction in the channel cross section. A strait and a channel straitened by hydraulic structures are examples of constrictions in an open channel flow. As the flow through a constriction is usually complicated and affected by the boundary geometry, the local scour also becomes complicated. Generally speaking, local scour is induced by a horseshoe vortex. In this paper, another kind of local scour, which is caused by secondary flow, is discussed.

Local scour around bridge piers is known for being an important factor threatening the safety of bridges. It is related to the subjects of turbulence, vortex, sediment transport, and others. Because of the random nature and complexity of the scouring phenomenon around bridge piers, the risk of failure due to excessive local scour around a pier during its service life always exists. Thus, the time-dependent reliability analysis of local scour is important in designing new bridges and in evaluating the vulnerability of existing bridges to local scour. There have been numerous empirical formulae developed in the past to estimate the maximum scour depth under the conditions of live-bed scour or clear-water scour, whereas still little work has been done in a probabilistic manner. In this paper, a framework of time-dependent reliability analysis of local scour around bridge piers is presented which considers both hydrologic uncertainty as well as the hydraulic and model uncertainties. A hypothetical example is used to illustrate how the factors, such as service life, pier dimensions, and footing depth of pier, affect the reliability of the pier.

Study on maximum depth of scour downstream of culvert has received considerable attention by different investigators. However less information about the scour hole geometry at the downstream of a culvert is available. Therefore, it is required to reanalyze the existing data to study the scour hole geometry. The available experimental data on scour downstream of a culvert have been analyzed. It was found that the scour hole geometry, in addition to culvert diameter and discharge intensity, is a function of drop height also. New equations for prediction of scour hole geometry are presented.

Circular jets impinging on a solid plane surface as well as the scour caused by it on a movable sand bed have been studied in the past. However, the effect of seepage on scour has not been included though it is important for many hydraulic structures. Hence, experimental investigations were undertaken to study the effect of upward seepage on the scour caused by an impinging circular submerged jet for a range of exit hydraulic gradients. The role of impingement height, velocity of jet and the time of scour were also investigated. The maximum scour depth produced by a jet in the presence of upward seepage is found to be somewhat less than that without seepage. The maximum scour depth is found to decrease with an increase in the value of exit gradient of seepage. For the range of investigations, the maximum scour depth is found to increase with an increase in the impingement height.

The 2-D flow field at several horizontal planes around piers and abutment has been presented from the results of flume experiments in a fixed bank straight rectangular channel with both flat bed and erodible bed condition. The experiments are conducted in the clear-water scouring. Previously identified restricted flow concentration region around abutments found to be equally valid for piers where pier centerline is considered to be the mirror image of the channel wall for abutments. From the characteristics of the vortex systems at different horizontal plane, the 3-D flow structures are reduced to 2-D and the above phenomenon has been treated analytically in order to develop an integrated scour depth prediction method around piers and abutments. The developed method is then applied to predict the maximum scour depth around piers and abutments both against the available laboratory data.

Submerged breakwaters and artificial reefs have been used to protect coastal erosion, and are now replacing detached breakwaters. Although constructions of the artificial reefs sometimes cause significant score around the reefs, the manuals for the design describe mainly on wave decay but scarcely on the local scour. In order to know the state of the constructions, we have conducted questionnaire research on the reef construction in Japan to all the central and local governments that have coasts and collected bathymetric charts before and after the construction. Comparisons of these charts show that topographic changes relate with opening width of the structures.

Rivers are one of the most essential sources of sand and gravel supply for civil works. However, undesirable effects of irregular in-stream mining have been reported on natural sources, environment and infrastructures close to rivers. It is necessary to find the effects of mining on rivers in more details. This research concentrates on mining pit migration phenomenon and its effects on the channel bed.

In this paper, first various effects of sand and gravel mining is presented, then migration of rectangular mining pit and variation of longitudinal profile in channel bed composed of uniform sediments is reported. Different values of widths and lengths were used for pit while pit depths and flow variables were kept constant. It is shown that migration speed is changing by (L/b) ratio (where: (L) is length of pit and (b) is width of pit). Also it was found that migration speed in convection period is more than that in diffusion period. In addition, by increasing (L) or (b), filling rate of pit increases, where the effect of width is more important than the effect of the length. Also it was found that the maximum bed scouring upstream of pit occurs close to pit (flow picks up most of the sediment particles close to the pit).

Bangladesh, one of the largest deltas in the world, has been mainly formed with sediment deposited by the three mighty rivers namely the Ganges, the Jamuna and the Meghna. These alluvial rivers are continuously shifting their positions and changing shapes as a consequence of hydraulic and geomorphic forces acting on its bed and banks. The present study presents some analytical results reflecting some idea about the hydraulic geometry and morphological behavior of the Jamuna River of Bangladesh.

At a station hydraulic geometry of the Jamuna River has been evaluated using the hydraulic geometrical parameters such as width, mean depth and mean velocity as a power function with increasing discharge. Use of daily data of Jamuna River for relating the above three parameter presents that the concept of hydraulic geometry of stream channels proposed by Leopold et. al is followed by the Jamuna River. Results suggested that in case of Jamuna River, width increases rapidly and depth increases slowly with increasing discharge, which represent the characteristics of Jamuna River as an alluvial river.

Moreover, to study the morphological aspects of the Jamuna River, variation of the cross-sectional profile and bank shifting of the Jamuna River near Sirajganj were studied. Variation of the cross-sectional profile shows that there are no significant and systematic changes over the last ten years due to highly dynamic braided nature of the river. However, comparative study shows that downstream of the river near Jagannathgaj and Bahadurabad shows decreasing trend.

Morphological study was further extended to observe the bank-shifting pattern of the Jamuna River near Sirajganj Hard Point, which is located at upstream of the Bangabandhu Bridge. It has been revealed from the study that at about 4 km upstream of the Sirajganj Hard Point the bank erosion rate has decreased and the riverbank has become more or less stable. But at about 2 km upstream of the hard point bank erosion has increased from 1998. At downstream of the Sirajganj Hard Point the riverbank remains quite stable from 1995 to 2000.

The results of the flow and bed topography measurements at a reach of the Upper Meghna River in the vicinity of the Meghna Bridge (23.6027⁰N, 90.6165⁰E) have been presented. The existing bank erosion in the study reach is compared with the velocity vector field and currently available models are used to explain the current condition.

In this paper, tow-dimensional mathematical model is adopted to simulate the river flow with local projects. To research the influence between river flow and local projects, coordinate transformation method and finite analytic method are used, so we can generate computational grids automatically and concentrate the grids as desired near local projects in physical plane. As an application, the upper Meigong River flow with the channel improvement projects is simulated; the results show that the mathematical model and computational method is reasonable.

Unsteady depth-varying open-channel flows are really found in rivers in flood. Owing to the highly accurate laser Doppler anemometers (LDA) a valuable database of unsteady open-channel flows is now available. Almost all researches have been conducted not by numerical simulations but by laboratory experiments with LDA. These LDA measurements of unsteady flows are, however, sometimes very difficult to be conducted. Therefore, in this study, numerical simulation of unsteady open-channel flows on a smooth bed was carried out by using the RANS model and VOF method.

The flood wave resulting from the sudden collapse of a dam in a channel, known as the dam-break flow, always leads to a great amount of property damage and loss of human life. In order to investigate this flood wave phenomenon, this paper simulates the dam-break flow based on a high-resolution total variation diminishing (TVD) scheme. First, the first-order flux vector splitting (FVS) with an entropy fix is applied to the shallow water equations for solving the 1-D dam-break problem. Furthermore, the extension of this first-order upwind scheme based on a Sweby's flux limiter approach is implemented to ensure the second-order accuracy and to avoid spurious oscillation. In addition, a comparative study of the second-order TVD scheme is made with different flux limiters.

In this study, a computational method has been proposed for free surface flows taking account of the treatment of the deforming free-surface shapes and the numerical accuracy for the internal flows. In this paper, the free-surface profiles are represented by curvilinear coordinates generated on the basis of the ALE formulation. The governing equations are discretized on the collocated grid system. The velocity-pressure correction is performed with C-HSMAC method, which is effective to preserve fluid mass during the unsteady computation with free-surface deformation. In addition, a QSI (quintic spline interpolation) scheme is applied to convection terms to improve the numerical accuracy for internal flows. The free oscillation with small amplitude and nonlinear waves were solved with the present method. As a result, it has been shown that the proposed scheme and numerical algorithm have sufficient numerical accuracy and that they are effective to predict free-surface flows.

The gridless Lagrangian model of water flow, so-called particle method, is extended by being installed the rigid-body-tracking routines, to analyze the triangular interaction among a fixed structure, a water flow and floats. The submerging process of ice floes beneath the ice cover induced by the wave and the uni-directional flow is simulated. The three categories of ice floe submergence, which was found by the physical experiment, such as the under-turning, the half-turning and the sliding, are well reproduced by the present simulation.

A two-dimensional depth averaged model for supercritical and subcritical flow in rectangular channels is developed. The model includes the effective stress terms by using spatial velocity averaging technique. The MacCormack explicit finite difference scheme is applied to solve the governing equations with the assumption of perfect slip wall boundary condition. The model is applied to two case studies: 1) supercritical flow in gradual expansion and 2) subcritical flow circulation due to jet discharge in a rectangular pool. The model results are found to be in close agreement with the measured flow velocities and depth data obtained from previous laboratory experiments.

Fully developed three-dimensional turbulent flow over sand ribbons in an open-channel is computed to clarify the generation mechanism of secondary currents of the second kind by direct numerical simulation (DNS) using a regular grid under a generalized curvilinear coordinate system. Stable secondary currents and turbulent characteristics are reasonably reproduced. Detailed evaluation of each term in a mean voracity transport equation revealed that the secondary currents of the second kind is generated principally by cross-planar turbulent shear stress , and that the anisotropy of the cross-planar turbulent normal stresses restrains the generation of the secondary currents, where v⁺ and w⁺ represent vertical and spanwise velocity fluctuations normalized by friction velocity u_τ, respectively and overbar denotes the time average.

This study deals with development of a new numerical technique with high-accuracy and high-resolution for advection. The 6-point scheme proposed by Komatsu et al., which is a numerical solver based on the characteristics, is modified in order to make it possible to be applied to the conservative advection equation. The modified 6-point scheme is named the conservative 6-point scheme. The universal limiter proposed by Leonard and Niknafs and a new discriminator are incorporated in the conservative 6-point scheme to obtain numerical results which are not only high-accurate but also free from numerical oscillations. It is found from the model computations that the numerical technique presented in this study is able to give good numerical results.

While channelization usually shows positive effects in flood control for medium or high slope regions of a river basin by increasing the conveyance capacity of the river, it seems not so good as expected in lowland regions where the hydrodynamic interactions in the river network become more complex. To access these effects of channelization on the targets of flood control in the lowland regions, a dynamic one-dimensional unsteady flow model is used. Proposed scenarios of channelization are applied to the Red River Delta of Vietnam. Simulated results of the development of flood flow in the river network and the hydrodynamic interactive relations between rivers are presented. Conclusions of the paper are drawn with the expectation that they will be useful in flood control planning and water resources management for the basin as well as for the delta.

Dam-break wave has been an important research topic for centuries. Both experiments and numerical simulation are used in modeling this very specific and difficult phenomena. This paper presents a MacCormack type scheme for the computation of two dimensional dam-break flows. The widely used MacCormack scheme is modified in order to avoid the nonphysical oscillation in the vicinity of the wave front with strong gradient in the numerical solution. To simulate dam-break wave moving on real ground, a simple but effective scheme is designed to treat the uneven topography. Example computations show that the model is robust in modeling dam-break wave traveling in the real ground.

In this study, a two-dimensional numerical model of multi-phase flow is developed based on a CIP method and an extended SMAC method. In order to validate the proposed numerical model, hydraulic phenomena with not only gas-liquid interface but also solid-gas-liquid interfaces have been computed; for example, collapse of liquid column, gravity current surge due to exchange of two fluids, and collision between water and a solid body. It has been demonstrated from the computation results that the numerical model can provide stable results for both gas-liquid phase flow and solid-gas-liquid phase flow and simulate the hydraulic phenomena precisely.

A large eddy simulation (LES) model has been developed to study turbulent flow in open channel with the lower part of the flow domain occupied by a drag force layer representing vegetation. One equation model is used for subgrid scale turbulence closure. The length scale of turbulence l is proportional to the grid size and the turbulence energy k is obtained from the solution of the turbulence energy transport equation. The results show that the model has the capacity of describing the three-dimensional structure of large eddies appearing at the interface of the vegetated and non-vegetated region and tracing the development of large eddies. The agreement between the numerical results and the available experimental data is satisfactory.

Because air-rate reflects the operating reliability of the reactor, the simulation and forecast of the concentration of dissolved oxygen (C_DO) or the air-rate distribution in aeration tank plays a key role in engineering practice. The two-phase flow in aeration tank is complex and air-rate varies due to different fluid situation and aeration situation, so most studies are based on experimental observations. Up to now, the references about the numerical simulation of two-phase flow in aeration tank are rather limited, even though there are so many reports on solving two-phase flow problems or 2D equations of flow and mass transportation in other areas.

In this paper, a serial numerical model has been set up. The numerical model focus on this study combines two-dimensional shallow water flow model and two-dimensional mass transport model with the capability of predicting the flow and C_DO distribution in aeration tank. Numerical simulation is carried out based on ADI (Alternative directional implicit) scheme. ADI scheme is a classical finite difference method and its solution is stable and accurate for the present numerical model. The 2D model has been chosen; furthermore, a wastewater aeration observation in Yizheng city indicated that the present model could be served as an effective tool for hydrodynamics and studies on aeration tank. At last, a 1D two-phase flow numerical model was established for discussing air-rate change along upright direction of aeration tank. These results will head to a possibility of improvement of operating reliability of aeration tank and designing proceeding.

The flow through the throat-type energy-dissipators is calculated by using an axis-symmetrical K ~ ε turbulence model. The velocity field, the pressure field and the distributions of turbulent energy and its dissipation rate are acquired. The energy dissipation through the throat-type energy-dissipators can be seen in detail. The calculated pressure distribution is compared with the measured and in good agreement. The results are useful to understand deeply the flow characteristics of the throat-type energy-dissipators.

Owing to the historical eruption of Mt. Pinatubo in the Philippines on June 15, 1991, in the rainy season, the mudflow (lahar) flowed and deposited in the downstream area and brought serious damage to several villages. In order to conduct proper countermeasures against the mudflow hazard, it is necessary to estimate the deposited area of mudflow exactly. In this paper, a two-dimensional numerical model of the mudflow was developed. The resistance law of the turbulent mudflow, which has been proposed by Arai and Takahashi [1], was used in the model. The model was applied to the overland mudflow in the southeast area of Mt. Pinatubo. It was found that the proposed model is useful to be applied to the overland mudflow by giving the proper topography.

This paper describes the results from a numerical study of the flow structure at a horizontal intake with a step. A three dimensional numerical model is developed that solves Reynolds Average Navier Stocks (RANS) and turbulence closure equations. The acceleration length for the horizontal velocity component close to the pipe is about twice the pipe diameter, which is in close agreement with predicted results for a horizontal intake in the absence of a step. Vortices are formed in three-dimensions and their strength and locations are estimated. Results show that in this very geometry main vortices are formed in longitudinal direction due to the step geometry. Similarly, secondary vortices are present in other cross sections due to the pressure gradients inside the flow. The maximum strength of the secondary vortices, at the vortices centre, is about one third of the longitudinal vortices. It is finally recommended when a step is used in order to increase the volume of a reservoir, low submergence, less than twice the pipe diameter, should be avoided in the intake design procedure.

Mountain-river usually shows the steep slopes bed and consists of a sand-gravel mixture with a wide range of grain size, and also is locally crooked. In the present study, the calculations of three dimensional turbulent flow, sediment discharge with sand-gravel mixture and bed variation in the locally crooked river in mountain region, were conducted by means of standard k-ε model, bed load function and continuity equation of sand, respectively. Then, the suitable design of riprap bed protection with natural stones is considered from the result of the turbulence calculation and estimating the shear stress on the bed.

The deposition profile of sand-gravel mixture (of fine sand and one or two types of coarse sediment) is studied in a reservoir with a steep channel and the deposition profile is numerically simulated. A hydraulic jump (formed in the channel on building a model dam at the downstream end) divides the whole flow region into a subcritical region below the jump and a supercritical section above the jump. The deposition of sediment occurs in the subcritical region, where the flow velocity decreases. One-dimensional continuity equation of flow and the sediment transport are applied with the modification of bed load function i.e. shear stress for the grains of the mixture. The difference of mobility of each grain size is considered in the sand-gravel mixture, where the sediment sorting in the part of the sediment deposition is occurred.

A numerical model to predict the formation processes of dunes and antidunes in open channel flows was developed. Flows and bed shear stresses over dunes were evaluated by a depth averaged model considering the effect of vertical acceleration, so-called Boussinesq type equation. Irrotational condition of vertical velocity distributions far from a dune bed and the acceleration/de-acceleration effect near a bed were considered in the depth averaged model to evaluate the bed shear stresses correctly. It was shown that the initiation and development processes of dunes can be simulated incorporating a non-equilibrium sediment transport model proposed by Nakagawa & Tsujimoto in the water surface profile analysis with a Boussinesq type equation. Calculated results on the temporal development processes and shape characteristics of dunes were compared with previous theoretical and experimental studies. It was indicated that the calculated wave length caused by initial instability is coincident with the resonant relation of open channel flows over a wavy bed, and the wave length and height of dunes in the equilibrium state are dependent on the step length, though further investigations are needed to clarify the increase of flow resistance during the development processes of dunes.

In the paper a numerical model using a finite-volume method is presented to calculate flow and bed configuration produced by a jet discharged into a shallow pool with erodable bed. The model system consists of an unsteady hydrodynamic module, a sediment transport module and a bed-deformation module. The hydrodynamic module is based on the two-dimensional shallow water equations and the depth-average version of the k-ε turbulence model. The sediment transport module comprises semi-empirical models of suspended-load and non-equilibrium bed-load. The bed-deformation module is based on the mass-balance for sediment. The effects of bed slope on the direction of bed-load transport are also taken into account.

The evolution of the scour hole and the deposition dune is well simulated by the model. Results of these predictions are compared with those of laboratory experiment. Good agreement is obtained.

A local scour of sandbed behind hydraulic structure due to an effluent discharge is calculated by a 2-D morphological model developed through analytical manner, which provides clear picture of this scouring process. Two-dimensional depth-averaged flow field is developed from the continuity and momentum equations together with the plane turbulent jet formula. It is then used further with the bedload transport formula and the first order differential equation of non-equilibrium sediment transport to solve for solution of sediment transport in this situation. The bed levels of the scour hole are computed by applying the calculated values of sediment transport into the equation of the net erosion/deposition on the bed. The models are calibrated and verified by juxtaposing the acquired results with the existing experimental data. The analytical models are also applied to a real field situation to predict the sedimentation in flow field and the bed changes behind the outlet, which are found satisfactory.

This study presents a numerical model for the study of air entrainment on the pressure surges in a pumping system. Free and dissolved gases in the liquid and cavitation at vapour pressure are modeled. The numerical procedure was applied to a pumping system with different types of check valves in unsteady operation. The results show that reasonable predictions of transient pressures with proper phasing and attenuation of pressure peaks can be obtained. A critical range of air entrainment values was noted to exist.

In water hammer analysis, a fluid flow is usually dealt with as one dimensional unsteady flow governed by the momentum equation and the continuity equation when the flow is one phase liquid flow. When the negative surge pressure reaches vaporization point, the bubbles start to occur and the flow becomes a liquid-vapor two-phase flow. The momentum equation of a two-phase flow includes the void fraction and the governing equation changes from a hyperbolic type partial differential equation to a parabolic type partial differential equation because of phase changes from liquid to gas. Those equations are successfully solved by the upstream finite difference method. This kind of phenomena is very rare and it is also rare to deal with analysis and experiment. The precise experiment of bubble occurrence and the measurement by the sapphire optical probe sensor are introduced in this study. The occurrence of bubble is also taken by a high-speed video camera every 0.001 second. The occurrence of each bubble and behavior of the bubble is shown precisely as the result of experiment. Those experimental results are compared with the above results of numerical analysis of liquid-vapor two-phase flow equations. From this study it is known that the bubbles increase suddenly when nonlinearity affects negative pressure, which has been considered as gradual increase with velocity changes.

The large complex piping systems are considered. Water distributing systems, drainage networks and so on are the examples of them. The pressure flow regime takes place in water-supply systems as a rule, but both pressure flow regime (under maximal loading) and free flow one may take place in drainage networks.

The mathematical modeling apparatus is described in the paper. The considered problem is reduced to the solution of mixed graph-defined problem. Here the system structure is simulated by one-dimensional complex ("graph"). The liquid flow along the pipes is described by unified system of equations, transforms to water hammer equations in case of pressure flow, or Saint Venant equations in case of free flow. The mathematical models of various nodes of piping network, where the various hydraulic devices may be located, serve as boundary conditions for aforesaid differential equations. The examples of such boundary conditions are demonstrated.

Liquid column separation is considered as the set of isolated cavities emergence. Mathematical model of this phenomenon is described.

It is necessary to specify the initial data for completing the problem definition. This implies the discharges and pressures distribution along the all of pipes and node initial parameters must be specified at start time. The ways of this problem's solution are discussed.

The unsteady flows calculation techniques for piping systems are discussed. Algorithms based on finite-difference scheme of running calculation are suggested.

The examples of calculations are demonstrated.

For the visualisation of the occurrence of submerged vortex in hydraulic pump sump model tests, the present studies showed that the simulated flow should be higher than that corresponding to Froude number simulation. A "k-Froude" velocity simulation is used in this study. The upper limit of the model simulation for the occurrence of the submerged vortices was observed to be when the ratio of viscous forces to surface tension forces is the same for the prototype and the geometrically similar model. If the corresponding swirl angles of the flow in the inlet ducts measured at Froude scaling velocity is less than 5 degrees, the occurrence of submerged vortices generally does not exist for model flow tested below the critical model test flow velocity defined by the similarity of the ratio of Weber Number and the Reynolds number of the flow filed in model and prototype.

In this paper cavitation coefficients of hydraulic turbine in sediment laden flow have been studied experimentally by means of energy approaches. It is concluded from test results that both of incipient cavitation coefficient and critical cavitation coefficient of hydraulic turbine in sediment laden flow are different from those in clear water. The cavitation coefficients vary along with silt content and there exists a maximum of cavitation coefficients within a range of sediment concentration considered in the test.

When a pump station is built, the pump sump is very important, which directly affects the efficiency and safety of the pump station. The most important thing is to reduce the vortex in the flow of the sump, because the vortex is the primary reason which could cause vibration, cavitation and the decrease of the efficiency of the pump station. All of these can exacerbate the performances of pump. Although the flow conditions in the sump are very complex and it is impossible to avoid fully the vortex, the vortex generally distribute around the pump bell, their generation relies on the construction of the sump and the pump bell, and their generation is also related to the moving conditions of the pump. So we have designed a model pump sump with special dimensions in order to reduce the vortex in the flow of the sump. The propose of our experiment is to measure the internal flow field in the model of closed pump sump with special dimensions under five typical conditions of the pump with PIV. The PIV technology is an important mean among the flow measurement instruments, its result appears roundly the overall flow status in the measurement side, overcoming the limits that traditional measurement could only measures one-point. By PIV we have obtained the datum about the velocity distribution, streamline distribution, velocity variance, turbulent kinetic energy and so on. Now we know the distribution of the vortex in the whole flow field in the sump from these datum. On the base of all these work, we have done some improving design, adding a T-type baffle below the pump bell to reduce the possibility that the vortex generates, we have done again the experiment to check the effect of this model with improving design with PIV, the results and the data we have got certify that this model pump suction sump with a T-type baffle has good performances under kinds of conditions, it is important for reducing vibration, decreasing cavitation and increasing efficiency of pump station.

Howell Bunger valves are the most common valves used in bottom outlet conduits to control the flow discharge. These structures are subjected to high velocity flow and pressure. In this paper, experimental information regarding the hydraulic model studies of three new valves, which were designed for the recently constructed dams in Iran, are presented. These information include, discharge coefficient, pressure distribution, cavitation index and hydrodynamic force of these valves.

Under the aerated conditions of wall and top in tube, the turbulent flow field in the tube was measured by using LDA. The turbulent structure of the flow field and the mechanism of aerating drag reduction in the tube were discussed. It is shown that the energy dissipations of turbulence flow and mean flow will reduce and the flow velocity (or flow rate) will increase by injecting mini-bubbles to the wall or top of tube, namely the effect of aerating drag reduction is attained.

In recent year, the high-density soft mud transport pipeline systems using a compressed air are utilizing in the field of marine construction works and coastal zone developments. This tonsport system is very useful for high-density slurry transport because it is easily to separating air from slurry. The purpose of this investigation is to clarify the mechanism of slurry tonsporting system using a compressed air in the experimentally. In the experiment, the air-liquid two-phase flows have been focused on liquid of low viscosity in long distance pipelines with narrow diameter and discussed the mechanism of generating, development and breakdown of water slug flows. The present paper shows some results which are summarized as follows. Slug flow occurs in the approximately same point for the all experimental conditions which we carried out. The important governing factor for generating of slug flow is the water depth pipe. The velocity of slug flow is controlled in the air volume, and that flow velocity becomes fast with the increase in the air volume. The occurrence period of slug flow is controlled in the water quantity, and the period of the occurrence becomes short when the volume of water is large. There is a water air ratio which becomes steady slug flow.

This paper makes a comparative study of loss characteristics between gooseneck-type and U-type pipes from geometric aspects. In fact, the gooseneck-type and U-type pipes can be considered as a geometric symmetrical or asymmetrical compound bend pipe, respectively, which both consists of two elbows and a transition section. Hydraulic characteristics of the compound pipes are primarily dependent upon transition length between the two elbows as well as orientation of lower elbow. This paper develops empirical formulae of loss coefficient of asymmetrical gooseneck-type pipe through experimental investigation, which are compared with loss coefficients of symmetrical U-type pipe and linear superposition. Experimental results show that loss coefficient of the compound bend pipe can not be simply calculated by linear superposition principle, that is, a sum of loss coefficient from geometrical constituent parts, which should be calculated according to the intrinsic loss law. In addition, variations in loss of gooseneck-type and U-type pipes are analyzed and compared. And criteria suitable for linear superposition calculation are also given.

The higher the dams, the more difficulties the energy dissipation has for flood discharge. For this reason, many costly huge-size educe tunnels have to be abandoned when construction assignments are fulfilled. By making full use of energy loss of sudden-varied high speed flow, a throat-type dissipator, which is similar to an orifice dissipator, can satisfy not only the flood educe in the period of construction but also permanent discharge release, so that the construction flood educe tunnel can be rebuilt into discharge tunnel economically. The key problems were solved skillfully through theoretical analysis and experimental investigation, and the results are in good agreement with to those of theoretical calculation. The features are of simple configuration, stable flow, non-cavitation phenomena, reliable safety, etc. The throat-type dissipator will play an important role in huge hydraulic engineering.

Developed at Colorado State University, CASC2D-SED is a physically-based model simulating the hydrologic response of a watershed to a distributed rainfall field. The time-dependent processes include: precipitation, interception, infiltration, surface runoff and channel routing, upland erosion, transport and sedimentation. CASC2D-SED is applied to Goodwin Creek, Mississippi. The watershed covers 21km² and has been extensively monitored both at the outlet and at several internal locations by the ARS-NSL at Oxford, MS. The model has been calibrated and validated using rainfall data from 16 meteorological stations, 6 stream gaging stations and 6 sediment gaging stations. Sediment erosion/deposition rates by size fraction are predicted both in space and time. Geovisualization, a powerful data exploration technique based on GIS technology, is used to analyze and display the dynamic output time series generated by the CASC2D-SED model.

Laboratory experiments concerning scour development around a group of two cylindrical piers were conducted to study details of flow characteristics and accompanying scour hole formation. A series of experiments under unidirectional flow and clear water scour conditions were conducted in a flume to obtain descriptions of velocity profiles around the two cylinders using an Acoustic Doppler Velocimeter. Ensuing final local morphologic patterns around the piers indicated that when piers are placed in a group of two, factors such as spacing, sheltering, reinforcing and horseshoe vortex greatly influenced the potential formation of the equilibrium scour hole depth. A multiple linear regression model was also used to develop empirical relationships to predict maximum scour hole depth in the case where two piers are present to obstruct the flow.

A modified temperature index approach of snowmelt modeling (SDSM-MTI) using near surface soil and air temperature data was developed and tested at the Paddle River Basin (PRB) of Alberta. The ability to simulated reasonably accurate snowmelt runoff, snow water equivalent (SWE) and snow depth at PRB accurately demonstrates the advantage of using near surface soil temperature data (in addition to air temperature) in capturing the snowmelt processes. The use of soil temperature data can eliminate/replace the need of more sophisticated data proposed in recent operational snowmelt models such as updating the depletion curve, or updating snow covered area by remotely sensed data, and other site specific information. Our results show that SDSM-MTI avoids the general excessive demand for data required by energy-balance snowmelt models.

The correlation dimension D2 of precipitation (Canada and Africa), air temperature (Canada, New Zealand and Southern Hemisphere), geo-potential height (Canada) and un-regulated streamflow (Canada, USA and Africa) were estimated using the Hill procedure of [1] and the bias correction of [2]. After bias correction, it seems that D2 is distinct between climate sub-systems, such that for precipitation it is between 8 and 9, for streamflow between 7 and 9, for temperature between 10 and 11, and for geo-potential heights between 12 and 14. The results seem to suggest that climate might be viewed as a loosely coupled set of fairly high dimensional, sub-systems and different selected variables can yield different D2. Further, results also suggest that D2 of the climate sub-systems generally have low geographic variability, as found between precipitation of Western Canada and Uganda, between streamflow data of basins representing wide range climate and scales from Canada, USA and Africa; between temperature data of Western Canada, New Zealand, and southern hemisphere; and the original D2 analyzed from Canadian geo-potential heights are similar to that of the Western Europe, eastern North America and Germany. There is at most a weak relationship between basin physical characteristics, location, basin scale and streamflow D2. Climatic influence is more obvious, as shown by drier basins having slightly higher D2 than basins of wetter climate, basins from temperate climate having higher D2 than those from cold or hot climates.

A model of water balance and evapotranspiration during plant growth is proposed based on field observations. Water balance measurements were carried out for plots of planted corn using a weighing lysimeter, and soil moisture and sap flow were measured using an amplitude domain reflectrometry probe and the stem heat balance method, respectively. The influence of plants on the water balance was clarified, and the consumption of water by planted crops was found to be hundreds of times the weight of the dry crop. The model of evapotranspiration was constructed using the based on the characteristics of plant growth, the meteorological conditions, and soil moisture content. The model coefficients and functions were determined using the measured data, and the model was used to estimate evapotranspiration during corn growth. The results-produced by the proposed model are in close agreement with the observed results.

Root distribution has a great influence on soil moisture movement in fields. It is important for rational irrigation scheduling to clarify the relationship between a root distribution and the change in soil moisture. In this study, numerical experiments using the Soil – Plant – Atmosphere – Continuum model are conducted to make this relationship clear. Simulations of a 20-day drying period are performed under the conditions of three root distributions: 0.3, 0.5, and 0.7 m. The trend of decrease of evapotranspiration depends on the depth of the root zone. Although a capillary rise over 1.0 mm d^-1 is expected in case of a shallow root zone, the rate of drought in a root zone is very rapid and the effect of mitigation of drought is small. It is not adequate to adopt the layer from the surface to the zero flux plane as an objective layer for irrigation scheduling because zero flux planes are stable at a deep point, even in a shallow root zone.

Water is the most important thing for the human life in the world. In developing countries governments can only provide a little part of fresh water demand by means of water purification installation. The majority of water demand is fulfilled by spring water and other water sources such as dug wells, which is basically extract shallow groundwater. In urban areas, the decrease of groundwater recharge is proportional to the increase of the roof, pavement area and the density of the population. Sunjoto (1988) proposed a system of water conservation in urban area by means of recharge wells as a drainage system and now is implemented in most of big cities in Indonesia. This system is simple construction, easy to build, and low of cost but highly efficient. The method of analysis to determine the minimum dimension of the wells to get a maximum quantity of water infiltrated using a new equation of calculation was derived mathematically. In addition to this equation Sunjoto had developed other formulas of well tip shape factors based on the shape factors of piezometer tips to be used with the testing using cased holes on field measurements to find a value of soil hydraulic conductivity, such studies which were carried out by many researchers, e.g. Forchheimer (1930), Samsioe (1931), Harza (1935), Dachler (1936), Taylor (1948), Hvorslev (1951), Aravin (1965), and on the graphs form by Luthian & Kirkham (1949), Hvorslev (1951), Smiles & Youngs (1965), Wilkinson (1968), Al-Dhahir & Morgenstern (1969), Raymond & Azzouz (1969) and Olson & Daniel (1981).

Besides the rainfall amount and duration, the time distribution of rainfall intensity during the storm is also a very important information in rainfall-runoff modeling. More than 5000 rainstorm events based on hourly data over Hong Kong were extracted. A procedure using statistical cluster analysis is applied to identify event-based representative storm temporal patterns in Hong Kong. To facilitate proper selection of rainstorm pattern, factors affecting the occurrence of various storm patterns were examined using statistical contingency tests by which the interdependence between the occurrence of storm patterns and elevation, storm depth and duration, as well as season are investigated.

This paper deals with an economic assessment on the "time and regional extended effects" by flood mitigation projects to give more efficiency than those, which have been calculated based on an existing standard method in feasibility study. The "time extended effect" is an accumulated benefit of properties and capital protected from flood by infrastructures for long period. The "regional extended effect" is an accumulated benefit by flood mitigation infrastructures in the wide area under the influence of direct flood damage. This paper is the first study to explore the captioned effects to add to the existing flood mitigation projects more economic efficiency near the real value and to give more appropriate standard for the criteria of decision. We investigated two effects in detail, using the following projects.

The time extended effect on the Kiso River Improvement Project in Japan: A 50 km of left dyke on the Kiso River in Japan was 0.9 meters higher than the right one from 1610 to 1887. On the left side plain there has been no flood from the river since 1610 for almost 400 years. Before the construction of the left dyke any differences were not found on social, economic and geological conditions between both sides of the river. At the moment the left side plain has been developed more remarkably.

The regional extended effect on the Flood Mitigation Project in Metro Manila of Philippine: The most central region of Metro Manila was assessed less economic and less feasible than the Mangahan region on the north east of the Lake of Laguna according to the study on the Flood Control and Drainage Project in Metro Manila by JICA. The most central region of Metro Manila is the administrative and commercial center of Philippine, of which regional extended effect was not accounted in the study.

Estimation of flood hydrograph is a key step in design of water resources projects. The design flood varies from a flow with specified return upto probable maximum flood. The steps in derivation of probable maximum flood using calibrated rainfall-runoff model are presented. The data from a subbasin of Kalinadi river in Karnataka state are used. Different alternatives of probable maximum precipitation are considered. Maximization factor of 1.23 was used and PMF hydrographs for 3 different centerings and directions of storm were derived. The maximum peak flood amongst these alternatives is 1016 m³/s. A comparison of the PMF hydrographs obtained by deterministic model and unit hydrograph method is carried out. The difference in peak floods is noticed to be about 2% which is marginal in nature.

In Sylhet, a low-lying region located in northeastern Bangladesh, a large number of depressions store rain and floodwater during the rainy season. These flooded areas become large lakes. Such a flood lakes is referred to as a Haor. The largest flood lake (Haor) in Bangladesh is Hakaluki Haor, which extends over as much as 700 km². Local People use Hakaluki Haor as grassland, for farms and for conditional paddy fields that fill during the dry season. During the rainy season, Hakaluki Haor acts as a water reservoir and allows transportation via boat or bamboo raft. In the present paper, in order to clarify the hydrological and hydraulic behavior of Hakaluki Haor during the rainy season a numerical inundation model was developed, in which one-dimensional and two-dimensional unsteady flow equations are applied to rivers and the flood plain, respectively. In addition, the behavior of Hakaluki Haor and the possibility of developing this area after simulating the flooding process of 1988 are discussed.

The Japan Society of Civil Engineers (JSCE) seconded a survey team for the 2000 flood in the lower Mekong River to understand the processes, phenomenon and the damage. The team made interviews to some related ministries, organizations and agencies, and made field survey in Cambodia and Vietnam. Interviews for resident people and water level data at some observing stations are helpful for understanding of physical phenomenon on inundation. There were many child casualties because they approached to water intake with high velocity to catch fishes and they fallen to water from stilt houses during night. Inundated water body generated long fetches for wind generating high wave. The flood made not only economic and infrastructure damages but also some benefits such as fishery, irrigation and ground water storage. Especially, fishing in flooded area is a good chance for rural people to obtain cash. In Vietnam, flood changed from uncultivated field with acid soil to cultivable field. Canal network and dike system were very effective for flood life. Numerical simulation provides us good information of physical processes. Expansion process and the distribution of water depth by numerical simulation results are helpful for discussion and consideration comparing with field survey.

Numerous distributed hydrological models, starting from lumped hydrological models, have being developed during last couple of decades in different parts of the world. These models are competent of simulating hydrological processes using simplified governing equations. Since the formulation of the first numerical hydrological model, calibration of hydrological models has been one of the uphill tasks. Block wise TOPMODEL with Muskingum-Cunge flow routing method (BTOPMC) is a semi-distributed runoff model. The introduction of block wise approach with Muskingum-Cunge flow routing methods has enhanced the applicability of TOPMODEL from hundreds of square kilometers to several ten thousands of square kilometers. In this research work, BTOPMC model has being applied to a part of the Mekong river basin. Hydrological processes in the effective watershed of 277,000 square kilometers from Luang Prabang to Pakse in Lao People's Democratic Republic (PDR) have been simulated. Daily Observed discharges at upstream station are used as a boundary condition. The watershed is divided into several blocks and the average saturation deficit is calculated for each block. Four parameters namely, lateral transmissivity under saturated conditions T₀, decay factor m, maximum root zone storage S_rmax, and Manning's coefficient n, are estimated according to the land cover. Mekong river's Manning's values were determined using the shape of the hydrographs without any rainfall input. Initially saturation deficit and root zone storage values were assigned block wise. As simulations were carried out only for 1993, values at the end of each year replace the initial assumed values in the next iteration. The calibration of the model has been carried out by trial and error method. Nash-Sutcliffe coefficient is used to evaluate the simulation efficiency. It has been found that temporary reservoir storages cannot be fully interpreted by illusory optimized model parameters.

Data from erosion plots and micro-basins installed in a semiarid region of Brazil were used to calibrate the main parameters of a physically based model called WESP. In order to estimate the soil moisture tension parameter of the Green and Ampt equation, used for modeling the infiltration process, it was related to the Kohler index, an antecedent precipitation index. The other parameters showed no such clear trend with any single physical factor, due to the interaction effect between the main parameters of the model. A relationship between the above soil moisture tension parameter and the parameter affecting the erosion process on overland flow planes was sought to verify the existence of such an interaction. This relationship was used to estimate the value the erosion parameter for each of the events. The validity of the relationship was tested by comparing the results obtained from using the calibrated and estimated parameters in an adjacent micro-basin. The results show that the model simulated the runoff satisfactorily, but the calculated erosion values varied in a wide range, in both the cases.

Implementation of a catchment modelling system requires three steps, which are the calibration of the system, the validation of the calibration, and the extrapolation of the system to different hydrologic events and catchment conditions. The robustness of the simulations when this extrapolation is undertaken is related to the calibration and validation of the catchment modeling system, and will reflect the more detailed representation of rainfall input. Within the generation conceptual component, an important aspect is the model used to transform the point rainfall measurements into a spatially distributed rainfall over the catchment. There have been many alternative models proposed for this transformation. Presented herein is an analysis of the influence of alternative rainfall models on the simulated hydrograph and hence the influence on the system calibration. An enhanced rainfall representation in both space and time scale is made feasible by the application of the hydroinformatic tool Arc/Info-GIS. The analysis will be based on real events recorded over the Upper Parramatta River catchment (110km²) and the Centennial Park catchment (1.3km²) in Sydney, Australia. Based on the comparisons of runoff predictions with the recorded runoff at the outlet of the Centennial Park catchment, it will be shown that the prediction error is related to the rainfall model and the spatial variability of the storm event.

To compromise the conflict of flood control and hydroelectric energy production, two different flood control plans of the first cascade step power station were suggested, based on the regularity of precipitation and flood in the Gutianxi basin. The two plans consider the effect of short-time forecasting. The dispatching calculation and the comparison between the plans with forecasting and without forecasting shows that the limited level of reservoir in flood season could be at least raised 0.3m, accordingly the available capacity could be increased 10.26 million m³, and four cascade step reservoirs could increase total 7.26 million KW.h power production.

The movement characteristics in observation wells are consulted for the description of the actual flow conditions in an aquifer. The interactions between aquifers and observation wells remain however almost completely unconsidered. It is common to determine the velocities of a groundwater flow due to the hydraulic gradients and the permeability of the soil, although these determinations are limited regarding to the processes actually occurring in the soil. The borehole observations enter the interaction between the borehole and the actual groundwater flow not sufficiently so far, i.e. it is not clarified yet how the actual, small-scale soil composition around the borehole and the effect of the creation (drilling method etc.) of the borehole influences the observation. Therefore these interactions were examined by varying different variables (soil types, filter parameters, design of the filter pipes). All these cases were numerically simulated at first and then investigated in a physical model. The particle image velocimetrie (PIV) was used in order to determine whether significant influences of the filter pipe and the borehole surrounding field occurs in the borehole itself.

Difficulties associated with simultaneous consideration of the conflicting multiple objectives in determining the optimum reservoir operation policy has always remained a challenging task for the researchers. The application of Classical methods in Pareto solution generation and subsequent decision making is found to be inefficient and unsuitable for real time operations. Particularly, many a times the reservoir operator finds difficulty to specify his preferences in the form of parameter values of the model.

This study suggests the use of Multi Objective Evolutionary Algorithm, for efficient generation of Pareto solutions, which is robust and easily applied to complex system. The process of selecting the most preferred solution is suggested through a novel approach where the reservoir operator need to deal only with certain representative solutions from the entire set, and as per the need focus on a particular region of the Pareto surface. These benefits make the proposed methodology attractive from real time operation point of view where decisions are to be taken in a considerably short time and the reservoir operator may have to deviate from the rule curve prescriptions in order to account for the practical situation (such as occurrence of a sudden flood). The proposed methodology is demonstrated in a non-linear four-reservoir test problem.

In this study, the goal is to improve the distribution system, make rationalized analysis, and find out the reasonable distribution method under the minimized capital and maximized reliability. The method can finish water supply allocation and check the leakage pipeline in an instant, being the essential condition of modernized water supply system. That is, to separate the water delivery pipe and distribution system, and divide into small independent water distribution districts. In addition to designing two water intakes and water supply pipe connection in every district, the model is completely isolated from other places on normal operation. The water is transported in pipeline with double core tube. Besides local areas, the pipes can support each other when emergency, and smoothly supply water depending on liability analysis. The design can cooperate with the establishment of water stations in the emergent situation of water shortage so that water of people's livelihood is free from want. It proceeds problem solving with enumeration method, and divides the network system into small independent water distribution districts that conform to each design criterion. Besides designing each one of major and minor intakes and the connection of the pipe of water delivery in every district, it is completely isolated form other parts. In this way, we can get nice effect of distributing water. Meanwhile, we will gain conveniences of desirable administration and leakage examination and amendment on the management and maintenance of water distribution in the days to come.

This paper deals with the development and application of an optimization model which combines nonlinear programming and genetic algorithms for the realtime operation of a water resource system composed by a multipurpose reservoir and a set of wells. The system is responsible for the water supply of Matsuyama City, located in Ehime Prefecture, Japan. The aim is to determine the optimal daily allocation of water from the reservoir and wells for all the uses according to the forecast of rainfall during a determined operating horizon. For comparison purposes, the model is also solved by standard optimization techniques but the results show that genetic algorithms are more efficient in finding better solutions.

This study applies Genetic algorithms (GAs) to get more sufficient operating policies in multiple reservoir system. But it's different from traditional methods that the variables of rule curves are modified in accordance with curve shape. Two advantages are clearly shown, one is that the numbers of variables for coding are less than usual; the other that practicality for engineering is getting more powerful. Through the method proposed by this study, engineers can obtain better answers than the past, and will save much time to apply from theory to practice.

Flood and inundation are annual event, which is utilized for agriculture in the Lower Mekong basin. Inundation area can be associated with agricultural land. A numerical simulation was carried out to understand change of inundation area by flood control, and irrigation area estimated from reserved water. The decrease of inundation area caused by flood control is much smaller compared with potential irrigation area. Although decrease of inundating area influence agricultural land, that can be made up for by irrigation. However it is hard to prevent inundation of floodplain even if there is large-scale water control system.

On Earth, water is not only a kind of nature resource, bet also a necessary material during each construction process. For example, concrete activity needs lots of mixing and curing water, job-site environment uses a lot of cleaning water. Although creating an eternal global village is the most important career of each person. But up to today, water resource is getting insufficient due to careless use including the ineffective application of constructional draining water. Therefore, how to develop an appropriate real-time watering information system to reuse water resource will be an effective research.

This study intends to organize a structure of watering information system as the first step. Then based on the field investigation of several construction job-sites, a real-time watering database of management system will be developed with Microsoft Access software. The goal of this research to develop such system is trying to supply and connect the constructional water information to any other requirement - application. Once the supply channel is worked, then the process of water reuse will be automatically worked.

Conjunctive use of surface water and groundwater is recognized as an effective strategy for the optimum development and management of regional water resources. The possible applications of this concept are stressed. Case studies are presented to reflect the role of mathematical models in defining policies for the integrated use of surface water and groundwater. Different issues in implementing this concept are highlighted and a staged development strategy is recommended.

The Command Area Development Project (CADP) aims at increasing the productivity of land by achieving the full potential benefit of irrigation in the project areas. The Meghna Dhonagoda Irrigation Project (MDIP) is located in the Southeast Region of Bangladesh. An extensive irrigation system has been implemented over the entire project area. Irrigation water is supplied to the project area by withdrawing water from the Meghna and Dhonagoda rivers by pumps at Kalipur and Udumdi. The pre-CAD performance was only 30% area could be provided with irrigation water.

Mathematical model study was earned out to evaluate the performance of the existing system and to review and recommend hydraulic design parameters of the irrigation system. Topographic data, cross section of irrigation and drainage networks and the relevant hydrometeorological data were collected. Rainfall runoff and MIKE 11 hydrodynamic models were developed. Review the existing system. Several development options were carried out. Finally design hydraulic parameters were suggested to ensure full supply level and required discharge in the canal systems to the design cell of Bangladesh Water Development Board (BWDB). The project was rehabilitated as per hydraulic parameters obtained from the model study. During the irrigation season of 2000-2001, U2 system could be provided with irrigation. It was found that the post- CAD performance is about 90%. This is a very good achievement by increasing command area as well as production.

The present paper deals with irrigation water requirement and modelling study, implementation and achievement in the U2 irrigation system of Meghna Dhonagoda Irrigation Project (MDIP).

In order to alleviate the freshwater shortage in the world, the following methods have been proposed: storing the flood water in the sea, delivering fresh water to upstream in river courses during dry seasons, as well as fresh water transfer along shoreline. This paper discusses the possibility of utilizing the new strategy in China as an alternative to South-North Water Transfer Project (SNWTP). The comparison of two ways is given including the investment, risk, operation cost, feasibility and the amount of possible water supply. Analysis shows that water shortage in northern China is basically resulted from unevenly temporal distribution of rainfall, then the new proposal would be better than SNWTP, the major problems in SNWTP are discussed in the paper, such as high investment, high risk, limited water quantity, as well as the impact on ecological environment.

A pipe network system design is a combinatorial optimization problem. In order to solve a complex system by enumeration algorithm within a reasonable amount of computer time, it is necessary to improve the searching efficiency. In this study, three procedures are proposed to improve searching efficiency based on the enumeration theory and the characteristics of pipe network systems. These procedures include the initial feasible solution procedure, the decreasing upper bound procedure, and the system's lower bound procedure. Four water distribution network design cases were employed to illustrate the performance of the proposed methods. The results verified that the proposed methods can improve searching efficiency and obtain the global optimal system design. It can be expected that the similar ideas are useful in solving other combinatorial optimization problems.

At present the planning and design of water distribution networks tend towards regional design in order to facilitate the manipulation, administration, and maintenance afterward. The relative discussions of theories and practice are not many, and it is necessary to make further understanding and research. This article aims at the optimal design problem of local area water distribution network, establishes the optimal model of network system design that confirm to each design criterion, and proceeds problem solving with enumeration method. We take Taichung local area water distribution network, the fifth section, as the subject in this study for research and comparisons, and take the newly built system, expansion, renovation, and major and minor intakes, etc. into consideration. The result indicates that the establishment and problem-solving seeking of optimal design model can amply meet practical needs of the local area water distribution network, and become a useful tool for the minimum cost design program.

Singapore is an island country in which urbanization is high and majority of areas except some forest reserves area are paved with urban structures. Due to the fact that there is a limited area for surface catchments and reservoirs. Most of the reservoirs are mainly located either in the west or north of the area. The remaining eastern portion of the Singapore does not have favorable catchments for the reservoir. In addition distribution of geological formation of Singapore is not favorable for groundwater occurrence. The central area has granite core whereas on the flanks either recent deposit of marine clay or impermeable Jurong formation are widely distributed. Therefore majority of water are losing into the sea without infiltrating into the ground. However since from early 1970 Singapore has been extending its island by means of land reclamation using granular fill material, which is highly permeable, and large storage capacity of ground water. It seens that the Singapore is forming artificial groundwater aquifer unintentionally. With this expansion of highly permeable land, the meteoric water is no longer running directly into the sea and now infiltrated into the reclaimed land. With time significant amount of fresh water could have been already stored in these artificial aquifers. Since freshwater and seawater are known to have different densities, therefore freshwater which has lower density than the seawater, would be floated above the seawater. It could be skimable with freshwater skimming technique. Exploitation of coastal aquifer, may lead to the saltwater intrusion problem, however it could be overcome by several methods such as physical and hydraulic barriers and controlling interface by hydraulic balancing. Another possible problem is land settlement and subsidence caused due to groundwater lowering. However both problems can be prevented and solved by geotechnical and hydraulic principles. If systematic water management is carried out, ultralization of this fresh ground water is possible since seasonal replenishment by high rainfall is existed. This paper discussed the exploration and exploitation of possible fresh groundwater resources from reclamation lands.

Shore based salinity observations at a number of important locations (e.g. Qinglonggang, Xinjian, Gaoqiao and Baozhen) along the Changjiang Estuary have been carried out since 1978. In the dry seasons from 1992 to 1994, hourly measurements for flow speed, flow direction, water depth and salinity during a complete spring-neap period were carried out by two ships, one located on the south of Ruifongshazhui (C₁) and the other at north of Qingcaosha (C₂). In the same period water samples were collected at six observation stations along the riverside including stations Gaoqiao, Baozhen and Qinglonggang. From 1995 to 1996 two instruments were installed at stations C₁ and C₂, which automatically recorded the chlorinity in every half an hour. In March 1996, another large field measurement campaign is carried out. The large amounts of field data collected are analyzed in this paper. The results show that there are two sources of saltwater intrusion in Qingcaosha water area, one directly from the outer sea and the other from North Branch.

The presented strategy provides one of solutions for fresh water shortage in small islands and a case study on Singapore water supply is discussed. By analyzing Singapore's geographic conditions, it is found the fresh water or brackish water in the mouth of Johor River might function as an alternative water resource. The hydrodynamic model is applied for salinity prediction at the mouth of Johor River. The membrane technology drastically reduced the treatment cost of brackish or clear water that is collected during ebb tide. Modeling results show that the water level variation ranges from 1.45m to 1.82m, the equilibrium salinity 2.1kg/m³ after the river mouth is partially closed. Therefore, it is concluded that Singapore may generate enough fresh water to meet its' demand in the own territory.

Over the last three decades, Hsichih City has become a rapidly developed urban area in the Taipei Basin. Enormous flood damage is frequently caused by typhoons, between June and October every year, due to the high population density, low-lying terrain and meandering course of the Keelung River that runs from east to west. An atypical typhoon event, Typhoon Xangsane on October 31, 2000, attacked northern Taiwan and led to extremely severe inundation damage and serious loss of property in that booming city area.

This paper analyzes the hazard risk of typhoon damage in the Hsichih area, using grey system theory. First, the basic data of every unit village were collected and analyzed using the Geographic Information System. Second, the inundation was simulated using a 2-D unsteady hydraulic model. Third, the basic data with residential property losses and a map of inundation zones and the depths of Typhoon Xangsane, are used to develop a grey model GM(1,3) of the spatial index. The model was simulated and verified according to the original data. Then, the various maps of inundation zones and depths of eight different return periods (1.1, 2, 5, 10, 25, 50, 100 and 200 years) were adopted and the GM(1,3) of the spatial index applied; the property losses under the above conditions were sequentially determined. Finally, the hazard risk of typhoon damage in the Hsichih area was determined from the losses and their corresponding frequencies. The results confirmed that the grey system model could be applied to estimate the hazard risk of typhoon damage in the project area.

Reliability of the flood control capacity (FCC) of river levee reflects a quantity relationship between the flood peak stage of a river and the level of river levee. In this paper, the FCC of river levee is analyzed using the stochastic analysis method. The definitions of the reliability and the risk level of a river levee are proposed and a computational model of the risk level is suggested.

Accurate river channel and flood plain representation plays vital part in flood risk analysis. Terrain models such as TINs and DEMs are normally used to represent floodplains. But unfortunately finding a terrain model with a high density of stream channel elevation points that are sufficient for hydraulic modeling is not a easy task. However for years engineers and researchers have developed a high-resolution cross-section data for hydraulic modeling from field surveys, photogrametries and topographic maps. This research presented here introduces the procedures for creating integrated multiresolution TIN (ITIN) models for highresolution flood plain representation for flood risk analysis. The high-resolution river channel geometric data stored in HEC-6 hydraulic model and low-resolution flood plain data in the form of DEM created in Arc View GIS 3.2a were integrated by resolving the coordinate incompatibility in the both system. An integration procedure (ArcView extention) namely AVHEC6.avx has been developed between HEC-6 Hydraulic Model and ArcView GIS 3.2a to visualize model outputs in a more presentable manner through 3D capabilities of GIS.

The present study is concerned with finding the best rainfall simulation model that could describe accurately various stochastic properties of the underlying rainfall processes. More specifically, two popular stochastic rainfall-modeling schemes were assessed for their accuracy and suitability in the simulation of the rainfall series. The first model (MCME) represents a combination the first-order two-state Markov chain for describing the rainfall occurrence process and the mixed exponential for representing the distribution of rainfall amounts on wet days. The second model (NSRP) is based on the structure of the Neyman-Scott stochastic point process. The proposed models were assessed using a 19-year historical daily and hourly rainfall records from Dorval Airport (Canada). Results of this assessment have indicated that both models were able to adequately describe the seasonal variation of many statistical properties of the rainfall processes for various time scales. However, the MCME was found to be more accurate than the NSRP in the estimation of daily rainfall characteristics and requires a simpler parameter estimation procedure.

Water level variation in a river mouth is very complicated. One of the reasons for this fact the relationship between water level in a river mouth and external forces is strongly nonlinear. In this study, an artificial neural network method is introduced to overcome the highly nonlinear problem. For an artificial neural network, four kinds of input data namely river discharge, tidal level, significant wave height and sand spit length are used. The sand spit length is obtained from oblique photographs after interpolation to utilize as one of the input data for artificial neural network. Results indicate that morphology data is useful to predict precise superelevation of the water level in the river mouth.

The storage function model is a nonlinear rainfall runoff model that has been developed and applied in Japan. This paper studies the model applicability at some catchments outside Japan. The model parameters for each flood event are estimated by using a series of techniques i.e. wavelet transform analysis, numerical filter separation technique and fuzzy linear regression. The wavelet transform analysis is applied to estimate a recession constant of flood hydrograph whereas the numerical separation technique is chosen to separate the flood hydrograph into baseflow and direct flow based on the resulted recession constant. By using the resulted direct flow, the fuzzy linear regression is then used to estimate the model parameters. The study clearly shown that the model parameters could be well estimated by using the techniques. Moreover, the storage parameter K and the delay time parameter T are found to be a function of catchment area.

Success of any forecasting model depends heavily on reliable historical data. However, historical data very often contain high level of noise. This study proposed a scheme that extracts only effective and efficient data from raw data set. Subtractive Clustering Method and General Regression Neural Network were used for this purpose. The scheme was demonstrated on Bangladesh water level forecasting problem. Out of the originally available 467 patterns from each of 8 stations used for training, the proposed scheme extracted only 47 patterns and 5 stations. The model trained with this effective and efficient data set yields even slightly higher prediction accuracy than that trained with the original data set, R² = 0.9903 and 0.9885, respectively. With this effective and efficient data set, some advantages can be achieved: (i) shorter model training time; (ii) smaller storage space; and, more importantly (iii) equally, if not slightly higher, good forecasting accuracy than model trained with the original data set.

During the design of eco-sci-tec park in Suining, Sichuan Province, GIS technology is used to draw basic geo-data, and set up data base of watershed information. But the most important application is to arrange various facilities for soil and water conservation, tourism and sustainable economic development. This main aim of paper is to introduce how GIS technology is used in the process of map drawing, spatial analysis during the design.

Support vector machine (S VM) is relatively new machine learning technique, which is based on the statistical learning theory. The present study explores coupling of SVM method with techniques inspired by chaos theory, to yield higher prediction accuracy. The new algorithm is developed and applied to a runoff time series of Tryggevaelde catchment, Denmark. For a one day forecast horizon, the normalized root mean square error (NRMSE) of the prediction data using traditional approach was 0.444. For the approach proposed here the NRMSE is reduced to 0.347, i.e. about 22% improvement was achieved. Moreover, the prediction improvement was also observed for peak values and the recession parts of hydrograph.

Adverse impacts of not-well planned or managed urbanization on the catchment have been witnessed in many parts of the world. This has prompted the ever increasing use of physically based urban catchment simulation models. Especially in countries with rapid urbanization like Singapore, it is imperative to resort to such models. The success of these rainfall-runoff models, however, depends heavily on how well the model is calibrated. A robust and efficient calibration technique is required. In the recent past, Evolutionary Algorithms (EAs) have been extensively used for this purpose.

Inspite of its wide applications, EAs have been reported, in some applications, not able to locate the global optima of the calibration parameters of rainfall-runoff models. This study proposed a scheme which enhances the robustness and efficiency of an EA. The scheme, sEA, proposes the use of: (1) a variation operator based on the simplex search method of Nelder and Mead; and (2) a systematically selected initial population instead of randomly generated population. The performance of the enhanced real-coded sEA is tested on a suite of test functions whose optima are known and also on calibration of a rainfall-runoff model using synthetic data. Its performance is then compared with that of the shuffled complex evolution (SCE), the best performing model-calibrating evolutionary algorithm in use at present. The proposed scheme is also linked with Storm Water Management Model (SWMM) and applied to calibrate a catchment using real rainfall data and the corresponding simulated runoff data. The simulated runoff was obtained with a specified set of calibration parameter values. The study shows that the proposed scheme performs much more robust, in both the test functions and the calibration of the rainfall-runoff model, than the SCE.

The application of Artificial Neural Network (ANN) methodology for modeling daily flows during monsoon flood events for a large size catchment of river Krishna in Karnataka State of India is presented. A linear multiple input single output (MISO) model is employed for determination of the response function of the catchment. The spatial variation of rainfall is accounted for by subdividing the catchment into two parts and treating each of the sub catchment as separate lumped input to the model. The ANN is applied for each input scenario above with different input combinations. The results of this analysis show that performance of ANN with previous day's runoff along with current and antecedent rainfall as input is best in term of Nash-Sutcliffe efficiency (R²). The conclusion can be drawn that the ANN model can be successfully used for modeling of daily flows in a large size catchment, which has a highly non-linear rainfall runoff relationship.

Under-fitting problems usually occur in regression models for dam safety monitoring. To overcome the local convergence of the regression, we proposed a genetic algorithm (GA) using a real parameter coding, a ranking selection operator, an arithmetical crossover operator and a uniform mutation operator, and calculated the least-square error of the observed and calculated values as its fitness function. The elitist strategy was used to improve the speed of the convergence. After that, the improved genetic algorithm was applied to reassess the coefficients of the regression model and a genetic regression model was set up. As an example, a slotted gravity dam in the Northeast of PR China was introduced. The computational results show that the genetic regression model can solve the under-fitting problems perfectly.

The need to build and live along rivers creates the necessity for accurate calculation of water levels and flow rates. Also, it requires developing flow routing models. The models, which can be used for low flows as well as high flows through rivers, is of present day need for the civil engineers. A river flow prediction model has been developed in this study based on fuzzy-neural network approach and it gives better performance than artificial neural network model.

The largest reservoir of Bangladesh – the Karnafulli is generally operated on an ad hoc basis resulting into a non-optimal power generation and sometimes causes severe flooding of downstream areas including the city of Chittagong. An integrated approach, combining flood management, optimization, and simulation models, was developed and applied for the optimal operation of the Karnafulli reservoir. Particular attention was paid to incorporate flood damage functions of downstream areas in reservoir operation. Potential flood damages were assessed by using a neural network which was trained by an extensive data set generated by a combined hydrodynamic-GIS model (MIKE11-GIS) for the rivers and flood plain. An optimal operation policy was derived from the optimization-simulation model results. The performance of the suggested policy was evaluated by comparing with the existing operation rales. Using the model derived policies, the reservoir operation would result in higher energy generation while keeping the downstream flooding to a minimum.

The drainage congestion in the Noakhali area is a long-standing and complicated issue. It is seen that large-scale siltation in the drainage channels due to reduction in tidal prism arising out of and subsequent manmade interventions (Cross-dam I and II) [1] are the causes behind such development. Due to manmade interventions in the past the south of the area has undergone major morphological changes resulting in channel and bay siltation. Thus new land formations have developed with the constriction and closure of major drainage routes. Some 200,000 hectare remains water logged for more than half of the year. This has led to severe environmental hazards in the area.

Study has been undertaken to use mathematical modelling technique to analyze the complex problem and obtain a comprehensive solution. A 1-Dimensional sub-model for the area has been set up from the existing South East Regional Model of Bangladesh. The calibrated sub-model has been used to study various options of channel improvement and structural measures at the outfall channels. Later GIS flood depth maps have been produced to show the amount of improvement obtained in the various options.

It has been observed that by controlling the outfalls of the rivers it has been possible to reduce siltation and flooding inside the area, but the major problem still remained outside the river outfalls where the discharge from the rivers and the tidal currents of the sea play a significant role in inducing the sedimentation process.

A high-order accuracy conservative numerical method is developed for solution of the nonlinear hyperbolic equation. The upwind polynomial approximation is utilized for the advection term discretization. The method is applicable to a wide range of CFD problems, such as shock wave propagation or jet flow modeling, where the nonlinear advection term is of a special importance. Using polynomials of up to fourth degree, several computational tests are performed to validate the developed numerical method against other conventional algorithms and analytical solutions. The shock wave propagation and soliton interaction problems are solved using the model Korteweg - de Vries - Burgers' equation. The computations demonstrate a good performance of the scheme.

A new set of depth-averaged equations has been derived from the Euler Equations in this paper. The dynamic pressure derived from the linear wave theory is used in the equations to correct the gravitational term. The nonlinear convection term is modified with a parameter derived from the linear wave theory as well. The new equation can not only simulate propagation of long waves but also short waves, under which the conventional Boussinesq equations fail. Numerical examples are used to demonstrate the accuracy of the new equations by comparing the simulation results with the analytical solutions.

The present study is mainly concerned with reflection of monochromatic water waves propagating normally and obliquely over a train of sinusoidal and arc-shaped bottom topographies. In this study, a numerical model based on the boundary element method is employed to describe diffraction of waves by depth changes. The model is used to simulate the reflection of monochromatic water waves propagating over sinusoidally varying topographies. Solutions are compared with those of the eigenfunction expansion method (EFEM). The Bragg resonant reflection is investigated in detail.

In this study, random wave transformations over non-uniform beaches are simulated by using the fully nonlinear Boussinesq equations. In order to verify the applicability of the wave model in detail, the calculated results are compared with the experimental data with regard to surface elevations, wave heights and wave energy spectra.

The hydrodynamic performance of vertical wave screen of different porosity has been studied through an experimental investigation. The variations in the dynamic pressures exerted on a vertical wall as well as its reflection characteristics due to the presence of a wave screen on its seaward side have been studied with an experimental investigation in a wave flume. The studies were conducted for four different porosities of the screen in random wave field. The effects of the screen porosity on the reflection from the wall and the dynamic pressures on the vertical wall have been reported as a function of relative gap ratio between the screen and the wall. The details of model, instrumentation and results are presented and discussed in this paper.

The refinement on a depth-averaged model with effects of vertical acceleration is tested in this paper. A refined type equation is firstly derived with the iteration procedures to modify a vertical velocity distribution under irrotational condition, which is slightly different from the model by Madsen et al and Nwogu. The pressure distribution is determined by using the modified vertical velocity distribution. The similar way used by Madsen is further applied to the depth-averaged momentum equation, which is derived by substituting the modified vertical velocity and pressure distribution, to avoid the singularity in linear dispersion relation. To evaluate the model performance, the equation is applied to the free surface oscillation in a water tank and the solution of linearized equations is compared with the Airy waves. In addition, the non-linear approximate solution of the equation is analytically derived and the characteristics of the equation are examined through the comparison with the numerical solution by vertical 2-D CFD model.

The paper addresses on the redistribution of the near shore currents due to the wave structure interaction, especially in a groyne field. The study emphasizes the need for considering wave diffraction induced by the structure in determining the flow field. The studies reveal that the flow velocity distribution around the structure is a function of water depth, wave approach angle, length of the structure and its orientation. The results show that the velocity at the seaward tip of the groyne increases by 66% when compared with the velocity in the absence of the structure. The effect of length of the groyne on the flow field indicate that by increasing the length by 40%, the velocity at the seaward end increases by 60%.

Semi-submersibles and tension leg platforms are nowadays are considered as strong contenders for Floating Production Systems (FPS). Mainly wave effects dominate the hydrodynamic forces, motions and mooring forces on these platforms in exposed locations. Apart from first order forces, there are mean and low frequency drift forces. The latter forces can be theoretically calculated by 3-dimensional potential theory. But the theoretical predictions always show discrepancies in both regular and irregular waves when compared with results of model tests. Such divergence is further pronounced in the low frequency range (storm condition) where diffraction effects are smaller for such structures and the divergence is thus believed to be induced by viscous effects. In this paper, such viscous effects have been shown in the low frequency drift forces in irregular waves compared to present day predictions of such forces only due to potential effects. The viscous drag term of the Morison equation in combination with the linear (Airy) theory up to the instantaneous wave elevation has been considered as the basis in order to develop the theory. In order to deal with such viscous effects in the low frequency behavior of a moored semi-submersible, results of experiments when compared with to 3-dimensional (potential) predictions in time domain show increasing divergence in the low frequency drift force. The viscous contributions are now applied in irregular waves in the time domain using the FFT for some test results. It has been shown that the correlation between measurements and predictions is improved when force coefficients obtained from regular wave tests are applied carefully in consistent with the slowly varying wave envelope and its associated frequencies.

A soft bottom mud, which is easy to be entrained, sometimes brings a problem of turbidity. The ordinary layered fluid model for the wave induced seabed-motion, which assumes the existence of the sinusoidal-curved interfaces of fluid- and mud-layers, cannot be applied to a wave breaking. To overcome this limitation of the layered fluid model, the wave-seabed interaction is simulated based on the Lagrangian gridless analysis of solid-liquid two-phase flow.

The spatial distribution of turbulent wave energy dissipation is investigated by applying the concept of equilibrium profile energy balance to results obtained from laboratory experiments of uniform wave attack on a plane sloping beach. Comparisons are made with the equilibrium models of beach profiles for non-barred beaches.

The shoreline is changing due to beach erosions in front of seawall recently. Therefore, the measure to prevent the beach erosion is urgently required by constructing the concrete block-type breakwater in front of seawall. However, if the position of the concrete block-type breakwater is not appropriate, it is in some cases only to lead a further progress of beach erosions. Model tests were carried out by setting up a concrete block-type breakwater at some positions in front of the seawall in this study. The wave tank of model tests was length 20m, width 10m and depth 0.7m. The sand of the median diameter 0.36mm in fields was finished in slopes 1/15 and 1/20. A seawall was set up at the end of the slope. The slope of seawall face was 1:0.5 on foreshore side. The concrete block-type breakwater was rip-rapped in front of the seawall, and model tests of 7 cases were carried out by changing distances between a concrete block-type breakwater and a seawall.

The coastal zone management has to be generally in harmony with protections, environments and utilizations of coast areas. Changes of cross-shore profiles in sandy beaches will have considerable influence over the coastal zone management in particular. The relation among the shoreline, the long-shore bar and the stable point of cross-shore profiles is discussed by field data in Japan coast and the site plan of offshore breakwater, artificial reef, etc. is proposed in this paper. Cross-shore profiles of sandy beaches are changed by factors of incident wave, water depth, near-shore current, beach material, etc. The data of waves, tides, beach materials, bottom sounding charts surveyed in fields for the past few years was used to investigate cross-shore profiles of sandy beaches along coasts of the Sea of Pacific, the Sea of Okhotsk and the Sea of Japan in Hokkaido of Japan. Results are as follows;

1. A stable point where the sediment transport was not moved remarkably on the bottom slope existed on cross-shore profiles obtained by overlapping sounding charts of every season and year.

2. The sediment transport was mainly moving between the shoreline and the stable point.

3. The sand bar arising between the shoreline and the stable point was influenced by the wave reflection from sandy beaches.

4. On-offshore movements of the sand bar were classified by advancing or retreating of the shoreline.

5. The water depth of the sand bar crest was in proportion to the water depth of trough on-shore side of the sand bar.

6. The sand bar was closely related to the position of the shoreline and the stable point.

7. The sand bar was moved for the shore by constructing the offshore breakwater for accretion.

8. It is good to construct the artificial reef on the position of sand bar, and set up harbor or fishing port entrances off the coast of the stable point.

The propeller wash of a planing speed boat advancing in shallow marine waters may cause severe hydrodynamic interference effects on the seabed and increase sediment movement rates. If these effects are not properly accounted for, boating activities may lead to the resuspension of the deposited contaminated sediment, which may cause impact to the environment. This paper reports our measurements of the velocity field of the propeller of an outboard motor, and also presents mathematical models established for estimation of the velocity fields induced by outboard motor propellers. Verification of the mathematical models was by deploying an Acoustic Doppler Velocimeter at various positions downstream of an outboard engine to measure the generated velocities. Measurements were carried out in a shallow tidal lake (about 6m deep) with minimal co-flow. The mean axial velocity was found to approximately follow the Gaussian propeller wake profile of previous investigators. The long-term aim of the present research is to build a model to quantitatively predict the effect of resuspension of deposited sediment in shallow waters induced by the far field propeller wake of an outboard motor.

To design an armor block of breakwaters, the instability of single block has been analyzed without considering the interaction between neighboring blocks. While, under the extreme waves above a design wave, the large scale failure of armor layer can be happen. To simulate the large scale failure of armor layer, the block/block interaction model is proposed on the basis of the Distinct Element Method. The block/ block, gravel/gravel and block/gravel interactions are numerically tracked under the extremely high bottom shear.

By carrying out the hydraulic experiments in the open-channel, we clarified the process of tsunami generating caused by landslide. The effect of the interactive force occurring between the debris flow layer and the tsunami is significant important. The continuous lowing of the debris in the water lets the wave period of the tsunami short. The numerical simulation using tie model of two-layer with shear sfress models on the bottom and interface was proposed, and compared with the results of experiment. Simulated the debris flow shows good agreement with the measured results. Hie model with the Manning coefficient of 0.01 (see/m^1/3) for the smooth slope and 0.015 (sec/m^1/3) for the rough slope, and the horizontal viscosity of 0.01 (m²/sec) for landslide is recommended. However, the modeling of interactive force required farther analysis to determine its coefficient Mid the acting duration.

Applying floating bulkhead to dynamic water have many advantages such as no interruption of shipping during construction, easy to installed and constructed, conveniences to be shipped and maintained et cetera. But research on floating bulkhead is very scarce. Stability and its affecting factors of novel floating bulkhead in standing and dynamic water theory is analyzed in detail in this paper according to craft. An improved formula for calculating the floating bulkhead barycenter is deduced by the method of moving weight. Condition of sinking and uplifting stability of floating bulkhead in dynamic water is presented, accordingly, and measures to increase stability characteristics in dynamic water is given.

This paper describes the performance of a floating breakwater system having a stepped-slope designed as a wave attenuation structure. Laboratory experiments have been conducted with the aim to determine the wave transmission characteristics in various breakwater geometry and wave conditions. A series of unidirectional regular wave only condition was generated on the floating structure. Transmitted wave heights were investigated behind the modeled structure in order to obtain the coefficient of transmission, reflection and the amount of energy lost. The experimental results showed that the degree of wave attenuation was dependent strongly upon geometrical factors and wave conditions. It increases as the number of rows or as the breakwater draft increases. Wave transmission was also found to be higher if the system is exposed to long waves or waves with low steepness and where the water depth is relatively large. Empirical equations for predicting the coefficient of transmission, reflection and loss were derived for the SSFBW system. A comparison was made between the SSFBW and the tested rectangular pontoon for their wave attenuation ability. Comparisons were also made, in terms of C_T and C_L against B/L, with experimental results of various floating breakwater designs.

In this study, the head failure of rubble-mound breakwater at Sohuksando Port in Korea is investigated. The failure was caused by the typhoon Prapiroon attacking on August, 2000. A series of laboratory experiments was carried out by using 1:64 scale model. In experiments, the breakwater was protected with Tetrapods (T.T.P.) corresponding to 64ton and 72ton classes and modified cubes corresponding to 75ton and 108ton classes. It was proved that both T.T.P. and cube need heavier classes to sustain target waves. Experiments showed that the head of breakwater with 108ton class cube yields a reliable safety to the system for an allowable damage range. However, an additional reinforcement scheme has to be considered against the damage caused by waves exceeding design criteria. The covering depth of the head was proven to be most appropriate in a range of 1.5H_1/3 ~ 1.8H_1/3.

The present study is mainly concerned with reflection of monochromatic water waves propagating normally and obliquely over submerged breakwaters. Four different shapes of submerged breakwaters are employed and compared for reflecting capability of incident monochromatic waves. The eigenfunction expansion method is employed to estimate reflection coefficients of monochromatic waves. By comparing reflection coefficients, perimeter and sectional areas, the trapezoidal shape is recommended for a desirable submerged breakwater. Predicted coefficients are compared with those of early results of laboratory experiments.

The applicability of 28 existing breaker height formulae is compared against measured data from the large-scale experiments of CRIEPI (1983) and SUPERTANK (1994). The comparison shows that the errors of the selected formulae vary from 7.6% to 84.0%. Overall, the formulae that give very good predictions are those by Ostendorf and Madsen (1979), Gourlay (1992), and Rattanapitikon and Shibayama (2000).

This research is one of the joint research between Toyo University, JAPAN and Sepulur Nopember Institute of Technology, INDONESIA. The research object area is Madura strait between Java island and the northeast of Madura island. The hydraulics and remote sensing team from both universities focused on the Progress of shoreline near the mouth of Surabaya River and Coastal zone. Because, the rapid sedimentation is generated in near the Surabaya river mouth, and the environmental problems are due to be arising in Madura strait.

A well-designed evacuation system against a tsunami, a storm surge, and high wind along the coast to save human lives is required for the coastal management, and a lack of tools to evaluate an evacuation system lets such problem remain for long time. The aim of the present study is, therefore, to develop a model simulating human behaviors and vehicular movement, and to assist in evacuation planning, by applying a network model with a link-node system in a residential area. In order to improve the evacuation model by including the recognition of the people on tsunamis, the consciousness survey is studied in an area along the coast. The inputs and outpuls are examined by the simulations with the different replying rates, so that we could propose the guideline of the rate more than 30 % in order to consistent result from the simulation. And, we developed the model for evacuation starting based on the idea of quantification theory Type I by using the data on past tsunamis and their disasters. The model was applied to the case of Arahama to study its reliability, showing good performance for the case of the natural phenomena, and not for human provided one.

3-D morphological change on Sendai Coast, Japan has been measured for these three years. Empirical eigenfunction is applied to the present data set to detect predominant modes of beach evolution in this area. The relationship between primary two components and wave condition is investigated, and a simple estimation method is proposed for 3-D behavior of the coast.

Field observations for shoreline were carried out using the GPS measurement machine once a month in Misawa Coast. At the same time, the geographical bottom changes in long term were obtained by using the aerial photographs. Using the results of the observations and the aerial photograph analysis, the beach deformation after the construction of artificial headlands was shown, and the characteristics of the geographical bottom changes are investigated, and the effect of the countermeasures using the artificial headlands for beach erosion was shown.

This paper presents the results of Bakelite small-scale models. These models are due to a thorough research on the scale effect in coastal physical modelling. This research has involved the use of many sand models and has led to an experimental law to correct distortion of the models profiles.

The purpose of this study is to investigate the processes of long-term shoreline change around the mouth of Nagase River in Lake Inawashiro from 1908 to 2001 by using three topographical maps and six aerial photographs. Furthermore, short-term topography change is also discussed on the basis of sand grain characteristics obtained from on-site surveys. In summer this lake has a large inflow from Nagase River, and in winter it has strong and high waves because of seasonal wind. Thus, the lake does not have both of those influences of natural force simultaneously in a year. That is why the processes of the shoreline change are simpler in the lake. The main conclusion is that the sediment supplied from the river moves to the east, because the seasonal wind from northwest direction causes the strong and large waves propagates in eastern direction in winter, resulting in longshore sediment to the east.

The goal of this research is to study the configuration patterns in the Krueng Aceh estuary vicinity. The research has been done in an unsteady two dimensional integrated wave and current numerical model, and a periodic type of boundary conditions has been applied along cross shore sides. Numerical calculation shows that the breaking wave positions for the area form an almost parallel line to the shore line. Waves come from northwest drive the longshore currents to the east direction.

The concept of semicircular breakwater (SBW) is one of the recently emerging special types of composite breakwater. The SBW function as a barrier dissipating the incident wave energy and to create tranquility condition on its leeside. The horizontal and vertical forces due to regular and random waves exerted on seaside of SBW with 7 and 11% of its exposed area with perforations were measured. The effect of perforations, water depth and rubble mound height on variation of dimensionless forces were studied. In addition, the reflection characteristics of the perforated SBWs as a function of relative water depth, h_w/L is reported and discussed in this paper.

The phenomena about lagoon must be analyzed by combining both hydraulic and soil mechanical viewpoints. In this paper, authors show four physical models on the lagoon those are two hydraulic models for the flow and sediment movement and two soil mechanical models for sediment is hardening and consolidating under the tidal motion. The flow on the surface of lagoon has different shapes of water surface between up-tide and down stage tide. Because the friction on the surface of lagoon acts in reverse direction of water flows, this makes the un-reversible effect on water flow and sediment movements also. The deposited materials on the surface of lagoon become hardening by evaporation of water by sunshine while tide become down stage and the void in consolidated material becomes smaller by un-reversible effect of permeability of water movement. Our final goal is to present the final results of the solution of physical models on four stages of the phenomena, which are, described the former section as hydraulic models and soil mechanical models. But in this paper, the concepts for the analysis on the phenomena and the physical models can be shown.

A series of numerical simulations based on Boussinesq equation for horizontally two-dimensional wave fields are carried out to estimate the transformation of waves, run-up of waves, near-shore currents and temporal variation of seabed topography in shallow water area with coastal structures. The incident wave conditions for the model are irregular and multi-directional in the same way as real fields. Temporal changes of the variables calculated by the numerical model are shown and discussed.

The hydrodynamic pressures due to random waves around the circumference of a pipeline near a sloping rigid bed and placed parallel to the wave direction have been measured. The pressures were integrated to obtain the force time history, from which the peak horizontal and vertical forces were evaluated. The effects of relative clearance of pipe from the bed and its relative position from the toe of the sloping bed on the pressures and forces on the pipeline as a function scattering parameter and wave steepness are reported. The reflection characteristics of the sloping bed in the presence of the pipeline are reported as a function of surf similarity parameter and compared with the results from existing literature. The details of the model setup, experimental procedure, results and discussion are presented in this paper.

By using Saint-Venant equations and two-dimension shallow water equations, the unsteady flow for flood meeting with tide is calculated. The link is achieved for one-dimension calculating area with Two-dimension calculating area by means of overlapping the area of one-dimension with area of two-dimension in area of river mouth and repeated computation. The result of calculating hydrodynamic characteristics in Shenzhen River proves that this method is valid and has a good agreement with actual cases.

The Meghna Estuary is formed by the combined flows from three great rivers in the south-east Asia, the Ganges, the Brahmaputra and the Meghna. The estuary consists of a number of deltaic islands, generally densely populated, and exposed to extreme meteorological and hydrological conditions like recurrent tropical cyclones and high flood flows etc. those have devastating effects in the area. The area is also characterised by high level of hydrodynamic activities. Erosion and accretion occur simultaneously at very high rates; such that, the flow and sediment discharge through the estuary are the third highest and the highest, respectively, in the world. Although lands are accreted as some of this huge volume of sediment is deposited in the estuary, severe erosion along the riverbanks and in the islands threatened physical safety and social security of inhabitants and of infrastructure. A development plan has been proposed under Meghna Estuary Study to increase the physical safety and social security of the inhabitants of the Meghna Estuary area and to promote sustainable development in the coastal areas and on the islands. Under this plan a model for Sandwip area has been developed and applied for assessing the impacts of different development interventions for the purpose of land reclamation in the Meghna Estuary.

A natural accretion process is going on around Sandwip the north-east part of the coastal area of Bangladesh for the last several decades. This trend emphasised on the study of possible acceleration of the accretion process by implementing artificial structures at strategic locations. However, development of an integrated management plan is essential to address the associated problems of pre and post project scenarios. Understanding the hydraulic behaviour in the Bay of Bengal is crucial before undertaking any action in connection with any development activities in the coastal area. With this end in view a hydrodynamic model study has been carried out for Sandwip area for assessing the impacts on the surrounding hydrology for different development interventions. The study has been done based on the Two Dimensional General Model of the Meghna Estuary as developed under Meghna Estuary Study Phase II. It has been found from the study that the proposed development interventions with different options have different degree of impact on the surrounding hydrology in respect of flow speed as well as net flow distribution. The option of two interventions with 10% permeability showed least impact among all.

Coastal zone serves as a precious habitat, in which any living beings inhabit. In recent years, however, living beings, such as algae, are decreasing in number under artificial influences. Therefore, it is necessary to minimize the influence of construction of coastal structures on the living beings in the coastal area. However, very little has been clarified regarding the relationship between ecosystem and coastal environment. In the present study, the relation between mean flow characteristics around coastal structure and seaweed growth is quantitatively investigated.

In this paper the effectiveness of three approaches for setting-up conditions along the open sea boundaries of coastal models is verified. They include the prescription of water levels from gauge measurements; the consideration of astronomical constituents from the analysis of long term gauge records and the application of a large-scale model nesting. The assessment of the approaches was carried out for a coastal area model on the German North Sea. A two-dimensional depth integrated model was used. Water level measurements at six locations covering a 65 days period with calm winds and two periods with storms were considered. The results indicate that all the approaches are capable of capturing the water levels in good agreement with observations. More significant discrepancies resulted with respect to the phases. The best agreement with observations for periods with calm winds and storms was obtained considering the approach set-up on the basis of measured water levels. For periods with calm winds the mean and standard deviation of the discrepancies in amplitudes and phases at high and low water levels resulted respectively less than 6% (about 20cm) and 2% (about 6cm) of the tidal range and about 3% of the tidal period. For storm conditions the discrepancy in terms of water levels resulted less than 10cm.

A proposal has been drawn up to transform the coastal frontier of the state of Kedah through coastal reclamation works. In concept, 13 man-made islands and one peninsular type of reclamation configuration will be created along its entire coastline. After completion in 2020, the reclamation has been tipped to be the biggest coastal reclamation scheme in the world. Prior to the implementation of such an enormous project, proper planning, design, execution as well as monitoring programmes are required. Therefore, in the conceptualization of this plan potential impacts that could result from this mega development have been thoroughly addressed. This paper describes an example of how computer models have been adopted to determine the potential physical impacts that could arise from implementing the mega coastal reclamation project at the conceptual stage. Generated outputs from simulations made have eased the drafting out of further detail plans to mitigate potential impacts.

This paper presents the experimental and numerical analysis to understand and evaluate the tsunami reduction effect by the coastal permeable structures as costal forest and artificial wave dissipating structures. The hydraulic experiment for the tsunami of two different amplitudes with five kinds of models; mangrove, coastal forest, wave dissipating block, rock breakwater, houses, with different structure and porosity was carried out in order to measure an effectiveness in reducing tsunami disaster. Wave height, the horizontal current velocity, and wave pressure were measured for each model. The measuring points are arranged by considering the impact of the tsunami due to the existence of permeable structure, and the change of tsunami at the front and rear side of a model, and the reduction effect by model conditions was compared. Comparing with the forest case and the artificial structure case, the quantity of reduction on the forest case is smaller than the artificial structure. Although there is the reduction effect by the forest existence and the coastal forest is effective in the damage mitigation by tsunami. Experimental results suggest that the tsunami reduction effect in the water level, the flow velocity and fluid force in the structure back by the permeable structures was fully expectable. The numerical simulation model in considering with these reduction effects was adapted to hydraulic experiment. This model can estimate the tsunami reducing effect quantitatively.

This paper presents an application of the neural network (NN) model for forecasting problem. In stead of using the gradient descent method as used by the standard back-propagation network, the present study adopts the Levenberg-Marquardt algorithm. Multilayer feedforward (MLFF) network was constructed by trials to forecast the tidal-level variations at the Chao Phraya river mouth in Thailand. Unlike the well-known conventional harmonic analysis, the neural network model uses a set of previous data for learning and then forecasting directly the time series of tidal levels. It was found that lead time of 1 to 24 hourly tidal levels can be successfully predicted using only a short-time hourly learning data.

Reducing river discharge occurs during dry season at several rivers in Indonesia, such as Wawar, Opak and Telomoyo Rivers. In some cases, the extreme reducing discharge and an active longshore sediment transport can form river mouth closure. The previous study [1] has indicated that tidal effect can play an important role in keeping open the mouth before complete close. The domination of river flows in maintaining the open mouth has been switched into a domination of tides in this condition. In order to understand the tidal effect correlated with the cross-sectional area of river mouth, tidal inlet evaluation has been applied for the three rivers in Indonesia. The model for evaluation is based on an equation of volumetric sediment transport conservation proposed by Aota and Shuto [2]. Brown-Kalinske[3] bed load transport formula has been employed for evaluation of sediment transport rate due to tidal current. The Komar and Inman longshore sediment transport formula [4] has also been utilized for calculating the sediment transport due to waves. The assumptions that tides is sinusoidal and the littoral drift is "the disturbing force" to reduce the cross-sectional area with the tidal current acting as "the restoring force" keeping the open river mouth have been used in the evaluation. Validation of the model has also been examined using the Janet's model of tidal inlet [5]. The evaluation of the three river mouths can show the relationship between tidal prism and cross-sectional area of the mouths in good agreement with field data. The relationship diagram between cross-sectional area of river mouth and tidal prism has been also resulted from this study.

Long-term transition of the potential of Hydrogen (pH) in a sulfuric-acid lake in mountainous basin was discussed using a simulated model based on inflow and outflow of sulfuric-acid load and flow discharge. When pH reached five or more in 1993, cloudy or black suspended matter was observed around the lakeshore and in the lake. This phenomenon coursed misgivings among residents who warned of the worsening of water environment. The prefectural authorities established guidelines for purification of the lake, and initiated some countermeasures to prevent domestic waste and industrial discharge. However, the tendency toward increased pH was not improved. The simulated analysis suggests that the rising pH trend was based on the regulation of water usage for hydroelectricity in the upper reaches of the basin. Finally, it was indicated by this investigation that, if a objective pH value were proposed, optimal control of water usage could be achieved.

PHABSIM is one of the most famous methods to estimate condition of fish habitat. In this study we derived the criteria for habitat of Japanese dace (Tribolodon hakonensis) and suggested a new estimation method. At first, we paid attention to the temporal change of the target site topography and concluded that the target site where the discharge is decreased have problems associated not only with discharge but also with topography. Next, we focused on the distribution of Japanese dace. Then they utilized a different area in each season, but the local condition of depth and velocity was approximately constant all the year round. So we clarified that the neighboring condition affects the condition of fish habitat. Finally, we evaluated the seasonal change of the fish habitat, and we quantified the impacts that are caused by flattening of sand bars and degradation of riverbed on fishes. Based on these analyses we improved original PHABSIM to estimate the topographical impacts, and suggested the new framework of estimation method focusing on the rapid-pool conditions.

A method is developed to optimize the allocation of pollutant loads from non-point sources in a watershed by combining the application of optimization theory and GIS technique. The study area is modeled as a watershed with land use map and digital elevation model by ArcView GIS. Using calculated values of flow length from each land management unit (LMU), in the study area, to the outlet and area of each LMU, and assumed value of watershed-wide self-purification coefficient, a linear programming model is formulated. The objective function maximizes total allowable discharged pollutant loads from LMUs in the study area subject to the constraints of effluent limitation at the outlet of the watershed, i.e., study area, relation among mean effluents from different LMUs, and minimum limit of effluent in each LMU. Optimization is carried out at different weight values depending on decision-maker's preference order of LMU type with respect to mean load discharged from unit area. The developed model is applied to a sub-catchment of Yasu river basin in Shiga prefecture, Japan, which demonstrates the model's ability to determine optimum allocations of discharged loads of total nitrogen from different types of LMUs in the sub-catchment.

We have developed a ladder-type fishway, which can be constructed in a short time and at a low cost, and installed conveniently. This fishway with 50cm wide has the Jakagos which are attached to the fishway body at intervals of 50cm as baffles. The Jakagos consist of gravels which are wrapped in a polyethylene net. Installation tests for the upsteam migration of fishes on the proposed fishway were carried out at the diversion weirs in Japan and Indonesia.

In the installation test at the Chofu diversion weir in the Tama-gawa River, Tokyo Metropolitan, Japan, May 2001, three fish species and four crustacean species ascended the fishway. Especially for the juvenile Ayu, it was recorded that 18,347 individuals ascended the fishway for 12 hours period in total. Also, the fishway was available for not only fish but also crustacean ascent. Because, the Jakagos in the fishway decreased the inside velocity and created resting pools and an ascent route. In order to extend the application range of the proposed fishway, the fishway was installed at the Sicincin diversion weir in the Ulakan River, Padang, Indonesia, September 2001. In this case, the same size and interval of the Jakagos were used as in the case of Chofu weir (19 degrees), even if the small flow rate and the steep slope of the diversion weir (45 degree slope), and no swimming fish ascended the fishway. From these tests, the key points how to install the proposed fishway have been noted.

We have analyzed the water of all tubewells used for drinking in Samta village in the Jessor district, Bangladesh since 1997. The following fact has been confirmed from the survey. The tubewells with arsenic concentrations exceeding the limit in Bangladesh(0.05 mg/l) were approximately 90%. High contamination of arsenic was found in the south part of the village and arsenic concentration tended to decrease towards the north. The distribution of ferrous ion concentration is in accordance with that of arsenic contamination. The pentavalent arsenic concentration in groundwater was higher than that of trivalent in the north of Samta, but in the south trivalent arsenic concentration was higher than that of pentavalent It seemed that the groundwater was in oxidation state in the north part of the village but in south it was in reduced state. Arsenic elution to the groundwater is mainly caused via the reduced state in the groundwater: iron oxyhydroxide (FeO-OH), which trapp the arsenic in the groundwater, changes to iron hydroxide (Fe(OH)₂) in reduced state. Then the arsenic is became free and released in the groundwater.

By applying the above arsenic elution mechanism, we developed the arsenic removal experiment, namely, by oxidizing iron hydroxide and trivalent arsenic in the groundwater and settling co-precipitation of iron oxyhydroxide and pentavalent arsenic between the gravels of the HRF (horizontal roughing filter).

The impacts of proposed alternative wastewater control schemes for restoring the water quality of an urban stream, which is highly polluted by urban wastewater in the city of Kandy in Sri Lanka, are investigated. The paper consists of the identification and quantification of the spatially varied wastewater discharges and accompanied pollutant loads along the 4km length of the stream, development and verification of a one-dimensional water quality model and the predictions of total-N, BOD₅ and DO concentrations along the stream. The different levels of improvement in the stream water quality during the dry weather season that could be expected by the implementation of two different wastewater control projects are elaborated by the model application.

The Bisan-Seto is located to part of Seto-Inland Sea, apan (see Fig.1). There are many spawning grounds of valuable marine resources. On the other hand, recently variable environmental problems have been caused by red tide, severe gather up sand resources for construction materials and many kinds of coastal developments. It has been decreased aquaculture habitats in and around the Bisan-Seto area. In the field experiments, we measured water quality, tidal current velocity and biological condition including marine resources eggs and larvae in and around that area. After the field experiments, it was found the tidal current and bottom topography are important factors to movement of fish eggs and larvae. The authors proposed more appropriate the planning system of creating nursery ground by using 3-dimensional Euler-Lagrangian numerical model. Furthermore we planned and located the new type of artificial reef (named Sea-Mark Reef) to the sea. Now we are researching physical and biological effects of planned artificial reef as diving it has been confirmed are becoming good biological environments including prey abundance for marine resources.

Landsat-TM, ETM+ data are utilized to estimate water quality infomiation in the Ariake Sea, Japan. Observed data in the field are schematized by GIS and used to understand the seasonal and local characteristics of this bay and to estimate temporal changes of the water quality. The estimation model for not only the water transparency or temperature but also the salinity, chlorophyll-a etc. are developed through regression analysis.

The objective of this study is to correlate stream water quality with vegetation cover changes in an agricultural-forested catchment. Firstly, a time-series TM-based Normalized Difference Vegetation Index (NDVI) data set was made for the Kamafusa Lake catchment based on 11 Landsat Thematic Mapper images and one image-based atmospheric correction algorithm-COST method. Secondly, the application of this data set in analyses of vegetation cover changes and their influences on stream water quality variation were conducted. The results showed that the concentrations of suspended solids and total nitrogen in stream water were closely correlated with the vegetation cover and depended on different land use coverage during the field surveys from April to October. Thirdly, the concentration-discharge relations (model 1: C=kQⁿ) were summarized through literature reviews, and relationship of constant k or n with vegetation cover changes was analyzed. Finally, an improved model 2: C=k'QⁿNDVI^m was proposed by incorporating the consideration of vegetation cover changes. The results showed that the model 1 is applicable to short-term period, such as storm event and snow-melting period, and the model 2 is applicable to long-term period, such as non-storm period in growth seasons. During the long-term period, the vegetation cover changes should be taken into account when studying the stream water quality variation.

A mathematical model has been developed to optimize the design of a bubbler for reservoir destratification. Two important bubbler performance criteria, the mechanical efficiency and the destratification time, more specifically the cost and the mixing time of the bubbler operation, are analyzed as functions of two dimensionless parameters G, the strength of stratification, and M, the bubbler source strength. The mechanical efficiency and the mixing time are found optimum at the first detrainment point, a condition of single outflow just forming at the surface. It was found that the mechanical efficiency and the mixing time at G before the first detrainment point, corresponding to single out flow just forming at the surface, drop at a much lower rate than at G after the same first detrainment point. Though, at higher numbered detrainment points, the gaseous dissolved oxygen per unit plume entrainment is higher, the mixing effectiveness reduces steeply. This in turn requires longer bubbler operation to achieve a fully or to nearly mixed state reservoir and hence a high operating cost. A conservative practice would, therefore, be to reduce the design value of G by around 10% if attempting to operate at the first peak mechanical efficiency by adjusting the airflow rate or some form of real time operation as the reservoir destratifies.

There have been significant infrastructural developments in Hong Kong since the late 1980s. Further developments are in planning. A significant portion of the land required for the developments come from coastal reclamation. As such, many of the coastal developments affect the flow regime and water quality in the Hong Kong waters. While the impact of individual projects may appear insignificant, the total or cumulative impacts of all the coastal developments may be substantial.

To plan against unacceptable environmental impacts, the cumulative effects of the coastal developments needed to be assessed. To this end, the largest water quality modelling and field data collection exercises so far for Hong Kong waters were conducted to assess the cumulative hydrodynamic and water quality impacts resulting from both the historical and the planning coastal developments.

The predicted receiving water quality was evaluated against the Water Quality Objectives for each Water Control Zone in the Hong Kong waters. Sensitivity tests were carried out to investigate the response of the receiving water quality to possible variations in the planning coastal developments and the projected pollution loads, and the significance of the Pearl River discharges and local pollution loads.

This paper uses CE-QUAL-W2 model, developed by U.S. Army Corps of Engineers, for two-dimensional thermal, hydrodynamic and water quality modeling in Te-Chi Reservoir located at central Taiwan. Field data of 1998 and 1999 were used for model calibration and verification. The agreement between simulated results and field measurements of temperature and water quality are quite good. Risk analyses of water quality modeling were further performed to consider the uncertainty due to model parameters. The methods used include mean-value first-order second-moment (MFOSM) method, advanced first-order second-moment (AFOSM) method and Latin hypercube sampling (LHS) technique. Risk analyses from these three methods are compared and discussed in this paper.

A comprehensive modelling study of near-shore coastal waters was carried out to assess the impact of faecal coliform input loads on the receiving waters in a coastal basin in the UK. In this paper the emphasis has been focused on investigating the sensitivity of the coliform bacterial die-off rates to the receiving solar radiation. The bacteria were modelled numerically using a 2-D depth integrated hydro-environmental model. It was found that the mortality rate of the faecal coliform bacteria was highly sensitive to the strength of the receiving water radiance. A time varying formulation was developed to relate the faecal coliform bacterial decay rate to the level of the solar radiation. This formulation was included in the hydro-environmental model to predict faecal coliform concentration distributions at two survey sites in the basin. Comparisons of the predicted results obtained using varying decay rate with the corresponding measured values showed a significant improvement in comparison with the results obtained using constant decay rates.

This paper presents two-dimensional flow characteristics in a pool type fishway by using the VOF method. The fishway with five pools was used as an object of the study. Considering the flow pattern of a pool type fishway, the analytical region is divided into three parts, one is the upstream part of the fishway, the second is the midstream part and the other is the downstream part. As a result, the proposed method is able to reproduce the flow regime in the pool type fishway with many pools. And it is also clarified that the down stream water level condition plays a very important role in designing the pool type fishway.

Raptorial birds are rapidly decreasing in the upstream river basin and only the few habitats are remained in Japan. In order to environmental protection of Raptorial birds, nesting place study of distribution of Raptorial birds began from 1994. As result of long time fieldwork, we recognized the some conditions, which were necessary in the nesting place of theme. The necessary conditions are follows, there is a forest of quercus, serrate, cedar, and Japanese red pine over the 15m height, and then, the shape of the village is complicated, distance from bait field, slope in the valley etc.

The object of this study is to identify the platform where the nesting of Raptorial birds is possible using satellite remote sensing data.

The long-term metabolism of water quality is investigated based on field data of Lake Onogawa for cases where the water level is above reservoir capacity. In spite of a high circulation flow rate in the lake, strong thermal stratification is formed every summer. This phenomenon is caused by a huge water inflow from upper Lake Hibara, and this flux influences the water temperature quality of the epilimnion.

Hence, in this study, the water balance in the lake is investigated from the viewpoint of heat balance. An increase in the acid nitrogen at the bottom of the lake is caused by high rainfall in summer. The variability of acid nitrogen due to rainfall is modeled. As a result, a denitrification rate can be estimated at the bottom of the lake.

The 3-dimensional mathematical model and its calculational method for the near field of wastewater in side-discharge is given in this paper, and the buoyancy effect is considered in this model. Through the comparison between the calculated and experimental data of Chu, the method presented in this paper is feasible and effective. Based on a series of numerical calculations, tit is possible to determine if the side discharged jets attached again by using a simple criterion and the corresponding formula is also given.

Most of the earlier studies on fishways have been focused on the flow structure by means of hydraulic models. Since the flow structure in a fishway is complicated with free surface and sub- and super-critical flow conditions usually coexist, only a few papers have been published which had applied numerical methods to the flow in fishways. This paper deals with applications of a second order accurate Godunov-type numerical model of the two-dimensional shallow water equations discretized using finite volumes to the flow in vertical slot fishways. Roe's approximate Riemann solver is used for the convection terms to calculate the flux through computational cell edge, and a slope limiter is applied to prevent non-physical oscillations. The model is based on hierarchical quadtree grids automatically generated to fit the boundary configuration. The flows in three types (two types for single-slot and one for double-slot) of vertical slot fishway are simulated and discussed.

Hydrodynamic modelling of near-shore waters has involved significant advances in recent years as rapidly expanding computer power has facilitated step change in the complexity of hydrodynamic models in terms of additional dimensions and reduced grid sizes which could not have been envisaged a decade ago. However, this model refinement has not been paralleled by advances in the representation of two core drivers of near-shore water quality models. Predicting bacterial concentrations is essential for assessment of compliance of near-shore waters with existing and proposed standards for recreational waters (EU, 2000, WHO, 1998, 2002). It is for this reason that hydrodynamic models have generally failed to provide accurate, and, therefore operationally useful, prediction of microbiological concentrations at bathing beach compliance points. This has led to unexpected, and often disappointing, results from significant infrastructure investments designed to improve bathing water quality.

This study reports on two advances which have been used to drive the numerical modelling described by our co-investigators (Kashefipour et al., 2002). This approach seeks to make 'dynamic' two 'static' elements of existing modelling frameworks. The first element (addressed in this paper) is the input, or delivery, of faecal indicators into the near-shore zone from multiple sources. This is often difficult to assess because the available data are limited by: (i) sparse and imprecise microbiological enumerations in the various input streams, preventing adequate characterisation of the effects of, for example, discharge on faecal indicator delivery, (ii)sparse 'discharge' information from most sources, especially intermittent discharges from the sewerage infrastructure and (iii) a lack of knowledge on diffuse, i.e. non-sewage, sources of faecal indicator organisms e.g. from river and stream systems. Using data from a UK investigation this paper examines how these issues have been addressed to provide a dynamic, spatially referenced hourly input sequence to the near-shore models explained by our colleagues.

The second aspect (addressed by our colleagues' paper) in which the existing models are 'static' is the general assumption of a uniform day time and night time decay rate for faecal indicators. This element examines the factors influencing bacterial survival and disappearance and provides the theoretical underpinning for the dynamic modelling strategy which facilitates consideration of the complex mix of bactericidal factors within the hydrodynamic modelling framework as outlined by (Kashefipour et al., 2002).

The aim of this study is to examine the concentration distribution characteristics of sulfide and the heavy metals, iron, manganese, copper, titanium, lead and zinc, in Lake Koyama, situated in the eastern part of Tottori Prefecture in Japan, and to comprehensively evaluate the sediment environment. Samplings of sediments were carried out at 58 sites in the neighborhood of grid points at approximately 400 m intervals in November 2000. As a result, sulfide concentrations were high in the neighborhood of inflow rivers and at the deepest point in the lake, but their values were low compared with the limit of concentration for a habitat in which Corbicula japonica can be kept. Also, there was an obvious distinction in the concentration distribution of certain metals. As a result of a comprehensive evaluation of the sediment environment using the principle component analysis and cluster analysis, Lake Koyama can be divided into the three categories in order of the total amount of heavy metals and the concentration of sulfide. In addition, the aggravation of the sediment environment has proceeded in the western part of the where four inflow rivers congregate.

Semarang coastal area is used for many purposes such as harbors, marine cultures, etc. There is a big river mouth located in this area, where three rivers discharge their water into the ocean. Various kinds of pollutants exist in the rivers water, including contaminants from agriculture and domestic sources, which contain high concentration of nutrients. Two-dimensional model have been developed to support the monitoring activity of the nitrogen compounds distribution in Semarang coastal waters. In this research, the kinetics reactions of nitrification process in the model were studied to obtain the appropriate transport equation representing the field condition. Two kinds of kinetics reactions established by Thomann (1987) and US Geological Survey (1985) were evaluated. Water samples were taken from 19 stations on March 1999 and October 1999. The nitrogen compound analysis used in the laboratory was spectrophotometric method. Equations in the model were solved numerically by using the explicit finite difference method. Gridding process divided the model area into 108 × 80 grids, with each grid having Δx = Δy size of 50m. Model calibration process was conducted by using the October data set, whereas verification process used the March data set. Calibration process using October 1999 field data showed that diffusion coefficient resulting the smallest RMS (root mean square) error were 4m²/sec, 15m²/s, and 1m²/s for ammonium, nitrite and nitrate respectively, both for Thomann and US Geological Survey kinetics reactions. Verification showed that Thomann kinetics reaction gives better performances with MRE (mean relative error) of 35% for ammonium, 55% for nitrite, and 35% for nitrate, whereas US Geological Survey gives MRE of 61% for ammonium, 60% for nitrite, and 158% for nitrate. Field data resulted by the model simulation showed that pollutant concentration at the river mouth in March 1999 was higher than that in October 1999. It influenced the distribution pattern of the pollutant, therefore March 1999 dispersion was wider than that of October 1999.

Planning operation of storage reservoir considering water quantity and quality objectives is formulated. An example application is presented for the Barra Bonita reservoir in the state of Sao Paulo, Brazil. It is a multi-purpose reservoir for the basic purposes of energy production, navigation, and recreation. Eutrophication is considered to be a serious problem within this reservoir.

Emphasis is given to optimization and simulation assessment of physical and biological characteristics of the system to achieve the most appropriate operation for long-term planning through the use of statistic, optimization and artificial intelligence (AI) techniques.

Water quality is assessed by the application of the box-type, two-layers model (PAMOLARE) developed by UNEP/ILEC. Due to the enormous number of quality parameters, water quality membership functions are constructed to easier evaluate and compare alternatives.

A Genetic Algorithm (GA) based model is developed for the calibration of the water quality model. The model is constructed using elitism, crossover and mutation operators.

Fuzzy membership functions are to be elaborated based on the operation objectives and goals. A fuzzy deterministic dynamic programming model is developed to handle the water quantity and quality operation for maximum satisfaction and benefit.

High quality life is the purpose of the whole world's human development in the future. Green building will be the challenge issue of human life in 21st century. There are seven indexes in this issue, such as green land, water conservation of surface, water resource, gas exhaling, energy consuming, construction waste, waste water and garbage. There are four indexes relating with water. In Taiwan, civil and construction working activities are the fundamental industries of social improvement. Therefore, how to follow the ideal of green building to save the limitary resource, and act in the practice of construction job-site will be an important research.

To echo the concept of eternal development with the Earth, this paper investigates situations of water using and waste water recycling in Taiwan. Then inspects and analyzes the real data of constructional using water based on field investigations and questionnaires. After all, an appropriate management system with constructional using water is derived to follow the concept of green building's construction.

This paper is a summary of the research of hyperconcentrated sediment-laden flow in China. The paper begins with an introduction of the concepts of hyperconcentrated sediment-laden flow. The properties of rheology, settlement, flow pattern and velocity distribution, transport capacity, resistance, and fluvial processes are then discussed in detail. The applications of the basic theory to practical engineering such as design of physical models and establishment of mathematical models are also presented. In particular, the applications to the Lower Yellow River show very good agreements with field observations.

Current rainfall-runoff analysis techniques concerning rainfall distribution, being used in engineering design, are reviewed and runoff hydrographs are presented. The aim of this paper is to simulate reservoir water level due to the inflows from watersheds and tidal variations. In addition, it is another purpose to develop a program which can compute the maximum reservoir water level through the seawall-gate operations under the maximum and minimum tidal ranges.

The runoff of Cao'e River varies greatly yearly and monthly. There are two flood seasons, i.e., plum rains and typhoon. Due to the erosion and deposition of the riverbed, water stage of flood-peak of the same peak flow can be very different. Tide in Cao'e estuary has irregular semidiurnal tide, and tidal wave distorts sharply. Tide varies greatly with the erosion and deposition of riverbed. The sediment of Cao'e estuary is fine silt easily eroded and deposited. The conditions mentioned above identities the characteristics of great erosion in flood season and deposition in dry season, whereas those characteristics affects its tide condition, that is different from other macro-tidal estuaries.

Flood studies to plan for optimal utilization and to control this natural phenomenon is main concern in the world and our country. Great damages caused by floods in different parts of the country during past few years demand comprehensive plans; knowing that it is impossible to plan and apply flood control methods without a good knowledge about the behaviour of this phenromenon. The extend of flood damages in various conditions depends on the amount of inflow and the geometrical characteristics of flow bed and adjacent areas. Thus flood hazard zonation for different return periods is necessary to predict the extend of damages caused by floods in different conditions and to justify socio-economical aspects of flood control proggrams.

To achieve this important goal, the amount of inflow in different return periods and different geometric characteristics of flow path must be determined. Considering the fact that most basins all over our country have not been equipped with hydrometry stations, it is unavoidable to apply experimental methods to estimate the amount of floads. Regarding the advantages and capabilities of Remote Sensing (RS) and Geographical Information Systems (GIS) in supplying, analyzing, saving, updating and storing data and controlling given changes, the needed data to estimate the floods of basins lacking data can be supplied with acceptable speed and accuracy.

For flood hazard zonation in a given river the following steps have been taken:

1. To prepare the maps of vegetation density and land surface cover using satelite TM Images through remote sensing techniques.

2. To prepare digital elevation model (DEM) of the basin under study, basin slope map, the map of soil hydrologic groups and the basin Curve Nnmber (CN) map using GIS (ILWIS software).

3. To estimate the flood hydrograph for given return periods using hydrologic model (HEC-1).

4. To determine the maximum water level using hydraulic model (MIKE 11) for floods with given return periods.

5. To prepare the maps of flooded areas in given return periods using collected data during previous steps and digital elevation models (DEM)of the alignment and adjacent areas of the river using GIS.

6. Flood hazard zonation by combining the prepared maps in previous steps using GIS along given part of the river channel.

Recently, Komatsu et al.(1997) proposed new water-purification method in semi-enclosed coastal area. In the present method, to activate tidal exchange between inner and outer sea area a pattern of tidal residual current is controlled by setting many bottom structures "BOTTOM ROUGHNESS", which have an unsymmetrical 3-dimensional shape. In order to confirm the effect of the present method in an actual coastal area we started prototype test from May, 2000 in New Nagasaki Fishery Port, Nagasaki, Japan. In this test, 60 units of bottom roughness were set on the bottom near mouth of the port in May, 2001. As a result of field measurements of water quality (COD, DO, etc.) between before and after setting bottom roughness, it is clear that the condition of water quality in the port has a tendency to be improved.