Coastal Engineering Journal

Models for shallow water wave processes are routinely applied in coastal, estuarine and river engineering practice, to problems such as flood waves, tidal circulation, tsunami penetration, and storm tides. Evaluation and confirmation of application codes can be facilitated by analytical solutions that may represent this wide range of physical problems, without significantly compromising the contributing flow processes. The appropriate linearized shallow water wave equations are defined, together with quite general initial and boundary conditions that will represent the expected variety of shallow water wave problems. A completely general analytical solution for both water surface elevation and flow is established, in a manner suitable for the evaluation of shallow water wave codes. The contribution of both free and forced modes is identified, together with the role of friction.

A sequence of analytical solutions explore the spectrum of response patterns expected from numerical codes for flood and tide propagation in channels. Complete analytical details of the solutions are provided, together with specific suggestions for an associated set of analytical benchmark tests. Illustrations of predicted response patterns provide the basis for a discussion of many significant physical aspects and their representation in discrete numerical codes.

A new system for directional wave spectrum observation was developed by improving the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS). Either Doppler Type Wave Directional Meter (DWDM) or Wave Gauge Array System is adopted for wave observations. Directional spectra are estimated by EMLM method for DWDM and EMEP method for array system. For the convenience, the obtained directional spectra are expressed as the frequency banded wave heights and directions corresponding to the wave spectrum. Examples of annual statistics of the directional wave spectra at three typical NOWPHAS wave stations are introduced in this paper.

Doppler ocean radar is being increasingly used in estuarine research. The advantage of using this instrument is that it can measure sea surface flow velocity field in all weather conditions due to its remote sensing capability. In the present study, the accuracy of the surface current velocities in Osaka Bay measured by very high-frequency (VHF) Doppler radar is investigated. The radar system uses a frequency of 41.9 MHz and allows a radial range resolution of 500 m at ranges up to 20 km from a coastline. Data from VHF ocean radar are compared with that using Acoustic Doppler Current Profilers (ADCP) in order to quantitatively verify the surface shear and wind-induced current. They are also used to enhance an assimilation technique in order to assimilate the observed surface flow velocities into a three-dimensional baroclinic flow model. The correlation coefficient and rms difference between the velocities measured by the VHF ocean radar and the in situ current profiler are in the order of 0.69 and 6.4 cm/s, respectively.

Assimilation of the surface velocity is carried out using ocean radar observations. Two assimilation schemes, blending and nudging, are examined. The blending scheme including the vertical mixing induced by wind stress and with a logarithmic profile for the decrease in surface velocity downward performs better than the nudging scheme. Application of the assimilation model shows good agreement with the in situ current and salinity data.