Narrow Results

The lattice Boltzmann model for the shallow water equations (LABSWE) is applied to the simulation of certain discontinuous flows. Curved boundaries are treated efficiently, using either the elastic-collision scheme for slip and semi-slip boundary conditions or the bounce-back scheme for no-slip conditions. The force term is accurately determined by means of the centred scheme. Simulations are presented of a small pulse-like perturbation of the still water surface, a dam break, and a surge wave interaction with a circular cylinder. The results agree well with predictions from alternative high-resolution Riemann solver based methods, demonstrating the capability of LABSWE to predict shallow water flows containing discontinuities.

Open coast storm surge water levels consist of a wind shear forcing component generally referred to as a wind setup; a wave setup component caused by wind induced waves transferring momentum to the water column; an atmospheric pressure head component due to the atmospheric pressure deficit over the spatial extent of the storm system; a Coriolis forced component due to the effects of the rotation of the earth acting on the wind driven alongshore current at the coast; and, if astronomical tides are present, an astronomical tide component (although the tide is not really a direct part of the meteorological driven component of storm surge). Typically, the most important component of a storm surge is the wind setup component, especially on the East Coast of the US and in the Gulf of Mexico. The importance of bathymetry to this wind setup storm surge component is considered herein with special reference to the coastline of Florida where eight Florida transects consisting of a cross-section of bathymetric data perpendicular to the shoreline were investigated. Effects of Coriolis, wave setup, atmospheric pressure head, and astronomical tide are not considered herein but will be addressed in future papers. The present study findings show that the wind setup component can vary over an order of magnitude for the same wind speed depending on the bathymetry leading up to the coast.

Landslides can result in rocks and soil falling into reservoir at high velocity, thereby triggering large surface waves, which may threaten navigation vessels, dam stability, and lives and properties along the shore. This paper presents the results of an experimental study into surges caused by landslides entering reservoirs. First, eight factors — water depth, sliding impact velocity, slide volume, slide width, slide thickness, the mass of the slide blocks, sliding slope, and drop height of the mass center — were chosen as key parameters. Then, these were combined into four dimensionless factors: Froude number for sliding velocity, landslide scale, slide thickness and slide impact angle (radian measure). In addition, based on data from 145 model tests, empirical equations for prediction of the first and second impulsive wave heights were developed through nondimensional multiple linear regression analysis. These equations were applied to landslides triggered by the Wenchuan Earthquake along the shore of Zipingpu Reservoir. The calculated results were found to be in good agreement with field surveys and with calculations by other formulas; the proposed formula is believed preferable in that it incorporates dimension parameters and slope of the sliding surface.

This paper primarily investigates the surge wave of the barrier lake during an earthquake and clastic flow landslide simultaneously. Earthquakes can trigger clastic flow landslides with strong mobility enabling them to move a significant distance underwater. However, there have been few studies on the simultaneous superposition of seismic surge and clastic flow landslide until this study. First, we designed an experiment to analyze the influence of landslide motion under surging water; then, we investigated the effects of the clastic flow landslide and earthquake on the variation of surge wave height, with large-scale shaking table water tank model experiments. The experimental variables included the initial water depth, peak ground acceleration, landslide impact velocity, and landslide volume. According to the experimental results, we analyzed the maximum wave height under the combined action of an earthquake and clastic flow landslide. Furthermore, we defined a reduction factor of the seismic surge and put forward an equation to predict the reduction factor by means of dimensionless multiple linear fitting analysis. Finally, we present a method for calculating the maximum wave height of the combined surge during both an earthquake and clastic flow landslide using the reduction factor and provide a case to verify the reliability of the formula. Our study could provide the basis for the analysis of the burst of the barrier lake.

The storm surge residual of 2.35m was measured during Typhoon Anita in 1970 in the Tosa bay, Japan. Since the Tosa bay widely open to the Pacific Ocean, surge heights are usually small. The present study examined the reasons why the abnormal storm surge was generated due to Typhoon Anita 1970 by numerical simulations using a coupled model of surge, wave and tide with six levels computational domains of which grid sizes are from 12150m to 50m. The storm surge simulation driven by only wind and pressure fields was not able to compute the measured sea surface levels. However, when wave radiation stress terms were included in the storm surge model the computed sea surface levels showed a good agreement with the measurement data. This study clarified that the effect of wave-induced radiation stress is significant on water level rising of up to 0.5m-1.0m in the Tosa bay.

A system is described, based on finite-difference discretisations of the governing hydrodynamic equations, which determines the three-dimensional motions in well mixed coastal seas, produced by tidal and meteorological influences. It has been thoroughly tested and has been found to be very robust and accurate.

Closure of the system of equations is achieved using forms of the Boussinesq approximation to determine the coefficients in the turbulent eddy viscosity terms. A method of calibrating the model is also described.