Journal of Waterway, Port, Coastal, and Ocean Engineering

Dam break evolution over dry and wet beds is analyzed with a smoothed particle hydrodynamics model. The model is shown to accurately fit both experimental dam break profiles and the measured velocities. In addition, the model allows one to study different propagation regimes during the dam break evolution. In particular, different dissipation mechanisms were identified: bottom friction and wave breaking. Although breaking dominates over wet beds at the beginning of the movement, bottom friction becomes the main dissipation mechanism in the long run.

This paper demonstrates a practical application of coupling a hydrodynamic model with a wave model for the calculation of storm tide elevations in the St. Johns River (Northeastern Florida). Hurricane Floyd (1999) is chosen as the storm of interest due to its track which paralleled the northeast coast of Florida without making a direct landfall on the St. Johns River. The advanced circulation (ADCIRC) numerical code is applied as the hydrodynamic model for the computation of two-dimensional circulation resulting from astronomic tides and meteorologically induced storm surge. The simulating waves nearshore (SWAN) numerical code is applied as the wave model for the computation of wind-induced waves. Two model implementations are considered in order to investigate the effect of short wave contributions on the overall storm tide water level: (1) a one-way coupling procedure that transfers gradient of wave radiation stresses from SWAN to ADCIRC; and (2) a two-way coupling procedure that builds on the former to include feedback of water levels and currents from ADCIRC to SWAN. Simulated storm tide elevations are compared to historical National Ocean Service data to result in two major conclusions: (1) wind-induced waves play a significant role in the storm tide (contributing 10–15% of the peak water level), namely with respect to the transfer of momentum from the dissipation of short waves to the long-wave motion of the storm surge; and (2) a local-scale hydrodynamic model requires the application of a hydrograph boundary condition in order to account for the remote effects of the storm surge response.

Long-term and large-scale morphological changes in the integrated watershed from the Tedori River basin to the Ishikawa Coast, Japan have been examined based on survey records over a long time scale, spanning more than $40\text{years}$ . Contemporary data for coastal and riverbed evolution were compiled and compared in order to assess the implications of anthropogenic modifications of the river basin. Focus is placed on the influence of sand extraction and dam construction on sedimentary deficit resulting in accelerated coastal erosion. The correlation between existing records of the integrated watershed shows that persistent sand mining, flood control operations, and retention of sediment in terrestrial reservoirs have led to a serious imbalance of the coastal sediment budget: this has resulted in a decrease of coastal sediment volume by more than $10\times {10}^6{\mathrm{m}}^3$ from 1960 in an area of $21.5{\mathrm{km}}^2$ . During periods of greatest erosion, the eroding rate exceeded $1\times {10}^6{\mathrm{m}}^3∕\text{year}$ . The results clearly indicate that such anthropogenic impacts should be examined at the scale of the integrated watershed in order to fully identify the cumulative influences.