[1] This paper investigates the effects of waves on storm surge, currents, and inundation in the Outer Banks and Chesapeake Bay during Hurricane Isabel in 2003 through detailed comparison between observed wind, wave, surge, and inundation data and results from an integrated storm surge modeling system, CH3D-SSMS. CH3D-SSMS, which includes coupled coastal and basin-scale storm surge and wave models, successfully simulated measured winds, waves, storm surge, currents, and inundation during Isabel. Comprehensive modeling and data analysis revealed noticeable effects of waves on storm surge, currents, and inundation. Among the processes that represent wave effects, radiation stress (outside the estuaries) and wave-induced stress (outside and inside the estuaries) are more important than wave-induced bottom stress in affecting the water level. Maximum surge was 3 m, while maximum wave height was 20 m offshore and 2.5 m inside the Chesapeake Bay, where the maximum wave-induced water level reached 1 m. Significant waves reached 3.5 m and 16 s at Duck Pier, North Carolina, and 1.6 m and 5 s at Gloucester, Virginia. At Duck, wave effects accounted for $36 cm or 20% of the peak surge elevation of 1.71 m. Inside the Chesapeake Bay, wave effects account for 5-10% of observed peak surge level. A two-layer flow is found at Kitty Hawk, North Carolina, during the peak of storm surge owing to the combined effects of wind and wave breaking.

The time‐dependent flow and dispersion of suspended sediments in the western basin of Lake Erie are being studied by means of numerical models utilizing data from remote‐sensing studies and flume experiments. Mechanisms of sediment dispersion included in the models are convection and turbulent diffusion, river loading, gravitational settling, and physical resuspension and deposition at the sediment‐water interface. The time‐dependent currents are computed by means of a free surface hydrodynamic model. A wave‐hindcasting model is used to compute the wave parameters needed for estimation of shear stress generated at the sediment‐water interface under given wind conditions. The rate of sediment resuspension as a function of bottom shear stress and sediment properties is based on data from flume experiments using lake sediments. A series of numerical calculations with the models were performed on a two‐dimensional lake with a variable bottom representing a transverse cross section of Lake Erie. It was found that wind direction and fetch length can significantly affect the sediment dispersion patterns. The two‐dimensional and the three‐dimensional models were both used to simulate realistic short‐term events in Lake Erie, and the model outputs compare favorably with the synoptic surface sediment dispersion patterns deduced from the multispectral scanner data.

[1] Significant buffering of storm surges by vegetation canopies has been suggested by limited observations and simple numerical studies, particularly following recent Hurricanes Katrina, Rita, and Wilma. Here we simulate storm surge and inundation over idealized topographies using a threedimensional vegetation-resolving storm surge model coupled to a shallow water wave model and show that a sufficiently wide and tall vegetation canopy reduces inundation on land by 5 to 40 percent, depending upon various storm and canopy parameters. Effectiveness of the vegetation in dissipating storm surge and inundation depends on the intensity and forward speed of the hurricane, as well as the density, height, and width of the vegetation canopy. Reducing the threat to coastal vegetation from development, sea level rise, and other anthropogenic factors would help to protect many coastal regions against storm surges. Citation: Sheng, Y. P., A. Lapetina, and G. Ma (2012), The reduction of storm surge by vegetation canopies: Three-dimensional simulations, Geophys. Res.

A vertical gradient of suspended sediment concentration often exists in estuaries, particularly within the bottom boundary layer where sediment erosion and deposition take place. This results in a vertical density gradient and hence modification of the flow. However, this important effect has often been ignored in past sediment studies. Because of this and because of other empirical assumptions, exisiting erosion models cannot be used as predictive tools. This paper employs a simplified second-order closure model to simulate the effect of sediment-induced stratification on bottom boundary layer dynamics, and particularly the erosion process. Numerical models, which employ the concept of Richardson number dependent eddy viscosity, have been developed in the past for stratified flows. These models require a large number of data for tuning parameters of the eddy viscosity formula. The simplified second-order closure model used here consists of the dynamic equations of motion for mean variables (velocity, temperature, salinity, density, and suspended sediment concentration) and turbulent quantities of turbulent kinetic energy and turbulence macroscale. Model constants are thus invariant owing to the added physics. Model simulations of laboratory sediment-laden boundary layers indicate that, as sediments are eroded or resuspended from the bottom, a vertical gradient of suspended sediment concentration can lead to a significant reduction of the turbulent shear stresses and a slowdown of the erosion-resuspension process. Hence significant error may be contained in some empirical sediment erosion rate formulae, which were derived by ignoring flow-sediment interactions. Simulations of a wave boundary layer and a thermally stratified boundary layer, obtained with the same numerical model, are also presented. There is good agreement between measured and simulated mean and turbulent quantities in both cases. column, which can significantly affect the vertical transfer of momentum and materials (e.g., oxygen and sediments). Near the bottom of estuaries and •Now at Woods Hole Oceanographic Institution, Woods Hole, Massachusetts. lakes, strong currents can cause erosion or resuspension of bottom sediments, producing a vertical stratification in suspended sediment concentration, which can in turn affect the flow. Although the effect of sediment stratification on flow is qualitatively understood, a predictive model is lacking. In addition to the stratification, many mechanisms such as wave-current interaction and large bottom features often exist which affect the bottom boundary layer (BBL) dynamics. Thus both for the sake of fundamental understanding and for practical prediction, there is a need for a rather comprehensive boundary layer model which incorporates such effects as stratification, waves, and wave-current interaction. While relatively simple eddy viscosity models have been developed and calibrated to simulate 14,429 14,430 SHENG AND VILLARET: SUSPENDED SEDIMENT STRATIFICATION AND EXCHANGE bottom boundary layers where ...

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