Wave runup on high energy dissipative beaches and the prediction of coastal erosion

ave runup has been investigated on the high energy dissipative beaches typical of the Pacific Northwest of the United States. This has been accomplished through field investigations on the central Oregon coast utilizing video image processing techniques. Extreme runup statistics have been found to linearly depend on the deep-water significant wave height. This relationship and other potential runup models have been used to develop a methodology which evaluates the susceptibility of coastal properties to erosion. Extreme water elevations, including water elevations measured by tide gauges as well as elevations achieved by wave runup, are compared with measured elevations of the beach face junction on a variety of beaches. The model, valid for conditions when the beach face junction is landward of the mean water line, predicts susceptibilities to erosion that agree well with observations.;Finally, an analytic model is presented which predicts longshore currents and sediment transport on beaches backed by vertical structures with toes seaward of the mean water line. A partial standing wave develops in front of the structures causing modulations of the bottom stress, radiation stresses and the resulting setup, longshore current and longshore sediment transport. Model results suggest that the magnitudes of these processes can be either greater or less than on a similar beach without a structure, depending on the position of the structure across the surf zone, the beach slope and the wave conditions.;A more detailed investigation into the frequency response and frequency-wave number structure of swash motions is also presented. Overlap in the coverage of 3 video cameras allowed for runup elevations to be analyzed at any longshore position over a 1600 m reach of beach. Runup spectra show a large saturated region with an...