Numerical modeling of wave transformation, breaking and runup on dikes and gentle slopes

Kobayashi, NobuhisaThe numerical cross-shore model CSHORE is extended to predict irregular wave runup on impermeable dikes. CSHORE is tested against 40 wave runup tests on an impermeable dike on a barred beach and 97 wave runup tests on an impermeable dike with a gently sloping beach. CSHORE is also tested against 97 wave overtopping tests. The spectral wave period and peak wave period from a seaward boundary located outside the surf zone are both used as the representative period for input to CSHORE. The difference between these two periods is compared. The significant wave height at the seaward boundary is also used as input. The significant wave height transformation from the seaward boundary to the location of the dike toe is compared for all 137 tests to show the capability and limitation of CSHORE. The measured 2% and 1% exceedence runup heights are predicted within errors of about 20%. CSHORE predicts the threshold of wave overtopping but the minor wave overtopping rates can be predicted only within a factor of 10. The upper limit elevation of wave action along coastal regions has become increasingly important over the past decade, especially as the sea level to rises. Wave action during storms can cause beach and dune erosion. Areas of high risk for flooding need to be determined in order to create coastal flood risk maps such as those produced by the U.S. Federal Emergency Management Agency (FEMA). CSHORE is thus compared with 120 tests for wave runup on gentle uniform slopes and wave runup data on natural beaches in order to assess the utility of CSHORE for coastal flood risk mapping on sand beaches. CSHORE is a good practical choice because it can also be used to predict beach and dune profile evolution during a storm.University of Delaware, Department of Civil EngineeringM.C.E