LINKING NEARSHORE PROCESSES AND MORPHOLOGYMEASUREMENTS TO UNDERSTAND LARGE SCALE COASTAL CHANGE

摘要

Two field experiments on the ebb-tidal delta and adjacent beaches near Grays Harbor,rnWashington USA provide detailed information about bed sediments, waves, currents,rnsuspended-sediment concentrations, and sea-bed change for the calibration andrnverification of numerical models of sediment transport and morphology change. For thernfirst time, process and nearshore bottom change measurements are being coupled alongrnthe high-energy dissipative beaches typical of the U.S. Pacific Northwest. Thernexperiments successfully capture the transition between low-energy beach-buildingrnconditions typical of summer and the high-energy erosive conditions of winter (Fall 1999rnexperiment), as well as the spring transition back to progradational conditions (Springrn2001 experiment). Process-based morphological models are tested with fieldrnmeasurements to improve our ability to predict coastal profile and shoreline change atrnseasonal and interannual time scales. Model simulations indicate net southerly andrnonshore sediment transport during the Spring 2001 experiment, agreeing withrnobservations. The magnitude of simulated net onshore sediment transport is highlyrndependent on the wave-related bed roughness height, a parameter estimated to havernvaried by approximately 3 orders of magnitude during the experiment. Initial modelrnresults suggest that cross-shore sediment transport processes are more important thanrnalongshore processes for seasonal scale (months) morphological change.