The influence of tectonics, sea level, and sediment supply on coastal morphology in the oceanside littoral cell, CA

Two studies, conducted within the Oceanside littoral cell, reveal how different earth processes (i.e. climatic, fluvial, and tectonic) affect and control both marine and subaerial morphology. The first study uses terrestrial LIDAR techniques to record changes in subaerial beach sediment due to seasonal transitions, on the San Luis Rey rivermouth in Oceanside, CA. The study period spanned from winter to fall in 2008, so the majority of the data represents the transition from a winter to summer beach profile. A reversal in the seasonal accumulation trend (observed from April-May 2008) may be the result of two erosional wave events, with one occurring concurrently with increased precipitation and river discharge from the San Luis Rey River. The occurrence of two directionally favorable wave events, the second of which occurred during a pulse in precipitation and a slight increase in river discharge, appears to have caused sufficient beach erosion to reverse the seasonal accumulation trend.;The second study used high resolution CHIRP seismic reflection data, collected offshore, to provide new insights into tectonic control on coastal morphology and regional shelf width. Within the Oceanside littoral cell, a marked change in shelf width is observed and may be a result of faulting and folding in the region associated with splays off the Cristianitos Fault. There is an abrupt transition in the geology onshore, exposed in the sea cliffs. The tectonic feature responsible for the observed placement of adjacent geologic formations is proposed to be an oblique slip fault.