Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

Figure 7

Early historic map of the Seaside area from Coast of Oregon Survey (1874) with overlays of modern beach and bay shorelines (bold lines). Map overlays are based on visual best-fit scaling of Necanicum River shorelines. The beach shorelines show relatively little change since 1874. However, forest cover patterns on the Necanicum Bay spit suggest that substantial shoreline changes occurred in the bay mouth prior to the 1874 survey. The seawardmost beach ridges show apparent decreases in forest cover north of Avenue N and north of 12th Avenue, suggesting recent northward extensions of the spit prior to 1874. The historic 1874 map base is from U.S. Coastal Survey [10].