Shoreface Response to Sediment Deficit

This paper evaluates shoreface change in response to a decrease in sediment supply over three timescales — Holocene (millennia), historical (century), and contemporary (interannual). The reduction of sediment supply is due to northern migration of the Columbia River ebb-tidal delta over the past few thousand years and construction of jetties during 1885–1917. Data analyzed include shoreface vibracores, historical regional bathymetry since 1868, and upper shoreface and beach profiles since 1997. At late Holocene to historical time scales the lower shoreface eroded while the upper shoreface and barrier accreted. At recent interannal time scale, the primary dune prograded. This behaviour resulted in a net rotation (i.e., steepening) of the shoreface and implies onshore sediment supply from the lower shoreface to the barrier. The study area is along northern Clatsop Plains, Oregon, USA.