Stream erosion and beach deposition during the December 2007 storm, Hood Canal, Washington
Elizabeth K. Phillips
May 10, 2011
Department or Program
A strong winter storm hit western Washington and Oregon in the first week of December 2007. An accumulation of snow was closely followed by high sustained winds with gusts up to 130 kph (80 mph), much warmer temperatures, and about 300 mm of rain, causing record flooding, substantial tree blowdown, and significant damage to roads and property. An example of the geomorphic effects is found in an area along Hood Canal just north of Dewatto Bay where abnormal discharges along high-gradient streams (12°-17°) in small drainage basins (0.073-0.259 km²) resulted in severe erosion and the deposition of large fans (313-4985 m²) onto beaches. Storm waves quickly cut scarps up to 1.5 m high into the alluvial fans; at some fans longshore currents deposited beach ridges at the high tide line. The correlation between drainage basin area and the estimated volume of sediment deposited is inconsistent and therefore best investigated on a case-by-case basis bearing in mind such factors as substrate, vegetation, land use, and road and culvert placement.