Searching for sand, Malibu, California
A coastal community in California suffered beach erosion and wanted to renourish their beach with additional sand. Coastal Frontiers, as subcontractor to Moffatt & Nichol Engineers, contracted e4sciences to perform underwater and subsurface measurements to identify and characterize nearshore sand deposits that could be used to replenish the beach. The objective was to make measurements in the vicinity of the shore to map the locations and volumes of beach-quality sand deposits totaling 600,000 cubic yards that could be placed on the beach.
e4sciences performed single-beam bathymetry, side-scan sonar imaging, sub-bottom reflection seismology to map the current position of sand deposits in four areas near Santa Monica, California.
Reflection seismology provided a clear picture of the thickness and lateral extent of the sand bodies. Quaternary sediments, mostly sands in excess of 1,000,000 cubic yards, were observed in all four areas. Sampling quantified the sand grain size and silt content, and helped rank the locations as candidates for beach nourishment.
e4sciences identified three suitable resource areas: offshore Broad Beach, offshore Zuma Beach, and near the Dume submarine canyon. The available volume was more than sufficient to nourish the beaches.