Erosion in Southern Monterey Bay

The coastal cliff top line recession has historically been used to calculate erosion along the Southern Monterey Bay. Digital photogrammetry is used in this work to produce Digital Terrain Models (DTM), representing the coastal cliff top line of 1984. This links the historical recession data sets with the LIDAR measurements of 1997 and 1998 and a 2003 cliff top line measured using Kinematic DGPS. Recession time series starting in the 1940's are produced for several locations. Least square linear fits of the recession data are computed for the periods 1940-84, 1940-98 and 1940-03. At Fort Ord and Sand City the resulting slopes show a persistent erosion trend of 1 meter/year, unchanged in the last 19 years. The mean sea level (MSL) evolution is studied using historical San Francisco MSL data because of its high correlation with Monterey MSL. Higher MSL occurred during El Nino years, coincident with higher erosion rates show the correlation between erosion and MSL. In the long term, high-erosion El Nino years combine with normal years averaging to a near constant erosion trend. For Phillips Petroleum and Beach Lab, a significant decrease in the erosion rate is observed after sand mining stopped in Sand City. Digital Photogrammetry provides a high-quality representation of the shoreline topography, offering useful information to the warfighter in terms of detailed beach or landing zone characterizations.
The original document contains color images.