Sedimentation Processes in Morro Bay, California

by Jeffrey P. Haltiner, Philip Williams & Associates, Ltd, San Francisco, United States,
Devin Thor, Philip Williams & Associates, Ltd, San Francisco, United States,

Document Type: Proceeding Paper

Part of: Coastal Sediments


A series of field investigations and historical data analyses were conducted to determine historical sedimentation processes in Morro Bay, California. Three sources of sediment were identified: littoral transport through the lagoon mouth, fluvial transport of sediment from the watershed, and aeolian sand transport from the barrier beach. Periodic dredging of the harbor area represents the major source of sediment loss from the system. Net rates of sedimentation were estimated for different zones within the Bay, and the relative contribution from the three sources was estimated. The results indicate that the mean diurnal tidal prism in the lagoon has decreased by about 25 percent over the past century. Although littoral sand transport through the harbor mouth is the largest (67 percent) input source of sediment, it is removed by regular dredging. Fluvially transported sediment from the watershed likely represents the largest net source of sediment accumulating in the Bay, with an additional contribution from aeolian sand. The implications of these sedimentation rates on the life of the lagoon, its biota, and the frequency of maintenance dredging are discussed.

Subject Headings: Sediment transport | Littoral drift | Sediment | Bays | Water supply systems | Transport rates | Sand (hydraulic) | California | United States

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