Geomorphic Analysis for Enhancement and Restoration of the Tijuana Estuary, Californiaby Joan Florsheim, Philip Williams & Associates, San Francisco, United States,
Larry Fishbain, Philip Williams & Associates, San Francisco, United States,
Philip Williams, Philip Williams & Associates, San Francisco, United States,
Abstract: Geomorphic analysis and results of field investigations in the Tijuana Estuary, California, are used in developing the rationale for an enhancement and restoration design that increases the tidal prism while protecting sensitive wetland vegetation. A primary cause of degradation of the estuary is the decrease in the diurnal tidal prism from about 1.9 × 10-3 km3 (1,550 ac-ft) in 1852 to 3.6 × 10-4 km3 (290 ac-ft) in 1989. Geomorphic processes and human modifications responsible for the reduction in tidal prism include migration of the barrier spit (at a rate of approximately 0.7 m/yr), sedimentation from the Tijuana River and tributaries, and road building and agriculture. The present tidal prism is not sufficient to maintain an open inlet following severe wave storms that fill slough channels with sand from wave overwash. Inlet closure may negatively impact salt marsh vegetation and habitat in the estuary by changing water quality. The restoration design proposed includes shallow excavation and re-creation of slough channels in the southern portion of the estuary in order to increase the tidal prism and improve tidal circulation.
Subject Headings: Tides | Estuaries | Prism | Ecological restoration | Field tests | Vegetation | Highway barriers | Rivers and streams | North America | California | United States
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