Morphodynamics of Southern California Inlets

Abstract

The morphology of small tidal inlets common to the coast of southern California responds dynamically to tidal, wave, and stream stormflow processes, and they often become unstable. This paper analyzes inlet morphology in relation to process and material parameters, and compares spatial and temporal patterns of morphodynamics at three small southern California tidal inlets. Topographic surveys and velocity measurements were made, and aerial photographs acquired for the inlets to the Tijuana River Estuary, Los Penasquitos Lagoon, and San Dieguito River. Analyses of these data and corresponding hydrologic data from archives showed that the morphology of these small inlets changes rapidly to variations in tidal range. Spring tidal flows and stream stormflows are effective at scouring littoral sediment from inlets and restoring inlet stability, The inlets were most unstable and occasionally closed when high waves coincided with neap tide conditions. Inlets with cobble-size bed sediment tend to be less stable than those with sandy beds due to bed armouring.