Watershed Controls on the Geomorphology of Small Coastal Lagoons in an Active Tectonic Environment

Abstract

This study investigates the relations between watershed precipitation, upstream channel slope, and the geomorphology of 19 small (40 to 18,658 m 2 ), fluvial-incised lagoons in the actively uplifting piedmont near Santa Barbara, CA. Lagoons in the study are funnel-shaped, shallow (<2 m), riverdominated, and enclosed by a sandy to cobble-sized beach barrier for much of the year. Results indicate a strong link between watershed processes and lagoon geomorphology, such that a significant portion of the variability in lagoon area, length, volume, average width, circularity, and lagoon width expansion can be explained by the variability of watershed precipitation and channel slope upstream of the lagoons. Performing multiple regression analysis with watershed precipitation and channel slope as independent variables, coefficients of determination for the power function regressions are 0.88 (lagoon area), 0.88 (lagoon volume), 0.83 (lagoon volume), and 0.74 (average width). Upstream slope is the best single predictor of lagoon geomorphology.

Advancing the Science of Environmental Flow Management for Protection of Temporarily Closed Estuaries and Coastal Lagoons

“…To be useful in guiding environmental flow requirements for TCEs, a classification system should emphasize the role of physical and hydrological factors that control morphology and ecological response in small to medium sized systems. Such systems tend to be heavily influenced by watershed characteristics and process, such as rainfall, catchment geology and associated sediment supply [29]. Most existing classifications are based on some combination of watershed characteristics and runoff patterns, tide or wave energy, and estuary basin size and morphology.…”