Opening and Closure of a Marginal Southern California Lagoon Inlet

Abstract

ARSTRACT: Over the past 50 yr, direct observations of the inlet status (open or closed) of San Dieguito Lagoon, a typical southern California lagoon located in Del Mar, California, have shown that river flooding is the major natural determinant of inlet conditions on time scales longer than a few years. River flooding is strongly dependent on rainfall in the San Diegnito River watershed and on the influences of two water storage reservoirs in the area. Rainfall fluctuates on yearly and longer time scales and undergoes cycles of wet and dry periods. Over short thne periods, ranging from a few months to several years, inlet status is prhnarily determined by the available tidal prism and littoral sand transport. Recognition of these factors is crucial in order to correctly evaluate the probability that a small lagoon will remain open naturally. A probability approach is essential because the variables controlling inlet conditions are random in nature. The results of our study show that the inlet will remain open naturally 34% of the time. The tendency to remain open is vastly smaller during years of dry weather (12%) versus times of above-average rainfall (66%).

Availability, usage and expected contribution of potential nursery habitats for the California halibut

“…Although fluvial discharge is not expected to directly impact the distribution of juvenile halibut, it can impact nursery habitat availability by modulating the periodicity of inlet closures and openings in southern California (Elwany et al, 1998). Inlet closures can seal off whole estuaries or lagoons that otherwise would serve as productive nurseries.…”

Consequences of human-mediated marine intrusions on the zooplankton community of a temperate coastal lagoon

“…rainfall, streamflow) and longshore processes, respectively (Kjerfve 1994). The timing of seawater influence on lagoons should thus be fairly predictable (Elwany et al 1998). Lagoons are strongly impacted by anthropogenic effects, such as by increased nutrient inputs from their catchments and high siltation rates, with the effects exacerbated by the lagoons typically shallow depth (Suzuki et al 1998;Santos et al 2006).…”

Predicting the dynamics of intermittently closed/open estuaries using attractors

“…Floods widen and relocate the channel, with their effect dependent on the volume of sand stored in the flood tide delta. Elwany et al (1998) looked at 50 years of data for a small southern Californian estuary, San Dieguito Lagoon, which they stated was typical of the estuarine lagoons along the southern Californian Pacific coast. They developed a simple statistical model for the probability of an open/closed state, considering the probability of high/low streamflow and the response of the entrance to these two conditions.…”