GEOMORPHOLOGY OF SMALL COASTAL LAGOONS IN SOUTHERN CALIFORNIA

Regression analysis on 23 small coastal lagoons near Santa Barbara, Ca., suggests that 83%, 85%, 81% and 65%, respectively, of the variability of lagoon area, length, volume and average width (dependent variables) can be explained by the variability of stream slope upstream of the lagoon and total annual catchment precipitation (independent variables). Lagoon area, length, volume and average width vary from 40 – 11,782 m², 14 - 390 m, 6 – 6,191 m³, and 3 - 36 m, respectively, and upstream slope and catchment precipitation vary form 0.01 - 0.16 and 1.9x10⁶ - 29 x 10⁶ m³/yr, respectively. Statistical relations between dependent and independent variables are significant at the 95 % confidence level, and hypothetically are a consequence of: 1) a stream slope to watershed area power-law; and 2) a stream width to discharge power-law. Streams with larger watersheds have lower slopes and a wider stream cross-section and therefore tend to have larger lagoons.

The small lagoons are formed by interactions between tectonic, fluvial, subsurface hydrologic, coastal, and tectonic processes. Uplift rates along the coast vary from less than 1m/ka to several m/ka. Tectonic uplift and faulting can significantly influence lagoon geomorphology and hydrology.

Very little is known about the geomorphology and hydrology of small lagoons in active tectonic environments of Southern California. They are potentially important nursery habitat for endangered southern steelhead trout, and thus better understanding of lagoon structure and processes will assist in habitat evaluation and restoration efforts for steelhead.