A 30-Year History of the Tides and Currents in Elkhorn Slough, California

Abstract

Elkhorn Slough was first exposed to the waters of Monterey Bay with the construction of Moss Landing Harbor in 1946. It follows a 10-km path inland from Moss Landing Harbor. Today, it is a habitat and sanctuary for a wide variety of marine mammals, fish, and seabirds. The currents, tides and physical properties of Elkhorn Slough have been observed since 1970. It is an ebb-dominated estuary due to the asymmetric rise and fall of the tides which produces ebb currents that dominate. Tidal distortion increases inland due to frictional effects and extensive mud flats and Salicornia marsh. Tidal distortion also produces overtides and compound tides. Tidal elevations and currents often reveal the characteristics of a standing wave system. The temperature and salinity of lower Elkhorn Slough reflect the influence of Monterey Bay waters, whereas the upper Slough is more sensitive to local processes. Maximum tidal currents in Elkhorn Slough have increased from (cid:1) 75 to (cid:1) 150 cm/s since 1970. This increase is primarily due to the change in tidal prism which has increased from (cid:1) 2.5 to (cid:1) 7.6 (cid:3) 10 6 m 3 between 1956 and 2003. Finally, this increase is due to both man-made changes and continued tidal erosion.