American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 1126603 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, F02018, doi:10.1029/2006JF000662, 2007

Suspended-sediment rating curve response to urbanization and wildfire, Santa Ana River, California

Jonathan A. Warrick

U.S. Geological Survey, Santa Cruz, California, USA


David M. Rubin

U.S. Geological Survey, Santa Cruz, California, USA


Abstract

River suspended-sediment concentrations provide insights to the erosion and transport of materials from a landscape, and changes in concentrations with time may result from landscape processes or human disturbance. Here we show that suspended-sediment concentrations in the Santa Ana River, California, decreased 20-fold with respect to discharge during a 34-year period (1968−2001). These decreases cannot be attributed to changes in sampling technique or timing, nor to event or seasonal hysteresis. Annual peak and total discharge, however, reveal sixfold increases over the 34-year record, which largely explain the decreases in sediment concentration by a nonlinear dilution process. The hydrological changes were related to the widespread urbanization of the watershed, which resulted in increases in storm water discharge without detectable alteration of sediment discharge, thus reducing suspended-sediment concentrations. Periodic upland wildfire significantly increased water discharge, sediment discharge, and suspended-sediment concentrations and thus further altered the rating curve with time. Our results suggest that previous inventories of southern California sediment flux, which assume time-constant rating curves and extend these curves beyond the sampling history, may have substantially overestimated loads during the most recent decades.

Received 15 August 2006; accepted 22 January 2007; published 18 May 2007.

Keywords: sediment rating curve; southern California; Santa Ana River.

Index Terms: 1803 Hydrology: Anthropogenic effects (4802, 4902); 1856 Hydrology: River channels (0483, 0744); 1862 Hydrology: Sediment transport (4558).

Read Full Article (file size: 1126603 bytes)    Cited by

Citation: Warrick, J. A., and D. M. Rubin (2007), Suspended-sediment rating curve response to urbanization and wildfire, Santa Ana River, California, J. Geophys. Res., 112, F02018, doi:10.1029/2006JF000662.