HR: 08:15h
AN: H51M-02    [Abstracts]
TI: Runoff Response at Three Spatial Scale from a Burned Watershed
AU: * Moody, J A
EM: jamoody@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street Suite E-127, Boulder, CO 80303,
AU: Kinner, D A
EM: dkinner@email.wcu.edu
AF: Western Carolina University, Stillwell Building, Cullowhee, NC 28723,
AB: The hypothesis that the magnitude and timing of runoff from burned watersheds are functions of the properties of flow paths at multiple scales was investigated at three nested spatial scales within an area burned by the 2005 Harvard Fire near Burbank, California. Water depths were measured using pressure sensors: at the outlet of a subwatershed (10000 m2); in 3-inch Parshall flumes near the outlets of three mini-watersheds (820-1780 m2) within the subwatershed; and by 12 overland-flow detectors in 6 micro-watersheds (~11-15 m2) within one of the mini-watersheds. Rainfall intensities were measured using recording raingages deployed around the perimeter of the mini-watersheds and at the subwatershed outlet. Time-to-concentration, TC, and lag time, TL, were computed for the 15 largest of 30 rainstorms (maximum 30- minute intensities were 3.3-13.0 mm/h) between December 2005 and April 2006. TC , elapsed time from the beginning of the rain until the first increase in water depth, averaged 1.0 hours at the micro-scale, 1.7 hours at the mini-scale, and 1.5 hours at the subwatershed scale. TL is the lag time that produced the maximum cross- correlation coefficient between the time series of rainfall intensities and the series of water depths. TL averaged 0.15 hours at the micro-scale, 0.35 hours at the mini-scale, and 0.39 hours at the subwatershed scale. The coefficient was >0.50 for 43% (N=168) of the measurements at the micro-scale, for 61% (N=54) at the mini- scale, and for 67% (N=6) at the subwatershed scale indicating the runoff response lagged but was often well correlated with the time-varying rainfall intensity.
DE: 1804 Catchment
DE: 1821 Floods
DE: 1826 Geomorphology: hillslope (1625)
DE: 1840 Hydrometeorology
DE: 1850 Overland flow
SC: Hydrology [H]
MN: 2007 Fall Meeting