HR: 0800h
AN: H11F-0368    [Abstracts]
TI: Anatomy of a Flash Flood in the Amargosa Desert, U.S.A.
AU: * Stonestrom, D A
EM: dastones@usgs.gov
AF: USGS, 345 Middlefield Rd., MS-421, Menlo Park, CA 94025
AU: Prudic, D E
EM: deprudic@usgs.gov
AF: USGS, 333 W. Nye Ln., Ste. 203, Carson City, NV 89706
AU: Glancy, P A
AF: USGS, 333 W. Nye Ln., Ste. 203, Carson City, NV 89706
AU: Beck, D A
EM: dabeck@usgs.gov
AF: USGS, 160 N. Stephanie Street, Henderson, NV 89074
AB: In August 2004, intense convective rainstorms caused flash flooding throughout the Amargosa River drainage network, temporarily closing Death Valley National Park and causing two fatalities when runoff from Furnace Creek and other channels overtopped roadways in the Park. In 1998, we began installing streambed temperature loggers, pressure transducers, and scour chains in the normally dry channel and selected tributaries of the river in the Amargosa Desert and Oasis Valley. The primary objective of this work is to improve understanding of ground-water recharge from ephemeral streamflows under current climatic conditions. Two weeks after the flash flooding, we visited instrumented sites and estimated peak flows by surveying high-water marks and corresponding channel geometries. Time series of temperatures and stages, together with peak-flow estimates, reveal the routing and evolution of distinct flood pulses in the upper Amargosa River basin. The data also reveal previously undocumented details of individual flash-flood hydrographs, including initial and subsequent flood pulses at two sites. Arid environments are prone to flash flooding not only because vegetation is sparse, but also because the surface-water network is decoupled from underlying ground water by a thick unsaturated zone. Nonlinear interactions between runoff (with energy potentials on the order of a meter of head) and the unsaturated zone (with energy potentials on the order of negative hundreds of meters of head) keep advancing fronts of flood pulses sharp. Profiles of water content beneath the main channel before and after the passage of a flood pulse, together with down-channel attenuation of flow volume within individual pulses, show the leaky nature of dry alluvial channels and the efficiency at which flash floods become potential recharge.
DE: 1821 Floods
DE: 1829 Groundwater hydrology
DE: 1848 Networks
DE: 1860 Runoff and streamflow
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting