Buckingham, Susan EÌý1Ìý;ÌýWhitney, JohnÌý2
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The Las Vegas Wash was a typical desert wash before settlement began in 1905. Upstream population has grown from about 5,000 in 1930 to about 1.6 million in 2004. Concurrent with a growing urban center was increasing wastewater discharge to Las Vegas Wash: streamflow increased from a mean-daily flow of about 1 ft3/s (cfs) in mid-1955 to about 160 cfs in 1989 and to 275 cfs in 2004. Increasing amounts of wastewater added to the floodplain eventually saturated the floodplain resulting in perennial surface flows since 1955. Continually increasing wastewater-dominated streamflow initiated two headcuts in 1969 that grew during the 1970’s and were integrated into a large erosional channel in 1984 by a series of eight summer rainstorms.
This study applies spatial analysis to examine the linkages between urban expansion and changes in the hydrological system. Three sets of aerial photos in a GIS document the geomorphic history of the Las Vegas Wash. New spatial techniques were used to make quantitative measurements of the erosion at three specific time intervals in the hydrologic evolution of the wash. The spatial analysis quantifies channel changes for discrete time periods and provides a foundation for further research to examine how the specific mechanisms relate to urban expansions during discrete time periods.