Flood potential of Topopah Wash and tributaries, eastern part of Jackass Flats, Nevada Test Site, southern Nevada

Guidelines for the evaluation of potential surface facilities for the storage of high-level radioactive wastes on the Nevada Test Site in southern Nevada include the consideration of the potential for flooding. Those floods that are considered to constitute the principal flood hazards for these facilities are the 100- and 500-year floods, and the maximum potential flood. Flood-prone areas for the three floods with present natural-channel conditions were defined for the eastern part of Jackass Flats in the southwestern part of the Nevada Test Site. The 100-year flood-prone areas would closely parallel most stream channels with very few occurrences of overland flooding between adjacent channels. The 500-year flood and the maximum potential flood would exceed the discharge capacities of main channels and cause overland flooding between adjacent channels throughout most of the study area. Excluded areas would be those located immediately east of the upstream reach of Topopah Wash and between upstream channel reaches of some tributaries. Floodflow characteristics for the three floods were determined at 47 cross sections. The magnitudes of the estimated velocities indicate severe erosion of channels and flood plains would occur in parts of the study area. (USGS)