Review Of Ordinary High Water Mark Indicators For Delineating Arid Streams In The Southwestern United States PDF Download

The U.S. Army Corps of Engineers (Corps) delineates the jurisdictional extent of wetlands and other "Waters of the United States" (WoUS) under Corps and Environmental Protection Agency (EPA) regulations implementing Section 404 of the Clean Water Act(33 U.S.C. 1344). As part of this responsibility Corps districts in the southwestern United States and elsewhere must delineate the extent of WoUS in arid areas, including arid-land stream channels. In non-tidal waters lacking adjacent wetlands, Corps jurisdiction extends to the ordinary high water mark(OHWM). Unlike wetlands, for which there are criteria for hydrology, soils, and vegetation specified in a national wetland delineation manual, there is no hydrologic definition of ordinary high water (OHW), and the identification of WoUS relies entirely on physical features of stream channels. This literature review investigates the climatic and regional conditions controlling hydrologic discharges in arid-land streams and the resulting physical features that develop within channels and floodplains. The review covers three main features associated with arid stream systems that might be useful for delineation purposes: hydrology, fluvial geomorphology, and vegetation. Based on the reviews, certain physical features were selected as potential OHWM indicators and were categorized by location above, at, or below the OHW line. To support the identification of OHW, these potential indicators are intended to be tested in selected locations across the Southwest to identify consistent and reliable indicators of the OHWM.