Headcut retreat in a semiarid watershed in the southwestern United States since 1935

Headcuts are prominent features in the southwestern United States. Within the Walnut Gulch Experimental Watershed (WGEW) survey data was available to quantify the retreat of the three most prominent headcuts in sub-watershed 63.011 from 1935 to 2006. The headcuts serve as major sediment sources and were investigated to identify and understand factors controlling retreat rate in this watershed. The data was incorporated and analyzed in a geographical information system (GIS). The headcuts have retreated persistently since 1935. A power relationship was fitted by regression (R2 = 0.89) correlating the retreat rate with the product of contributing drainage area and areal precipitation for precipitation exceeding a threshold intensity (I30 ≥ 25 mm hr− 1). This site specific relationship may not apply universally in other regions. Headcut retreat was not induced by external forcing. The autocyclic behavior of headcut retreat was found typical for the southwestern United States. The data did not allow timing or identification of initial causes for headcut retreat. Data suggests that all three headcuts will continue to retreat in the future, even though the retreat rate of one headcut was severely inhibited by exhumation a layer of cemented material, acting as local base level control. Most of the sediment eroded at the active headcut scarp was not transported very far, indicating that headcutting in this area results in local reworking rather than removal of material from the watershed.