MEASURING SEDIMENT TRANSPORT AND REDISTRIBUTION IN A SMALL SEMIARID WATERSHED NEAR TOMBSTONE, ARIZONA

The Lucky Hills 103 is an intensively monitored 3.7 ha subwatershed within the USDA-ARS Walnut Gulch Experimental Watershed in southeast Arizona. Runoff and erosion generating rainfall typically occurs as short duration, high intensity events during the summer monsoon season. Transported sediment is measured at the watershed outlet with a traversing slot sediment sampler and coarse sediment, generally bedload, has been measured with a pit trap. Sediment concentration data for individual events is available since 1995. Acoustic sensing field experiments explore the possibility of relating acoustic bedload signals retrieved from a hydrophone to actual yield collected in a pit trap below the outlet. The acoustic signal was closely correlated with course sediments bedload measurements of three different size brackets, between 12 mm and 64 mm. Seven runoff events were recorded in the 2014 field season. Sediment redistribution including gully erosion and landscape deposition information was collected by repeat microtopography measurements after runoff events with a ground-based terrestrial LiDar system. Point clouds were used to generate visual models of sediment redistribution resulting from high-intensity runoff occurrences in the 2015 field season.