Fluvial Sediment Yields in Hyper-Arid Areas, Exemplified by Nahal Nehushtan, Israel

Abstract

Floods rarely occur in hyper-arid deserts and little is known about the magnitude and frequency of sediment delivery from their basins, despite their importance to changes to the landscape, infrastructures and engineering activities. Sediment yield from the Nahal Nehushtan watershed (11.9 km2) located in the Timna Valley in southern Israel was determined by assessing stratigraphic sections in its 60-year reservoir deposits. Stratigraphic correlation between event couplets allowed for quantification of sediment yields representing 13 former flow and flood events. Based on the sediment volume in the reservoir, the 29.8 t km−2 year−1 average specific sediment yield is one of the lowest among other studied warm deserts. Among the event layers, the thickest layer, deposited by a flash flood caused by a single short rain event, contributed 31% of the total sediment yield. Based on event reservoir sedimentation from watersheds located in several hyper-arid areas in the Middle East and North America, we demonstrate that sediment yield increases with drainage area as expected and mean annual sediment yield increases in hyper-arid areas with flood frequency. Our quantitative results, together with previous studies of hyper-arid areas, provide complementary evidence of fluvial sediment transport—the main landscape designer in hyper-arid fluvial landscapes.