The Role Of Large Floods In Maintaining Hyperarid Floodplains And Riparian Vegetation

Hyperarid ephemeral streams have limited floodplains. However, when the do form they, together with active channels edges have crucial role in establishing riparian ecosystems. Large floods (a) can continually accrete floodplains or destroy them, (b) recharge shallow alluvial aquifers that maintain vegetation during dry periods, and (c) allow vegetation germination on rarely wetted higher surfaces. Whereas the active channel is subjected to short-term destruction by floods and vegetation rejuvenation following it, floodplains can support vegetation fed by shallow water table for longer periods. Here, we report short- and long-term fluvial activity and floodplain accretion and vegetation distribution in relationship to flood stage-magnitude and frequency. At the lower reaches of the coarse gravelly, braided to anabranching Nahal Arava, Israel and the sandy Kuiseb River, Namibia (