Desert streams flow only during infrequent but intense rainstorms, and when they do, only parts of the channel contain water, making the flow irregular and erratic. One rainstorm may erode sediment grains in one section of the channel, while another storm moves sediment in a different area.
"Given this localized sediment movement during rainstorms, one might expect desert channels to contain mounds of sediment that undulate down the stream course reflecting the irregular flow, but they don't," Singer said. "The water produced in the channel only flows partially down the stream and then stops because it seeps into the riverbed, and there's not enough water from upstream to replace it, so it just disappears."
Because desert river channels do not feature the river bars, pools or riffles common in perennial streams, they decline in elevation downstream very smoothly. According to the researchers' findings, feedback between two variables -- complex water and sediment movements -- shape such basins.
http://www.sciencedaily.com/releases/2014/10/141023142314.htm
No comments:
Post a Comment