冲决


冲决（英语：）是指一条河流废弃原河道而流向新河道。当河道梯度比地面坡度小，就会发生冲决。[1]在河流三角洲，冲决很常见。[2]此过程也称为三角洲换位。例如密西西比河的鸟足形三角洲，它就是由连续的冲决形成。

从密西西比河鸟爪状三角洲涌入海洋的沉积物。这些沉积物能建造三角洲往外海延伸。同时减低河流梯度，河道淤积. 导致冲决

当一条河流进入海洋时，会形成一个单独的三角洲[3]，随着三角洲向海推进，河道变长坡度也变低，河道变得不稳定。在重力作用下，河流将趋向最直接的下坡方向流动。在洪水期，河流能溢出其天然堤坝，冲决出一条新的陡坡河道。[4]

相关条目

参考文献
  1. Slingerland, Rudy; Smith, Norman D. (2004). "River Avulsions and Their Deposits". Annual Review of Earth and Planetary Sciences. 32: 257–285. Bibcode:2004AREPS..32..257S. doi:10.1146/annurev.earth.32.101802.120201
  2. Marshak, Stephen (2001), Earth: Portrait of a Planet, New York: W.W. Norton & Company, ISBN 0-393-97423-5 pp. 528–9
  3. Stanley, Steven M. (1999) Earth System History. New York: W.H. Freeman and Company, ISBN 0-7167-2882-6 p. 136
  4. Perignon, M. C. (2007). Mechanisms governing avulsions in transient landscapes: Analysis of the May 2006 Suncook River Avulsion in Epsom, New Hampshire (S.B. Thesis). Massachusetts Institute of Technology
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