沖決


沖決（英語：）是指一條河流廢棄原河道而流向新河道。當河道梯度比地面坡度小，就會發生沖決。[1]在河流三角洲，沖決很常見。[2]此過程也稱為三角洲換位。例如密西西比河的鳥足形三角洲，它就是由連續的沖決形成。

從密西西比河鳥爪狀三角洲涌入海洋的沉積物。這些沉積物能建造三角洲往外海延伸。同時減低河流梯度，河道淤積. 導致沖決

當一條河流進入海洋時，會形成一個單獨的三角洲[3]，隨著三角洲向海推進，河道變長坡度也變低，河道變得不穩定。在重力作用下，河流將趨向最直接的下坡方向流動。在洪水期，河流能溢出其天然堤壩，沖決出一條新的陡坡河道。[4]

相關條目

參考文獻
  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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