Rainfall-induced lahars in the Belham Valley, Montserrat, West Indies
Rainfall-induced lahars in the Belham Valley, Montserrat, West Indies
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DOI：
10.1144/0016-76492006-078
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发表时间：
2007-07-01
影响因子：
2.7
通讯作者：
Susnik, Janez
中科院分区：
文献类型：
--
作者：
Barclay, Jenni;Alexander, Jan;Susnik, Janez
雨水落在蒙特塞拉特火山的苏弗里埃山上松散的火山碎屑上，在贝勒姆山谷造成危险的洪水。这些火山泥流的流量和含沙量在空间和时间上变化很大。它们与其他火山记录的例子不同之处在于：（1）自1995年7月以来，火山一直在持续喷发，产生了重复的过量沉积物脉冲;（2）降雨是唯一的重要触发因素;（3）系统很小，离海不远，集水区顶部的海拔相对较低。重复制图和与喷发前数据的比较表明了显著的地貌变化，c。120 RN海岸线覆盖和C。0.4 m a（-1）中、下谷平均淤积速率。随着山谷的淤积、河道的拓宽和径流效率的提高（由于灌溉和植被的清除），灾害的性质和风险区域发生了变化。Belharn山谷的火山泥流与24小时内降雨量> 10转的天数相关，雨季后期触发的事件更多。流动主要是牛顿的，但一个非牛顿流动事件已被证明，并详细描述（2000年3月20日）。这种流动被解释为火山灰直接输入径流。
Rain falling on loose volcanic debris over the Soufriere Hills Volcano, Montserrat generates hazardous floods in the Belham Valley. These rainfall-induced lahars vary greatly in discharge and sediment concentration in space and time. They differ from examples documented on other volcanoes in that: (1) the eruption has been continuing since July 1995, generating repeated pulses of excess sediment; (2) rainfall is the only significant trigger; (3) the system is small, with short distance to the sea and relatively low altitude at the catchment top. Repeat mapping and comparison with pre-eruption data demonstrate significant geomorphological change, with c. 120 rn shoreline progradation and c. 0.4 m a(-1) mean aggradation rate in the middle to lower valley. The nature of the hazard and area of risk have changed as the valley has aggraded, the channel widened and the runoff efficiency increased (as a result of rilling and vegetation removal). Lahars in the Belharn Valley correlate with days when > 10 turn rain fell in 24 h, with more events triggered in the late rainy season. The flows are mainly Newtonian but one non-Newtonian flow event has been demonstrated and is described in detail (20 March 2000). This flow is explained by direct volcanic ash input to the runoff.