Experimental insights on geomorphological processes within dam break outburst floods
Experimental insights on geomorphological processes within dam break outburst floods
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DOI：
10.1016/j.jhydrol.2011.07.037
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发表时间：
2011-09
影响因子：
6.4
通讯作者：
J. Carrivick;Richard R. Jones;G. Keevil
中科院分区：
文献类型：
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作者：
J. Carrivick;Richard R. Jones;G. Keevil
溃坝洪水的水力特性和非恒定输沙特性是相互依赖的，但约束性较差。本研究通过实验确定了河床沉积物的流动性和碎屑大小如何影响峰值流深和流速、波的传播和衰减、泥沙夹带和运输持续时间、洪水功率、能量转移和突发洪水的地貌影响。由于我们选择的碎屑大小和单峰粒度分布的主要泥沙运输机制是推移质。我们发现，锋面波传播较慢，衰减较快的流动在一个移动的床与那些在一个固定的床。峰值流动深度更大，并达到了较早的流动超过移动的床，并增加碎屑的大小。地貌动力在重力超过摩擦力的初始阶段后随时间呈几何下降趋势。峰值和时间峰值地貌功率与碎屑大小成反比。峰值沉积速率最大粗床沉积物，但达到峰值沉积速率的时间是成反比的碎屑大小。体积变化通道，我们认为，这表明泥沙输运进行了波通过平移和色散机制的指数曲线。悬移质峰值出现与流速峰值相一致，推移质峰值出现与水深峰值相一致，输沙峰值滞后于输沙峰值。这些对运动学变换、多相流和突发洪水造成的地貌作用的描述有助于为数值建模提供数据，减轻突发洪水的危害，并为突发洪水的近期和长期地质遗留问题提供信息。
Hydraulic behavior and unsteady sediment transport within dam break outburst floods are inherently inter-dependent, yet poorly constrained. This study experimentally determined how the mobility and clast size of channel bed sediments affected the peak flow depth and flow velocities, wave propagation and attenuation, sediment entrainment and duration of transport, flood power, energy transfer and geomorphological impact of outburst floods. Due to our choice of clast size and of a unimodal size distribution the predominant sediment transport mechanism was bedload. We found that frontal wave propagation was slower and attenuated faster for flows over a mobile bed versus those over a fixed bed. Peak flow depth was greater and was attained earlier for flows over a mobile bed and with increased clast size. Geomorphological power declined logarithmically with time after an initial period where gravitational forces exceeded frictional forces. Both peak and time-to-peak geomorphological power varied inversely with clast size. Peak deposition rates were greatest with coarser bed sediment but time to peak deposition rate was inversely proportional to clast size. Volume changes down channel were described by an exponential curve, which we suggest indicates that sediment transport proceeded in waves via both translation and dispersion mechanisms. Peak suspended load occurred coincident with peak flow velocity, peak bedload occurred coincident with peak flow depth, and peak sediment discharge lagged behind peak water discharge. These descriptions of kinematic transformation, multi-phase flow and of geomorphological work due to outburst floods help to provide data for numerical modelling, for mitigating outburst flood hazards and for informing on the immediate and longer-term geological legacy of outburst floods.