Sensitivity of a hydraulic model to channel erosion uncertainty during extreme flooding SENSITIVITY OF A HYDRAULIC MODEL TO CHANNEL EROSION UNCERTAINTY
Sensitivity of a hydraulic model to channel erosion uncertainty during extreme flooding SENSITIVITY OF A HYDRAULIC MODEL TO CHANNEL EROSION UNCERTAINTY
复制标题
极端洪水期间水力模型对河道侵蚀不确定性的敏感性 水力模型对河道侵蚀不确定性的敏感性
DOI：
10.1002/hyp.10148
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发表时间：
2015
影响因子：
3.2
通讯作者：
Wong J
中科院分区：
文献类型：
--
作者：
Wong J
最近的洪水模拟研究主要集中在模拟淹没流，而不考虑河道形态的影响。河道通常由简化的几何体表示，该几何体在洪水模拟期间隐含地假设保持不变。然而，现场证据表明，在洪水期间可能会发生重大的形态变化，以动员边界沉积物。尽管如此，通道形态对模型结果的影响在很大程度上还没有得到研究。为了解决这个问题，渠道横截面的几何形状和渠道长剖面的变化对洪水动力学的影响进行了检查，使用的集合的一维-二维水力模型（LISFLOOD-FP）的~1：2000年重现期洪水在英国科克茅斯，在一个不确定性框架。基于一个简单的基于速度的临界卷吸模型，构建了一系列模拟的河道侵蚀变化情景。采用蒙特卡罗模拟框架来量化这种河道形态以及河道和洪泛区粗糙度系数、粒度特征和临界剪切应力变化对洪水淹没措施的影响。结果表明，由简化方程产生的河床高程修正反映了所观察到的侵蚀深度的空间侵蚀模式的近似值。不确定性对河道长剖面变化的影响仅影响当地洪水动力学，对摩擦敏感性和洪水淹没绘图没有显著影响。结果意味着，水力模型一般不需要考虑事件内的形态动力学变化的类型和规模的事件建模，因为这些有一个可以忽略不计的影响，是小于其他的不确定性，例如边界条件。相反，形态动力学变化需要发生在一系列事件中，以变得足够大，以改变供应有限的砾石河床河流（如本研究中使用的河流）中洪水的水动力学。版权所有© 2014约翰威利父子有限公司.
Recent research into flood modelling has primarily concentrated on the simulation of inundation flow without considering the influences of channel morphology. River channels are often represented by a simplified geometry that is implicitly assumed to remain unchanged during flood simulations. However, field evidence demonstrates that significant morphological changes can occur during floods to mobilize the boundary sediments. Despite this, the effect of channel morphology on model results has been largely unexplored. To address this issue, the impact of channel cross‐section geometry and channel long‐profile variability on flood dynamics is examined using an ensemble of a 1D–2D hydraulic model (LISFLOOD‐FP) of the ~1 : 2000 year recurrence interval floods in Cockermouth, UK, within an uncertainty framework. A series of simulated scenarios of channel erosional changes were constructed on the basis of a simple velocity‐based model of critical entrainment. A Monte‐Carlo simulation framework was used to quantify the effects of this channel morphology together with variations in the channel and floodplain roughness coefficients, grain size characteristics and critical shear stress on measures of flood inundation. The results showed that the bed elevation modifications generated by the simplistic equations reflected an approximation of the observed patterns of spatial erosion that enveloped observed erosion depths. The effect of uncertainty on channel long‐profile variability only affected the local flood dynamics and did not significantly affect the friction sensitivity and flood inundation mapping. The results imply that hydraulic models generally do not need to account for within event morphodynamic changes of the type and magnitude of event modelled, as these have a negligible impact that is smaller than other uncertainties, e.g. boundary conditions. Instead, morphodynamic change needs to happen over a series of events to become large enough to change the hydrodynamics of floods in supply limited gravel‐bed rivers such as the one used in this research. Copyright © 2014 John Wiley & Sons, Ltd.