Two‐dimensional hydraulic flood modelling using a finite‐element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry
Two‐dimensional hydraulic flood modelling using a finite‐element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry
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使用根据机载扫描激光测高得出的植被和地形特征分解的有限元网格进行二维水力洪水建模
DOI：
10.1002/hyp.1201
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发表时间：
2003
影响因子：
3.2
通讯作者：
P. Bates
中科院分区：
文献类型：
--
作者：
D. Cobby;D. Mason;M. Horritt;P. Bates
机载扫描激光测高（LiDAR）是一种重要的新数据源，可以提供具有空间分布的洪泛区地形的二维河流洪水模型，用于模型水深测量，以及用于模型摩擦参数化的植被高度。描述了通过分解模型的有限元网格以反映洪泛区植被特征（例如与其周围环境具有不同摩擦特性的树篱和树木）以及具有高高度曲率的显著洪泛区地形特征来改进此类模型的方法。使用图像分割系统实现分解，该系统将LiDAR高度图像转换为每个点处的表面地形和植被高度的单独图像。植被高度图用于估计每个网格节点处的摩擦因子。空间分布的摩擦模型的优点是，它是基于物理的，并消除了需要的模型校准练习中，自由参数指定的渠道和河漫滩的摩擦进行调整，以实现最佳拟合之间的建模和观察到的洪水范围。该计划进行了测试，在模拟研究的洪水发生在河塞文，英国，在1998年。洪水范围的卫星合成孔径雷达图像用于验证模型预测。使用分解网格的模拟水力学比更简单但计算效率更高的方法更好地代表了观测到的洪水范围，即在未分解网格中对较大的洪泛区元素进行地形和植被摩擦系数采样，以及传统方法，不使用LiDAR衍生数据，而是简单地使用恒定的洪泛区摩擦系数。使用的分解网格也允许速度的变化，以预测在附近的植被功能，如树篱。这些变化可以用于预测局部侵蚀和沉积模式，可能导致发生洪水。版权所有© 2003约翰威利父子有限公司
Airborne scanning laser altimetry (LiDAR) is an important new data source that can provide two‐dimensional river flood models with spatially distributed floodplain topography for model bathymetry, together with vegetation heights for parameterization of model friction. Methods are described for improving such models by decomposing the model's finite‐element mesh to reflect floodplain vegetation features such as hedges and trees having different frictional properties to their surroundings, and significant floodplain topographic features having high height curvatures. The decomposition is achieved using an image segmentation system that converts the LiDAR height image into separate images of surface topography and vegetation height at each point. The vegetation height map is used to estimate a friction factor at each mesh node. The spatially distributed friction model has the advantage that it is physically based, and removes the need for a model calibration exercise in which free parameters specifying friction in the channel and floodplain are adjusted to achieve best fit between modelled and observed flood extents. The scheme was tested in a modelling study of a flood that occurred on the River Severn, UK, in 1998. A satellite synthetic aperture radar image of flood extent was used to validate the model predictions. The simulated hydraulics using the decomposed mesh gave a better representation of the observed flood extent than the more simplistic but computationally efficient approach of sampling topography and vegetation friction factors on to larger floodplain elements in an undecomposed mesh, as well as the traditional approach using no LiDAR‐derived data but simply using a constant floodplain friction factor. Use of the decomposed mesh also allowed velocity variations to be predicted in the neighbourhood of vegetation features such as hedges. These variations could be of use in predicting localized erosion and deposition patterns that might result in the event of a flood. Copyright © 2003 John Wiley & Sons, Ltd.