Dynamics of Surface‐Water Connectivity in a Low‐Gradient Meandering River Floodplain
Dynamics of Surface‐Water Connectivity in a Low‐Gradient Meandering River Floodplain
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DOI：
10.1029/2018wr023527
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发表时间：
2019-03
影响因子：
5.4
通讯作者：
J. Czuba;Scott R. David;D. Edmonds;A. Ward
中科院分区：
文献类型：
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作者：
J. Czuba;Scott R. David;D. Edmonds;A. Ward
高分辨率地形显示，在印第安纳州，沿沿着河流的洪泛平原通常包含间歇性流动的河道网络。我们研究了洪泛区河道的存在如何影响河流和洪泛区之间的横向地表水连通性（特别是交换通量和运输时间尺度），作为低梯度河流-洪泛区系统中流量阶段的函数。我们利用激光雷达高程数据和测量的河流水深，使用水文工程中心的河流分析系统（HEC ‐ RAS）2D沿着32 km洪泛区（沿沿着56 km）构建了一个二维地表水动力学模型，该洪泛区位于美国印第安纳州西摩附近的东福克怀特河。该模型使用美国地质调查局测量仪的土地覆盖特定粗糙度与高程流量数据进行校准，并根据高水位标记、显示洪泛区淹没空间范围的航拍照片和测量流速进行验证。利用模型结果，我们分析了河流中的流量，淹没的空间格局，流动路径，河流-洪泛区交换，以及洪泛区上的水停留时间。我们的研究结果强调，平滩流量是一个过于简化的概念，用于解释河流-洪泛区的连通性，因为一些河岸被淹没，主要的低洼洪泛区渠道每年大约有19天被淹没。随着流量的增加，洪水泛滥平原渠道在更高的海拔解剖泛滥平原，直到泛滥平原渠道成为完全淹没。此外，我们发现河流-洪泛区交换是由河岸高度或河道方向驱动的，这取决于水流条件。我们提出了一个概念模型的河流-洪泛区连接动力学和开发指标，定量分析复杂的河流-洪泛区系统。
High‐resolution topography reveals that floodplains along meandering rivers in Indiana commonly contain intermittently flowing channel networks. We investigated how the presence of floodplain channels affects lateral surface‐water connectivity between a river and floodplain (specifically exchange flux and timescales of transport) as a function of flow stage in a low‐gradient river‐floodplain system. We constructed a two‐dimensional, surface‐water hydrodynamic model using Hydrologic Engineering Center's River Analysis System (HEC‐RAS) 2D along 32 km of floodplain (56 km along the river) of the East Fork White River near Seymour, Indiana, USA, using lidar elevation data and surveyed river bathymetry. The model was calibrated using land‐cover specific roughness to elevation‐discharge data from a U.S. Geological Survey gage and validated against high‐water marks, an aerial photo showing the spatial extent of floodplain inundation, and measured flow velocities. Using the model results, we analyzed the flow in the river, spatial patterns of inundation, flow pathways, river‐floodplain exchange, and water residence time on the floodplain. Our results highlight that bankfull flow is an oversimplified concept for explaining river‐floodplain connectivity because some stream banks are overtopped and major low‐lying floodplain channels are inundated roughly 19 days per year. As flow increased, inundation of floodplain channels at higher elevations dissected the floodplain, until the floodplain channels became fully inundated. Additionally, we found that river‐floodplain exchange was driven by bank height or channel orientation depending on flow conditions. We propose a conceptual model of river‐floodplain connectivity dynamics and developed metrics to analyze quantitatively complex river‐floodplain systems.