Dynamic connectivity in a fluvial network for identifying hotspots of geomorphic change
Dynamic connectivity in a fluvial network for identifying hotspots of geomorphic change
复制标题
DOI：
10.1002/2014wr016139
复制
发表时间：
2015-03
影响因子：
5.4
通讯作者：
J. Czuba;E. Foufoula‐Georgiou
中科院分区：
文献类型：
--
作者：
J. Czuba;E. Foufoula‐Georgiou
在河网的等级分支结构上发生的动态过程倾向于在河网上不均匀地分布通量，通常将它们集中成“簇”，即过量通量积累的地方。在这里，我们提出了一个假设，即网络中（由于过程动力学和网络拓扑）在相当长的河段和相当长的一段时间内倾向于积累过量泥沙的地方反映了可能发生局部泥沙通量不平衡的位置，从而突出了对潜在河流地貌变化的易感性。我们开发了一个动态连通性框架，该框架使用河流网络结构和简化的拉格朗日输运模型来跟踪网络中的通量，并通过集群持久性指数（CPI）整合紧急“集群”。该框架应用于明尼苏达河流域大蓝土河网的沙粒运输。河流地貌变化的三个热点被定义为观察到高通道迁移率的地点，高CPI的地点与可能由沉积物驱动的变化的两个热点重合。第三个热点不是由高CPI确定的，而是基于附加信息和高床层剪应力与该热点相吻合的事实，被认为是水流驱动变化的热点。所提出的基于网络的动态连接框架有可能将发生在小尺度上的动态过程置于网络环境中，以了解到达尺度的变化如何级联为网络尺度效应，这对于告知本地管理行为的大规模后果很有用。
Dynamical processes occurring on the hierarchical branching structure of a river network tend to heterogeneously distribute fluxes on the network, often concentrating them into “clusters,” i.e., places of excess flux accumulation. Here, we put forward the hypothesis that places in the network predisposed (due to process dynamics and network topology) to accumulate excess sediment over a considerable river reach and over a considerable period of time reflect locations where a local imbalance in sediment flux may occur thereby highlighting a susceptibility to potential fluvial geomorphic change. We develop a dynamic connectivity framework which uses the river network structure and a simplified Lagrangian transport model to trace fluxes through the network and integrate emergent “clusters” through a cluster persistence index (CPI). The framework was applied to sand transport in the Greater Blue Earth River Network in the Minnesota River Basin. Three hotspots of fluvial geomorphic change were defined as locations where high rates of channel migration were observed and places of high CPI coincided with two of these hotspots of possibly sediment‐driven change. The third hotspot was not identified by high CPI, but instead is believed to be a hotspot of streamflow‐driven change based on additional information and the fact that high bed shear stress coincided with this hotspot. The proposed network‐based dynamic connectivity framework has the potential to place dynamical processes occurring at small scales into a network context to understand how reach‐scale changes cascade into network‐scale effects, useful for informing the large‐scale consequences of local management actions.