Inception of channelization and drainage basin formation: upstream-driven theory
Inception of channelization and drainage basin formation: upstream-driven theory
复制标题
渠道化和流域形成的开始：上游驱动理论
DOI：
10.1017/s0022112095002357
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发表时间：
1995
影响因子：
3.7
通讯作者：
G. Parker
中科院分区：
文献类型：
--
作者：
N. Izumi;G. Parker
在陆地环境中，河流流域的普遍存在表明，降雨产生的分布式地表径流往往会自发地组织成离散渠道的树枝状系统。最近的几个数值模型描述了完整的流域的演变，从降雨的初始条件下，在一个平坦的，倾斜的高原，其表面已提供了随机高程扰动。这些分析通过假设重力和摩擦项之间的完美平衡（即正常流量）来模拟地表径流。线性稳定性分析应用于正常流模型已被证明，但是，未能选择一个波长对应于一个有限的距离之间的分离初始盆地。这表明，正常流量模型可能不是研究流域发展的充分基础，特别是在最细尺度的形态意义。在这里，一个阈值条件的概念相结合的浅坡面流的完整方程的分析，以研究波长的选择。经典的线性稳定性分析被证明是不够的，在初始水平上分析的问题。另一种线性分析的基础上的阈值条件的床扰动的发展，并显示导致选择正确的数量级的有限波长。这里的分析是从上游方向进行的，因为只有当降雨从上游聚集了足够的水流时，才会首先引起河床冲刷。Izumi（1993）提出了一种下游驱动的初期渠化理论，该理论不一定取决于降雨量，目前正准备出版。
The ubiquitous presence of river drainage basins in the terrestrial environment suggests that distributed overland flow generated by rainfall tends to spontaneously organize itself into dendritic systems of discrete channels. Several recent numerical models describe the evolution of complete drainage basins from the initial condition of rainfall on a flat, tilted plateau, the surface of which has been provided with random elevation perturbations. These analyses model overland flow via the assumption of a perfect balance between gravitational and frictional terms, i.e. in terms of normal flow. Linear stability analysis applied to the normal flow model has been shown, however, to fail to select a wavelength corresponding to a finite distance of separation between incipient basins. This suggests that the normal flow model may not be a sufficient basis for studying drainage basin development, especially at the finest scales of morphologic significance. Here the concept of a threshold condition for bed erosion is combined with an analysis of the full equations of shallow overland flow in order to study wavelength selection. Classical linear stability analysis is shown to be inadequate to analyse the problem at the level of inception. An alternative linear analysis of bed perturbations based on the threshold condition is developed, and shown to lead to the selection of finite wavelength of the correct order of magnitude. The analysis here is driven from the upstream direction in that bed erosion is first caused only when sufficient flow has gathered from upstream due to rainfall. A downstream-driven theory of incipient channelization that is not necessarily dependent upon rainfall is presented in Izumi (1993), and is presently in preparation for publication.