Groundwater Affects the Geomorphic and Hydrologic Properties of Coevolved Landscapes
Groundwater Affects the Geomorphic and Hydrologic Properties of Coevolved Landscapes
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DOI：
10.1029/2021jf006239
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发表时间：
2022-01-01
影响因子：
3.9
通讯作者：
Harman, Ciaran J.
中科院分区：
文献类型：
--
作者：
Litwin, David G.;Tucker, Gregory E.;Harman, Ciaran J.
流域的水文动力学和地貌演化密切相关——径流产生和储水受地形和地表和地下性质的控制，同时也影响这些性质随地质时间的演变。然而，它们的时间尺度之间的巨大差异使得很难检查对新兴水文地貌特性的相互依赖的控制，例如山坡长度、排水密度和地表饱和程度。在本研究中，我们开发了一种耦合水文学和景观演化的新模型，以探索径流产生如何影响长期流域演化，并使用无量纲框架分析数值结果。我们关注潮湿气候中主导的水文过程，其中风暴径流主要来自浅层地下流和饱和区域的降水。该模型求解地下水水力方程，以在给定规定的恒定地下水补给的情况下预测地下水位高程。超过地下输送能力的水会变成地表水流，在地表产生剪切应力，并可能分离和输送沉积物。这会影响景观形态，进而影响径流的产生。我们表明（a）四个无量纲参数描述了在稳定补给下共同演化的可能稳态景观； (b) 山坡长度随着相对于补给率的透射率的增加而增加； (c) 三个地形指标——陡度指数、拉普拉斯曲率和地形指数——共同为解释与浅层地下流产生的径流共同演化的景观提供了基础。最后我们讨论了模型结果与真实景观之间进行定量比较的可能性和局限性。
The hydrologic dynamics and geomorphic evolution of watersheds are intimately coupled-runoff generation and water storage are controlled by topography and properties of the surface and subsurface, while also affecting the evolution of those properties over geologic time. However, the large disparity between their timescales has made it difficult to examine interdependent controls on emergent hydrogeomorphic properties, such as hillslope length, drainage density, and extent of surface saturation. In this study, we develop a new model coupling hydrology and landscape evolution to explore how runoff generation affects long-term catchment evolution, and analyze numerical results using a nondimensional scaling framework. We focus on hydrologic processes dominating in humid climates where storm runoff primarily arises from shallow subsurface flow and from precipitation on saturated areas. The model solves hydraulic groundwater equations to predict the water-table elevation given prescribed, constant groundwater recharge. Water in excess of the subsurface capacity for transport becomes overland flow, which generates shear stress on the surface and may detach and transport sediment. This affects the landscape form that in turn affects runoff generation. We show that (a) four dimensionless parameters describe the possible steady state landscapes that coevolve under steady recharge; (b) hillslope length increases with increasing transmissivity relative to the recharge rate; (c) three topographic metrics-steepness index, Laplacian curvature, and topographic index-together provide a basis for interpreting landscapes that have coevolved with runoff generated via shallow subsurface flow. Finally we discuss the possibilities and limitations for quantitative comparisons between the model results and real landscapes.