A new topographic index to quantify downslope controls on local drainage
A new topographic index to quantify downslope controls on local drainage
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DOI：
10.1029/2004wr003130
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发表时间：
2004-05-18
影响因子：
5.4
通讯作者：
Rodhe, A
中科院分区：
文献类型：
--
作者：
Hjerdt, KN;McDonnell, JJ;Rodhe, A
地形是水文过程的重要控制因素。量化这种控制的一种方法是地形ln（a/tanbeta）指数。该指数已被广泛用于水文学，但它利用了数字高程模型（DEM）中包含的相对较小的一部分信息。在实施ln（a/tanb）指数时未考虑的一个潜在重要特征是下坡地形对局部排水的增强或阻抗。这种效应在某些地形中对于控制水力梯度可能很重要。我们提出了一种新的方法来估计水力梯度，计算多远下坡（L-d，[m]）的一个包裹的水必须移动，以失去一定量的势能（d，[m]）。用梯度tanalpha（d）= d/ L-d表示，与局部梯度tanbeta相比，凹坡剖面上的值往往较低，凸坡剖面上的值往往较高。我们认为，参数d控制的水力梯度从表面坡度的偏差。虽然这是我们主观决定的，但在选择d时应考虑景观起伏、DEM分辨率和土壤透明度。我们发现，下坡指数值的影响较小，在DEM分辨率的变化比当地的坡度。三个应用程序中，新的指数被证明是有用的水文，地貌和地球化学的应用。
Topography is an important control on hydrological processes. One approach to quantify this control is the topographic ln(a/tanbeta) index. This index has become widely used in hydrology, but it utilizes a relatively small portion of the information contained in a digital elevation model (DEM). One potentially important feature not considered in the implementation of the ln(a/tanb) index is the enhancement or impedance of local drainage by downslope topography. This effect could be important in some terrain for controlling hydraulic gradients. We propose a new way of estimating the hydraulic gradient by calculating how far downhill (L-d, [m]) a parcel of water must move in order to lose a certain amount of potential energy (d, [m]). Expressed as a gradient, tanalpha(d) = d/ L-d, values tend to be lower on concave slope profiles and higher on convex slope profiles compared with the local gradient, tanbeta. We argue that the parameter d controls the deviation of hydraulic gradient from surface slope. While we determine this subjectively, landscape relief, DEM resolution, and soil transmissivity should be considered at the selection of d. We found the downslope index values to be less affected by changes in DEM resolution than local slope. Three applications are presented where the new index is shown to be useful for hydrological, geomorphological, and biogeochemical applications.