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On the calculation of the topographic wetness index: evaluation of different methods based on field observations

机译：关于地形湿度指数的计算：基于现场观测的不同方法的评估

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The topographic wetness index (TWI, ln(a/tanβ)), which combines local upslopecontributing area and slope, is commonly used to quantify topographiccontrol on hydrological processes. Methods of computing this index differprimarily in the way the upslope contributing area is calculated. In thisstudy we compared a number of calculation methods for TWI and evaluated themin terms of their correlation with the following measured variables:vascular plant species richness, soil pH, groundwater level, soil moisture,and a constructed wetness degree. The TWI was calculated by varying sixparameters affecting the distribution of accumulated area among downslopecells and by varying the way the slope was calculated. All possiblecombinations of these parameters were calculated for two separate borealforest sites in northern Sweden. We did not find a calculation method thatperformed best for all measured variables; rather the best methods seemed tobe variable and site specific. However, we were able to identify somegeneral characteristics of the best methods for different groups of measuredvariables. The results provide guiding principles for choosing the bestmethod for estimating species richness, soil pH, groundwater level, and soilmoisture by the TWI derived from digital elevation models.
机译：结合局部上坡贡献面积和坡度的地形湿度指数（TWI，ln（ a / tan β））通常用于量化水文过程的地形控制。计算该指数的方法主要区别在于计算上坡贡献面积的方式。在这项研究中，我们比较了TWI的多种计算方法，并评估了它们与以下测量变量的相关性：维管植物物种丰富度，土壤pH值，地下水位，土壤湿度和人工湿度。通过改变影响下坡单元之间累积面积分布的六个参数以及改变坡度的计算方法来计算TWI。这些参数的所有可能组合都是针对瑞典北部的两个不同的北方森林站点进行计算的。我们没有找到一种对所有测量变量都表现最佳的计算方法。最好的方法似乎是可变的和针对特定地点的。但是，我们能够为不同组的测量变量确定最佳方法的某些一般特征。结果为通过数字高程模型导出的TWI选择最佳方法估算物种丰富度，土壤pH，地下水位和土壤水分提供了指导原则。

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