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

Abstract. The topographic wetness index (TWI, ln(a/tanβ)), which combines local upslope contributing area and slope, is commonly used to quantify topographic control on hydrological processes. Methods of computing this index differ primarily in the way the upslope contributing area is calculated. In this study we compared a number of calculation methods for TWI and evaluated them in 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 six parameters affecting the distribution of accumulated area among downslope cells and by varying the way the slope was…

• SF
  Stiftelsen för Miljöstrategisk Forskning
• SF
  Svenska Forskningsrådet Formas
• V
  Vetenskapsrådet