Review of methods for deriving physical descriptors of the watershed topography from DEM

Some widely used physical descriptors of the watershed topography,such as slope gradient,the flow allocation coefficient,the specific contributing area,the contributing area,and the wetness index,are described and discussed in the context of the DF1VI-based distributed hydrological modeling. Fmstly,the methods for deriving these physical descriptors of the watershed topography from DFM are reviewed in detail. Then,according to its definition,each physical descriptor is interpreted with the focus on the corresponding hydrological meaning in relation to the water rmvements in watersheds. Finally,based on the DF1VI information required for calculating these physical descriptors,the ability of each physical descriptor to represent the effect of the watershed topography on the spatial distribution of hydrological response to rainfall in water-sheds is explored and a hierarchical structure of these physical descriptors is proposed. Thus,the review of these physical descriptors of the watershed topography will be very useful to enhance understanding of the mechanisms of runoff generation in watersheds,to explore the temporal and spatial distribution of hydrological processes,and to study the DFM-based distributed hydrological ridels.