Spatial resolution sensitivity of catchment geomorphologic properties and the effect on hydrological simulation

The geomorphologic area function and width function that characterize the forms of hillslope and river networks are two key parameters employed in the GBHM (geomorphology-based hydrological model) for representing the hydrological processes together with other spatial information. One fundamental issue on the use of the geomorphologic properties is the spatial resolution sensitivity in both the threshold area for river network generation and digital elevation model (DEM) resolution. The threshold area is the minimum drainage area required to initiate the river; the DEM resolution depends on the available elevation data. In the present study, multifractal analysis was used to investigate the sensitivity of width functions extracted by different threshold areas and the sensitivity of area functions extracted from various resolutions of DEMs. Fifteen Japanese catchments were selected for the sensitivity analysis based on 250 m mesh DEM data. It was found that the river networks generated with larger threshold areas tend to lose the detailed scaling information. When the DEM mesh size increases, the river networks extracted with the same threshold area become sparser and the topography tends to be flat and scaling structures of the area functions become simpler. The runoff generations of the GBHM were influenced by the DEM resolution. The effect of the DEM resolution on the hydrological response is related to the temporal resolution with more influence on the hourly response compared with the daily response. From the relation between the scaling structure expressed by the multifractal spectrum and the hydrological response of a catchment, it was found that the detailed scaling information had more effect on the hydrological response of higher temporal resolution. Copyright © 2001 John Wiley & Sons, Ltd.