On the effect of digital elevation model accuracy on hydrology and geomorphology

This study compares published cartometric and photogrammetric digital eleva tion models (DEMs) of various grid spacings with a ground truth data set, o btained by ground survey, and studies the implications of these differences on key hydrologic statistics. Inferred catchment sizes and stream networks from published DEMs were found to be significantly different than those fr om the ground truth in most instances. Furthermore, the width functions and cumulative area relationships determined from the published DEMs were foun d to fall consistently outside the 90% confidence limits determined from th e ground truth for more than 60% of the relationship, suggesting that these hydrologic properties are poorly estimated from published DEMs. However, t he slope-area relationships determined from published DEMs were found to be less sensitive to catchment shape, size, and stream network, with the rela tionship falling outside the 90% confidence limits for less than 40% of the relationship for all catchments identified from the published DEMs. A publ ished relationship linking the horizontal resolution with the vertical accu racy of the DEM was tested, predicting a horizontal resolution of about 10 m for the published DEMs tested.