Development of Topography-Based River Width Estimation Model for Medium-Sized Mountainous Watersheds

Abstract

River width is an essential physical variable for the simulation of rainfall-runoff processes using distributed hydrologic models. In this paper, a model of river width integrating the effects of an upstream drainage area and terrain topography is proposed for the derivation of a spatial variation of a river width of medium-sized mountainous watersheds based on a digital elevation model (DEM). Tests of the model for three medium-sized watersheds, including Daheba, Changhua, and Yuqian, suggest that the spatial variation of the river width is dominated by topography in terms of slope near the riverbed. Wider river reaches are often located at flatter terrains with a larger upstream drainage area. In addition, the river width estimated method of the TOPographic Kinematic Approximation and Integration (TOPKAPI) model, which only uses the upstream drainage area to estimate river widths, is compared with the proposed model. Relative to a percent bias of 15%–19% of the river width model (GeoRW), the error of the method in TOPKAPI is obviously larger, at about 32.9%–65.4%. A comparison of the proposed model with the river width estimated method of the TOPKAPI model based on the upstream drainage area justifies its usefulness for medium-sized mountainous watersheds.