Comparative Analysis of Geomorphologic Characteristics of DEM-Based Drainage Networks

Abstract

Identifying the optimal drainage network based on digital elevation models (DEMs) is a fundamental task in rainfall-runoff modeling. Rapidly improving geographic information system technology enables hydrologists to use a variety of DEM-based hydrologic models that yield spatially concrete outputs. However, reliable drainage networks are still difficult to represent due to insufficient information about the dynamic behavior of water movement on catchment hillslopes. This study proposes an efficient method for drainage network identification through a comparative analysis of geomorphologic characteristics, such as drainage density, length of hillslope flow path, source area, etc., using area threshold and slope-area threshold criteria that incorporate scaling properties between the local slope and the contributing area. The results demonstrate that both criteria yield different drainage networks from “blue lines” based on topographic map from the Korean National Geographic Information Institute. Although the drainage networks obtained from the two criteria are visually similar, the area threshold yields an incorrect drainage structure due to excessive constraint of the draining source area size. In contrast, use of the slope-area threshold produces a relatively acceptable drainage structure in terms of preserving constant geomorphologic similarity to the study catchment. The proposed drainage network identification procedure may be used to describe landscape evolution for channel initiation in catchment hydrology. In addition, the comparative analysis of geomorphologic characteristics is found to provide important preprocess information for selecting a threshold value to generate reliable drainage networks based on DEMs before the application of hydrologic models.