Distinctions of geomorphological properties caused by different flow-direction predictions from digital elevation models

Abstract

Several algorithms for flow-path determination have been proposed to pursue a more realistic simulation for flow transmission in watersheds. However, the diversity of existing algorithms may lead to significant differences in the extraction of geomorphological properties. Therefore, preliminary knowledge about these approaches is necessary. In this study, the five most widely used methods – the D8, D, MD, D4, and MD8 algorithms – for flow-direction determination were implemented to investigate watershed extent, water mass contribution, and the track of the longest watercourse. Distinctions of these properties should affect subsequent applications of hydrological analyses, such as the time of concentration calculation and peak discharge estimation. For an example case in Taiwan, the watershed extent and the longest watercourse obtained from the multiple-direction (MD8) algorithm could reach 1.2 and 1.8 times, respectively, that derived from the single-direction (D8) algorithm; moreover, the multiple-direction (MD8) algorithm manifested the weakest ability of collecting water mass from the watershed. A simple index was developed in this study to rank the effects of flow dispersion and flow concentration among the different flow-direction algorithms.

Keywords:

• flow direction
• digital elevation model
• watershed boundary
• stream network extraction
• flow dispersion

Additional information

Funding

This research was supported by the Ministry of Science and Technology, Taiwan, R.O.C. [grant MOST 103-2625-M-019-002], [MOST 103-2923-E-019-001-MY3]. The authors acknowledge the financial support provided by the Ministry of Science and Technology.