Impact of DEM Resolution on Flood Inundation Mapping (Case study: Karun River)

Articles in Press

Document Type : Research Paper

Authors

1 Department of Water Engineering, Agricultural Sciences and Natural Resources University of Khuzestan, Iran

2 Department of Nature Engineering, Agricultural Sciences and Natural Resources University of Khuzestan, Iran

3 Head of Innovation and Technology Development - Khuzestan Water and Power Organization, Khuzestan, Iran

Abstract

One of the fundamental aspects of flood modeling is the digital elevation model (DEM) of the riverbed and its floodplains. Given that high-accuracy digital elevation maps (DEMs) are not available in many regions of the country, this study seeks to examine the impact of DEM quality of the Karun Riverbed and its floodplains, specifically from the Molasani to Farsiat stations, on flood inundation mapping.

The study area encompasses approximately 110 kilometers of the Karun River, including three hydrometric stations: Molasani, Ahvaz, and Farsiat. Due to the unavailability of riverbed elevation maps, riverbed reconstruction was conducted in a GIS environment. In this study, to evaluate the quality of DEMs on flood mapping, maps with resolutions of 30, 50, 100, and 150 meters were utilized. For analyzing different scenarios, Sentinel-2 satellite images, along with 12 quantitative indices, were employed.

The analysis results show that the Threat Score (TS) decreased from 67% for 30-meter resolution to 66%, 59%, and 56% for 50 m, 100 m, and 150 m resolutions, respectively, indicating an 11% reduction in accuracy with a fivefold decrease in map resolution. The results of various quantitative criteria indicate that intermediate pixel sizes (50×50 or 100×50 meters) can provide reasonable accuracy while reducing computational efforts. This is particularly useful for regional-scale studies or trans-regional analyses. Overall, the findings emphasize the importance of adjusting pixel resolution in accordance with the specific objectives and constraints of flood modeling tasks.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 08 March 2025

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