Document Type : پژوهشی
Authors
1 PhD Candidate in Geomorphology, Department of Physical Geography, Faculty of Geography, University of Tehran, Tehran
2 Associate Professor, Department of Physical Geography, Faculty of Geography, University of Tehran, Tehran, Iran.
3 Professor of Department of Physical Geography, Faculty of Geography, University of Tehran, Tehran, Iran
Abstract
There are various methods for determining flood-prone areas, including hydraulic and geomorphological approaches. Due to the extensive nature of flood-prone watersheds, 1:1000 scale maps are either not available in all regions or require significant time and resources to produce. This study aims to identify optimal methods for determining flood-prone areas in regions lacking topographic data. It examines three separate 25-kilometer segments of the Sefidrud River: Yasavol in Kurdistan Province, Gilvan in Zanjan Province, and Astaneh in Gilan Province, using hydraulic and geomorphological approaches. The hydraulic method was implemented using a 1:1000 scale topographic map and two freely available remote sensing DEMs: SRTM (30 meters) and ALOS PALSAR (12.5 meters) in the HEC-RAS . The geomorphological identification of flood-prone areas was conducted based on aerial photographs, both old and new satellite images, field visits, and evidence of past flooding. The results indicate that in mountainous areas, in the absence of high-resolution spatial data, the use of 30-meter SRTM and 12.5-meter ALOS PALSAR DEMs provides acceptable accuracy for delineating flood-prone areas, provided that modeling results are refined and adjusted based on expert opinions and field observations. The comparison of the 30-meter SRTM and 12.5-meter ALOS PALSAR DEMs indicates that in mountainous and hilly areas, both DEMs yield relatively similar results. However, the 30-meter SRTM DEM, particularly in mid-term and long-term return periods, produces more favorable outcomes. In flat and lowland areas, remote sensing DEMs do not provide satisfactory results, and the use of geomorphological methods for delineating flood-prone areas yields higher accuracy
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