Basin geomorphology is a complete system of landforms and topographic features that play a crucial role in the basin-scale flood risk evaluation. Nepal is a country characterized by several rivers and under the influence of frequent floods. Therefore, identifying flood risk areas is of paramount importance. The East Rapti River, a tributary of the Ganga River, is one of the flood-affected basins, where two major cities are located, making it crucial to assess and mitigate flood risk in this river basin. A morphometric calculation was made based on the Shuttle Radar Topographic Mission (SRTM) 30-m Digital Elevation Model (DEM) in the Geographic Information System (GIS) environment. The watershed, covering 3037.29 km² of the area has 14 sub-basins (named as basin A up to N), where twenty morphometric parameters were used to identify flash flood potential sub-basins. The resulting flash flood potential maps were categorized into five classes ranging from very low to very high-risk. The result shows that the drainage density, topographic relief, and rainfall intensity have mainly contributed to flash floods in the study area. Hence, flood risk was analyzed pixel-wise based on slope, drainage density, and precipitation. Existing landcover types extracted from the potential risk area indicated that flash flood is more frequent along the major Tribhuvan Rajpath highway. The landcover data shows that human activities are highly concentrated along the west (Eastern part of Bharatpur) and the east (Hetauda) sections. The study concludes that the high human concentrated sub-basin “B” has been categorized as a high flood risk sub-basin; hence, a flood-resilient city planning should be prioritized in the basin.

中文翻译：

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尼泊尔东部拉普蒂河流域识别山洪暴发潜力区域的地貌方法

流域地貌是一个完整的地貌和地形特征系统，在流域规模的洪水风险评估中起着至关重要的作用。尼泊尔是一个以多条河流为特征并受频繁洪水影响的国家。因此，确定洪水风险区域至关重要。东拉普蒂河是恒河的支流，是受洪灾影响的流域之一，这里有两个主要城市，因此评估和减轻该流域的洪灾风险至关重要。在航天飞机地理信息系统（GIS）环境中，基于航天飞机雷达地形任务（SRTM）30米数字高程模型（DEM）进行了形态计量计算。分水岭，占地3037.29 km ²该地区有14个子流域（命名为A盆地，直至N），其中二十个形态计量学参数用于识别山洪潜在子流域。产生的山洪暴发潜力图被分为五类，从极低风险到极高风险。结果表明，排水密度，地形起伏和降雨强度是造成研究区山洪暴发的主要因素。因此，根据坡度，排水密度和降水量对洪水风险进行了逐像素分析。从潜在风险区域提取的现有土地覆盖类型表明，沿Tribhuvan Rajpath主要公路的山洪泛滥更为频繁。土地覆盖物数据显示，人类活动高度集中在西部（巴拉特普尔的东部）和东部（Hetauda）部分。研究得出的结论是，人类高度集中的次流域“ B”已被归类为高度洪水风险的次流域。因此，该流域应优先考虑具有抗洪能力的城市规划。