Assessing Flood Vulnerability Zones and Their Driving Factors to Guide Community-Based Resilience Planning Across Ngororero District, Rwanda

Abstract

Floods are recognized as devastating and deleterious natural disasters which are contemporary substantial threats to communities, exerting profound impacts on human lives, infrastructure, and the environment. Hence, the aims of this research were to assess and map the flood vulnerability zones, determine the primary local factors driving flood vulnerability, and evaluate the existing flood mitigation measures and propose evidence-based recommendations for enhancing community-based flood resilience. Using an integrated approach, this study combined remote sensing, Geographic Information Systems (GIS) techniques and expert knowledge, to map and model flood vulnerability zones, determining the risk levels using the AHP model considering a set of driving independent variables including elevation, slope, rainfall, land use/land cover (LULC), soil type, distance to streams, distance to roads, flow accumulation, and topographic wetness index (TWI). The results of the study for the first objective showed that 66.6% of the area classified as very high and high vulnerability zones, mainly in the northern and north-western regions. Moderately vulnerable areas covered 18.1%, predominantly in the southern and central parts, while low and very low vulnerability zones comprised 15.3%, mainly in the central and north-eastern regions. This highlights the heterogeneous distribution of vulnerability across the district, emphasizing the need for tailored mitigation strategies. The results of the second objective revealed rainfall (26.7%), proximity to rivers (21.4%), flow accumulation (13.3%), and LULC (12.5%) as the most influencing factors to flood vulnerability in the study area. In addition, the soil texture (9.4%) and elevation (8.2%) exhibited moderate influence, while TWI (4.1%), proximity to roads (2.8%), and slope (1.6%) disclosed a low influence. Understanding these factors enables prioritization of mitigation efforts, focusing on addressing rainfall patterns and proximity to rivers. The third objective suggested sustainable land management practices such as afforestation, agroforestry, terracing, and engineering strategies such as dam construction, resilient drainage systems in addition to strengthening