Assessing the past and adapting to future floods: a hydro-social analysis

Floods are extreme events affecting millions of people worldwide and causing loss worth billions. The magnitude and frequency of floods are likely to increase with altered climate, and developing countries tend to suffer the most because of low resilience and adaptive capacity. This research aimed to analyze existing and preferred future flood adaptation strategies in a flood-prone West Rapti River (WRR) Basin of Nepal, using hydrological analysis and flood modelling, and a social survey of 240 households (HHs) and several focus group discussions (FGDs). The specific objectives were to (1) understand the rainfall-flood behaviour of the basin in a simplistic way, (2) carry out flood modelling to generate inundation maps for informing the local people, and (3) identify flood adaptation strategies based on people's perception. Flood inundation maps are generated for four scenarios based on return periods: scenario I (2 years), scenario II (20 years), scenario III (50 years), and scenario IV (100 years). Results show that the southern parts of three rural municipalities (Duduwa, Narainapur, and Rapti Sonari) get inundated almost every year irrespective of the flood magnitude. This information was presented to local communities before administering the HH survey and FGDs so that they could make informed decisions. During the survey, the preference of people's adaptation strategies for the four flood scenarios was explored and prioritized. Our findings suggest that peoples' thoughts and preferences for adaptation strategies changed with exposure to flood magnitudes. For example, bamboo mesh with sand filled bags-simplest and least expensive adaptation strategy-was preferred for a less severe flood while a complex and expensive technique reservoir/flood regulating structures was preferred for a devastating flood scenario. Thus, this study has highlighted firstly, the importance of inundation maps to understand and inform the local people about floods and their impacts; and secondly, the value of information to the people enabling them to make informed decisions. The novelty of this empirical study lies in a multi-disciplinary assessment framework which integrates scientific information, stakeholder knowledge, and local people's perceptions of flood risks and adaptation strategies for the future. Such an approach of hydro-social analysis has the potential for replication in flood-prone regions globally, with similar bio-physical and socio-economic conditions.