Flood Risk Assessment and management in the Benue Trough Nigeria

This research was borne out of the reoccurring flood in Nigeria but especially the extreme flooding in 2012 in the Benue Trough which brought into focus regional and national impacts by creating refugee communities and food insecurity. Previous reports within the study area did not consider vulnerability, resilience, community-based risk approach, flood extent and inundation mapping, management strategies, or multiple flood sources nor did they use geospatial methods. This research makes the contribution to knowledge by including these factors and approaches and an historical record for the 2017 flood event, which has previously received little or no attention in published literature or government archives. The multi-dimensional and holistic approach used here has shed more light on prevalent issues that will lead to hyper-local and more efficient management by both government and stakeholders, which can be replicated for other Nigerian states and beyond. The research examines the 2017 flood event in the Makurdi area, evaluating, and mapping the flood extent, perceived causal factors, proximity to water bodies, and flood impacts. It uses mixed methods and DPSIR model, analyzing land use, hydrological and meteorological data, stakeholder interviews and field survey with both residents' and stakeholders. Rapid risk assessment was integrated with geospatial mapping showing spatial distribution of damage and flood depth. Flood extent and inundation data reveal inland flooding and the possibility of varied causes of the flood, while analysis shows decreases in natural forest and, farmland and increases in 'bare ground' and ‘built-up’ areas, possibly related to accelerated rates of population growth and anthropogenic activities. Hydrological and meteorological trends show increased river water levels and discharge, slight increases in rainfall, increases in rainfall intensity, changing monthly peaks, and changes in seasonality, and frequency. Flooding in 2017 occurred south of the river Benue and was not restricted to the floodplain. Although flood depth was greater near to the main channel, damage away from the channel was similar to or, in some cases, more serious than that on the floodplain. Residents’ perceived flood types were surface water, river, groundwater, rainfall, smaller courses, and public sewer with causes mentioned as river overflow, blocked drains, surface water, ground water, rains, and indiscriminate waste disposal. Peak discharge in the 2017 event were directly attributed to rainfall, urbanisation, and increased occupation of flood risk zones. 3700 people were displaced, mainly from inland areas showing high levels of vulnerability using the CBDRI assessment. The research shows that there is a combination of increased vulnerability, lack of preparedness, poor understanding of risk and inadequate government response. Underlying causes of vulnerability are lack of capacity: early warning systems, emergency funds, application of building codes and protective structures; Economic: attitude to disaster and lack of priority for protection, budgets, and accessibility; Social: high poverty and low adult literacy; and Physical: high population growth and limited access to essential services. The 2017 floods provided a local scale test of mitigation plans, which is lacking, and exposed the failure of the current management strategy. Revitalizing of existing and implementation of recommended strategies such as dredging, building embarkments, Sendai framework, risk communication, Blue-green solutions and recovery programs that will rebuild affected communities, individuals and livelihood while building a safe environment in the face of disasters is key