Assessment of Flood Risk and Drainage Infrastructure in Agricultural Lowlands in Anambra State

This study assesses flood risk exposure and evaluates drainage infrastructure adequacy in agricultural lowlands in Anambra State, South East Nigeria. Anambra State's Niger River floodplains support productive lowland rice, vegetable, and yam farming, but recurrent flooding causes significant crop losses and soil degradation in these productive areas. Understanding flood risk patterns and the performance of existing drainage structures is essential for designing effective flood management interventions. This study uses a combination of hydrological measurement, GIS mapping, and survey methods. Rainfall and river gauge data from the Anambra-Imo River Basin Development Authority for 2018 to 2023 are used to characterise flood frequency. GIS analysis of topographic data identifies flood-prone agricultural zones in Ogbaru, Anambra West, and Ayamelum local government areas. Field surveys assess the condition and capacity of drainage channels, culverts, and flood embankments in the study area. A survey of 160 farmers documents flood damage frequency and agricultural production losses. Findings reveal that agricultural lowlands experience an average of 2.3 significant flood events per year, with peak inundation durations of 8 to 21 days. Drainage infrastructure is in generally poor condition, with 41 percent of channels blocked or collapsed. Average annual crop losses from flooding are estimated at 35 percent of seasonal production in low-lying areas. The study concludes that drainage rehabilitation is urgently needed in Anambra State agricultural lowlands. It recommends prioritised drainage maintenance and flood-tolerant variety introduction.

Keywords: flood risk, drainage infrastructure, Anambra State, lowland agriculture, flood management.