Structural Impact of Flooding on Buildings in Low-Lying Communities of Anambra State

Recurrent flooding in the low-lying communities of Anambra State, particularly along the Niger-Anambra floodplain in the South East geopolitical zone, poses a severe and escalating threat to the structural integrity of residential buildings. This study investigates the structural impacts of flooding on buildings in selected flood-prone communities including Oguta, Ogbaru, and Awka-Etiti, drawing on post-flood structural surveys conducted following the 2022 flooding season, one of the most extensive on record in the region. Fifty buildings were assessed using a modified rapid damage assessment protocol, with defect categories including foundation undermining, wall saturation and collapse, plinth cracking, and loss of floor finish integrity. Hydrological data from the Anambra-Imo River Basin Development Authority was used to characterise flood depths, durations, and return periods at each site. Findings indicate that buildings with shallow strip foundations below the 0.9-metre depth threshold exhibited four times the rate of structural failure compared to deeper-founded structures. Sandcrete blocks with high water absorption rates, averaging 14.2 percent, showed significant strength degradation after prolonged inundation. The cumulative cost of structural damage across the fifty surveyed buildings was estimated at over 180 million Naira. The study recommends the adoption of flood-resilient construction standards for high-risk zones, including reinforced concrete plinth beams, waterproofed foundation systems, and construction floor levels set a minimum of 0.6 metres above the 100-year flood level. Keywords: flooding, structural damage, Anambra State, flood resilience, foundation failure.