Integrated Framework for Valuing Urban Wetlands as Flood-Mitigation Infrastructure in Rivers State, Nigeria

Abstract

Urban wetlands provide key services and support natural hydrological regulation; yet the values and flood-mitigation services they provide could be under-quantified in rapidly urbanizing coastal areas of Africa. Here, Geographic Information System (GIS) flood-risk mapping, spatial hedonic pricing and community perception studies are used to evaluate the capitalized impact of wetland and flood-risk exposure on residential property values within four Local Government Areas of Rivers State, Nigeria (Port Harcourt, Obio-Akpor, Eleme and Oyigbo) based on a novel sample of 1,200 property transactions, of which 742 are validated residential sales, supplemented with 458 long-term property lease equivalents that were converted to annual figures, in addition to survey-based responses from 612 valid household responses in 680 questionnaires, with a 90.0% response rate. Using a conventional hedonic Ordinary Least Squares (OLS) model, augmented with GIS-estimated elevation and proximity measures, together with a qualitative, structural thematic analysis of survey inputs, the model estimates that residential properties near functioning urban wetlands are likely to see a median price premium of 8.55% (p < 0.05) in benefit of this amenity, in addition to localized drainage benefits; where properties in high flood hazard areas lacking wetland buffer protection could suffer a capitalized price penalty of -10.78% (β= -0.114, p < 0.001). While 78.4% of residents are aware of flood hazards, institutional failure may in fact delay wetland buffer protection, the study points to the need for the incorporation of nature-based solutions into municipal planning laws to establish obligatory wetland buffer zones, alongside blended green-urban financing strategies.