Green infrastructure for urban resilience:integrating nature-based solutions into stormwater management in Nairobi

Abstract

Increasing climate variability challenges urban stormwater management in rapidly growing African cities, with Nairobi exemplifying the crisis: traditional grey infrastructure proves structurally unsound, socially inequitable, and inadequate against frequent floods. This study systematically introduces green infrastructure (GI)—such as permeable surfaces, rain gardens, and bioretention systems—as a resilience-building mechanism. Objectives encompass assessing current stormwater challenges, evaluating GI's hydrological and ecological benefits, analyzing socio-economic and governance barriers to adoption, and identifying mainstreaming strategies in Nairobi's planning. Employing a mixed-methods case study across five sub-areas (Kibera, Mukuru, Langata, Lunga Lunga, Kasarani), the research integrates surveys (N=150 residents; N=26 officials/stakeholders), field observations, GIS mapping, and reviews of policy documents. Quantitative data underwent SPSS analysis via descriptive statistics, ANOVA, and chi-square tests; qualitative insights employed thematic analysis in NVivo; GIS visualized drainage networks, impervious surfaces, and flood hotspots. Findings reveal stark infrastructural inequities: 82-88% of informal settlement residents rate drainage as poor, versus 47% in Kasarani, with ANOVA confirming significant flood frequency disparities (p<0.05). Kibera and Mukuru experience nearly triple Kasarani's annual floods, exacerbated by a 32% impervious surface increase since 2000 (χ²=28.7, p<0.01) and poor maintenance (r=-0.46, p<0.05). Socio-economic tolls include average annual household losses of KES 35,000, business losses of KES 70,000, industrial damages up to KES 250,000, and 38% cholera prevalence in Kibera/Mukuru (χ²=34.5, p<0.01). GI demonstrates hydrological, ecological, and socio-economic advantages, yet requires integration with waste management, preventive maintenance, and community engagement for efficacy. Governance hurdles—fragmented mandates (58%) and inadequate budgets (72%)—persist, but enabling mechanisms like participatory stewardship and innovative financing (e.g., climate funds, green bonds) offer pathways forward. Theoretically and practically, this positions GI not merely as ecological but as a socio-political-economic tool for resilient urban Africa.