Integrating Grey and Green Engineering in Infrastructure Risk and Resilience Assessment: A Case of Kangundo Road

Abstract

This study assesses the climate change resilience of Kangundo Road, Nairobi, using an integrated modelling approach combining hydrological, geotechnical, and thermal analyses within the Fisher Climate Model framework. Historical climate data and future projections under SSP 4.5 and SSP 8.5 scenarios were used to evaluate the influence of precipitation variability, temperature change, and ex-treme events on road performance. Statistical results show rainfall variability (mean 77.761 mm, SD 201.410 mm) as the dominant hazard driver, with αSea level,a rainfall proxy, weighted at 0.9967, compared to αTemperature at 0.0027, reflecting low thermal variability (mean 18.70˚C, SD 0.627˚C). Sensitivity analysis revealed drainage deterioration (R) and hydrological flow (Qflow) as the most critical resil-ience determinants, with their exclusion reducing resilience scores by over 80% and 55%, respectively. Interaction between R and thermal expansion (ΔL) pro-duced non-linear risk escalation, indicating that multi-hazard impacts accelerate vulnerability beyond single-hazard effects. Grey engineering measures, including reinforced culverts, elevated embankments, and thermally resistant pavements,combined with green infrastructure such as bioswales, vegetative buffers, and permeable pavements, offer optimal resilience. The findings emphasize prioritiz-ing drainage and stormwater capacity in adaptation planning, while incorporat-ing thermally adaptive materials for long-term durability. Limitations include re-liance on model-based projections and focus on a single corridor, warranting ex-pansion to multi-route, socio-economic, and governance-integrated resilience assessments.