V3I7P63

A Coupled Multi-Physics Climate-Responsive Model for Predicting Performance Degradation of Kangundo Road under Coupled Hydrological–Thermal–Geotechnical Loading

Caroline M. Mbengei^1*, Simpson Osano², Calvince Othoo³

Abstract

Conventional resilience assessment of road infrastructure treats hydraulic, thermal and geotechnical stressors as independent contributors that are combined by simple weighted superposition. This assumption ignores the physical reality that these processes interact: standing water accelerates drainage siltation, saturation lowers effective stress and slope stability, and moisture accelerates thermal and oxidative damage of the bituminous surfacing. This paper reformulates an existing indicator-based resilience model developed for the flood-prone Kamulu–Kangundo Road corridor in Nairobi into a coupled multi-physics degradation system. Hydraulic-capacity deficit, accumulated thermal strain, geotechnical instability and drainage deterioration are represented as time-dependent state variables governed by a system of coupled ordinary differential equations, driven by downscaled CMIP6 climate forcing under the SSP2-4.5 and SSP5-8.5 pathways over a 75-year horizon. Simulation shows that neglecting inter-process coupling underestimates cumulative degradation at end of design life by approximately 35 percent relative to the coupled formulation. A structural sensitivity analysis, in which each component and the feedbacks it drives are removed simultaneously, confirms that hydraulic loading is the dominant systemic lever, its removal reducing predicted degradation by about 78 percent, while drainage deterioration emerges as a substantially larger systemic contributor (about 55 percent) than its additive share alone would suggest. The high-emission SSP5-8.5 pathway produces the steeper degradation trajectory and is recommended as the design baseline. The results support a shift from empirical, indicator-based resilience scoring toward mechanistic, performance-based road design in which climate-driven feedbacks are represented explicitly.

Keywords:

Climate resilience; Coupled multi-physics model; Road infrastructure; Hydrological–thermal–geotechnical loading; Performance-based design; Kangundo Road