A global analysis approach for investigating structural resilience in urban drainage systems

TLDR

Urban drainage resilience must account for diverse threats, yet current hydraulic reliability methods mainly address extreme rainfall or dry‑weather flow overloads while overlooking equipment failure, pipe collapse, and blockage. This study introduces a global resilience analysis framework to systematically evaluate system performance under a broad spectrum of structural failure scenarios caused by random cumulative link failures. Link‑failure envelopes are derived from the upper and lower bounds of simulated flood volume and duration, and a composite resilience index that integrates magnitude and duration quantifies residual functionality at each failure level. Applying the method to Kampala’s drainage network revealed its resilience characteristics and demonstrated that targeted adaptation strategies can enhance performance against cumulative link failures.

Abstract

Building resilience in urban drainage systems requires consideration of a wide range of threats that contribute to urban flooding. Existing hydraulic reliability based approaches have focused on quantifying functional failure caused by extreme rainfall or increase in dry weather flows that lead to hydraulic overloading of the system. Such approaches however, do not fully explore the full system failure scenario space due to exclusion of crucial threats such as equipment malfunction, pipe collapse and blockage that can also lead to urban flooding. In this research, a new analytical approach based on global resilience analysis is investigated and applied to systematically evaluate the performance of an urban drainage system when subjected to a wide range of structural failure scenarios resulting from random cumulative link failure. Link failure envelopes, which represent the resulting loss of system functionality (impacts) are determined by computing the upper and lower limits of the simulation results for total flood volume (failure magnitude) and average flood duration (failure duration) at each link failure level. A new resilience index that combines the failure magnitude and duration into a single metric is applied to quantify system residual functionality at each considered link failure level. With this approach, resilience has been tested and characterised for an existing urban drainage system in Kampala city, Uganda. In addition, the effectiveness of potential adaptation strategies in enhancing its resilience to cumulative link failure has been tested.