A safety factor approach to designing urban infrastructure for dynamic conditions

TL;DR

This paper introduces a safety factor approach for designing urban flood infrastructure that accounts for climate change uncertainties, showing that traditional methods underestimate risks and proposing adjusted safety factors for more robust infrastructure.

Contribution

It proposes a novel safety factor method for urban infrastructure design that explicitly incorporates deep climate and socioeconomic uncertainties.

Findings

Climate uncertainty dominates hydraulic reliability factors.

Adding safety factors of 1.4 to 1.7 improves robustness.

Traditional design methods underestimate flood risks.

Abstract

Current approaches to design flood-sensitive infrastructure typically assume a stationary rainfall distribution and neglect many uncertainties. These assumptions are inconsistent with observations that suggest intensifying extreme precipitation events and the uncertainties surrounding projections of the coupled natural-human systems. Here we demonstrate a safety factor approach to designing urban infrastructure in a changing climate. Our results show that assuming climate stationarity and neglecting deep uncertainties can drastically underestimate flood risks and lead to poor infrastructure design choices. We find that climate uncertainty dominates the socioeconomic and engineering uncertainties that impact the hydraulic reliability in stormwater drainage systems. We quantify the upfront costs needed to achieve higher hydraulic reliability and robustness against the deep uncertainties surrounding projections of rainfall, surface runoff characteristics, and infrastructure lifetime. Depending on the location, we find that adding safety factors of 1.4 to 1.7 to the standard stormwater pipe design guidance produces robust performance to the considered deep uncertainties. The insights gained from this study highlight the need for updating traditional engineering design strategies to improve infrastructure reliability under socioeconomic and environmental changes.