Development of a Multi-Objective Optimal Design Framework for Integrated Green-Grey Infrastructure

Abstract

Rapid urbanization and climate change have exposed the limitations of traditional grey infrastructure (e.g., UDN and DR), which often lack the resilience needed to address urban water management challenges. The integrated optimal design of green-grey infrastructure is a promising solution, with studies verifying the effectiveness of green infrastructure—such as Low Impact Development (LID)— in reducing runoff and enhancing sustainability, as well as the efficiency and flood mitigation benefits of grey infrastructure. However, previous methodologies have overlooked spatial constraints in integrating green and grey infrastructures, resulting in suboptimal site-specific designs. In this study, a multi-objective optimal design framework is proposed for the integrated green-grey infrastructure. The framework enhances efficiency by identifying feasible locations, narrowing the optimization space, and preventing overlaps. Based on GIS data (e.g., land use maps, slopes, and digital elevation model) and UDN information, the framework identifies potential installation locations for LID and DRs according to the UDN. Additionally, the framework prioritizes facilities based on flood reduction effectiveness to prevent overlaps and maximize efficiency. The results showed that the types of LID and the feasible installation locations for DR significantly decreased, while the design cost of UDN tended to increase further.