A new framework to assess and optimize urban flood resilience with green-grey-blue system

Abstract

The vulnerability of cities to flood has become a global issue due to urbanization. Although various studies have been evaluated urban flood resilience using various indicators, a comprehensive flood resilience assessment method considering the entire process of stormwater runoff production and concentration remains a gap. To cope with this issue, a three-step new framework integrating index system construction, coupled model simulation and scenario optimization with green-grey-blue system (GGBS) was established. The results showed that poor flood recovery ability contributed mainly to low urban flood resilience (FR) in urbanizing areas. Optimization of GGBS preferred for blue and grey facilities, due to high marginal cost of green infrastructures (GIs). However, FR could increase by 78%-104% when incorporating GIs. Nevertheless, either few or excessive GIs would result in higher marginal costs, possibly due to the tradeoff between benefits and cost. Synergistic effects of GGBS were characterized by flood resistance and recovery enhancement, with mean recession time, mean runoff discharged into river, and storage capacity being the most sensitive indicators. Incorporation of GIs could reinforce the synergies by regulating landscape composition and hydrological connection.