Exploring the Hydrological Benefits of a Lid-Based Stormwater Park at the Block-Level: A Case Study in Nanjing, China

Numerous cities are facing frequent urban floods due to high rates of imperviousness and increasingly extreme rainfall events. The Stormwater Park (SP) is an effective nature-based solution way to alleviate urban flood risk and improves stormwater utilization. This study proposed a block-level perspective to measure the hydrological benefit of the SP case in Nanjing, southern China. After clarifying the land use and surface configuration of the study area, different low-impact development (LID) measures, connection patterns and one terminal retention pond were considered to improve stormwater management. Four scenarios (S1: Predevelopment scenario, S2: decentralized LID development scenario, S3: integrated LID development scenario, S4: integrated LID with terminal retention pond development scenario) are simulated by Stormwater Management Model (SWMM) under long- and short-duration precipitations. The results showed the volume capture ratio of annual rainfall (VCRa) of four scenarios: S4 > S3 > S2 > S1. LID practices can effectively reduce runoff volume as decentralized source control in small- and medium-rainfall events. And S4 can better effectively delay peak discharge time and increases the retention volume. The study provides a block-level scenario comparison to evaluate the hydrological effectiveness of SPs and to facilitate decision-making for implementing urban blue-green infrastructure that retains, detains and infiltrates stormwater.