Green Space Optimization Strategy to Prevent Urban Flood Risk in the City Centre of Wuhan

Assessment of urban flood susceptibility and role of urban green space (UGS) on flooding susceptibility using GIS-based probabilistic models

With rapid urbanization, the green space in urban areas is replaced with impervious built-up areas, which increases the frequency of urban floods. Kamrup Metropolitan District, Assam, is near the Brahmaputra and is highly prone to urban flooding. The present study aims to develop the urban flood susceptibility index (FSI) and to analyze the role of urban green space (UGS) as a nature-based solution (NBS) for urban flood susceptibility. Two types of flooded urban areas are observed using a two-stage cluster analysis. A GIS-based urban FSI is developed using logistic regression (LR), frequency ratio (FR), Shannon entropy (SE), certainty factor (CF), and weight of evidence (WoE) models, and variation of FSI is assessed for different UGS areas. According to the area under curve (AUC), the performance of all five models falls under the good to excellent class. The average UGS ratio for non-flooded is higher than for flooded areas, and with an increase in the area of UGS, the flooding probability decreases for all the models. The findings of the present study emphasize the importance of UGS and can be used for effective urban flood risk mitigation and management planning.

Systematic Application of Sponge City Facilities at Community Scale Based on SWMM

In the context of global climate change, many countries have taken corresponding measures to cope with the stormwater problems in urbanization. The Chinese government introduced the concept of Sponge City to improve the urban water ecological security, which is a systematic project. Taking the urban community as our research object, we studied the combination application of LID (low-impact development) measures and retention ponds in the community and then discussed the practicability of the systematic application of Sponge City facilities in the construction of community drainage systems. There are four simulation scenarios in SWMM (stormwater management model): traditional drainage scenario, LID scenario, retention pond scenario, and LID-retention pond scenario. By comparing the effects of different facilities on runoff and outflow under the six return periods of 1a, 2a, 5a, 10a, 20a, and 50a, we find that LID measures have evident effects on runoff and outflow reduction. Still, they are greatly affected by the return period. The retention pond has no noticeable impact on runoff, but it reduces the peak value of outflow and is less affected by the return period. The combination of LID and retention pond can combine their advantages, reduce the peak flow rate of the site stably and relieve the pressure of the urban drainage system. This study provides a basis for the graded implementation of Sponge City, especially for community-scale rainwater regulation.