Rapid urbanization in China has caused severe water and environmental problems in recent years. To resolve the issues, the Chinese government launched a sponge city construction program in 2015. While the sponge city construction initiative is drawing attention and is spreading fast nationwide, some challenges and risks remain. This study surveyed progress of all 30 pilot sponge cities and identified a broad array of challenges from technical, physical, regulatory, and financial, to community and institutional. The most dominant challenges involve uncertainties and risks. To resolve the issues, this study also identified various opportunities to improve China’s sponge city construction program. Based on the results, recommendations are proposed including urging local governments to adopt sponge city regulations and permits to alleviate water quality and urban pluvial flooding issues, fully measuring and accounting for economic and environmental benefits, embracing regional flexibility and results-oriented approaches, and focusing on a wider range of funding resources to finance the sponge city program. Coordination among other government agencies is critical, and this is true at all level of governments. Only through greater coordination, education, and broader funding could the sponge city program be advanced meaningfully and sustainably.

With digital information technology based on limited data, disaster simulation review is an important guideline for analyzing disaster mechanisms, planning post-disaster reconstruction, and improving defense capability. Taking the “7.20” flash flood in the Wangzongdian river basin as a research area, a hydrological-hydrodynamic model was established using limited measured data. The results showed that the extreme rainstorm caused flooding in mountainous areas and the collapse of subgrade water damming, and the high-level flood quickly flowed into Wangzongdian Village in a short distance, which was the main cause of this serious disaster. Considering the collapse due to the congestion of the upstream bridge, the simulated flood flow in Wangzongdian Village reached 782 m³/s, which was basically consistent with the post-disaster survey results, with a relative error of only +8%. The modeling strategy proposed in this paper is applicable in the review of sudden heavy rainstorms and flash floods and can provide technical guidance for future flash flood simulation review analysis in other areas.

Hubei province is located in the center of China with 56% total area characterized with mountainous area. Thus, flash flood caused by extreme rainfall has become one of the significant obstacles that highly affect the social and economic development of the province. In order to scientifically understand the mechanism of flash flood disasters and provide technological support to the local flood prevention and control work, the IWHR designed and developed a new distributed hydrological model named China-FFMS that can simulate the evolution of natural disasters and make an assessment by setting the flood water sources in line with the flow discharge. The FFMS was further applied to simulate the 8.12 flash flood disaster that occurred in the Liulin county of Hubei province on 12 August (“8.12”) and fed by the data collected from the national flash flood disaster investigation and assessment. The calculated peak flow was 666.22 m³/s with an error of +13% compared with postdisaster investigation data (589 m³/s). The results showed that using a multisourced modelling approach, e.g., mixing spatiotemporal variables and sources, to simulate the flash flood process was able to accurately reproduce the flood process and the consistence of the flow discharge, thereby explaining the underlying reason of the disaster formation and evolution. Regarding the case of the Liulin county, the main factor leading to the disaster was the overlapped peak flow where the Dunne flood peak of three different tributaries from the upper reach met together at the same time. Moreover, the peak flow of the Lianhua river at the downstream of Liulin County also arrived at the same time as the upstream peak, which obstructed the flood progress and increased the damage of the disaster. According to the analysis, several suggestions and recommendations are proposed such as the improvement of the forecast and early warning system of the upstream areas, the optimization of the current flood defense plan, and the enhancement of the residents’ awareness of flash flood disasters.

From 11 to 12 August 2021, an extreme rainstorm attacked the Liulin Town, a very common town in Hubei Province, China. The rainstorm triggered flash flood and caused heavy live losses. This study first conducted an analysis on the causes of the flash flood disaster, then, performed a simulation to review the flash flood process, and finally discussed the technical strategies and approaches to avoid life losses in similar cases. The main understandings include: (1) accumulative rainfall of shorter interval and time-sliding is significantly helpful to improve warning accuracy; (2) flash flood risk needs to be evaluated at catchment scale and making room for floods is necessary; (3) residential buildings threatened by flash floods need to rebuild some structures for live-saving in emergency circumstances; and (4) early warning system needs to have capabilities to collect real basin-wide rainfall and flood information, especially in case of rainstorm, and to be smart to judge hazard level.

China has a large number of county-level cities in mountainous areas which are very prone to rainstorm-caused floods. Moreover, as county-level city, the exposures, as well as available funding and technologies, are very limited, and flood control standards are also constrained, therefore, resilience building is essential for flood management. Taking Xichuan as an example, this paper performed the analysis on the present, future, and residual flood risks in the urban area using flood simulation and scenario analysis methods, in which several key factors were taken into account, including built-up area expansion, flood control infrastructure improvement, rainfall change due to climate warming, and changes in the hydrological characteristics of the underlying surface due to human activities. Based on these findings, the strategies were proposed and analyzed for resilience building, including (1) practicing systematic management at river basin scale to delay and cut down of peak discharge flow of floods to the city, (2) establishing a multi-level, synergistic defense system integrating gray, green, and blue infrastructures to mitigate flooding, waterlogging and river bank erosion in urban areas, (3) enhancing the resilience of key infrastructures to keep the basic functions for the city during flooding, (4) strengthening monitoring and early warning capabilities, and (5) raising public’s awareness of flood risks and capacity of responding to floods, both (4) and (5) are significantly helpful for the public to timely take correct actions in case of floods.

A nationwide project on soil loss change monitoring was successfully performed in 2018 in China, and a special technical regulation was developed for the purpose of unified approach and high-quality outcomes from the project. Taking the Dachaoling Watershed as an example, this paper aims to discuss the reasons for surface soil loss change by the monitoring approach which is from the technical regulation and includes steps of data preparation, surface soil erosion factor analysis, soil erosion analysis, soil loss change analysis, and countermeasures and suggestions for reducing soil loss. First, landuse, soil and water conservation measures for 2018 were extracted from remote sensing image of high spatial resolution while vegetation cover for 2018 from Landsat TM and MODIS NDVI product - MOD13Q1 data; second, surface soil erosion factors for were analysed for China Soil Loss Equation (CSLE) based on the outputs of first step; third, CSLE was used to make analysis on surface soil loss in the selected watershed; fourth and finally, transition matrix analysis method to make analysis on surface soil loss change from 2011 to 2018 and the reasons. The results indicate that the soil loss change monitoring approach is practicable and effective; landuse changes are both chief affecting factor and main controlling ways to soil loss; and human actions changing landuse need to be more cautious and far-sighted in the future.