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'Sponge City' is the term used to describe the Chinese government's approach to urban surface water management. The concept was conceived in 2014 in response to an increasing incidence of urban flooding or water-logging in Chinese cities. While ambitious and far-reaching in its aim (of decreasing national flood risk, increasing water supply and improving water quality), the initiative must be implemented by individual subprovincial or municipal-level government entities. Thus, while the concept is similar to sustainable drainage systems (SuDS) in the UK (or low-impact development (LID) in the USA), it is developing with different regional characteristics, and during continuing rapid urbanization. Indeed, the increasing use of national rather than international examples of best practice reflects a growing body of knowledge that has evolved since the start of the Sponge City initiative. In this paper, interpretation and development of the national Sponge City guidelines are assessed for the Ningbo Municipality, an affluent and rapidly expanding city on China's low-lying east coast. While climate, geology and socio-economic factors can all be seen to influence the way that national guidelines are implemented, project financing, integration and assessment are found to be of increasing influence. This article is part of the theme issue 'Urban flood resilience'. [ABSTRACT FROM AUTHOR]

Flood control risk is one of the main risks affecting the safe operation of large-scale water transfer projects. Systematically identifying the flood control risk in the project and carrying out risk classification and hierarchical management are problems for project managers. Based on the theory of system and risk assessment, this paper starts with the various risk sources and risk events involved in the whole process of the flood disaster chain, the risk of flood disaster factors, the exposure of the disaster-bearing body, and the vulnerability of the disaster-originating environment are combined. Then, we systematically and comprehensively identify the flood control risks of a large-scale water transfer project, which are divided into four types of risk elements: rainfall–runoff; confluence and flow capacity; the geological characteristics of canal section; economic and social layouts. Specific risk factors are identified for each type of risk element, and a flood control risk evaluation index system for a water transfer project is proposed. According to the framework of the analytic hierarchy process (AHP), a quantitative assessment of comprehensive flood control for water transfer projects is carried out. Taking the middle route of the South-to-North Water Transfer Project in China as an example, this paper evaluates the integrated flood control risks of 39 engineering units, identifies six units with higher risk levels, analyzes the causes, and suggests engineering and non-engineering countermeasures to prevent and reduce the occurrence of risk accidents. This method is not only used for comprehensive flood control risk assessment and risk management in the operation and management stage of the large-scale inter-basin water transfer project, but also has a reference value in considering the optimal layout of the project water transmission line from the perspective of flood control in the planning and design stage. [ABSTRACT FROM AUTHOR]

• The extent of flooding in China is greater than in any other country. • Nearly 66% of China's landmass is submerged by flooding. • Financial toll of flooding accounts for approximately 1.42% of the annual GDP. • Various forms of climatic change contribute to flooding. The extent of flooding in China is more significant than in any other country. Our research reveals that approximately 66 % of China's landmass is submerged by flooding, affecting about 50 % of the population. Furthermore, the financial toll of flooding now accounts for approximately 1.42 % of the annual gross domestic product (GDP), which is almost 40 times higher than the corresponding figure for the United States. We have observed that Zhengzhou city in Henan province, which faced a devastating flood in 2021, received a significant amount of rainfall, specifically a total of 552.5 mm within a 24-hour period. The floods in Henan province in 2021 caused considerable damage, including impacting nearly 15 million people, resulting in almost 400 deaths, damaging over 10,000 square kilometers of agricultural land, causing almost $19 billion in economic losses, and leading to the collapse of over 35,000 households and damage to various properties. In a similar manner, the significant flooding that occurred in southern China in 2020 impacted approximately 7.1 million individuals across eight provinces and resulted in 54 fatalities, the collapse of 6,700 houses, and incurred a direct economic loss of US$3.33 billion. We found that rainstorms have significantly increased to 10 % in the last 60 years in China. In this paper, we delved into exploring the existing published articles, reports, and government and authoritative legal texts to analyze the causes and impacts of flooding in China's flood-prone regions and potential mitigation strategies to reduce the repercussions of distressing flood events. We believe this study will help policymakers by providing new insights while formulating policy to reduce the loss caused by high-level flooding. [ABSTRACT FROM AUTHOR]

The Huaihe River Basin is a transitional river located in the transitional climate zone in China, and it has been frequently hit by big floods and suffered from flood disasters. Flood control and management of the areas are of vital importance of the Huaihe River Basin in its social and economic development. In this paper, pioneer works of summarizing the flood management has been done for the Huaihe River in China. It firstly introduces flood and flood disasters of the River basin, Moreover, the paper summarizes achievements in flood control and management. Furthermore, it discusses experiences and enlightenment in flood control and management and draws conclusions for the research. [ABSTRACT FROM AUTHOR]

Consecutive extreme rainfall events, especially those having unfavourable spatio-temporal patterns, always trigger large floods. This paper aims to examine, through the multivariate hydrological frequency analysis, the probability of the synchronous occurrence of rainfall extremes in the Pearl River basin. The copula method together with the stationarity and independence tests, which are crucial to the valid use of statistical methods in regional frequency analyses, were applied in the study. The obtained results indicate that: (1) major precipitation events of the annual maximum 1-, 3-, 5- and 7-day rainfall recorded at 42 stations are the flat looking series and variables are independent, (2) the marginal distribution of all extreme rainfall variables in four homogeneous hydrologic regions fits the log-normal probability distribution and most of their joint distribution fits the Gumbel-Hougaard distribution, (3) on that basis the contour maps of the joint distribution of annual maximum 1-, 3-, 5- and 7-day rainfall between different regions are drawn and the probability of the synchronous occurrence of the extreme rainfalls in different regions are estimated. These findings have great practical value for the regional water resources and flood risk management and are important in exploration of the spatial patterns of rainfall extremes in the Pearl River basin in order to reveal the underlying linkages between precipitation and floods from a broader geographical perspective. [ABSTRACT FROM AUTHOR]

The utilization of ecosystem services in flood management is challenged by the complexity of human-nature interactions and practical implementation barriers towards more ecosystem-based solutions, such as riverine urban areas or technical infrastructure. This paper analyses how flood management has dealt with trade-offs between ecosystem services and practical constrains towards more ecosystem-based solutions. To this end, we study the evolution of flood management in four case studies in the Dutch and German Rhine, the Hungarian Tisza, and the Chinese Yangtze basins during the last decades, focusing on the development and implementation of institutions and their link to ecosystem services. The complexity of human-nature interactions is addressed by exploring the impacts on ecosystem services through the lens of three management paradigms: (1) the control paradigm, (2) the ecosystem-based paradigm, and (3) the stakeholder involvement paradigm. Case study data from expert interviews and a literature search were structured using a database approach prior to qualitative interpretation. Results show the growing importance of the ecosystem-based and stakeholder involvement paradigms which has led to the consideration of a range of regulating and cultural ecosystem services that had previously been neglected. We detected a trend in flood management practice towards the combination of the different paradigms under the umbrella of integrated flood management, which aims at finding the most suitable solution depending on the respective regional conditions. [ABSTRACT FROM AUTHOR]

Abstract: Effective flood management measures incorporate the flood mitigation functions of natural ecosystems, but the exact functions and effects of forests, grasslands and other ecosystems in mitigating floods are not clearly understood. In this paper, a flood mitigation assessment model was established based on the Soil Conservation Service (SCS) method, and the function and potential capacity of ecosystems for mitigating flooding in the Upper Yangtze River Basin (UYRB) were assessed. The monetary value of flood mitigation service was calculated by formulating an exponential function with respect to the amount of storm and flood damage. The results showed that ecosystems in the UYRB reduced flooding by a total of 42.8 billion cubic meters. Statistical equations developed for the amount of storm and flood damage gave an average of 6.479 billion RMB Yuan as the value of ecosystem flood mitigation in the UYRB. Despite their small cost, ecosystems have the potential to reduce flood damage by more than half, an indication of the important role of ecological systems in flood management. This approach can be used to identify high-value areas for ecological protection, and also to provide the governments at various levels with important information for decision-making related to integrated flood management. [Copyright &y& Elsevier]

Abstract: This study aims to investigate whether, to what extent and how a transition toward integrated flood management has taken place in the Dongting Lake area at the middle Yangtze. Accordingly, we conducted a longitudinal research of its flood management (1949–2009). We developed an analytical framework linking regime components to two societal learning types (double and triple-loop learning) that are key to a regime transition. Our study shows that the transition toward integrated flood management has already started, but the whole regime transformation will still take time to complete, due to, for example, the not-yet-ready decision-making processes that shape the structure changes as well as the incompatibilities between what is on paper and real implementation. To understand how the regime transition took place, we investigated where and how triple-loop learning was initiated as well as how so-called “informal learning processes” has contributed to the transition of Dongting flood management. [Copyright &y& Elsevier]

Summary: After the Yangtze River was closed by the Three Gorges Project (TGP) in 2003, erosion occurred from the dam site to the river mouth, especially in the middle and lower reaches of the Yangtze River. However, in some local areas of Chenglingji reach which holds the key position for flood management, there is actually deposition in contrast to the expected erosion. In this paper, a one dimensional mathematical model of the river network with sediment transport is used as the tool to simulate flow and fluvial processes. The calculation domain is from Yichang, which is downstream of the dam, to Hankou, the controlling node of flood management, 694km long in total. The model is calibrated based on the field data of hydrology and sediment transport during the period from October 2003 to October 2008. Then the model is utilized to simulate the erosion and deposition of the middle and lower reaches of the Yangtze River in the next two decades, and produce the results of a new river channel after river bed deformation occurs. The typical flood processes of 1954 and 1998 in the Yangtze River basin are used to check the flood management scheme for the research area, and results show that water storage of Three Gorges Reservoir (TGR) and a flood diversion program downstream of the Yangtze River should be taken into consideration. [Copyright &y& Elsevier]

• The proposed optimization method resolved the conflicts of detention basins and protected regions. • Gate control is preferential because of significant loss reduction of detention basin. • Distance of diversion gate from upstream influenced the balance between protected region and detention basin. • The case study realized overall annual benefit of ¥3.86 billion and reduction of 0.64 billion of the expected annual damage. Utilizing detention basin to store flood water and reduce the risk of levee failure, as well as guarantee the security of important regions downstream, is an important flood control measure in some large river catchments. However, the populated and economic detention basins in China are facing the dual challenges of protecting the safety of lives and property and alleviating the pressure of flood control downstream. Maximizing the total benefits of a flood control system by balancing the flooding losses in the detention basin and the flood control benefit of the flood protected regions downstream has been the key factor in river basin flood management. In this paper, a framework is developed to optimize the flood diversion siting and operating policy of a detention basin, which consists of three modules: (1) the flood simulation module, which simulates the flood routing and flood diversion process via a one-dimensional and two-dimensional coupled hydrodynamic model; (2) the cost and benefit calculation module, which estimates the flood damage in the detention basin and the flood control benefit in flood protected regions based on the results of the flood simulation model, with the diversion structure cost considered; and (3) the optimization module, which optimizes the diversion siting and control strategy with the objective of the maximum system benefit by balancing the flood loss in the detention basin and flood control benefit of the protected area. The framework is applied to the Huayanghe detention basin, the most downstream detention basin along the Yangtze River basin, China. The results state that gate control upstream is the optimal strategy to decrease the flood losses in the detention basin, but the potential flood losses of the protected region increase significantly under this policy. Moreover, an operating policy that balances moderately the flooding losses in the detention basin and the flood control benefit of flood protected regions downstream is provided though the framework. Overall, this study highlights flood simulations and optimization approaches represent a promising solution for filling the gap of densely populated detention basin modeling and real-world management decision-making. [ABSTRACT FROM AUTHOR]