Optimization and Evaluation of Wetland Ecological Networks for Mitigating Urban Flooding

Ecological network resilience, the core capacity of ecosystems to maintain functional stability under external disturbances, is of great significance for ensuring regional ecological security and promoting sustainable development. This study takes the Wuhan Metropolitan Area as the research object. Based on multi-temporal data from 2000 to 2020, we innovatively constructed a comprehensive evaluation system of "water resources–soil conservation–ecosystem quality" to identify ecological source areas. Combined with a three-dimensional resistance surface model of "natural environment–human activities–physical barriers," the Minimum Cumulative Resistance (MCR) model was applied to extract ecological corridors, forming a "source–corridor" spatial frame-work. The gravity model was used to construct the ecological network and analyze its topological structure. Finally, a robustness model was employed to assess the dynamic changes in network resilience. The key findings include: (1) The number of ecological source areas exhibited a "rise-then-decline" trend, with spatial distribution shifting from fragmented to clustered and the global control of core nodes transitioning from decentralized to highly centralized. (2) Ecological corridors displayed a "dense-south-sparse-north, dense-periphery-sparse-center" spatial pattern. Although the number of corridors decreased, the interaction strength and species migration efficiency significantly improved. (3) The ecological network evolved from "expansion" to "quality enhancement," with significant improvements in network density and clustering coefficients, ultimately forming an efficient and stable structure. Based on these findings, strategic recommendations are proposed to optimize the ecological network and enhance environmental quality in the Wuhan Metropolitan Area's composite ecosystem.

A city-wide approach to reduce the uncertainty regarding the spatial variability of urban flooding events is required in urban catchments. The goal of this study is the development of a modelling framework independent of the spatial scale to address the most hazardous areas in the current state and the future. The framework starts with the definition of the study objectives (e.g. reducing flood risk), which have a direct impact on the spatial and temporal scale, the used model approach, the data requirement and the level of detail. Furthermore, potentially hazardous areas will be identified with the potential flood risk index (PFRIi). The determination of this is a risk-based approach (R=E*V*H) which combines the exposition (E) with the vulnerability (V) and the hazard (H). The population density of each object and the total number of persons in the catchment will quantify the exposition. The vulnerability includes the number of past damage events and the object use. How accurate the modelled hazard is considered, depends on the used model approach: i) GIS-based; ii) only 1D; iii) only 2D; iv) 1D/2D models. The combination of H and V resulted in the risk factor (RFi) in four levels of detail depending on the used model approach. This allows both, the quantification of hazardous areas at the current state and the change of the PFRIi by future scenarios such as climate change and urbanization.PFRIi = nP,k * RFi / (Ak * ∑P)                                                                                                                                                                                     PFRIi=Potential Flood Risk Index; nP,k= number of Persons on a private ground k; Ak=total object area; =total number of persons in the catchment; Rfi= risk factor depending on the used model approach kThe GIS-based flow path analysis as the first level of detail can be used to identify the urban flooding hot spots. This allows the identification of hazardous sub-catchments in a city or high-risk private ground in a catchment quantified by the PFRIGIS. This is useful for further detailed analysis with other model approaches (e.g. 1D/2D model). The next steps are the implementation of the demonstrated framework for each level of detail in the city of Graz in Austria. Furthermore, the framework will integrate different climate scenarios based on a high-resolution climate model to address the impact of climate change on the urban drainage system quantified by the PFRIi.Keywords: urban flooding, urban flood modelling, risk assessment, future changes

Rapid urbanization destroys the ecological network connectivity among habitat patches. The research on the construction of regional ecological network at the patch level is obviously insufficient. The morphological spatial pattern analysis (MSPA) and minimum cumulative resistance (MCR) were used to identify ecological sources and to extract potential ecological corridors in Qinling Mountains, respectively. The ecological network was effectively constructed. We analyzed the structural characteristics and landscape compositions of the network. Based on the gravity model, the importance of patches in the ecological network was graded and the structural characteristics and landscape composition of the network were analyzed. The results showed that there were 10 ecological sources, 45 potential ecological corridors and 38 stepping stones in the ecological network of Qinling Mountains in Shaanxi Province, with a total area of 29686.15 km2. There were good connectivity in potential ecological corridors and ecological network nodes as indicated by network closure (0.11), line point rate (1.18), network connectivity (0.42) and cost ratio (0.99). The connectivity between ecological source was low, but the cost of network reconstruction was high. The important ecological corridors were mainly composed of forest, grassland, and cultivated land. Fore-sts accounted for 89.2% of the total corridor area (571.00 km2), indicating the good landscape structure in Qinling Mountains. The protection of ecological source areas must be strengthened, and priority should be given to the establishment and protection of important ecological corridors and ecological nodes. Our results would provide the scientific reference and basis for the ecological environment protection and high-quality development in Qinling Mountains.

Rapid urbanization has greatly altered urban ecological spaces and habitat quality functions, threatening regional biodiversity and the sustainability of landscapes. Therefore, constructing a comprehensive ecological network and ecological safety patterns is crucial for ecosystem management and regional development. However, simple quantification of ecological networks fails to meet the construction needs of ecological safety patterns, and most studies focus solely on network quantification analysis, thus overlooking the importance of spatial analysis. This study proposes a method of ecological network quantification assessment combined with hotspot analysis and coupled with standard deviational ellipse spatial analysis, which not only satisfies quantitative analysis but also adds spatial analysis methods, facilitating a more comprehensive construction of safety patterns. Firstly, through morphological spatial pattern analysis (MSPA) and landscape connectivity indices, ecological source areas in the main urban area of Kunming were identified, integrating various resistance factors and corrective factors to construct an ecological resistance surface. The minimum cumulative resistance (MCR) model was used to identify potential ecological corridors, and their importance was evaluated using the gravity model, thus establishing an ecological network. Secondly, based on network structure indices, the ecological network was assessed and optimized. On this basis, combined with hotspot analysis coupled with standard deviational ellipse spatial analysis, an ecological safety pattern was constructed. The results show the following: the core area of the study region is 2402.28 km2, accounting for 52.07% of the total area; there are 13 ecological source areas, totaling 2102.89 km2, accounting for 45.58% of the total area; there are 178 potential ecological corridors, including 15 level-one ecological corridors and 19 level-two ecological corridors; and 103 ecological nodes, 70 “stepping stones”, and 48 ecological breakpoints were identified. In terms of ecological network optimization, six new ecological source areas were added, covering an area of 16.22 km2, and the potential ecological corridors increased to 324, including 11 new level two ecological corridors, 51 new ecological nodes, 15 “stepping stones”, and 24 major ecological breakpoints. After optimization, the network closure index (α), network connectivity index (β), and network connectivity rate index (γ) improved by 15.16%, 24.56%, and 17.79%, respectively. Based on the network structure quantitative analysis and hotspot analysis coupled with the standard deviational ellipse’s spatial analysis, a “one axis, two belts, five zones” ecological safety pattern was constructed.

Ecopolis: Strategies for ecologically sound urban development: Sybrand P. Tjallingii, Backhuys Publishers, Leiden, Netherlands, 159 pp., paper-back, 45.30 Dfl, 1995

Floods are the most common disaster in Canada. As results of rapid urbanization and climate changes, both frequency and risks of floods have been increased in Canadian urbanized areas, where the disasters have usually costlier impacts than in rural areas. Imagery data and technologies of optical remote sensing are helpful and can be applied for urban flood response and pre-disaster preparation. Especially high and very high optical remote sensing can be used for precise mapping of the floodwater distribution in dense urban areas and providing key information for disaster response management. In addition, the geospatial information about urban land surface and urban growth derived from optical remote sensing imagery can be the key inputs for urban flood risk analyses. In recent years, several case studies for different urban flood types, including fluvial (Calgary 2013, Ottawa-Gatineau 2017) and pluvial (the Greater Toronto Area) floods in Canada, have been carried out at Canada Centre for Mapping and Earth Observation, Natural Resources Canada. Methodologies/framework for urban floodwater mapping have been developed based on high resolution optical data, as well as the impacts of urban growth on the urban flash flood risks have been investigated using model simulations with remote sensing derived maps as inputs. This presentation demonstrates results from three Canadian urban flood case studies and introduces remote-sensing-based methodologies for different types of urban floods.

Urban areas are increasingly facing the limitations of existing drainage systems due to the growing frequency and intensity of extreme rainfall caused by climate change. As underground space becomes more developed and urban infrastructure grows more complex, effective flood mitigation requires a planning tool capable of systematically evaluating large-scale drainage facilities such as deep stormwater tunnels. This study proposes a SaaS-based integrated analysis and design system that automates the entire process of rainfall–runoff simulation, tunnel operation optimization, and surface inundation assessment.The system consists of three major components:(1) a SWMM-based hydrologic and hydraulic simulation engine,(2) an automated calculation module for determining the storage capacity, inlet configuration, pumping requirements, and diversion channel sizing of deep stormwater tunnels, and(3) a cloud-based data environment for storing, managing, and visualizing large hydrologic and topographic datasets.Input data—including terrain, catchment characteristics, sewer networks, and design storm information—are automatically processed in the cloud database. The computation server conducts repeated SWMM simulations for various rainfall scenarios, generating results related to pipe surcharge, water-level variation, and overall drainage performance. A 2D inundation model is integrated to assess surface flooding before and after the construction of a deep stormwater tunnel, enabling spatial comparison of flood reduction effects.The system outputs include required tunnel storage volume, surcharge-prone locations, inundation depth maps, and comparative scenario analyses. Users can easily generate, modify, and store multiple design alternatives and share them within a project team. This integrated modeling environment significantly improves the efficiency of complex drainage analyses and enhances the reliability of decision-making for urban flood mitigation infrastructure.Overall, the proposed system serves as a next-generation digital tool that supports intuitive and comprehensive evaluation of urban drainage conditions. It is expected to markedly improve the practical applicability and planning efficiency of deep stormwater tunnel projects in future urban flood management efforts. AcknowledgementsThis work was supported by Korea Environment Industry & Technology Institute(KEITI) through Technology development project to optimize planning, operation, and maintenance of urban flood control facilities, funded by Korea Ministry of Climate, Energy, Environment(MCEE)(RS-2024-00398012)

Stimulated by the recent USEPA’s green stormwater infrastructure (GSI) guidance and policies, GSI systems have been widely implemented in the municipal area to control the combined sewer overflows (CSOs), also known as low impact development (LID) approaches. To quantitatively evaluate the performance of GSI systems on CSO and urban flooding control, USEPA-Stormwater Management Model (SWMM) model was adopted in this study to simulate the behaviors of GSI systems in a well-developed urban drainage area, PSW45, under different circumstances. The impact of different percentages of stormwater runoff transported from impervious surfaces to the GSI systems on CSO and urban flooding control has also been investigated. Results show that with current buildup, GSI systems in PSW45 have the best performance for low intensity and short duration events on both volume and peak flow reductions, and have the worst performance for high intensity and long duration events. Since the low intensity and short duration events are dominant from a long-term perspective, utilizing GSI systems is considered as an effective measure of CSO control to meet the long-term control strategy for PSW45 watershed. However, GSI systems are not suitable for the flooding control purpose in PSW45 due to the high occurrence possibility of urban flooding during or after high intensity events where GSI systems have relatively poor performance no matter for a short or long duration event.

Flood risk and its reduction in China

It is difficult to imagine the city of Cartagena de Indias, Colombia, the “Pearl of the Caribbean”, without water, as sandy beaches, lush mangrove forests, swampy landscapes and a maze of canals both surround the emblematic historic city centre and shape the expanding neighbourhoods in the so-called urban periphery. Water and the city are so closely intertwined that we introduce Cartagena as an Archipelago City to explore how urban residents navigate the city during seasonal urban rain and flooding. As climate change and rising sea level have become a pressing environmental challenge for coastal cities worldwide, we nuance mainstream discourses on governing and planning environmental futures by applying an actor-centred approach. We use navigation as an analytical lens, to provide insights into the way urbanites experience, anticipate and improvise around urban floods and imagine their city. Drawing on 13 months of ethnographic fieldwork in two distinct neighbourhoods, we dialectically explore how urban flooding slows down, disrupts and also speeds up Cartagena’s everyday life while its residents navigate their way through the Archipelago City. By arguing that these everyday experiences and imaginaries reflect the historical and social legacies of profound inequalities in the city, we are offering a window into the complex constituents of everyday social worlds that prevail in many Latin American coastal cities.

The ecological security of a county is the basis for guaranteeing sustainable socio-economic development in the process of new urbanization, as well as the key to maintaining the rational functioning of natural ecosystems in urban and rural areas, and the primary prerequisite for satisfying the ecosystem service functions enjoyed by urban and rural residents. This study takes Pulandian, an estuary county with low mountains, hills, plains, and beach lands, as an example, and comprehensively applies various methods such as the model of driving–pressure–state–impact–response (DPSIR), the mainstream model of minimum cumulative resistance (MCR), the model of morphological spatial pattern analysis (MSPA), and the circuit theoretical model to assess the spatial and temporal evolution characteristics of the ecological spatial network of Pulandian District from 1990 to 2020 and evaluate its ecological risk from the socio-economic and environmental perspectives to provide a basis for the construction of ecological resistance surfaces. On this basis, an ecospatial network optimization model was constructed to reduce ecological risk and meet ecological security requirements. The results showed that the ecological space showed an upward trend of increasing, then decreasing, and then increasing in the area during the 30-year period, but there was serious fragmentation in the low area of the northeastern river valley, the low-hill plain area in the central part of the county, and the coastal area in the southeastern part of the county. High-resistance radiation centered on townships with high urbanization breaks the original ecological spatial network gradient, resulting in the absence of ecological corridors in large areas of the central and southeastern regions. Therefore, seven new ecological source sites were added for the central and southern portions of the study area, and the number of optimized ecological corridors increased from 47 to 66. In addition, we established an ecosystem consisting of an ecological barrier, an ecological coastal zone, multiple ecological corridors, and multiple ecological sites as an optimization system. This is of great scientific value and practical significance to provide reference for optimizing the ecological spatial network in Pulandian District of Dalian, to promote coastal ecological protection and construction, and to promote regional construction and sustainable development.

The July 1997 flood in Fort Collins was caused by the heaviest rains ever documented over an urbanized area in Colorado, and offers a data base and multifaceted set of lessons about flood planning, mitigation, response, and recovery for engineers, flood managers, and urban officials. The storm dropped 10 to 14 inches in 31 hours and some peak discharges greatly exceeded projected 100-year and 500-year flows. Five people died, 54 were injured, about 200 homes were lost, and 1,500 homes and businesses were damaged. Damages at Colorado State University were about $100,000,000, including catastrophic losses to the library. The paper summarizes the flood experience and provides lessons in five categories: urban drainage and flood control, risk management, mitigation, flood response, and public involvement.

Dhaka, the capital city of Bangladesh, is one of the most densely populated cities in South Asia. Urban flooding from extreme rainfall is a recurring phenomenon, with historic floods in 1988, 1998, and 2004 amongst the most catastrophic events in Dhaka. Prolonged urban flooding or water logging is a major concern for both Dhaka North City Corporation (DNCC) and Dhaka South City Corporation (DSCC) areas. This research investigates how “Citizen Science (CS)” could help individuals, communities, and stakeholders understand and manage the risk of current and future urban flooding, integrating formal flood risk management along with the affected area’s respondents’ self-perceived perception, concerns, experience, awareness, and opinions about flood risk management, and ability to cope with the flood risk. Fieldwork data were collected through the administration of a purposely designed questionnaire to 500 respondents in the water logging affected wards of the two city corporations’ areas in Dhaka. Preliminary findings from the fieldwork revealed that every year approximately 45.6% and 29.4% respondents in the study area experienced 1-3 days of urban flooding/water logging, mostly during the monsoon season (June – September), with a work time loss of 3-4 hours respectively. Respondents in the study area are aware and concerned about flooding and its associated risk, and approximately 36.9% respondents think that the frequency of urban flooding will increase in Dhaka in the next 10 years. In terms of the vulnerability, approximately 51.5% respondents mentioned that they are vulnerable to urban flooding and small business holders (Entrepreneurs) are most affected (61.5% respondents) by flooding. Although almost 61.2% respondents were not familiar with the “Citizen Science” concept, but approximately 42.8% of respondents expressed an eagerness to involve themselves in any Citizen Science based project to promote awareness and mitigation of urban flood risk/water logging issues in their community or in Dhaka City. In addition, preliminary findings from Key Informant Interviews (KII) and Focus Group Discussion (FGD) Meetings suggested that unplanned urbanisation, poor and inadequate drainage system management, and recent extreme rainfall events were the major drivers behind the urban flooding/water logging situation in Dhaka.The study also explored annual and seasonal trends of rainfall in Dhaka (using observed datasets from the Bangladesh Meteorological Department) over the period from 1953-2019 using extreme precipitation indices [Climate Change Detection and Indices (ETCCDI)]. It is revealed that over these 67 years, Annual Maximum Daily Rainfall has increased during winter (0.021 mm/year) but statistically significantly decreased during the monsoon (-0.636 mm/year). The overall annual rainfall has significantly decreased (-0.718 mm/year). Trends in Consecutive Dry Days, heavy, and very heavy precipitation days indicate an annual increasing rate of 0.158 days/year for CDD, 0.077 days/year with >= 10 mm rainfall and 0.019 days/year with >= 20 mm rainfall, respectively. Results from the rainfall datasets are now being integrated with the fieldwork findings and other secondary datasets to set up a Hydrodynamic Model (CityCAT) to investigate current and future flood risk in Dhaka in more detail.

Recently, frequent flood disasters in China have seriously threatened economic development and public safety. This paper addresses the need for a dynamic urban flood emergency knowledge management system in emergency management departments and the lack of systematic knowledge among emergency managers regarding urban flood control. A multimodal knowledge graph-based urban flood emergency knowledge management model was constructed to enhance the decision-making capabilities of emergency management departments, improve the efficiency of public emergency evacuation, and reduce losses from urban flood disasters by analyzing the shortcomings of the existing emergency management system. An intelligent and dynamic flood emergency knowledge management model was built. This paper integrates multimodal knowledge graph technology to establish a multimodal emergency knowledge management framework for urban flood control. It develops and simulates the proposed model’s application scenarios for urban flood emergency evacuation using the Flocking algorithm on the NetLogo platform. Through simulation experiments, the practicality and effectiveness of the model in real flood disaster situations were examined, particularly in simulating crowd evacuation behavior. The study found that the model significantly improves the accuracy of information and decision-making speed during emergency responses and supports emergency management departments in conducting targeted and personalized emergency decisions. This research provides a scientific basis for emergency management departments to optimize their emergency response strategies to flood disasters and serves as a reference and example for the application of multimodal knowledge graph technology in emergency management.

How to restore ecological impacts from wind energy? An assessment of Zhongying Wind Farm through MSPA-MCR model and circuit theory