Where do waterbirds settle down under heavy rain: Waterbird habitat planning and design from the perspective of rain and flood resilience

Where do waterbirds settle down under heavy rain: Waterbird habitat planning and design from the perspective of rain and flood resilience | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Where do waterbirds settle down under heavy rain: Waterbird habitat planning and design from the perspective of rain and flood resilience xinyi Chen, jinjin Gu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4343801/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Urban wetlands have ecological functions such as maintaining biodiversity and regulating runoff, and wetland waterbirds are also important biological indicators of wetland ecosystems, which can reflect the ecological conditions of wetlands and cities. In recent years, extreme weather occurs frequently, urban waterlogging is serious, rivers play the role of flood drainage, and rainwater backflow will have a serious impact on urban rivers, wetlands and aquatic organisms. Therefore, it is necessary to explore the inundation of urban wetlands under extreme rainfall conditions. In the past, most of the research on waterlogging was from the perspective of disaster prevention, and there was little research on the degree of habitat destruction of waterbirds. In this paper, the HEC-RAS hydrological model was used to simulate the extreme rainfall of the Shiwuli River in the study area of Hefei City, and the results showed that once a rainstorm occurred, the downstream wetland would be flooded in a large area and the inundation height would exceed the flood defense level, which would have a serious impact on the swimming birds such as coots nesting in the downstream wetland. Therefore, the landscape, foraging and habitat conditions of Coots were selected as the design factors, and the floating bird island was designed to alleviate the invasion of rain and flood waterlogging on Coots. The innovation of this study is to propose an optimization strategy for the impact of extreme weather on waterfowl habitat, which can provide a reference for waterfowl protection and wetland management, and improve the impact of environmental changes such as waterlogging caused by extreme rainfall on downstream lakes on waterfowl populations. Urban Wetland Extreme rainfall Combination of waterlogging and design HEC-RAS model Waterbird habitat planning Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Urban boundary wetland is an important ecosystem for sustainable development (Li et al., 2003; Chen and Jim, 2008), which can provide important ecological services for cities (Alikhani et al., 2021). It plays an important role in reducing urban heat island effect (Xue et al., 2019; Alikhani et al., 2021). In many developed countries, the blue-green space of urban wetlands is the only option to provide sustainable living conditions (Chiesura, 2004). At the same time, urban wetlands contain a large number of aquatic organisms, such as aquatic plants, birds, fish, amphibians and invertebrates. The bird community reflects the land use conditions of wetlands and cities better than other biological communities (Galatowitsch et al., 1999). Similarly, other studies have clearly shown the relationship between landscape patterns and wetland birds, suggesting that bird diversity increases with the percentage of riparian wetlands. Therefore, it is necessary to protect urban/suburban wetland ecosystems and wetland waterbirds to promote sustainable urban development (Zheng et al., 2012; Liu et al., 2016). However, in recent years, the number of extreme weather has increased significantly, and the number of days of continuous heavy precipitation has also gradually increased. Under this climate background, the process of urbanization has been accelerating, the scale of cities has been expanding, and the spatial pattern of land use has changed, which is characterized by a large increase in urban construction land. The hardening of urban underlying surface, low permeability and limited drainage capacity are the important reasons for serious urban water accumulation. The combined effect of human activities and natural environment change is the reason for the significant increase of urban waterlogging disaster risk. Because the drainage capacity of urban pipe network in major cities can not meet the needs of urban development, urban water is difficult to drain in time. Urban wetland, especially the urban boundary wetland, as the ecosystem of the city, is vulnerable to the threat of waterlogging disasters, and belongs to the area with high risk of waterlogging. In particular, floods can affect the survival, habitat, population, foraging activities, breeding and living environment of waterbirds. Some urban wetlands are important nodes for migratory birds to migrate and inhabit. If there is no perfect protection system to deal with extreme weather, once extreme events such as torrential rain break out, it is easy to cause serious impact on migratory bird populations and other aquatic organisms. Due to the concentration of bird populations and habitats, some swimming birds prefer to build nests and breed floating nests on the water surface. If a large external disturbance event occurs, the environmental quality of the original habitat will decline, especially when the water level of the habitat rises due to extreme rainfall, the floating nests and nestlings of waterbirds will be submerged, which will have a serious impact on the population of waterbirds. In the early 20th century, some European countries have taken bird richness as the second indicator of environmental quality when evaluating the quality of urban life. Therefore, the wetland area at the urban boundary should be provided with a habitat for bird populations under extreme rainfall conditions, so as to promote the improvement of biodiversity and environmental quality in the study area, create an ideal place for migratory birds such as waterbirds to migrate and breed, and become an important habitat paradise for resident birds and migratory birds during their migration. With the prominence of the importance of urban wetlands, scholars began to pay attention to the research between urban wetlands and urban waterlogging. Gogoaşe Nistoran et al. (2016) analyzed the Bicaz dam in Romania using HEC-RAS to assess the depth, velocity, and propagation time of dam-break flood waves. (Xiong (2011) considered the possible maximum flood to predict the downstream water level and discharge hydrograph. Chandrabose et al. (2014) used HEC-GeoRAS to derive the river geometry data from the SRTM digital elevation model and used HEC-RAS to perform the dam break analysis of Malankara Dam in India to obtain the water level, discharge hydrograph and inundated area. People's understanding of the ecological function and importance of natural drainage channels such as river networks and wetlands has been gradually improved, but few studies have considered the impact of extreme rainfall on wetlands and wetland aquatic organisms from the perspective of stormwater resilience. Currently, three types of models are used to assess urban waterlogging risk: hydrological and hydrodynamic models, qualitative models, and machine learning models (Bera et al., 2022; Motta et al., 2021; Xie et al., 2020). The mathematical models used to assess urban waterlogging and simulate river flood routing are mainly based on one-dimensional and two-dimensional hydrodynamic mathematical models. According to the function and application field, it can be divided into: river hydrodynamic model software for river flow, water level, water speed and other parameters calculation and flood monitoring, mainly including HEC-RAS, MIKE11, River2D, IFMS, etc.; Water resources management and river planning software for water resources management and planning decision support, mainly including WMS, WEAP, MIKE BASIN; Urban hydrodynamic model software for urban flood control, drainage system planning and regulation and storage mainly includes MIKE URBAN, TUFLOW, FLO-2D, IFMS, SWMM, etc. Compared with other software, HEC-RAS software has obvious advantages in flood routing and river flow calculation. It can predict and analyze flood characteristics such as flood discharge, water level, inundation range, flow rate and depth, and preliminarily identify vulnerable areas. Generally speaking, wetland is an important habitat for birds, and its rational planning and design plays an extremely important role in reversing the degradation of bird habitat and maintaining the level of biodiversity. Nowadays, the planning and design of bird habitat restoration mostly start with the characteristics of wetland itself, focusing on the restoration and construction of wetland water environment, or using some quantitative research methods of ecology in the planning and design of wetland bird habitat restoration to strengthen the implementation effect of protection and restoration. The research results generally focus on habitat selection, habitat suitability evaluation and the impact of habitat fragmentation on bird communities, and most of them are based on wetland bird communities, ecology and other related studies, combined with regional environmental characteristics. Habitat restoration design is defined from the aspects of water environment, vegetation resources and human disturbance that affect the planning and design of wetland bird habitats, so as to realize the protection and restoration of wetland bird habitats and the improvement of bird diversity. Most of the relevant restoration strategies are based on wetland bird communities, and lack of attention to the most protected bird species in the region, so it is inevitable to neglect the most protected species in the process of wetland bird habitat restoration, resulting in their migration. To sum up, scholars' research on urban waterlogging mainly includes analyzing the changes of surface runoff under different scenarios and revealing the most effective optimal allocation of surface space (Wang, 2021, Wu, 2022); According to the geographical conditions and economic development level of a specific region, the study on the optimization of the surface spatial pattern of a specific location (Sun et al., 2018, Liu, 2019) tends to solve the problems of a specific field, focusing more on local and specific factors, and less on the comprehensive optimization of the whole city or watershed; Or combine the hydrological model with the optimization algorithm to discuss the optimization of the spatial pattern of the impervious surface. Few studies have focused on the inundation of waterbird habitats under extreme rainfall and the corresponding preventive planning and design. Especially for the wetlands downstream of the urban boundary in some monsoon countries, the frequency of rainfall in the rainy season increases, and once extreme rainfall occurs, the downstream river jacking will have a serious impact on wetlands and wetland birds. Therefore, this study will focus on the changes of aquatic habitats when floods occur and the construction methods of flood-proof and resilient cities in the small patches of watershed scale within the city. According to the actual situation of the basin, fully considering the inundation of waterbird habitat under extreme rainfall conditions, quantitative simulation is carried out by combining with hydrological software, and targeted optimization strategies are put forward according to the inundation depth and inundation area of the river reflected by the simulation results. The main objectives of this study are: (1) indicator species selection in the Shiwuli River Basin; (2) wetland inundation range and inundation height in the lower reaches of the Shiwuli River under extreme rainfall conditions; (3) habitat optimization design of waterbirds from the perspective of stormwater resilience. 2. Study area This study takes Shiwuli River Basin as an example. Shiwuli River originates from the southeast foot of Dashu Mountain in Hefei City, flows from northwest to southeast, and is the last ecological barrier to Chaohu Lake (see Fig. 1 ). There is an artificial lake in the upper reaches called Swan Lake, which is an important tributary of Chaohu Lake. However, there is no stable clean water source in the upper reaches of Shiwuli River, and the river supply mainly comes from natural precipitation and tail water discharge from sewage treatment plants. The estuary wetland of the Shiwuli River plays an important role in water purification. After the wetland treatment, the water quality entering the lake can stably reach the third class water standard of surface water. In recent years, with the advancement of wetland restoration, Shiwuli River has gradually become one of the important protection sites for migratory birds (see Fig. 2 ). At the same time, a large number of migratory birds inhabit the lakeside National Wetland Park near the study area, including coots, winged ducks, spot-billed ducks, red sheldrakes, white-browed ducks, mallards, bulbuls, herons and night herons, etc. The population of migratory birds has reached more than 4000. Especially in the past two years, more and more migratory birds choose to live here. In April 2021, the white crane, a national first-class protected animal, reappeared in the lakeside wetland after about 20 years, with a population of 14, the largest number of white cranes recorded in the history of Hefei. In recent years, the population of birds in the wetland has been expanding, ranking first in the whole area around Chaohu Lake, which is the most concentrated area of various waterbirds in Chaohu Lake, including one species of national first-class protected birds, namely Oriental White Stork, five species of national second-class protected birds, namely White Spoonbill, Mandarin Duck, Common Buzzard, Skylark and White-breasted Emerald, and 15 species of local key protected birds in Anhui Province. However, due to the particularity of geographical location and the influence of weather, the Shiwuli River experienced basin-wide floods in 2016 and 2020. On July 9, 2016, the water level of Chaohu Lake in the lower reaches reached 12.77 meters, and many dangerous situations occurred in the areas of Shiwuli River and Majiadu Bridge; on July 22, 2020, the water level of Chaohu Lake broke through the historical extreme value and reached13.43meters. Leakage, piping and other dangerous situations occurred in the jurisdiction area, resulting in large flood disasters. The wetlands in the region were flooded and the habitats of aquatic organisms were destroyed, which had a serious impact on the population of waterbirds. As an important node for migratory birds to migrate and inhabit, there is no perfect protection system to deal with extreme weather in the Shiwuli River Basin at present. Once extreme events such as torrential rains in 2016 and 2020 break out, it is easy to cause serious impact on migratory bird populations and other aquatic organisms. At the same time, because the bird population and habitat are particularly concentrated, if a large external disturbance event occurs, the environmental quality of the original habitat will decline, and even have a serious impact on the population of waterbirds. At the same time, the lower reaches of Shiwuli River is connected with Chaohu Lake, and resident birds and migratory birds may not be able to find suitable habitats in this area as a substitute. Therefore, the wetland area in the lower reaches of the Shiwuli River should be provided with a habitat for waterbird populations under extreme rainfall conditions, so as to promote the improvement of biodiversity level and environmental quality in the study area, create an ideal place for migratory birds such as all kinds of waterbirds to migrate and breed, and become an important habitat paradise for resident birds and migratory birds during their migration. 3. Methodology This study method is divided into three parts, as shown in Fig. 3 . Firstly, the first step is to determine the indicator birds by comparing the differences of breeding and staying time of waterbirds, the level of rare species and the type of residence in the wetland of the lower reaches of the Shiwuli River; Secondly, the combination of GIS and HEC-RAS model was used to predict and analyze the flood characteristics of the study area under extreme rainfall conditions, such as flood discharge, water level, inundation range, flow velocity and depth, and to identify the vulnerable areas; Finally, according to the simulation results, the optimal design of waterfowl habitat in the study area is carried out from the perspective of stormwater resilience. 3.1 Target species selection For the selection of indicative waterbirds in the Shiwuli River Basin, the focus is on the habitat quality and population size of birds. It mainly chooses birds under the first and second class protection of the state. These birds are rare in number and have high requirements for habitats, and the habitat quality of the wetland in the basin can be improved by focusing on the protection of these birds. By focusing on the protection of these birds, the habitat quality of the wetland in the basin can be improved. Through habitat restoration and construction, more target birds will be attracted to live here. Birds can be divided into wading birds, swimming birds, climbing birds, raptors and songbirds according to their ecological habits. Among them, swimming birds live in various types of waters, most of them nest on the shore and shoals, and a few of them choose to live in the water islands. Swimming birds feed in different areas, some in the shallows and some in the water. Most of them are migratory birds, like to live in groups, and are good at swimming, diving and getting food in the water. They feed on aquatic plants, insects, fish, shrimp and shellfish. They are relatively insensitive to human activities and can be viewed at close range. The main representative species of swimming birds are Chinese merganser, coot, mallard, Mandarin duck, red Sheldrake, red-necked duck, pintail duck, magpie duck and green-headed diving duck. Among them, coots, red sheldrakes and green-headed diving ducks are listed in the Red List of Endangered Species of the World Conservation Union. At the same time, coots are also found inhabiting wetlands in the lower reaches of the Shiwuli River, so they are the key protected objects (see Fig. 4 ). According to the habitat type of the site, by comparing the differences of breeding and staying time of waterbirds in the wetland of the lower reaches of the Shiwuli River, the level of rare species and the type of residence (according to the order of resident birds first, followed by summer migratory birds, winter migratory birds and traveling birds), an indicator bird was finally determined, that is, (small and medium-sized) geese and ducks. Specifically, it is a rare water bird such as coot chicken and red Sheldrake. At the same time, this kind of representative species is also a sensitive indicator of wetland ecosystem, which can truly reflect the status of wetland ecosystem. Through the construction of high-quality waterbird habitats that can cope with extreme rainfall, the core and unique ecological resources of the wetland in the lower reaches of the Shiwuli River are formed. 3.2 Hydrologic modelling in HEC-RAS The HEC-RAS software is a computer program developed for modeling river flowing through open natural channels and used for computing water surface profile (Mapping and Field, 2017; Lamichhane and Sharma, 2018; Duvvuri and Narasimhan, 2013). HEC-RAS get accepted and being used for river simulation by hydraulic engineers and different researchers (Marimin et al., 2018) because of its capabilities and abilities to simulate unsteady flow and identifies flood-prone areas where the surface ground level is lower than the computed water profile and allows the researcher to visualize the flood extent along a river course (Maidment, 2017; Timbadiya et al., 2011). The modeling process of HEC-RAS is as follows (see Fig. 5 ), and its functions include steady and unsteady flow simulation, dam-break and dike-break analysis, water quality simulation, hydraulic design, and sediment transport. 3.2.1 Preparation of modeling data This study combines field survey, remote sensing images, data collection and other methods to obtain the basic data of the study, including rainfall, hydrology, land use and DEM data. The method of combining GIS with HEC-RAS model is used to analyze the hydrological and hydrodynamic processes of small watershed under historical rainfall-flood events. Based on the DEM data downloaded from the Geospatial Data Cloud, GIS software is used to modify and improve the river elevation according to the current situation of the site, and then the SHP format is exported to RasMapper to establish geometric data, and the corresponding river section and boundary are added at the location of the river according to the satellite image. In order to simulate the maximum possible flood inundation range of the habitat, based on the historical extreme rainfall flood flow information collected from the relevant units in Hefei, the 100-year, 50-year and 20-year design peak flows of the Shiwuli River were selected as the flow input conditions of the HEC-RAS model. At the same time, the flood inundation characteristics of historical rainstorm floods in the basin scale were studied by combining with GIS, and the flood characteristics such as flood discharge, water level, inundation area, flow velocity and depth were predicted and analyzed, and the vulnerable areas were preliminarily identified, and the feasibility of applying the HEC-RAS hydrodynamic model to the evaluation of waterfowl habitat was discussed (see Table 1 ). Table 1 Data required for simulation. Data category Date composition Description DEM Digital elevation data with 30 meter resolution For the river section without measured data, the information of the river section can be extracted from the DEM data of the study area as the basic data for the study. River flow 100-year river discharge Based on the existing drainage and waterlogging prevention instructions of Hefei City and other relevant data, input the river flow value once in a hundred years under extreme rainfall conditions. Manning coefficient Channel roughness is set according to empirical values For areas without measured data, the roughness can be determined based on experience and or with reference to adjacent similar basins or river sections. 3.2.2 One-dimensional model construction(Simulate inundation height) Prepare the terrain file of the area to be modeled and the point SHP shape file of the regional spatial coordinates, import the terrain file into the ras Mapper in HEC-RAS, create the river centerline, river shoreline and flow path (boundary line) in Ras Mapper, and draw the river cross section according to the length of the river. The discharge and other corresponding parameters are set according to the 100-year design flood level of Shiwuli River in the drainage and waterlogging prevention instructions of Hefei City. Finally, each section of the river and the maximum submerged height are obtained. (see Table 2 ) Table 2 Values of relevant parameters. Parameter Floodplain roughness Channel roughness Channel slope Numerical value 0.06 0.04 0.002 3.3.3 Two-dimensional model construction(Simulate inundation range) 2D Flow Area in RAS Mapper is a module for 2D grid and point establishment of topographic map in the study area. After the topographic map is processed, it is imported into HEC-RAS to define the projection, and then the topographic map is imported into RAS Mapper for two-dimensional modeling. After calculation, the water surface profile, flow velocity, water depth and other elements under different flood frequencies can be obtained, which can be visually displayed in Ras Mapper. 3.3 Design ideas Studies have shown that species have three possible responses to climate change: adaptation (evolutionary change or physiological adaptation), migration or extinction, and birds need to actively find the geographical location of the niche that sustains their livelihood (Holt, 1990; Peterson et al., 2001). Studies have confirmed that climate change will lead to changes in the range of bird species to some extent (Li et al., 2015; Peterson et al., 2001). Therefore, how to maintain the original ecological balance of wetlands under extreme weather conditions and prevent bird nests and nestlings from being flooded is the key content of this study. Therefore, in this study, "ecology and safety" are introduced into the planning and design of habitats at the same time, fully considering the habitat environment of waterbirds in the submerged state, and taking the floating mini-park in the famous Bangkok waters as inspiration for the design of wetland floating bird nests. A movable bird nest is assembled by filling the boat with soil and shade-tolerant and moisture-tolerant aquatic plants, so as to meet the daily feeding and perching of swimming birds and other aquatic organisms and avoid the interference of extreme weather (see Fig. 6 ). 4. Result and discussion 4.1 Habitat flooding results in flooding. According to the instruction of drainage and waterlogging prevention in Hefei City, the wetland area of Shiwuli River is 0.67 km2, the lake bottom elevation is 6.5-7.0 m, the normal water level is 11.5 m, the flood control level is 11.0 m, the maximum control flood level is not more than 12.0 m, and the regulation and storage volume is 670,000 m3. Through the establishment of HEC-RAS model for channel reconstruction, two-dimensional drainage surface construction, boundary line construction, roughness determination, boundary condition setting and operation plan formulation, the dynamic simulation results of the 100-year flood in the lower reaches of the Shiwuli River clearly show that the flood has submerged the whole channel in the study area, and is higher than the river bank in many areas, forming a submerged area. From the one-dimensional and two-dimensional simulation results, it can be intuitively observed that when the 100-year river flow value is input, the water area has completely exceeded the wetland river area under extreme rainfall conditions, causing a large area of erosion to the wetland riverbank and the waterfowl habitat in the region (see Fig. 7 ). According to the calculation of RAS Mapper, the maximum inundation depth of the study area is 12.8 m, which is higher than the flood control level of the river (12 m) (see Fig. 8 ). According to the flood simulation results of HEC-RAS for this control section, when the lower reaches of Shiwuli River are facing a once-in-a-century flood, the waterfowl habitat and the surrounding wetland parks will be greatly threatened, and corresponding measures should be taken to prevent the rare waterfowl from being homeless due to the inundation of the waterfowl habitat by the flood. 4.2 Floating Island Planning and Design Design floating bird nests in wetlands in areas prone to flooding. Floating bird's nest is a special habitat in a certain water area, which is still above the water surface at high tide and has a certain distance from the land. Floating bird nests were set up at least 10 meters away from the shore in the preferred habitat waters of coots and other swimming birds in the lower reaches of the Shiwuli River, and the location and design conditions of floating bird nests were determined according to the characteristics of coot nest site selection (see Fig. 9 ). At the same time, the bird's nest is fixed with an anchor to prevent the bird's nest from being unstable due to shaking on the water surface (see Fig. 10 ). The design of ship anchor shall follow the principles of safety, energy efficiency and environmental protection: the strength and corrosion resistance of the anchor body and anchor chain shall be fully considered to ensure that the anchor can bear the weight of the floating island and the river environment; the weight of the anchor shall be reduced as much as possible to improve its durability and service life, so as to save energy to the maximum extent while ensuring safety; Environmentally friendly materials are used to reduce the friction and noise of the anchor chain at the bottom of the river and reduce the impact on the wetland ecosystem. (see Table 3 ) Table 3 Design parameters of floating bird's nest. Condition Distance from water /m Depth of water /cm Nest depth /cm Parameter 29.00 ± 2.83 59.00 ± 1.41 18.00 ± 0.71 Note: Data are expressed as mean ± SD 4.3 Internal Habitat Design of Floating Island Waterbird habitat landscape design should provide good food sources and hidden spaces for habitats based on biodiversity factors and well-arranged plants. Plant communities create food sources for living organisms to survive. Aquatic plants are the main food for birds, fish, shrimp, and insects; the rich plant community and its insects and fruits are the food sources of birds; grassplot is the habitat of wading birds and mollusks (Haiting et al., 2018). For internal habitat planning of floating islands, previous studies have shown that water availability, food availability, habitat conditions and disturbance are the most important factors affecting habitat selection of waterbirds (Bo et al., 2008; Dong et al., 2013; Jiang et al., 2016; Maleki et al., 2016; Zhao et al.,2018). The nest site selection of swimming birds is often affected by natural and non-natural factors such as food, nest material, interspecific relationship and external interference. Therefore, it prefers the nest location with convenient foraging, easy access to nest materials, less interference and high degree of concealment. In addition, the dense and tall aquatic plants in the wetland environment can provide a safe environment for swimming birds to build nests with high degree of concealment and defense against natural enemies. Therefore, the plant factor design on the floating island adopts 0–10% arbor, 30–50% shrub and 40–70% emergent plants for planting, while ensuring 30–50% vegetation coverage. The current vegetation on the embankment around the current habitat is reserved to play a certain role in shielding the floating island. In addition, in order to give full play to the ecological benefits of wetlands and build an eco-friendly society, wetland protection laws should be formulated to protect the habitats of migratory birds while protecting and restoring the wetland landscape. Major land cover change projects should be prohibited. Enhance the ecological function of wetland and protect the wetland environment (Hu et al.,2020). 4.4 Optimized Waterbird Habitat Based on the field investigation and species analysis of the wetland in the lower reaches of the Shiwuli River, coots and other swimming birds were selected as indicator species for the study. The HEC-RAS hydrological model was used to simulate the submergence of preferred habitats of swimming birds such as coots under the extreme rainfall of 100-year return period, and the habitat optimization design of waterbirds was carried out in the context of landscape scale, foraging scale and habitat scale, combined with the proportion of water body and wetland preferred by waterbirds, landscape characteristics, foraging and habitat characteristics. At the same time, it focuses on enhancing the aggregation and connectivity of water bodies and wetlands to improve habitat quality (see Fig. 11 ). After the habitat landscape restoration design, swimming birds prefer to nest and inhabit on the optimized floating island. Even if the wetland is flooded due to extreme rainfall, the floating island will only float on the water surface with the fluctuation of water level, which will not affect the internal waterfowl habitat, and to a certain extent, alleviate and avoid the reduction of the number of rare bird species caused by the flooding of waterfowl habitat. 5. Conclusions and limitations In this paper, the HEC-RAS model was used to simulate the inundation of the wetland in the lower reaches of the Shiwuli River Basin in Hefei City under extreme rainfall conditions, and to optimize the habitat design of waterbirds. The innovation of this study lies in: (1) Transferring the perspective from people-oriented flood control and disaster prevention to stormwater protection of waterfowl habitat; (2) Transferring the way to deal with extreme rainfall from the previous engineering measures of building water storage weirs to the blue-green infrastructure design of biological habitat network system construction which integrates natural, semi-natural and green vegetation and water; (3) From the previous focus on the macro-level study of waterbird habitat restoration to the more targeted combination of hydrological quantitative simulation and habitat restoration design. The results show that: (1) swimming birds such as coots are sensitive indicators of the wetland ecosystem of the Shiwuli River, which can truly reflect the status of the wetland ecosystem; (2) in the case of extreme rainfall once in a century, the flood will submerge all the rivers in the study area, and in the downstream wetlands and other areas, it will be higher than the river bank, forming a submerged area; (3) Setting up floating islands in wetlands may alleviate the inundation of waterfowl habitats to a certain extent and play a protective role for waterfowl. This study is helpful to understand the change of waterfowl habitat under the condition of climate change, and based on the actual situation of the Shiwuli River Basin combined with hydrological software to carry out quantitative simulation, and according to the problems in the wetland and river reflected by the evaluation results, targeted optimization strategies are put forward to avoid the destruction of aquatic organisms in the wetland by floods. The study area of this study is located in the Shiwuli River Basin in Hefei City, Anhui Province, which is located in the typical monsoon climate zone, and the downstream is connected with lakes, so the regional characteristics are obvious and representative, which has a certain reference for some countries in the monsoon region where waterlogging is caused by the downstream lakes in the rainy season. At the same time, the strategies of wetland planning and design are put forward from the perspective of bird habitat construction, which will eventually be implemented in the actual landscape planning scheme, and the concept of ecological protection will be integrated into the urban landscape planning and design, which will help to create more suitable habitats for urban birds. However, there are still some limitations and shortcomings in the method and content: First, in terms of research objects, this study did not design different bird habitats from the perspective of stormwater preference, but only selected the most vulnerable swimming birds as indicator species, so it is difficult to provide more sophisticated strategies for the creation of bird diversity habitats. Secondly, in terms of research methods, due to the lack of systematic waterbird monitoring technology, the habitat optimization is only planned and designed with the actual case and the current situation of the study area, and the optimization results are not verified and analyzed. Therefore, in future studies, different bird habitats can be combined with stormwater simulation, and the optimization results can be analyzed by experimental design to further improve the accuracy and integrity of the study. Declarations Declaration of generative AI in scientific writing Declaration for the manuscript ‘Research on the method of optimizing the multi-scale layout of rural multi-pond landscape to cope with non-point source pollution from agricultural watersheds’, we have not used AI technology in scientific writing in the manuscript. Funding The authors did not receive support from any organization for the submitted work. No funding was received to assist with the preparation of this manuscript. No funding was received for conducting this study. No funds, grants, or other support was received. Ethical Approval Not applicable. There is no human experiment or animal experiment in the study, and the study does not address the ethical issue. Consent to Participate Not applicable. Consent to Publish Not applicable. Competing Interests The authors declare that there are no conflicts of interest regarding the publication of this paper. Availability of data and materials. All data generated or analyzed during this study are included in the manuscript. Author contribution All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Chen Xinyi. The first draft of the manuscript was written by Chen Xinyi and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. 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Application of ANN and HEC-RAS model for flood inundation map** in lower Baro Akobo River Basin, Ethiopia. Journal of Hydrology: Regional Studies, 36, 100855. https://doi.org/10.1016/j.ejrh.2021.100855 Vougioukalou, M., Akriotis, T., & Dimalexis, A. (2011). Waterfowl habitat restoration in a seasonal island wetland. Procedia Environmental Sciences, 9, 191-195. https://doi.org/10.1016/j.proenv.2011.11.029 Wang, G., Zhao, J., Li, W., Song, X., Zhang, Y., Li, C., & de Boer, W. F. (2023). Responses of breeding waterbird communities to environmental changes in subsidence wetlands in the North China Plain. Avian Research, 14, 100110. https://doi.org/10.1016/j.avrs.2023.100110 Whited, D., Galatowitsch, S., Tester, J. R., Schik, K., Lehtinen, R., & Husveth, J. (2000). The importance of local and regional factors in predicting effective conservation: Planning strategies for wetland bird communities in agricultural and urban landscapes. Landscape and Urban Planning, 49(1-2), 49-65. https://doi.org/10.1016/S0169-2046(00)00046-3 Wu, X. (2023). The digital landscape design and layout of wetlands based on green ecology. Energy Reports, 9, 982-987. https://doi.org/10.1016/j.egyr.2022.11.198 Xu, C., Yu, Q., Wang, F., Qiu, S., Ai, M., & Zhao, J. (2023). Identifying and optimizing ecological spatial patterns based on the bird distribution in the Yellow River Basin, China. Journal of Environmental Management, 348, 119293. https://doi.org/10.1016/j.jenvman.2023.119293 Yang, S., Yuan, Z., Ye, B., Zhu, F., Chu, Z., & Liu, X. (2024). Impacts of landscape pattern on plants diversity and richness of 20 restored wetlands in Chaohu Lakeside of China. Science of the Total Environment, 906, 167649. https://doi.org/10.1016/j.scitotenv.2023.167649 Yang, X., Liu, W., Li, S., Ma, Z., Chen, C., Gu, W., ... & Hu, H. (2022). Restoration of urban waterbird diversity: A case study of the construction of a waterbird ecological corridor in the Guangdong-Hong Kong-Macao Greater Bay Area, Southern China. Global Ecology and Conservation, 39, e02277. https://doi.org/10.1016/j.gecco.2022.e02277 Yao, S., Li, X., Liu, C., Zhang, J., Li, Y., Gan, T., ... & Kuang, W. (2020). New assessment indicator of habitat suitability for migratory bird in wetland based on hydrodynamic model and vegetation growth threshold. Ecological Indicators, 117, 106556. https://doi.org/10.1016/j.ecolind.2020.106556 Zhang, P., Zhang, S., Zou, Y., Wu, T., Li, F., Deng, Z., ... & **e, Y. (2023). Integrating suitable habitat dynamics under typical hydrological regimes as guides for the conservation and restoration of different waterbird groups. Journal of Environmental Management, 345, 118451. https://doi.org/10.1016/j.jenvman.2023.118451 Zhao, J., Ke, E., Wang, B., & Zhao, Y. (2024). An optimization model for the impervious surface spatial layout considering differences in hydrological unit conditions for urban waterlogging prevention in urban renewal. Ecological Indicators, 158, 111546. https://doi.org/10.1016/j.ecolind.2024.111546 Zhu, Y., Wang, H., & Guo, W. (2021). The impacts of water level fluctuations of East Dongting Lake on habitat suitability of migratory birds. Ecological Indicators, 132, 108277. https://doi.org/10.1016/j.ecolind.2021.108277 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4343801","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":298599918,"identity":"af0c25b1-3dbe-418b-8f5f-7f7a1e9c2bc0","order_by":0,"name":"xinyi Chen","email":"","orcid":"","institution":"Hefei University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"xinyi","middleName":"","lastName":"Chen","suffix":""},{"id":298599919,"identity":"0435e450-0d7e-460a-a0ea-3d5ae5b3585d","order_by":1,"name":"jinjin 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diagram.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/fe7fa8e8548306c9d5bee365.png"},{"id":56171443,"identity":"c3e12cb9-ab53-4973-b33a-a0f94a06d894","added_by":"auto","created_at":"2024-05-09 11:51:03","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1785552,"visible":true,"origin":"","legend":"\u003cp\u003eHabitat inundation range.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/9ca4aa4086bb7c609b1684bb.png"},{"id":56171446,"identity":"43bfef8a-8a8e-46d1-bf46-1fc7c589ad5f","added_by":"auto","created_at":"2024-05-09 11:51:05","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":178289,"visible":true,"origin":"","legend":"\u003cp\u003eHabitat submergence height.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/b6d99b4ec991eefd767c54e3.png"},{"id":56171911,"identity":"8e9d7d1b-3176-4860-a21a-700218d9bb85","added_by":"auto","created_at":"2024-05-09 11:59:04","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":318928,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of floating island section.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/f4987fa791a4c6b40da3203d.png"},{"id":56170730,"identity":"fd95aa36-970a-4ff6-af85-804777a0550d","added_by":"auto","created_at":"2024-05-09 11:43:03","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":58006,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of working principle of ship anchor.\u003c/p\u003e","description":"","filename":"floatimage10.png","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/93f259600c34031ad42b907f.png"},{"id":56170732,"identity":"ce180177-b582-4b07-b029-258c29d72ee5","added_by":"auto","created_at":"2024-05-09 11:43:04","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":679518,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic Diagram of Optimized Waterbird Habitat\u003c/p\u003e","description":"","filename":"floatimage11.png","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/08bfef7e32603829a47eed27.png"},{"id":56698329,"identity":"444b9e19-b343-4f98-8716-78923b59ffd8","added_by":"auto","created_at":"2024-05-18 07:37:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9147049,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4343801/v1/fef3612a-d34e-4a40-98e9-b3350fd33cd7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eWhere do waterbirds settle down under heavy rain: Waterbird habitat planning and design from the perspective of rain and flood resilience\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eUrban boundary wetland is an important ecosystem for sustainable development (Li et al., 2003; Chen and Jim, 2008), which can provide important ecological services for cities (Alikhani et al., 2021). It plays an important role in reducing urban heat island effect (Xue et al., 2019; Alikhani et al., 2021). In many developed countries, the blue-green space of urban wetlands is the only option to provide sustainable living conditions (Chiesura, 2004). At the same time, urban wetlands contain a large number of aquatic organisms, such as aquatic plants, birds, fish, amphibians and invertebrates. The bird community reflects the land use conditions of wetlands and cities better than other biological communities (Galatowitsch et al., 1999). Similarly, other studies have clearly shown the relationship between landscape patterns and wetland birds, suggesting that bird diversity increases with the percentage of riparian wetlands. Therefore, it is necessary to protect urban/suburban wetland ecosystems and wetland waterbirds to promote sustainable urban development (Zheng et al., 2012; Liu et al., 2016).\u003c/p\u003e \u003cp\u003eHowever, in recent years, the number of extreme weather has increased significantly, and the number of days of continuous heavy precipitation has also gradually increased. Under this climate background, the process of urbanization has been accelerating, the scale of cities has been expanding, and the spatial pattern of land use has changed, which is characterized by a large increase in urban construction land. The hardening of urban underlying surface, low permeability and limited drainage capacity are the important reasons for serious urban water accumulation. The combined effect of human activities and natural environment change is the reason for the significant increase of urban waterlogging disaster risk. Because the drainage capacity of urban pipe network in major cities can not meet the needs of urban development, urban water is difficult to drain in time. Urban wetland, especially the urban boundary wetland, as the ecosystem of the city, is vulnerable to the threat of waterlogging disasters, and belongs to the area with high risk of waterlogging. In particular, floods can affect the survival, habitat, population, foraging activities, breeding and living environment of waterbirds. Some urban wetlands are important nodes for migratory birds to migrate and inhabit. If there is no perfect protection system to deal with extreme weather, once extreme events such as torrential rain break out, it is easy to cause serious impact on migratory bird populations and other aquatic organisms. Due to the concentration of bird populations and habitats, some swimming birds prefer to build nests and breed floating nests on the water surface. If a large external disturbance event occurs, the environmental quality of the original habitat will decline, especially when the water level of the habitat rises due to extreme rainfall, the floating nests and nestlings of waterbirds will be submerged, which will have a serious impact on the population of waterbirds.\u003c/p\u003e \u003cp\u003eIn the early 20th century, some European countries have taken bird richness as the second indicator of environmental quality when evaluating the quality of urban life. Therefore, the wetland area at the urban boundary should be provided with a habitat for bird populations under extreme rainfall conditions, so as to promote the improvement of biodiversity and environmental quality in the study area, create an ideal place for migratory birds such as waterbirds to migrate and breed, and become an important habitat paradise for resident birds and migratory birds during their migration.\u003c/p\u003e \u003cp\u003eWith the prominence of the importance of urban wetlands, scholars began to pay attention to the research between urban wetlands and urban waterlogging. Gogoaşe Nistoran et al. (2016) analyzed the Bicaz dam in Romania using HEC-RAS to assess the depth, velocity, and propagation time of dam-break flood waves. (Xiong (2011) considered the possible maximum flood to predict the downstream water level and discharge hydrograph. Chandrabose et al. (2014) used HEC-GeoRAS to derive the river geometry data from the SRTM digital elevation model and used HEC-RAS to perform the dam break analysis of Malankara Dam in India to obtain the water level, discharge hydrograph and inundated area. People's understanding of the ecological function and importance of natural drainage channels such as river networks and wetlands has been gradually improved, but few studies have considered the impact of extreme rainfall on wetlands and wetland aquatic organisms from the perspective of stormwater resilience.\u003c/p\u003e \u003cp\u003eCurrently, three types of models are used to assess urban waterlogging risk: hydrological and hydrodynamic models, qualitative models, and machine learning models (Bera et al., 2022; Motta et al., 2021; Xie et al., 2020). The mathematical models used to assess urban waterlogging and simulate river flood routing are mainly based on one-dimensional and two-dimensional hydrodynamic mathematical models. According to the function and application field, it can be divided into: river hydrodynamic model software for river flow, water level, water speed and other parameters calculation and flood monitoring, mainly including HEC-RAS, MIKE11, River2D, IFMS, etc.; Water resources management and river planning software for water resources management and planning decision support, mainly including WMS, WEAP, MIKE BASIN; Urban hydrodynamic model software for urban flood control, drainage system planning and regulation and storage mainly includes MIKE URBAN, TUFLOW, FLO-2D, IFMS, SWMM, etc. Compared with other software, HEC-RAS software has obvious advantages in flood routing and river flow calculation. It can predict and analyze flood characteristics such as flood discharge, water level, inundation range, flow rate and depth, and preliminarily identify vulnerable areas.\u003c/p\u003e \u003cp\u003eGenerally speaking, wetland is an important habitat for birds, and its rational planning and design plays an extremely important role in reversing the degradation of bird habitat and maintaining the level of biodiversity. Nowadays, the planning and design of bird habitat restoration mostly start with the characteristics of wetland itself, focusing on the restoration and construction of wetland water environment, or using some quantitative research methods of ecology in the planning and design of wetland bird habitat restoration to strengthen the implementation effect of protection and restoration. The research results generally focus on habitat selection, habitat suitability evaluation and the impact of habitat fragmentation on bird communities, and most of them are based on wetland bird communities, ecology and other related studies, combined with regional environmental characteristics. Habitat restoration design is defined from the aspects of water environment, vegetation resources and human disturbance that affect the planning and design of wetland bird habitats, so as to realize the protection and restoration of wetland bird habitats and the improvement of bird diversity. Most of the relevant restoration strategies are based on wetland bird communities, and lack of attention to the most protected bird species in the region, so it is inevitable to neglect the most protected species in the process of wetland bird habitat restoration, resulting in their migration.\u003c/p\u003e \u003cp\u003eTo sum up, scholars' research on urban waterlogging mainly includes analyzing the changes of surface runoff under different scenarios and revealing the most effective optimal allocation of surface space (Wang, 2021, Wu, 2022); According to the geographical conditions and economic development level of a specific region, the study on the optimization of the surface spatial pattern of a specific location (Sun et al., 2018, Liu, 2019) tends to solve the problems of a specific field, focusing more on local and specific factors, and less on the comprehensive optimization of the whole city or watershed; Or combine the hydrological model with the optimization algorithm to discuss the optimization of the spatial pattern of the impervious surface. Few studies have focused on the inundation of waterbird habitats under extreme rainfall and the corresponding preventive planning and design. Especially for the wetlands downstream of the urban boundary in some monsoon countries, the frequency of rainfall in the rainy season increases, and once extreme rainfall occurs, the downstream river jacking will have a serious impact on wetlands and wetland birds. Therefore, this study will focus on the changes of aquatic habitats when floods occur and the construction methods of flood-proof and resilient cities in the small patches of watershed scale within the city. According to the actual situation of the basin, fully considering the inundation of waterbird habitat under extreme rainfall conditions, quantitative simulation is carried out by combining with hydrological software, and targeted optimization strategies are put forward according to the inundation depth and inundation area of the river reflected by the simulation results. The main objectives of this study are: (1) indicator species selection in the Shiwuli River Basin; (2) wetland inundation range and inundation height in the lower reaches of the Shiwuli River under extreme rainfall conditions; (3) habitat optimization design of waterbirds from the perspective of stormwater resilience.\u003c/p\u003e"},{"header":"2. Study area","content":"\u003cp\u003eThis study takes Shiwuli River Basin as an example. Shiwuli River originates from the southeast foot of Dashu Mountain in Hefei City, flows from northwest to southeast, and is the last ecological barrier to Chaohu Lake (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). There is an artificial lake in the upper reaches called Swan Lake, which is an important tributary of Chaohu Lake. However, there is no stable clean water source in the upper reaches of Shiwuli River, and the river supply mainly comes from natural precipitation and tail water discharge from sewage treatment plants. The estuary wetland of the Shiwuli River plays an important role in water purification. After the wetland treatment, the water quality entering the lake can stably reach the third class water standard of surface water.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn recent years, with the advancement of wetland restoration, Shiwuli River has gradually become one of the important protection sites for migratory birds (see Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). At the same time, a large number of migratory birds inhabit the lakeside National Wetland Park near the study area, including coots, winged ducks, spot-billed ducks, red sheldrakes, white-browed ducks, mallards, bulbuls, herons and night herons, etc. The population of migratory birds has reached more than 4000. Especially in the past two years, more and more migratory birds choose to live here. In April 2021, the white crane, a national first-class protected animal, reappeared in the lakeside wetland after about 20 years, with a population of 14, the largest number of white cranes recorded in the history of Hefei. In recent years, the population of birds in the wetland has been expanding, ranking first in the whole area around Chaohu Lake, which is the most concentrated area of various waterbirds in Chaohu Lake, including one species of national first-class protected birds, namely Oriental White Stork, five species of national second-class protected birds, namely White Spoonbill, Mandarin Duck, Common Buzzard, Skylark and White-breasted Emerald, and 15 species of local key protected birds in Anhui Province.\u003c/p\u003e \u003cp\u003eHowever, due to the particularity of geographical location and the influence of weather, the Shiwuli River experienced basin-wide floods in 2016 and 2020. On July 9, 2016, the water level of Chaohu Lake in the lower reaches reached 12.77 meters, and many dangerous situations occurred in the areas of Shiwuli River and Majiadu Bridge; on July 22, 2020, the water level of Chaohu Lake broke through the historical extreme value and reached13.43meters. Leakage, piping and other dangerous situations occurred in the jurisdiction area, resulting in large flood disasters. The wetlands in the region were flooded and the habitats of aquatic organisms were destroyed, which had a serious impact on the population of waterbirds. As an important node for migratory birds to migrate and inhabit, there is no perfect protection system to deal with extreme weather in the Shiwuli River Basin at present. Once extreme events such as torrential rains in 2016 and 2020 break out, it is easy to cause serious impact on migratory bird populations and other aquatic organisms. At the same time, because the bird population and habitat are particularly concentrated, if a large external disturbance event occurs, the environmental quality of the original habitat will decline, and even have a serious impact on the population of waterbirds. At the same time, the lower reaches of Shiwuli River is connected with Chaohu Lake, and resident birds and migratory birds may not be able to find suitable habitats in this area as a substitute. Therefore, the wetland area in the lower reaches of the Shiwuli River should be provided with a habitat for waterbird populations under extreme rainfall conditions, so as to promote the improvement of biodiversity level and environmental quality in the study area, create an ideal place for migratory birds such as all kinds of waterbirds to migrate and breed, and become an important habitat paradise for resident birds and migratory birds during their migration.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"3. Methodology","content":"\u003cp\u003eThis study method is divided into three parts, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Firstly, the first step is to determine the indicator birds by comparing the differences of breeding and staying time of waterbirds, the level of rare species and the type of residence in the wetland of the lower reaches of the Shiwuli River; Secondly, the combination of GIS and HEC-RAS model was used to predict and analyze the flood characteristics of the study area under extreme rainfall conditions, such as flood discharge, water level, inundation range, flow velocity and depth, and to identify the vulnerable areas; Finally, according to the simulation results, the optimal design of waterfowl habitat in the study area is carried out from the perspective of stormwater resilience.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Target species selection\u003c/h2\u003e \u003cp\u003eFor the selection of indicative waterbirds in the Shiwuli River Basin, the focus is on the habitat quality and population size of birds. It mainly chooses birds under the first and second class protection of the state. These birds are rare in number and have high requirements for habitats, and the habitat quality of the wetland in the basin can be improved by focusing on the protection of these birds. By focusing on the protection of these birds, the habitat quality of the wetland in the basin can be improved. Through habitat restoration and construction, more target birds will be attracted to live here.\u003c/p\u003e \u003cp\u003eBirds can be divided into wading birds, swimming birds, climbing birds, raptors and songbirds according to their ecological habits. Among them, swimming birds live in various types of waters, most of them nest on the shore and shoals, and a few of them choose to live in the water islands. Swimming birds feed in different areas, some in the shallows and some in the water. Most of them are migratory birds, like to live in groups, and are good at swimming, diving and getting food in the water. They feed on aquatic plants, insects, fish, shrimp and shellfish. They are relatively insensitive to human activities and can be viewed at close range. The main representative species of swimming birds are Chinese merganser, coot, mallard, Mandarin duck, red Sheldrake, red-necked duck, pintail duck, magpie duck and green-headed diving duck. Among them, coots, red sheldrakes and green-headed diving ducks are listed in the Red List of Endangered Species of the World Conservation Union. At the same time, coots are also found inhabiting wetlands in the lower reaches of the Shiwuli River, so they are the key protected objects (see Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAccording to the habitat type of the site, by comparing the differences of breeding and staying time of waterbirds in the wetland of the lower reaches of the Shiwuli River, the level of rare species and the type of residence (according to the order of resident birds first, followed by summer migratory birds, winter migratory birds and traveling birds), an indicator bird was finally determined, that is, (small and medium-sized) geese and ducks. Specifically, it is a rare water bird such as coot chicken and red Sheldrake. At the same time, this kind of representative species is also a sensitive indicator of wetland ecosystem, which can truly reflect the status of wetland ecosystem. Through the construction of high-quality waterbird habitats that can cope with extreme rainfall, the core and unique ecological resources of the wetland in the lower reaches of the Shiwuli River are formed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Hydrologic modelling in HEC-RAS\u003c/h2\u003e \u003cp\u003eThe HEC-RAS software is a computer program developed for modeling river flowing through open natural channels and used for computing water surface profile (Mapping and Field, 2017; Lamichhane and Sharma, 2018; Duvvuri and Narasimhan, 2013). HEC-RAS get accepted and being used for river simulation by hydraulic engineers and different researchers (Marimin et al., 2018) because of its capabilities and abilities to simulate unsteady flow and identifies flood-prone areas where the surface ground level is lower than the computed water profile and allows the researcher to visualize the flood extent along a river course (Maidment, 2017; Timbadiya et al., 2011). The modeling process of HEC-RAS is as follows (see Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), and its functions include steady and unsteady flow simulation, dam-break and dike-break analysis, water quality simulation, hydraulic design, and sediment transport.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Preparation of modeling data\u003c/h2\u003e \u003cp\u003eThis study combines field survey, remote sensing images, data collection and other methods to obtain the basic data of the study, including rainfall, hydrology, land use and DEM data. The method of combining GIS with HEC-RAS model is used to analyze the hydrological and hydrodynamic processes of small watershed under historical rainfall-flood events. Based on the DEM data downloaded from the Geospatial Data Cloud, GIS software is used to modify and improve the river elevation according to the current situation of the site, and then the SHP format is exported to RasMapper to establish geometric data, and the corresponding river section and boundary are added at the location of the river according to the satellite image.\u003c/p\u003e \u003cp\u003eIn order to simulate the maximum possible flood inundation range of the habitat, based on the historical extreme rainfall flood flow information collected from the relevant units in Hefei, the 100-year, 50-year and 20-year design peak flows of the Shiwuli River were selected as the flow input conditions of the HEC-RAS model. At the same time, the flood inundation characteristics of historical rainstorm floods in the basin scale were studied by combining with GIS, and the flood characteristics such as flood discharge, water level, inundation area, flow velocity and depth were predicted and analyzed, and the vulnerable areas were preliminarily identified, and the feasibility of applying the HEC-RAS hydrodynamic model to the evaluation of waterfowl habitat was discussed (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eData required for simulation.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eData category\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDate composition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDEM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDigital elevation data with 30 meter resolution\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFor the river section without measured data, the information of the river section can be extracted from the DEM data of the study area as the basic data for the study.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRiver flow\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100-year river discharge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBased on the existing drainage and waterlogging prevention instructions of Hefei City and other relevant data, input the river flow value once in a hundred years under extreme rainfall conditions.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eManning coefficient\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChannel roughness is set according to empirical values\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFor areas without measured data, the roughness can be determined based on experience and or with reference to adjacent similar basins or river sections.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 One-dimensional model construction(Simulate inundation height)\u003c/h2\u003e \u003cp\u003ePrepare the terrain file of the area to be modeled and the point SHP shape file of the regional spatial coordinates, import the terrain file into the ras Mapper in HEC-RAS, create the river centerline, river shoreline and flow path (boundary line) in Ras Mapper, and draw the river cross section according to the length of the river. The discharge and other corresponding parameters are set according to the 100-year design flood level of Shiwuli River in the drainage and waterlogging prevention instructions of Hefei City. Finally, each section of the river and the maximum submerged height are obtained. (see Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eValues of relevant parameters.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFloodplain roughness\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChannel roughness\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eChannel slope\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumerical value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e3.3.3 Two-dimensional model construction(Simulate inundation range)\u003c/h2\u003e \u003cp\u003e2D Flow Area in RAS Mapper is a module for 2D grid and point establishment of topographic map in the study area. After the topographic map is processed, it is imported into HEC-RAS to define the projection, and then the topographic map is imported into RAS Mapper for two-dimensional modeling. After calculation, the water surface profile, flow velocity, water depth and other elements under different flood frequencies can be obtained, which can be visually displayed in Ras Mapper.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Design ideas\u003c/h2\u003e \u003cp\u003eStudies have shown that species have three possible responses to climate change: adaptation (evolutionary change or physiological adaptation), migration or extinction, and birds need to actively find the geographical location of the niche that sustains their livelihood (Holt, 1990; Peterson et al., 2001). Studies have confirmed that climate change will lead to changes in the range of bird species to some extent (Li et al., 2015; Peterson et al., 2001).\u003c/p\u003e \u003cp\u003eTherefore, how to maintain the original ecological balance of wetlands under extreme weather conditions and prevent bird nests and nestlings from being flooded is the key content of this study. Therefore, in this study, \"ecology and safety\" are introduced into the planning and design of habitats at the same time, fully considering the habitat environment of waterbirds in the submerged state, and taking the floating mini-park in the famous Bangkok waters as inspiration for the design of wetland floating bird nests. A movable bird nest is assembled by filling the boat with soil and shade-tolerant and moisture-tolerant aquatic plants, so as to meet the daily feeding and perching of swimming birds and other aquatic organisms and avoid the interference of extreme weather (see Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Result and discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Habitat flooding results in flooding.\u003c/h2\u003e \u003cp\u003eAccording to the instruction of drainage and waterlogging prevention in Hefei City, the wetland area of Shiwuli River is 0.67 km2, the lake bottom elevation is 6.5-7.0 m, the normal water level is 11.5 m, the flood control level is 11.0 m, the maximum control flood level is not more than 12.0 m, and the regulation and storage volume is 670,000 m3. Through the establishment of HEC-RAS model for channel reconstruction, two-dimensional drainage surface construction, boundary line construction, roughness determination, boundary condition setting and operation plan formulation, the dynamic simulation results of the 100-year flood in the lower reaches of the Shiwuli River clearly show that the flood has submerged the whole channel in the study area, and is higher than the river bank in many areas, forming a submerged area.\u003c/p\u003e \u003cp\u003eFrom the one-dimensional and two-dimensional simulation results, it can be intuitively observed that when the 100-year river flow value is input, the water area has completely exceeded the wetland river area under extreme rainfall conditions, causing a large area of erosion to the wetland riverbank and the waterfowl habitat in the region (see Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). According to the calculation of RAS Mapper, the maximum inundation depth of the study area is 12.8 m, which is higher than the flood control level of the river (12 m) (see Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). According to the flood simulation results of HEC-RAS for this control section, when the lower reaches of Shiwuli River are facing a once-in-a-century flood, the waterfowl habitat and the surrounding wetland parks will be greatly threatened, and corresponding measures should be taken to prevent the rare waterfowl from being homeless due to the inundation of the waterfowl habitat by the flood.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Floating Island Planning and Design\u003c/h2\u003e \u003cp\u003eDesign floating bird nests in wetlands in areas prone to flooding. Floating bird's nest is a special habitat in a certain water area, which is still above the water surface at high tide and has a certain distance from the land. Floating bird nests were set up at least 10 meters away from the shore in the preferred habitat waters of coots and other swimming birds in the lower reaches of the Shiwuli River, and the location and design conditions of floating bird nests were determined according to the characteristics of coot nest site selection (see Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). At the same time, the bird's nest is fixed with an anchor to prevent the bird's nest from being unstable due to shaking on the water surface (see Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e). The design of ship anchor shall follow the principles of safety, energy efficiency and environmental protection: the strength and corrosion resistance of the anchor body and anchor chain shall be fully considered to ensure that the anchor can bear the weight of the floating island and the river environment; the weight of the anchor shall be reduced as much as possible to improve its durability and service life, so as to save energy to the maximum extent while ensuring safety; Environmentally friendly materials are used to reduce the friction and noise of the anchor chain at the bottom of the river and reduce the impact on the wetland ecosystem. (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDesign parameters of floating bird's nest.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCondition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDistance from water /m\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDepth of water /cm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNest depth /cm\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29.00\u0026thinsp;\u0026plusmn;\u0026thinsp;2.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e59.00\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eNote: Data are expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Internal Habitat Design of Floating Island\u003c/h2\u003e \u003cp\u003eWaterbird habitat landscape design should provide good food sources and hidden spaces for habitats based on biodiversity factors and well-arranged plants. Plant communities create food sources for living organisms to survive. Aquatic plants are the main food for birds, fish, shrimp, and insects; the rich plant community and its insects and fruits are the food sources of birds; grassplot is the habitat of wading birds and mollusks (Haiting et al., 2018).\u003c/p\u003e \u003cp\u003eFor internal habitat planning of floating islands, previous studies have shown that water availability, food availability, habitat conditions and disturbance are the most important factors affecting habitat selection of waterbirds (Bo et al., 2008; Dong et al., 2013; Jiang et al., 2016; Maleki et al., 2016; Zhao et al.,2018). The nest site selection of swimming birds is often affected by natural and non-natural factors such as food, nest material, interspecific relationship and external interference. Therefore, it prefers the nest location with convenient foraging, easy access to nest materials, less interference and high degree of concealment. In addition, the dense and tall aquatic plants in the wetland environment can provide a safe environment for swimming birds to build nests with high degree of concealment and defense against natural enemies. Therefore, the plant factor design on the floating island adopts 0\u0026ndash;10% arbor, 30\u0026ndash;50% shrub and 40\u0026ndash;70% emergent plants for planting, while ensuring 30\u0026ndash;50% vegetation coverage. The current vegetation on the embankment around the current habitat is reserved to play a certain role in shielding the floating island.\u003c/p\u003e \u003cp\u003eIn addition, in order to give full play to the ecological benefits of wetlands and build an eco-friendly society, wetland protection laws should be formulated to protect the habitats of migratory birds while protecting and restoring the wetland landscape. Major land cover change projects should be prohibited. Enhance the ecological function of wetland and protect the wetland environment (Hu et al.,2020).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Optimized Waterbird Habitat\u003c/h2\u003e \u003cp\u003eBased on the field investigation and species analysis of the wetland in the lower reaches of the Shiwuli River, coots and other swimming birds were selected as indicator species for the study. The HEC-RAS hydrological model was used to simulate the submergence of preferred habitats of swimming birds such as coots under the extreme rainfall of 100-year return period, and the habitat optimization design of waterbirds was carried out in the context of landscape scale, foraging scale and habitat scale, combined with the proportion of water body and wetland preferred by waterbirds, landscape characteristics, foraging and habitat characteristics. At the same time, it focuses on enhancing the aggregation and connectivity of water bodies and wetlands to improve habitat quality (see Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e). After the habitat landscape restoration design, swimming birds prefer to nest and inhabit on the optimized floating island. Even if the wetland is flooded due to extreme rainfall, the floating island will only float on the water surface with the fluctuation of water level, which will not affect the internal waterfowl habitat, and to a certain extent, alleviate and avoid the reduction of the number of rare bird species caused by the flooding of waterfowl habitat.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions and limitations","content":"\u003cp\u003eIn this paper, the HEC-RAS model was used to simulate the inundation of the wetland in the lower reaches of the Shiwuli River Basin in Hefei City under extreme rainfall conditions, and to optimize the habitat design of waterbirds. The innovation of this study lies in: (1) Transferring the perspective from people-oriented flood control and disaster prevention to stormwater protection of waterfowl habitat; (2) Transferring the way to deal with extreme rainfall from the previous engineering measures of building water storage weirs to the blue-green infrastructure design of biological habitat network system construction which integrates natural, semi-natural and green vegetation and water; (3) From the previous focus on the macro-level study of waterbird habitat restoration to the more targeted combination of hydrological quantitative simulation and habitat restoration design. The results show that: (1) swimming birds such as coots are sensitive indicators of the wetland ecosystem of the Shiwuli River, which can truly reflect the status of the wetland ecosystem; (2) in the case of extreme rainfall once in a century, the flood will submerge all the rivers in the study area, and in the downstream wetlands and other areas, it will be higher than the river bank, forming a submerged area; (3) Setting up floating islands in wetlands may alleviate the inundation of waterfowl habitats to a certain extent and play a protective role for waterfowl.\u003c/p\u003e \u003cp\u003eThis study is helpful to understand the change of waterfowl habitat under the condition of climate change, and based on the actual situation of the Shiwuli River Basin combined with hydrological software to carry out quantitative simulation, and according to the problems in the wetland and river reflected by the evaluation results, targeted optimization strategies are put forward to avoid the destruction of aquatic organisms in the wetland by floods. The study area of this study is located in the Shiwuli River Basin in Hefei City, Anhui Province, which is located in the typical monsoon climate zone, and the downstream is connected with lakes, so the regional characteristics are obvious and representative, which has a certain reference for some countries in the monsoon region where waterlogging is caused by the downstream lakes in the rainy season. At the same time, the strategies of wetland planning and design are put forward from the perspective of bird habitat construction, which will eventually be implemented in the actual landscape planning scheme, and the concept of ecological protection will be integrated into the urban landscape planning and design, which will help to create more suitable habitats for urban birds.\u003c/p\u003e \u003cp\u003eHowever, there are still some limitations and shortcomings in the method and content: First, in terms of research objects, this study did not design different bird habitats from the perspective of stormwater preference, but only selected the most vulnerable swimming birds as indicator species, so it is difficult to provide more sophisticated strategies for the creation of bird diversity habitats. Secondly, in terms of research methods, due to the lack of systematic waterbird monitoring technology, the habitat optimization is only planned and designed with the actual case and the current situation of the study area, and the optimization results are not verified and analyzed. Therefore, in future studies, different bird habitats can be combined with stormwater simulation, and the optimization results can be analyzed by experimental design to further improve the accuracy and integrity of the study.\u003c/p\u003e "},{"header":"Declarations","content":"\u003ch2\u003eDeclaration of generative AI in scientific writing\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eDeclaration for the manuscript \u0026lsquo;Research on the method of optimizing the multi-scale layout of rural multi-pond landscape to cope with non-point source pollution from agricultural watersheds\u0026rsquo;, we have not used AI technology in scientific writing in the manuscript.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eThe authors did not receive support from any organization for the submitted work.\u003c/p\u003e\n\u003cp\u003eNo funding was received to assist with the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003eNo funding was received for conducting this study.\u003c/p\u003e\n\u003cp\u003eNo funds, grants, or other support was received.\u003c/p\u003e\n\u003ch2\u003eEthical Approval\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eNot applicable. There is no human experiment or animal experiment in the study, and the study does not address the ethical issue.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eConsent to Participate\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003ch2\u003eConsent to Publish\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003ch2\u003eCompeting Interests\u003c/h2\u003e\n\u003cp\u003eThe authors declare that there are no conflicts of interest regarding the publication of this paper.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials.\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in the manuscript.\u003c/p\u003e\n\u003ch2\u003eAuthor contribution\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Chen Xinyi. The first draft of the manuscript was written by Chen Xinyi and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBharath, A., Shivapur, A. V., Hiremath, C. G., \u0026amp; Maddamsetty, R. (2021). Dam break analysis using HEC-RAS and HEC-GeoRAS: A case study of Hidkal dam, Karnataka state, India. Environmental Challenges, 5, 100401. https://doi.org/10.1016/j.envc.2021.100401.\u003c/li\u003e\n\u003cli\u003eBai, S., Wang, X., Zhang, Y., Liu, F., Shi, L., Ding, Y., Wang, M., Lyu, T., 2022. Constructed wetlands as nature-based solutions for the removal of antibiotics: Performance, microbial response, and emergence of antimicrobial resistance (AMR). Sustainability 14, 14989.https://doi.org/10.3390/su142214989.\u003c/li\u003e\n\u003cli\u003eBrinson, M.M., Bradshaw, H.D., Kane, E.S., 1984. 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Ecological Indicators, 132, 108277. https://doi.org/10.1016/j.ecolind.2021.108277\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Urban Wetland, Extreme rainfall, Combination of waterlogging and design, HEC-RAS model, Waterbird habitat planning","lastPublishedDoi":"10.21203/rs.3.rs-4343801/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4343801/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUrban wetlands have ecological functions such as maintaining biodiversity and regulating runoff, and wetland waterbirds are also important biological indicators of wetland ecosystems, which can reflect the ecological conditions of wetlands and cities. In recent years, extreme weather occurs frequently, urban waterlogging is serious, rivers play the role of flood drainage, and rainwater backflow will have a serious impact on urban rivers, wetlands and aquatic organisms. Therefore, it is necessary to explore the inundation of urban wetlands under extreme rainfall conditions. In the past, most of the research on waterlogging was from the perspective of disaster prevention, and there was little research on the degree of habitat destruction of waterbirds.\u003c/p\u003e \u003cp\u003eIn this paper, the HEC-RAS hydrological model was used to simulate the extreme rainfall of the Shiwuli River in the study area of Hefei City, and the results showed that once a rainstorm occurred, the downstream wetland would be flooded in a large area and the inundation height would exceed the flood defense level, which would have a serious impact on the swimming birds such as coots nesting in the downstream wetland. Therefore, the landscape, foraging and habitat conditions of Coots were selected as the design factors, and the floating bird island was designed to alleviate the invasion of rain and flood waterlogging on Coots. The innovation of this study is to propose an optimization strategy for the impact of extreme weather on waterfowl habitat, which can provide a reference for waterfowl protection and wetland management, and improve the impact of environmental changes such as waterlogging caused by extreme rainfall on downstream lakes on waterfowl populations.\u003c/p\u003e","manuscriptTitle":"Where do waterbirds settle down under heavy rain: Waterbird habitat planning and design from the perspective of rain and flood resilience","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-09 11:42:50","doi":"10.21203/rs.3.rs-4343801/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"fef14dfe-c3c5-499a-86fd-ded8df82320c","owner":[],"postedDate":"May 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-05-18T07:29:13+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-09 11:42:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4343801","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4343801","identity":"rs-4343801","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}