Inundation Area Research Articles

The effects of damming and dam regulation on a river–lake-aquifer system: 3D groundwater flow modeling of Poyang Lake (China)

Large numbers of dams are planned or constructed for hydroelectric power production, water supply, and flood control in many rivers around the world. While the social and environmental impacts of dams are now well-understood, there is little knowledge about the effects of dams on groundwater-surface water interactions in a complex lake–river-aquifer system. This study adopts a three-dimensional groundwater numerical model to quantify the potential impacts of dam construction, on regional groundwater flow system, exemplified by the proposed Poyang Lake Hydraulic Dam (PLHD) in China. Once implemented, the PLHD will regulate lake levels, artificially controlling the lake inundation area during the recession season (September-October) and the dry season (November-December). Modeling results indicated that the increase in lake infiltration induced by PLHD regulation would alter the regional water exchange pattern. The PLHD regulation will likely enhance the groundwater storage by 20.44 % in the general dry year (i.e., 2018), alleviating 78.1 % of the groundwater deficit in the extreme dry year (i.e., 2019). Additionally, the response of groundwater dynamics to the PLHD regulation exhibits significant spatial differences between the upstream and downstream areas of the dam, primarily depending on topographical changes. Overall, the PLHD regulation is most likely to impact groundwater levels across an area of approximately 5,700 km2, and the associated groundwater storage is anticipated to reach a stable state, under future long-term regulation. Our findings may guide policy-makers wishing to develop more suitable PLHD scheduling plans and floodplain protection strategies by providing reliable information regarding groundwater storage change and ecosystem succession.

Cumulative sedimentation hazard map of urban areas subject to hyperconcentrated flash flood: A case study of Suide County in the Wuding River basin, China

AbstractFlash floods can carry substantial sediment, posing significant sedimentation hazards in hilly cities. The sedimentation hazard map can reproduce the sediment thickness and extent of an extreme events scenario, playing an important role in sediment risk management. However, current research primarily focuses on modeling the inundation area and depth of floods, while studying sedimentation hazard caused by flash floods in urban areas remains insufficient. This paper aims to address this gap by utilizing a numerical model that simulates hyperconcentrated flow in hilly urban areas using the two‐dimensional hydro‐sediment‐morphological model to compile the cumulative sedimentation hazard map. The model, built upon the open‐source TELEMAC‐MASCARET framework, incorporates Zhang Hongwu's formula to simulate sediment‐carrying capacity, particularly suitable for hyper‐sediment concentration near the riverbed. This paper uses the data of extreme flash flood events in the Wuding River basin in 2017 to simulate and compile the cumulative sedimentation hazard map. The hazard map delineates the sedimentation hazard extent and level attributable to overbank floodplain sedimentation. Notably, the sediment thickness is highest in areas near the levees on both sides of the Dali River. Moreover, the map illustrates the extent of channel erosion resulting from hyperconcentrated floods, which could jeopardize bank stability.

Cross-Sectional Study of Flood Damage Assumptions in Medical Facilities Using Geographic Information Systems.

Introduction Floods not only directly damage medical facilities but also hinder access to medical facilities, potentially disrupting local medical services. The scale of damage that medical facilities suffer from floods in Japan is unknown. In this study, we assessed the potential impact of floods on Japanese healthcare facilities by facility characteristics. Methods We conducted a cross-sectional study involving medical facilities registered in the Japan Medical Association Regional Medical Information System. Geographic data for the inundation area was obtained from open data of the Japanese government. Facilities that overlap with flooded areas were designated as affected facilities. The primary outcomes were the percentage of damaged facilities and beds. We calculated odds ratios (OR) and 95% confidence intervals (95%CI) using the Wald method to assess the impact of disaster base hospital designation on damage extent. Results We included 140,826 general clinics and 8,126 hospitals, which had 137,731 and 1,483,347 beds, respectively. The planned scale of flooding is estimated to affect 8.0% of general clinics and 10.8% of their beds. For hospitals, these figures were 8.8% and 7.8%, respectively. The maximum potential scale of flooding is estimated to affect 23.6% of general clinics and 23.9% of their beds. For hospitals, these figures were 22.5% and 20.6%, respectively. At the planned scale of flooding, there was no difference found in therate of damaged facilities between disaster base hospitals and non-disaster base hospitals, and the rate of damaged beds was lower at non-disaster base hospitals (OR = 0.92, 95%CI = 0.71-1.18 for damaged facilities and OR = 0.79, 95%CI = 0.78-0.80 for damaged beds). At the maximum potential scale of flooding, there was no difference found in the expected damage between disaster base hospitals and non-disaster base hospitals (OR = 1.14, 95%CI = 0.95-1.38 for damaged facilities and OR = 0.99, 95%CI = 0.98-1.00 for damaged beds). Conclusion In Japan, floods can hinder nationwide medical functions, particularly in certain regions. Healthcare professionals should assess potential flood damage in advance and ensure that their workplace's business continuity plan includes appropriate countermeasures.

Ciujung river basin flood risk assessment due to climate change and its countermeasure

Ciujung River is experiencing recurrent flooding, which was caused by climate change factor and extensive land use change. Therefore, this study carried out risk assessment in this basin area. First, hydrology analysis was carried out using HEC-HMS software to obtain flood discharge hydrograph, with obtained peak discharge of 3534.3 m3/s for 25-year return period. This hydrograph was then modeled into an inundation map using HEC-RAS two-dimensional model to calculate hazard index. Meanwhile, the vulnerability and capacity index were calculate using the demographic data. Finally, the risk index was calculated by combining hazard, vulnerability, and capacity index using raster calculator on Arc-GIS. Overall, the flood risk analysis shows a medium level. The results shown that hazard index is the most contributing factor in causing a high risk index. Thus, in this study we proposed a structural approach to reduce the hazard index. An embankment with a length of 50.37 km was applied and remodeled to analyze its effectiveness. The modeling results show high effectiveness with a significant reduction in inundation area. The reduction of inundated area reached 39.6%, while the reduction of affected buildings reached 49.9%. Hopefully, the result of this study can provide theoretical support and recommendations for future development.

Modelling and Impact Analysis of Combined Dam Failure of Small Tandem Reservoir Groups in Hilly Areas

Numerous small reservoirs in hilly areas play a significant role in flood control and profit-making in the basin, but there is also a risk of dam failure when encountering special circumstances such as excessive flooding, which may cause large losses downstream. In this paper, we take the small reservoirs in Shandong Province as the research object, analyze the hydraulic topology of three types of tandem reservoirs, generalize the shape of the breach by using the transient lateral local one-break to the end, calculate the dam-break flooding process by using the quadratic parabolic method, and simulate the dam-break by using the MIKE21 model based on the principle of the two-dimensional incompressible Reynolds mean stress equation for the incompressible fluid, and analyze the peak flow under various combinations of dam-break flow by setting various combinations of the number of dam-breaks and the timing of dam-break simulation. By setting various combinations of dam failure numbers and timing, we analyzed the changing rules of peak dam failure flow, inundation area and other elements under various combinations, and sought the most unfavorable combinations and parameters such as the timing of dam failure, and the results of the analyses can provide technical support for the assessment of the risk of dam failure in the tandem reservoirs in the hilly area and the risk correspondence.

Adaptive water management in response to tidal inundation and sea level rise on tidal agricultural lowlands of Katingan, Central Kalimantan

Decreased water management systems and sea level rise cause inundation in the Katingan tidal agricultural lowland. Excessive and prolonged inundation can decrease rice production or even loss of rice land. A study was conducted to provide adaptive water management for controlling water levels in canals and rice crop fields inundation. For this purpose, a combined one- and two-dimensional unsteady flow method was used in HEC-RAS. The scenario of water level control uses sluice and flap gates in secondary canals. Under spring tide conditions, water level control with gates decreases the inundation area by 95.62%. Likewise, in the 25 and 50-year sea level rise scenarios, inundation decreased by 88.51% and 82.25%. In the spring tide condition, the duration of inundation is decreased from 3.5 to 0.9 days. Under 25 and 50-year sea level rise scenarios, the duration of inundation was decreased from 3.7 to 3 days and from 4.3 to 4.1 days. The use of gates significantly decreases inundation in the spring tide condition, but under sea level rise in 25 and 50-year, the depth and duration of inundation are still dangerous for rice crops; therefore, it is necessary to advance water management control for the sustainability of rice fields.

Urban inundation mapping by coupling 1D − 2D models and model comparison

Urban inundation mapping is important for early warning, management, and drainage network planning. Urban flood simulations typically utilize a 1D model focused on pipe nodes, whereas 2D simulations are required over a land area. In this paper, our focus is on their coupling, so that a dynamic 1D-2D model is obtained. We couple the Storm Water Management Model (SWMM), a widely utilized urban drainage model, with 2D models to simulate urban inundation. The 1D-2D coupled inundation model uses the 1D model output, which represents the overflow volume of sparsely distributed pipe nodes. After coupling, surface inundation distribution maps are obtained. We developed a physically-based 2D overflow diffusion model (2D-DM) and compared it with two geostatistical models: Ordinary co-kriging (OCK) and Regression Kriging (RK). The study area is the central area of Haining City in China, where a severe storm occurred on August 3, 2018. The 2D-DM performed best (RMSE = 0.232), followed by RK (RMSE = 0.286), and OCK (RMSE = 0.361), but did not provide uncertainty measures, in contrast to the geostatistical models. We conclude that 1D-2D coupling was done successfully, with the different 2D models showing different qualities. To enhance urban inundation mapping, it is suggested to couple the 1D model with both physical and statistically based 2D models for a more comprehensive assessment of potential inundation areas and depths.

SURFACE FLOW ANALYSIS AS AN EFFORTS FLOOD MITIGATION

Problems that often arise in the city of Cirebon are flooding caused by rain, land changes not supported by adequate infrastructure, narrowing of drainage channels and sedimentation of channels. This is the location where flooding often occurs in the Pemuda Street area and its surroundings. Therefore, it is necessary to carry out research on surface flow analysis as an effort to handle floods with the aim of inundation management strategies to reduce excessive rainwater runoff in drainage areas and channels. The research methods used were problem identification, literature study, data collection, analysis and design planning. The results can show that inundation is handled in two ways, first by changing the dimensions of the channel at the initial height H to 0.45m, it still experiences inundation, this is due to the difference in elevation which causes inundation in the channel. There was a change in the flood inundation area to 23,127 ha from the original 58,958 ha, meaning that the flood free area increased from 9,388 ha to 35,831 ha. The second way is by making 378 infiltration wells spread across 34 channels that experience flooding. With these infiltration wells, the flooding can be reduced to a minimum from an area of ​​23,127 ha to 0.040 ha. The success rate for flood management efforts reached 99.908%, with failure being 0.092%. Of the area of ​​68,346 ha, the flood-free area reached 68,306 ha and the remaining inundated area was 0.040 ha..

Resilient spatial design strategies research of urban inland rivers: The case of Xinghai Lake wetland in Ningxia, China

Improving the resilience of rivers is a crucial method for mitigating urban flooding, restoring the ecological role of rivers, and promoting sustainable ecological development. This study specifically examines the relationship between changes in river morphology and river elasticity space, using the Xinghai Lake wetland as a case study. The MIKE 21 numerical model is employed to simulate and analyze the morphology changes of Xinghai Lake under various conditions during both the low-water and high-water periods. The findings indicated that during the period of abundant water, the inundation area of Xinghai Lake increased by 1.64 times, the average water level rose by 0.96 m, and the average flow speed decreased by approximately 11.8 % compared to the flat water period under the circulating condition within the lake. By utilizing Xinghai Lake as a channel for overflowing Yellow River water, the stability of the lake's body is improved. When Xinghai Lake is utilized as the channel for water from the Yellow River, it contributes to the increased stability of the lake. Based on the morphological characteristics of various river sections, this study identifies the potential areas for scouring, eutrophication, and flooding in the future. It also suggests specific strategic solutions to improve the resilience and ecological robustness of the river. These proposals aim to provide scientific support for enhancing the ecological robustness of urban inland lakes.

Expansion of fluvial transport of commodities through the Pantanal floodplains of Brazil: Potential impacts and interference by climate change

AbstractInland waterways have historically been viewed as a desirable means for transporting commodities. However, creating and maintaining navigable river channels can entail substantial geomorphological modifications, resulting in changes to the ecohydrology of a river and its adjacent floodplains. In addition, barge traffic has important environmental impacts. The proposed expansion of the Paraguay River Hidrovia through the Pantanal floodplains of Brazil will negatively impact biodiversity due to bank erosion, water pollution, and the introduction of invasive species. Dredging would decrease the area and duration of inundation of connected floodplains renowned for their biodiversity, including fish and wildlife. Furthermore, the effects of the Hidrovia on greenhouse gas emissions are potentially important, although the net effects are complex and require further research. Global climate change is projected to cause greater variability in rainfall and river levels, with longer and more severe low water periods that would impede navigability and require further channel modifications. Modifications of the Paraguay River channel that lower the water levels and reduce the extent of surface water persisting during the dry season would negatively impact aquatic life in the main channel as well as in the floodplains, where recent increases in wildfire severity and excessive heat are already stressors. These changes threaten traditional livelihoods for people in the Pantanal, including artisanal fisheries, cattle ranching, and ecotourism.

Pemodelan 2D Daerah Rawan Banjir Sungai Lepo – Lepo Kota Kendari

Research was carried out to see the potential for flooding through Computational Fluid Dynamic simulations, namely a set of methodologies that allow computers to provide numerical simulations of fluid flow. The entire system is transformed into virtual form, and can be visualized via computer. Components in fluid dynamic computing include selection of mathematical models, discretization, numerical analysis schemes, numerical solutions and representation of processes numerically and graphically. Flood mapping can provide information about which areas need special attention so that it can be used as a reference in making policies related to flood management and can be used to increase wider public awareness regarding floods. The HEC-RAS permanent flow module is able to take into account the influence of various flow obstacles, such as bridges, culverts, bends, or obstacles on riverbanks. The permanent flow module is designed for use in riverbank management environments and the determination of flood risk insurance regarding the determination of riverbanks and floodplains. The permanent flow module can also be used to estimate changes in water level due to channel improvements or embankment construction. HEC-RAS permanent flow special module features include double plan analysis, double profile calculation, double culvert or gate analysis, flow optimization, and stable channel design and analysis. From the simulation results and depth classification, information on the area of inundation and areas prone to flood inundation on the Lepo-Lepo River is 29.34 Ha.

Advanced floodplain mapping: HEC-RAS and ArcGIS pro application on Swat River

AbstractFloods stand out as one of the most devastating environmental threats worldwide resulting in the tragic loss of human lives and significant damage to our essential infrastructure. This study focuses on creating floodplain maps for the two important reaches of Swat River in the Khyber Pakhtunkhwa Province of Pakistan, namely, Kalam–Khwazakhela and Khwazakhela–Chakdara reaches. The Advanced Land Observing Satellite Phased Array Type L-band Synthetic Aperture Radar (ALOS PALSAR) 12.5 m Digital Elevation Model (DEM) data has been used for this purpose. Furthermore, the sensitivity of the flood model was assessed for the Flood 2022 event, considering simulated flood depth, extent, and velocity in relation to various terrains derived from the 12.5-m ALOS PALSAR data. To estimate extreme flows for different return periods (2, 5, 10, 25, 50, and 100 years), the Log Normal (LN), Log Pearson III (LP3), and Generalized Extreme Value (GEV) distributions were employed for the frequency analysis. The GEV distribution turned out to be the best fit for modeling the Swat River for both the Chakdara and Khwazakhela gauge stations. To predict flood levels for the peak floods identified through frequency analysis and for the specific return periods the Hydrologic Engineering Center's River Analysis System (HEC-RAS) 2D simulations were performed. Subsequently the outcomes of this model were used to create floodplain maps using Geographic Information System Professional (ArcGIS Pro) software customized for various return periods. The analysis revealed a linear increase in flood inundation area with longer return periods. The floodplain maps developed hold significant importance for the governing authorities of the Swat region. These maps serve as essential tools for implementing proactive measures against potential infrastructure damage, thereby protecting against economic losses and enhancing public safety. This research effectively combines hydrological modeling and geospatial technology offering practical solutions for managing flood risks. It serves as a valuable guide for making well-informed decisions and promoting sustainable development in flood-prone areas.

Numerical Modeling of Potential Large Wood Entrainment in Rivers: Application of Hybrid Modeling in the Inter‐Dam Reach of the Dyje River, Czechia

AbstractMobilization of large wood in river channels during floods represents a hazardous factor, augmenting flood risk and endangering infrastructures such as bridges, weirs, and reservoir dams. A hybrid modeling approach combining numerical models with field‐based surveys has been recently used to elucidate the processes of LW entrainment and deposition in rivers. We used two‐dimensional hydraulic modeling performed in HEC‐RAS to simulate LW entrainment in two valley bottom segments of the Dyje River, Czechia, where LW deposition is a significant hazard to the dam of the downstream Znojmo reservoir. We surveyed all LW pieces in the inundation area of the 2002 extreme (>Q100) flood and simulated their entrainment for eight flood scenarios (1–100‐year recurrence interval). We used the equations of Braudrick and Grant (2000, https://doi.org/10.1029/1999WR900290) to calculate the LW entrainment threshold; we introduced coefficient k accounting for the incomplete submersion of LW pieces resting on an inclined surface into the original equations. Four entrainment categories — stable, wetted stable, wetted buoyant, and wetted entrained — were defined, and the proportion of LW pieces in each category was calculated for the flood scenarios. We found marked differences in entrainment categories for respective flood scenarios between the two valley segments. These were attributed to the differences in pieces' dimensions, their spatial distribution within the inundation area, and valley‐bottom topography, which affects the hydraulic conditions for a given discharge. The presented approach enables the calculation of the LW quantity potentially mobilized by the flood of a certain magnitude indicating the degree of potential risk for the infrastructures located downstream.

Flood Mapping Potential Areas Using HEC-RAS Software (Case Study: Kota Lama of Semarang)

Semarang has experienced floods every year, with a peak in the rainy season. At the end of 2022, there was heavy rain which caused the East Flood Canal River to overflow. As a result, the floods inundated several areas in Semarang City, including Kota Lama of Semarang. This study aims to determine the value of the designed discharge, the area of the flood inundation that occurred and the flood inundation map for return periods of 2, 5, 10, 25, 50 and 100 years. The methodology of this research consist of hydrological analysis, hydrological modelling with HEC-HMS and hydraulics modelling with HEC-RAS and integration with ArcGIS. In this study, it was found that for a return period of 2 years the planned flood discharge value was 153.7 m3/second with an inundation area of 406 Ha and a flood height of 17 cm to 68 cm, up to a return period of 100 years with a planned flood discharge value of 455.7 m3/second with an inundation area of 796 Ha and a flood height of 83 cm to 180 cm.

Flood Risk Assessment of the Middle Reach of the Helmand River, Afghanistan

The middle reach of the Helmand River is prone to floods, and flood hazard analysis is necessary to manage the flood risk. As the study site is a less-developed basin where available geographical and hydrological data are limited, we must utilize available limited data to conduct the flood hazard analysis. A frequency analysis of the annual peak flow rate was performed using available hydrological data for making representative flood hydrographs. A land-use map is derived by classifying recent Landsat images. Digital elevation model derived by Advanced Land Observing Satellite, roughness coefficient correlated with the land-use map, and the representative flood hydrographs are fed into hydraulic model HEC-RAS 2D. Flood inundation area, depth, and velocity for different flood return periods are estimated. Based on local hazard intensity and vulnerability, risk maps for evacuation and vulnerability of crops on the floodplain are obtained. Spatial flood risk characteristics differ at the upstream and downstream reaches because of distinct floodplain topography. Flood countermeasures for each reach are proposed based on the spatial characteristics of the flood risk. To provide risk information for residents within the region, the flood hazard, risk, and damage maps derived in this study are published as a web map application and a mobile native application.

Examining the Effects of a Flood Event in the Lower Ceyhan Basin in 1980 Using Historical Satellite Data

Analysis of past flood events contributes forecasting of effects of future flood events. Flood maps have been created in order to assess flood hazards in planning projects and to identify flood-inundated regions with flood damage following flood occurrences. Flood mapping in the context of flood monitoring enables development of flood management strategies to protect life and property. Although conventional terrestrial observations and measurements in flood control have been constrained by topographical and meteorological circumstances, remote sensing provides decision support with quick analysis capability. The flood event that occurred in the Lower Ceyhan Basin of Turkey in 1980 was examined in this work utilizing satellite-based remote sensing techniques, and flood inundation areas were calculated using NDWI (Normalized Difference Water Index). As a result, it was determined that 3493.45 ha in the north of Karataş in the Lower Ceyhan Plain, 7799.42 ha between Bahçe, Akdeniz, and Yumurtalık, 7404.9 ha around Çatalpınar and Yakapınar in the Lower Ceyhan Plain, and approximately 24890 ha in the Upper Ceyhan were affected by the flood event in 1980.

Anticipating a risky future: long short-term memory (LSTM) models for spatiotemporal extrapolation of population data in areas prone to earthquakes and tsunamis in Lima, Peru

Abstract. In this paper, we anticipate geospatial population distributions to quantify the future number of people living in earthquake-prone and tsunami-prone areas of Lima and Callao, Peru. We capitalize upon existing gridded population time series data sets, which are provided on an open-source basis globally, and implement machine learning models tailored for time series analysis, i.e., based on long short-term memory (LSTM) networks, for prediction of future time steps. Specifically, we harvest WorldPop population data and teach LSTM and convolutional LSTM models equipped with both unidirectional and bidirectional learning mechanisms, which are derived from different feature sets, i.e., driving factors. To gain insights regarding the competitive performance of LSTM-based models in this application context, we also implement multilinear regression and random forest models for comparison. The results clearly underline the value of the LSTM-based models for forecasting gridded population data; the most accurate prediction obtained with an LSTM equipped with a bidirectional learning scheme features a root-mean-squared error of 3.63 people per 100 × 100 m grid cell while maintaining an excellent model fit (R2= 0.995). We deploy this model for anticipation of population along a 3-year interval until the year 2035. Especially in areas of high peak ground acceleration of 207–210 cm s−2, the population is anticipated to experience growth of almost 30 % over the forecasted time span, which simultaneously corresponds to 70 % of the predicted additional inhabitants of Lima. The population in the tsunami inundation area is anticipated to grow by 61 % until 2035, which is substantially more than the average growth of 35 % for the city. Uncovering those relations can help urban planners and policymakers to develop effective risk mitigation strategies.

Tsunami hazard evaluation of river embankment structures incorporating their vulnerability to seismic strong motion

Development of coastal areas in Japan for various land uses since the 1960s has contributed to industrial upgrades and improved the efficiency of transportation networks. However, there are concerns about the vulnerability of developments on alluvial plains and reclaimed lands to geological events, like ground subsidence due to liquefaction during large earthquakes. Realistic assessment of earthquake and tsunami hazards and evaluation of possible countermeasures require accurate estimation of the amount of subsidence that can be expected from liquefaction at coastal and riverside sites supporting various structures. In this study, to evaluate the amount a river embankment structure might be expected to settle as a result of strong motion from an assumed Nankai Trough great earthquake, we conducted a numerical simulation using the soil–water coupled finite deformation analysis code GEOASIA. We then investigated the effect of the estimated embankment subsidence on tsunami inundation, which was simulated by using nonlinear shallow-water equations and a grid spacing as fine as 3.3 m. The influence of urban structures on the inundated area was taken into account by using a structure-embedded elevation model (SEM). The results showed that subsidence of river embankments and the collapse of parapet walls on top of them would increase both the depth and area of inundation caused by a tsunami triggered by a Nankai Trough scenario earthquake. Our findings underscore the importance of evaluating not only earthquake resistance but also vulnerability of coastal and riverside structures to strong motion in tsunami hazard analyses. Furthermore, the importance of tsunami inundation analysis using a SEM for predicting the behavior of tsunami flotsam in urban areas was demonstrated.

Development of an automated method for flood inundation monitoring, flood hazard, and soil erosion susceptibility assessment using machine learning and AHP–MCE techniques

BackgroundOperational large-scale flood monitoring using publicly available satellite data is possible with the advent of Sentinel-1 microwave data, which enables near-real-time (at 6-day intervals) flood mapping day and night, even in cloudy monsoon seasons. Automated flood inundation area identification in near-real-time involves advanced geospatial data processing platforms, such as Google Earth Engine and robust methodology (Otsu’s algorithm).ObjectivesThe current study employs Sentinel-1 microwave data for flood extent mapping using machine learning (ML) algorithms in Assam State, India. We generated a flood hazard and soil erosion susceptibility map by combining multi-source data on weather conditions and soil and terrain characteristics. Random Forest (RF), Classification and Regression Tool (CART), and Support Vector Machine (SVM) ML algorithms were applied to generate the flood hazard map. Furthermore, we employed the multicriteria evaluation (MCE) analytical hierarchical process (AHP) for soil erosion susceptibility mapping.SummaryThe highest prediction accuracy was observed for the RF model (overall accuracy [OA] > 82%), followed by the SVM (OA > 82%) and CART (OA > 81%). Over 26% of the study area indicated high flood hazard-prone areas, and approximately 60% showed high and severe potential for soil erosion due to flooding. The automated flood mapping platform is an essential resource for emergency responders and decision-makers, as it helps to guide relief activities by identifying suitable regions and appropriate logistic route planning and improving the accuracy and timeliness ofemergency response efforts. Periodic flood inundation maps will help in long-term planning and policymaking, flood management, soil and biodiversity conservation, land degradation, planning sustainable agriculture interventions, crop insurance, and climate resilience studies.

Effects of multiple future environmental changes on flooding in coastal area: Case study in Qianshan River Basin, South China

Due to their unique geographical characteristics, coastal areas are not only impacted by climate change and urbanization but also by sea level rise-induced lower boundary jacking. This makes them vulnerable to rapid, intense, and short-duration flooding events. In this study, a comprehensive analysis was conducted considering future climate change, land use change, and sea level change. By employing a hydrological model, potential flood scenarios in Qianshan River Basin were simulated in efforts to understand the combined impact of multiple environmental changes on coastal flooding. The results indicate that the flood characteristics of Qianshan River Basin will increase due to multiple future environmental changes. Notably, Dachong experiences the most significant surge in peak discharge, while Hongwanchong and Guangchangchong experience the highest increase in peak water depth under normal and extreme conditions, respectively. The inundation area’s location remains predominantly situated in the southern part of the basin, with high-risk zones substantially increasing, particularly in Tanzhou Town and the outlet of Qianshanshuidao. The observed pattern of increasing flood characteristics follows a clear trend across future scenarios SSP126, SSP245, SPP370, and SSP585. The flood characteristics resulting from a design rainfall of grade n correspond to those produced by a design rainfall of grade (n + 1), (n + 2), (n + 3), and (n + 4) in the current period, respectively.