Inundation Depth Research Articles

A study on dynamic simulation and improvement strategies of flood resilience for urban road system

As one of the most important and directly affected infrastructure by flood disasters in urban areas, the road system plays a crucial role in maintaining the order of human production and life, as well as providing a foundation for the implementation of emergency response work in disaster scenarios. The existing flood resilience quantification methods based on maximum inundation depths of each individual road unit neglects the influences on flood resilience caused by the connectivity of road system. Therefore, this paper focuses on the road system, simulates the flood resilience of the road system in multiple disaster scenarios based on the functionality curve of road system under rainfall-inundation processes, then quantifies the improvement effect of Low Impact Development (LID) measures on flood resilience. A case study is conducted in Yunmen community, Jingdezhen city in China. The results indicate that: (1) The flood resilience of the road system decreases with the increase of rainfall intensity under different scenarios, and the magnitude of the decrease reduces. (2) The road system exhibits strong adaptability during the early stages of rainfall; The duration of functionality loss increases with increasing of rainfall intensity in different scenarios. (3) Implementation of LID measures can significantly improve system robustness by enhancing the reliability of the roads around critical nodes, thereby effectively enhancing flood resilience. The conclusions can provide a theoretical basis for decision-makers to develop urban flood mitigation engineering plans and resilience strategies tailored to local conditions.

Experimental Study on Submerged Horizontal Perforated Plates under Irregular Wave Conditions

This study presents novel analytical solutions for analyzing wave dissipation effect and bottom flow field characteristics of permeable submerged horizontal plates through physical model trials. The experimental results show that a solid submerged horizontal plate effectively attenuates wave cycles, with a greater periodic attenuation effect at smaller submerged depths. However, this attenuation effect becomes reduced or less pronounced after a certain threshold. Selecting an optimal opening ratio becomes key to achieving the desired cycle attenuation. When the inundation depth of the horizontal plate is large, the wave dissipation effect is weak. Reducing the opening rate can improve the wave dissipation effect, but only to a certain extent. Under irregular wave actions, the velocity field of the submerged horizontal plate is uniformly distributed. The relative submerged depth has minimal effect on the maximum flow velocity and root mean square flow velocity. Increasing the wave height and increasing the open holes on a plate can improve the flow velocity at the bottom of the plate. However, increasing the opening ratio also leads to insignificant changes in flow velocity. A correlation between the transmission coefficient of the open plate and the maximum flow velocity has also been determined. The findings of this paper serve as a research foundation for the implementation of submerged horizontal plate wave dissipation structures in engineering.

Five Years Measuring the Muck: Evaluating Interannual Variability of Nutrient Loads From Tidal Flooding

Due to sea level rise, tidal flooding is now common in low-lying coastal systems around the world. Yet, the contribution of tidal flooding to non-point source nutrient loads and their impact on the quality of adjacent waters remains poorly constrained. Here, we quantified dissolved nutrient loading and Enterococcus abundance during annual autumnal king tides (i.e., perigean spring tides), between 2017 and 2021, in a sub-watershed of the lower Chesapeake Bay. To calculate nutrient loading from tidal flooding, we used geospatial inundation depths from a street-level hydrodynamic model to estimate floodwater volumes during each of the five sampling events and the difference between nutrient concentrations in floodwater and pre-flood measurements. Results showed that dissolved nutrient concentrations were higher in floodwaters than in estuarine waters and resulted in dissolved nitrogen and phosphorus loads that reached 58.4 × 103 kg and 14.4 × 103 kg, respectively. We compared our load estimates to the tributary-specific total and land-based federal allocations (i.e., total maximum daily loads (TMDL)) for total nitrogen (TN) and total phosphorus (TP). Even the more conservative calculations indicate that inputs of dissolved nutrients during a single tidal flooding event can exceed 100% of the annual load allocation. Additionally, more than 80% of the floodwater samples collected each year showed Enterococcus abundance that exceeded the threshold for recreational water use in Virginia (104 MPN 100 ml−1). Failing to account for non-point source loading of nutrients and contaminants from tidal flooding as sea level rises could result in worsening eutrophication and deterioration of coastal economies and the health of coastal communities around the world.

Multidirectional Shifts in Hydrological Connectivity Result From Hydraulic Barriers

AbstractThe weakening of hydrological connectivity caused by hydraulic barriers and its impact on the ecological environment has gained worldwide attention. Previous studies have primarily focused on the obstructive effect of barriers, often overlooking its influence on the internal connectivity of regulated water systems. The study employed a new conceptual framework of hydrological connectivity and utilized the connectivity assessment tool to assess the impact of the proposed Poyang Lake Hydraulic Project (PLHP) on the lake's internal connectivity. The estimated impacts were based on various factors, including the connectivity function (CF), the spatial distribution of the connected object (CONNOB), as well as duration and timing of connection. Key findings indicate that the PLHP will enhance the total connectivity and general connectivity involving inundation depth of the lake. This enhancement will result in increased CF values, expanded CONNOBs and prolonged connection durations. Conversely, the PLHP will weaken the general connectivity involving flow velocity and effective connectivity. As a result, CF values will decrease, CONNOBs will shrink, and connection durations will be shorter. It is important to note that the impact of hydraulic barriers varies depending on evaluation metrics, duration, timing, direction, distance, location, hydrological year, and regulation stage. Therefore, it is not appropriate to simply categorize the barrier impact as “weakening” or “enhancing.” This study innovates the knowledge of hydraulic barriers from the perspective of internal connectivity and is expected to provide more comprehensive theoretical guidance for water resource regulation and eco‐environmental protection.

Flood hazard assessment in the Yesil River basin

Abstract Due to population growth and densification, and expanding construction, disaster risk in the world and its specific parts of the world is steadily increasing. Earthquakes cause the most damage, followed by floods. Floods are characterized by the highest frequency of events. In this research, annual data on 25 hydrological gauging stations of the considered territory were used to study the characteristics of maximum discharges and maximum levels of rivers in the Yesil water management basin. Data on maximum water levels and discharges are generalized because they are most important in the study of floods and the organization of flood control. It is the maximum level that determines the area and depth of flooding of territories. This study assessed the provided values of maximum levels and maximum water discharges by several methods (method of moments, the graph-analytical method for the full distribution, truncated distribution). For assessing flood damage, a map of the distribution of the maximum floodplain inundation depth over the basin area was constructed, taking into account the flood hazard classification by floodplain inundation layer. Quantitative assessment of hydrological extremes characterizing the danger of flooding has been carried out for gauging stations of Yesil water management basin during this research.

Flood Inundation and Depth Mapping Using Unmanned Aerial Vehicles Combined with High-Resolution Multispectral Imagery

The identification of flood hazards during emerging public safety crises such as hurricanes or flash floods is an invaluable tool for first responders and managers yet remains out of reach in any comprehensive sense when using traditional remote-sensing methods, due to cloud cover and other data-sourcing restrictions. While many remote-sensing techniques exist for floodwater identification and extraction, few studies demonstrate an up-to-day understanding with better techniques in isolating the spectral properties of floodwaters from collected data, which vary for each event. This study introduces a novel method for delineating near-real-time inundation flood extent and depth mapping for storm events, using an inexpensive unmanned aerial vehicle (UAV)-based multispectral remote-sensing platform, which was designed to be applicable for urban environments, under a wide range of atmospheric conditions. The methodology is demonstrated using an actual flooding-event—Hurricane Zeta during the 2020 Atlantic hurricane season. Referred to as the UAV and Floodwater Inundation and Depth Mapper (FIDM), the methodology consists of three major components, including aerial data collection, processing, and flood inundation (water surface extent) and depth mapping. The model results for inundation and depth were compared to a validation dataset and ground-truthing data, respectively. The results suggest that UAV-FIDM is able to predict inundation with a total error (sum of omission and commission errors) of 15.8% and produce flooding depth estimates that are accurate enough to be actionable to determine road closures for a real event.

Scenario-Based Hazard Assessment of Local Tsunami for Coastal Areas: A Case Study of Xiamen City, Fujian Province, China

In this study, three worst-case credible tsunamigenic scenarios (Mw8.0) from Xiamen fault 1 (XF 1), Xiamen fault 2 (XF 2) and Xiamen fault 3 (XF 3) located off the coast of Xiamen were selected to assess the local tsunami hazard for Xiamen city, Fujian province, China. The GeoClaw model was utilized to compute the propagation and inundation of the tsunami for each scenario. The simulation results show that local tsunamis from XF 1–3 hit Xiamen within 1.5 h of earthquakes. The highest level of tsunami hazard in Xiamen is level II, which corresponds to an inundation depth ranging from 1.2 to 3.0 m. The areas with tsunami hazard level II in each scenario are primarily concentrated in the coastal areas of southern Haicang district and eastern Siming district, which are in the primary propagation direction of the tsunami. Since XF 2 and XF 3 are aligned almost parallel to the coastline of Xiamen, local tsunamis from XF 2 and XF 3 could cause more serious hazards to the coastal areas of Xiamen city. This work provides a typical case for researchers to understand the local tsunami hazard assessment for coastal cities. The research results can provide scientific references for the development of tsunami hazard assessment and early warning systems for coastal cities in southeastern China.

Coastal and River Embankment Performance at Cengkareng Drain Estuary Under Compound Hazards Conditions Using HEC-RAS 2D

Jakarta is prone to pluvial, fluvial, and coastal flooding due to its geographical location and topography. In response to this problem, the Indonesian government has implemented several master plans, including the National Capital Integrated Coastal Development (NCICD). This ongoing program encompasses the construction of coastal and river embankment that stretch all over the coast of Jakarta. Since many coastal areas in Jakarta are residential or industrial, evaluating this performance of embankment has become crucial for effective flood management. The findings of this research can also support the development of other locations where NCICD embankment plan and enhance coastal resilience. Therefore, this research assessed the effectiveness of coastal and river embankment at Cengkareng Drain, a vital floodway in Jakarta, during extreme events that occur simultaneously. To simulate flooding events, two-dimensional HEC-RAS features were used to numerically calculate the area and depth of inundation. The simulation required geometry, terrain, land cover, and unsteady flow data. For the flow boundary conditions, a 100-year design rainfall, HHWL (Highest High Water Level), and 100-year design wave were considered to represent estuary conditions accurately. The simulation result showed that the maximum water level influenced by these factors was +3.145 mMSL, while the planned embankment top elevation was +3.40 mMSL. Furthermore, without the NCICD embankment, the simulation showed an inundation area of 1212.37 ha, which was reduced to 1111.22 ha after their implementation, leading to a decrease of 101.15 ha. This reduction significantly decreases potential damage to property and infrastructure, particularly in densely populated areas. The simulation also showed a reduction of 86.49 hectares or 66.22% in the inundation area with a depth exceeding 1 meter. These findings demonstrate the effectiveness of embankment in reducing the inundation area without any overtopping incidents.

Vulnerability of Coastal Infrastructure and Communities to Extreme Storms and Rising Sea Levels: An Improved Model for Grenada and Its Dependencies

Coastal areas of Grenada in the south-eastern Caribbean are particularly vulnerable to the adverse impacts of climate change. The effects of increasingly powerful hurricanes, sea-level rise, and reef degradation are often compounded by local anthropogenic activities. Many communities reside in low-lying areas, with development and infrastructure concentrated along the coast. Wave/storm surge models based on historic hurricanes Ivan and Lenny, and a hurricane with a predicted 100-year return period, were used to assess coastal inundation under different storm and sea-level rise scenarios. Coupled Tomawac and Telemac models were used in conjunction with high-resolution LiDAR data to provide a full vulnerability assessment across all coastal zones. Results were combined with census data at the Enumeration District level to assess impacts on the built environment. Qualitative and quantitative estimates were derived for the impact on natural features, land use, and infrastructure supporting critical economic activity in Grenada’s coastal zones. Estimation of both spatial extent and inundation depth improved the estimation of likely coastal impacts and associated costs at the national level. A general increase in extent and severity of inundation was predicted with projected future sea-level rise, with the potential for disruption to major coastal infrastructure evident in all scenarios, risking serious social and economic consequences for local communities. Coastal communities using poorer-quality building materials were most severely affected. This integrated method of assessment can guide disaster planning and decision-making to reduce risk and aid resilience in hurricane-prone regions.

Urban flood risk assessment characterizing the relationship among hazard, exposure, and vulnerability.

Risk assessment is an effective means to alleviate urban flood disasters and has attracted the attention of many studies. However, most previous studies about urban flood risk assessment often focused more on urban inundation area and depth, less on the inter-relationship of the components of risk. In this study, an urban flood risk assessment approach that characterizes the relationship among the three components of risk "hazard-exposure-vulnerability" (H-E-V) is developed. Firstly, eleven flood risk indicators are selected based on the flood simulation results of urban flood model and statistical data to establish the urban flood risk assessment index system. Then, the combination of analytic hierarchy process (AHP) and entropy weight method is employed to determine the weight of each indicator and the comprehensive urban flood risk is assessed. Most importantly, the coupling coordination degree model (CCDM) is used to reveal the relationship among H-E-V. After applying this method to Haikou city, China, the results show that the comprehensive effect and the coupling coordination degrees among H-E-V have a multidimensional impact on urban flood risk. For example, some sub-catchments, although at high risk of flooding, may experience a potential waste of resources. Urban flood assessment can be made more detailed and three-dimensional by comparing hazard, exposure, and vulnerability horizontally. Understanding and grasping the internal relationships among these three risk components can help implement flood prevention measures, optimize the allocation of flood prevention resources, and effectively reduce urban flood risks.

A Study on the Accessibility of the Emergency Medical Services for Urban Kindergartens and Nursing Homes Based on Urban Pluvial Flooding Scenarios

Vulnerable groups such as children and the elderly are the focus of emergency medical rescue during urban pluvial floods. Taking the Erqi District of Zhengzhou City as an example, the SCS-CN model and Chicago rainfall model are used to simulate pluvial flooding based on the comprehensive consideration of urban rainfall, runoff, topography, and drainage. Additionally, the accessibility of emergency medical aid for kindergartens and nursing homes is evaluated in the Erqi District of Zhengzhou under different pluvial flooding scenarios using GIS network analysis technology. The results showed that the number of kindergartens and nursing homes without timely access to emergency medical rescue increased with the increase in precipitation return periods. Under the 500-year and 1000-year pluvial flooding scenarios, kindergartens and nursing homes that can obtain emergency medical rescue had delayed response times. Furthermore, with the increase in the precipitation return periods, both the number and delay time of kindergartens and nursing homes significantly increased. The accessibility and delay time of emergency medical rescue in kindergartens and nursing homes were determined by the intensity of pluvial flooding (including inundation area and depth), road traffic conditions, and the number and location of medical institutions, nursing homes, and kindergartens. The research results can provide a scientific basis for improving the refinement level of urban flood disaster management and emergency response services.

Evaluating Inundation Characteristics under Climate Changes

A procedure of hydrodynamic modeling of floodplain inundation characteristics is presented; the procedure takes into account climate change scenarios and is based on the results of numerical experiments with river runoff formation model and the results of ensemble calculations by global climate models. The model calculations were based on Russian software systems ECOMAG and STREAM_2D. For the key segment of the Lena at Yakutsk C. (Tabaga gage), the calculations by all scenarios and models show a possible increase in the runoff by the mid-XXI century along with an increase in the inundation areas and depths by 9–15% due to the increase in runoff.

Dissolved organic carbon dynamics and fluxes in Mississippi-Atchafalaya deltaic system impacted by an extreme flood event and hurricanes: a multi-satellite approach using Sentinel-2/3 and Landsat-8/9 data

Transport of riverine and wetland-derived dissolved organic carbon (DOC) spanning tidal wetlands, estuaries, and continental shelf waters functionally connects terrestrial and aquatic carbon reservoirs, yet the magnitude and ecological significance of this variable and its spatiotemporal linkage remains uncertain for coastal deltaic regions, such as Mississippi River Delta Plain, which includes Mississippi (MR) and Atchafalaya (AR) rivers and estuaries with vast expanses of wetlands and coastal forests. We examined DOC dynamics and fluxes in this large river-dominated wetland-estuarine system for the period between 2019 and 2021 that included an extreme river flood event in 2019, two major hurricanes (Barry in 2019 and Ida in 2021), and cold front passage using an improved adaptive quasi-analytical algorithm (QAA-AD) applied to multi-satellite sensors (Sentinel 3A/B OLCI, Landsat-8/OLI and Sentinel-2A/B MSI) with varying spectral and spatial (10/30/300 m) resolutions. The DOC estimates from multi-satellite sensors in combination with water fluxes were used to assess DOC fluxes from two large rivers (MR and AR) and small channels across the delta plain. Overall, this system delivered a total of 6.7 Tg C yr-1(1 Tg = 1012g) into the estuarine zone and the northern Gulf of Mexico (nGoM) during 2019. High DOC fluxes from the AR (1.3 Tg C yr-1) and MR (4.5 Tg C yr-1) were associated with the extreme flood event in 2019. Hurricanes that occurred in the study period also contributed to the wetland and estuarine DOC fluxes into continental shelf waters; for example, the passage of Hurricane Barry in July 2019, delivered over a 3-day period ~1.33 ×109g DOC from Barataria Basin into the nGoM. Sentinel 2-MSI land and water classification revealed that Hurricane Ida eroded a total of 1.34×108m2of marshes in middle Barataria Basin, converting those habitats into open water with 3.0 m inundation depth and high DOC concentrations (16.4 mg L-1), a potentially large DOC source to the coastal waters. Overall, storms and flood events are major sources of DOC flux that facilitate transport of upstream carbon as well as transformation of carbon in the wetlands, through the conversion of vegetated wetland to open water.

Environmental determinants of vegetation in the drawdown zones of a Columbia River Treaty reservoir: a template for ecosystem enhancement.

Water storage reservoirs alternately inundate and expose the drawdown zones, limiting riparian vegetation that provides wildlife habitats and contributes to the aquatic food-web. To characterize plant distributions and hydrogeomorphic associations, we inventoried quadrats in transects extending from the full-pool (FP) margin, downwards 12 m through the drawdown zones at sites around the Duncan Reservoir in British Columbia, Canada. Among the 69 plant species, black cottonwoods (Populus trichocarpa), willows (primarily Salix sitchensis) and other trees and shrubs occurred sparsely, rarely extending below 2 m below FP. Perennial herbaceous plants, especially horsetail (Equisetum arvense) and sedges (primarily Carex utriculata), were most common, extending down ~5 m below FP, and ruderal annual plants occurred sparsely at greater depths. Vegetation Cover and Species Richness were correlated with environmental factors, with (1) Elevation being highly influential, reflecting inundation duration and depth. (2) Position, longitudinal location, reflected greater vegetation diversity downstream of the reservoir. (3) Finer Substrate texture was favorable to retain moisture, but coarse sediments would resist erosion. (4) Shallow Slope was favorable to reduce drainage and included finer sediments. (5) Distance from the FP shoreline could reflect seed source proximity. Stepwise linear modeling with combined environmental factors accounted for ~30% of the variation in Vegetation Cover and Richness, and Canonical Correspondence Analysis revealed plant groupings relative to the environmental influences. At this and other storage reservoirs, regimes that reduce the frequency and duration of inundation could promote vegetation in locations with suitable environmental conditions in the upper drawdown zones, thus providing ecosystem enhancement.

Impacts of rainstorm characteristics on flood inundation mitigation performance of LID measures throughout an urban catchment

The hydrological benefits of sponge city construction have sparked a variety of academic studies and discussions. However, the effectiveness of sponge city construction in mitigating flood inundation at the urban catchment scale remains rarely investigated. Therefore, the Jiaodong catchment in Zhenjiang City, which is a national sponge pilot city and has extensively implemented various LID measures, was selected as a study site. The SWMM-2DCA model was established and validated using measured rainfall and drainage pipe flow processes, as well as historical inundation-prone location records, and then applied to evaluate the accumulative effectiveness of LID measures in flood mitigation under different 2-hour design rainstorms with changing return periods (2, 5, 10, 20, and 30 years) and peak position coefficients (0.2, 0.5, and 0.8). The results revealed that nearly 90% of the inundated area had an inundation depth of less than 0.15 m, and the impact of rainstorm characteristics on the maximum inundation depth was very limited. Both the maximum inundation volume and area were positively related to the return period and the peak position coefficient of rainstorms. The increase in the rainstorm return period could advance the start of inundation and retard the occurrence of peak inundation. The maximum inundation volume and area could be significantly reduced by 63 ∼ 98% and 41 ∼ 96% respectively after the implementation of LID measures, but the average reduction rate for maximum inundation depth was only 3.7% for rainstorms with a return period longer than 10 years. This indicates that LID controls inundation better for volume and area than for depth. The changing patterns of absolute and relative reductions in maximum inundation volume and area with rainstorm characteristics exhibited reverse trends, while the absolute and relative reductions of maximum inundation depth demonstrated similar variations. The absolute reductions in both maximum inundation area and depth almost reached their extreme values at the 10-year rainstorm return period. The effects of LID on the timing of peak inundation depended largely on the peak position of rainstorms. These findings could contribute to a better understanding of the flood inundation mitigation performance of sponge city construction.

OPTIMUM WATER ALLOCATION FOR ABO-ZIRIQ MARSH ECOLOGICAL RESTORATION

Optimum allocation of water for restoration of Iraqi marshes is essential for different related authorities. Abo-Ziriq marsh area about 120 km2 is situated 40 km east of Al-Nassryia city. After comparing the measured annual water qualities with the Iraqi standards for surface water quality evaluation, Abo-Ziriq marsh water quality was in acceptable limit. Hydro balance computation were done for each month by using interface among the HEC-RAS, HEC-GeoRAS and ArcView GIS software and built a number of eco-hydro relationships to simulate the marsh ecosystem by using HEC-EFM program to estimate water allocation adequate for ecosystem requirement and constructs a GIS hydraulic reference map to show inundation area, depth grid and velocity distribution, the optimal flow result consists of three different scenarios (24, 30.3 and 33.6 m3 /s) for marsh operation during the year. A computer program in MATLAB 7 was developed to simulate the optimization model to determine the optimum flow value entry to lower zone. The priority of each parameter is represented by a weight associated with each of them (penalty factor). The model was used for different scheme of penalty factor value and examines three cases of flow (wet, moderate and dry years). The results obtained from the program run show that the optimum flow values are not affected significantly with changing the scheme of the penalty factors.Hence, any set of solutions can be use for operation the control structure of two inlets in the lower zone that best fits the objective of the system and increase flow release from Abo Jiry inlet to minimum deviation in water quality during the most time of the year

Flood dynamics and its spatial prediction using open-channel hydraulics and hydrodynamic model in the dam-controlled river of India

The spatial prediction of flood inundation, in the monsoon months (July–October), around the downstream southern part of the Damodar River Basin (Hooghly and Howrah districts of West Bengal) is very uncertain due to analytical lack of database, channel hydraulics and steady or unsteady flow anomaly. Using techniques of flood hydrology and HEC-RAS module of flood prediction, this study estimated the critical hydrological range of recurrent floods (1651–1822 m3 s−1 peak discharge) which are annually observed in the low-lying active floodplains of lower basin. The four days heavy rainfall (52.5 to 268 mm), yielded a runoff range of 10–207 mm which triggered maximum discharge of 7035 m3 s−1, causing havoc flood at downstream. There is possibility of channel shifting and embankmnet breaching during floods in the Mundeswari and Damodar/Amta channel, as Unit Stream Power can exceed 30 Wm−2 in tweleve cross-section stations. During 5-year and 10-year flood event (6676 m3 s−1) the floodplain inundation depth can reach 4–12 m in the Khanakul, and Udaynarayanpur region, having maximum chance of overbank flow. The most vulnerable site of embankment failure and overbank flow is stretch between Rajbalhat and Udaynarayanpur where the flood depth can cross 10 m limit for the critical discharge of 1811 m3 s−1. The flood risk is aggravated because within 42.5 km stretch of lower Damodar the channel can accommodate maximum flow of 1378 m3 s−1 (average flow area of 687 m2) at upstream cross-sections, but at downstream cross-sections the carrying capacity of channel is reduced to 1081 m3 s−1 (21.55 percent reduction) due to increasing siltation and decreasing average flow area (478 m2).

Simulation of dam-break flood and risk assessment: a case study of Chengbi River Dam in Baise, China

Abstract When a reservoir is damaged, it will bring destruction to people's lives and the regional economy. Flood simulation and risk assessment are two effective ways to mitigate flood risk. Flood risk is assessed by using flood hazard and vulnerability indices. However, one of the key concerns is how to quantify hazards and vulnerabilities more rationally. To this end, this study introduces a new quantitative method for flood risk assessment. Three schemes – full dam breach (S1), 1/2 dam breach (S2), and 1/3 dam breach (S3) – were proposed for flood simulation. HEC-RAS 2D was used to simulate the evolution process of dam-break floods. This study used a new quantification approach to calculate flood risk based on simulation results. The results show the following: (1) The inundation process is similar under the three schemes, but the degree differs. The greater the degree of dam break, the greater the inundation depth, maximum flow velocity, and inundation duration. (2) High-risk areas decrease with decreased dam break degree. Under the three schemes, the flood risk areas of Longjing Street account for 65.37, 71.41, and 66.22% of the total risk areas, respectively, which are the areas most affected by dam-break floods.

Hydrologic-hydraulic assessment of SUDS control capacity using different modeling approaches: a case study in Bogotá, Colombia.

Urban flooding has increased in response to impervious surface intensification, the loss of green areas, and high-intensity rainfall associated with climate change. Sustainable urban drainage systems (SUDS) are an appealing option for stormwater management; however, their hydraulic control capabilities have received little attention. We developed a comparative model-based approach with 24 scenarios to contrast the hydrologic and hydraulic response of a highly discretized (HD) 1D model and a coupled 1D-2D model, considering the impact of rainwater harvesting systems and tree pits. An additional scenario was modeled including attenuation storage tanks, green roofs, and pervious pavements. A heavily urbanized flood-prone catchment with severe land-use constraints in Bogotá, Colombia, was selected for analysis. The findings revealed that SUDS can contribute to reducing the number of flooded junctions, overloaded conduits' length, overloading time, nodal inundation depth, and waterlogging extent. Furthermore, the HD 1D model can reproduce the coupled 1D-2D model results in terms of hydrologic response and some hydraulic control indicators. Further research is needed for an accurate description of the internal hydraulic mechanisms of SUDS interacting with overland flow. The key findings of this study provide model-based evidence to support urban stormwater management decision-making in data-scarce environments.

Co-occurrence of pluvial and fluvial floods exacerbates inundation and economic losses: evidence from a scenario-based analysis in Longyan, China

Hydrodynamics and socio-economic impacts of compound floods as the result of co-occurring pluvial and fluvial floods, have not been well studied, which challenges conventional urban flood risk management that treats different types of floods separately. This study generates a high-resolution land surface digital surface model based on images from unmanned aerial vehicles, and incorporates it into a combined flooding model that integrates the 1D river hydrodynamic model, 1D urban drainage hydrodynamic model and 2D overland flow model, in order to simulate the inundation characteristics of extreme floods when local pluvial floods coincide with upstream fluvial floods, and in a further step to quantify the direct economic losses on urban physical systems. As demonstrated by an empirical study of Longyan, China, the combination of pluvial and fluvial floods leads to substantial exacerbation in inundation extent and depth. Consequently, the joining of pluvial and fluvial floods greatly amplifies economic losses to urban physical systems, indicating that ignoring co-occurrence of different types of floods will potentially lead to underestimation of flood risk and insufficient adaptation. Our study emphasizes the need to account for the co-occurrence of multiple types of floods in flood risk assessment and management, to avoid the shortcomings of fragmented responses.