Hasil untuk "River protective works. Regulation. Flood control"

Misagh Parhizkar, Manuel Esteban Lucas-Borja, Nikolaos Tziolas et al.

Very few studies have explored the effectiveness of polyacrylamide (PAM) application on soil in mitigating rill erosion, especially in deforested environments. This study has measured the soil detachment capacity (Dc) on samples of deforested soil (untreated or treated with PAM). Dc has been estimated by flume experiments under three bed slopes (6.9 %, 17.2 %, and 18.2 %) and five flow discharges (0.078, 0.096, 0.116, 0.138, and 0.154 L·s−1) together with three key soil properties (cation exchange capacity, mean weight diameter of soil aggregates, and organic matter content). Compared to the untreated soil, Dc has significantly (p < 0.05) decreased on average by 38 % after the PAM application, while the cation exchange capacity, stability of soil aggregates, and organic matter content have increased (p < 0.001) by 50 % to over 100 %. However, Dc is weakly correlated to the latter soil properties (r < 0.33, p < 0.05). A clear discrimination between treated and untreated sites has been revealed by a multivariate statistical analysis. The soil erodibility parameter (Kr) and critical shear stress (τc) in rills have also been estimated through linear regressions on Dc for use in erosion models. Dc can be accurately estimated by linear equations using the stream power as a predictor (R2 > 0.77). Overall, the study has demonstrated that PAM is an effective soil amendment that reduces soil detachment in rills of deforested hillslopes by about 40 %.

Dibyendu Ghosh, Somen Das

Alessa Truedinger, Joern Birkmann

ABSTRACT Severe flooding, induced by heavy rainfall in Central and Western Europe in July 2021, particularly affected the Ahr Valley in Rhineland‐Palatinate, Germany. Since flood preparedness and prevention of private households play a crucial role in the risk management cycle and in terms of climate adaptation, a household survey was conducted in the county of Ahrweiler in the aftermath of the disaster to examine the perceptions and actions of private households after such a disaster with regard to flood prevention. We have found that public information, communication, and education play a crucial role for improving flood prevention of private households. Furthermore, we were able to identify approaches for improved flood prevention, also in terms of spatial planning. In addition, we examined enabling factors for the implementation of flood risk reduction measures, where information and assistance from public authorities play a prominent role. Overall, the respondents expect a great amount of state support, both financially and in terms of information. Our results can help public authorities to improve their own flood prevention as well as the flood preparedness of citizens.

Maureen A. Wanzala, Elisabeth M. Stephens, Hannah L. Cloke et al.

Abstract The choice of model for operational flood forecasting is not simple because of different process representations, data scarcity issues, and propagation of errors and uncertainty down the modeling chain. An objective decision needs to be made for the choice of the modeling tools. However, this decision is complex because all parts of the process have inherent uncertainty. This paper provides a model selection with a filter sequence for flood forecasting applications in data scarce regions, using Kenya as an example building on the existing literature, concentrating on six aspects: (i) process representation, (ii) model applicability to different climatic and physiographic settings, (iii) data requirements and model resolution, (iv) ability to be downscaled to smaller scales, (v) availability of model code, and (vi) possibility of adoption of the model into an operation flood forecasting system. In addition, we review potential models based on the proposed criteria and apply a decision tree as a filter sequence to provide insights on the possibility of model applicability. We summarize and tabulate an evaluation of the reviewed models based on the proposed criteria and propose the potential model candidates for flood applications in Kenya. This evaluation serves as an objective model preselection criterion to propose a modeling tool that can be adopted in development and operational flood forecasting to the end‐users of an early warning system that can help mitigate the effects of floods in data scarce regions such as Kenya.

Amin Hassanjabbar, Xin Zhou, Todd Han et al.

ABSTRACT Floods can cause significant damage to land, infrastructure, and individual well‐being. In the Canadian prairies, flood is a recurring natural disaster for farmers and ranchers. The flat terrain and extensive agricultural lands make the region vulnerable to flooding. Climate change could alter hydrological processes, leading to an increase in both frequency and intensity of flood events. In this study, machine learning and hydrodynamic models were combined to predict flood risks on agricultural lands based on various possible climate change scenarios. For this research, outputs from CanESM2, SDSM, ANN, HEC‐GEORAS, and HEC‐RAS were integrated to generate 2D flood simulation outputs. Climate change models CanESM2 and SDSM were used to simulate the possible future temperature and precipitation regimes (RCP 8.5 and RCP 4.5). The Artificial Neutral Network (ANN) model was used to predict possible future snowfall levels based on simulated precipitation and ambient air temperature regimes. The second ANN was further trained with first ANN data to predict possible flow rates in the river. A flood‐frequency analysis was conducted using 10, 50, and 100 years flood return periods. The collective data output was used in HEC‐RAS to simulate flooding under respective return periods. The georeferenced vector and raster data were generated using ArcGIS and HEC‐GEORAS. Comparative flood simulation outputs were generated using historical data. The flood simulation results using historical data were compared to climate change conditions. The results indicate that climate change could potentially exacerbate the severity of floods in agricultural lands across the prairies. The greater return periods correspond to greater flood depths, velocities, and inundation areas, with RCP 8.5 creating the most extreme conditions. In addition, climate change could potentially accelerate peak flows in the river and increase hydrological pressure.

Laurie Saint Criq, Eric Gaume, Yasser Hamdi et al.

Abstract Coastal planning implies the estimation of extreme sea levels. As the distribution of astronomical high tides can be predicted, most recent publications suggest focusing on the estimation of extreme skew surges. Historical information, record sea levels observed before the beginning of systematic tide gauge recordings, can improve estimations. The corresponding skew surges can be estimated but are not necessarily exhaustive. Indeed, some historical extreme skew surges can remain unnoticed if they are combined with low or moderate tides, or for a variety of reasons. To deal with this exhaustiveness issue, a previous publication proposed an unbiased method for combining systematic period skew surges with historical period extreme sea levels. This method appeared more reliable than previously proposed approaches. The present study aims at presenting a broader evaluation of this method, based on its application to nine sites located on the English Channel and North Sea coasts. The method is also improved to consider several historical periods and various types of historical information. Results confirm the method to be reliable, useful, and relevant. A number of recommendations is also formulated for the selection and use of historical information for sea level frequency analyses.

Katarína Vilinová, Matej Vojtek, Gabriela Repaská et al.

ABSTRACT The primary focus of the Operational Programme Quality of Environment (OP QE) is the support of EU regions in terms of environmental protection, efficient use of natural resources, flood protection and adaptation to climate change, as well as support of a low‐carbon economy. The aim of this article is a spatial analysis of the distribution of financial resources from the OP QE (priority axes 2 and 3) in 2017–2022 at different spatial‐hierarchical levels (region, district, and municipality) of Slovakia. The results indicated that there were significant differences in the number of submitted as well as approved/declined projects among individual regions, districts, or municipalities. Regarding the district level, several districts did not submit any project during the studied period, despite the existing flood risk. At the municipal level, out of total municipalities that received funding, approximately half were marked as potentially significantly endangered and approximately another half were marked as not endangered by the Preliminary Flood Risk Assessment—PFRA (2018). Based on this, inclusion of municipalities in different flood risk categories defined by the PFRA (2018) is not being taken into account when approving/declining projects and the same applies to the occurrence of previous flood events in municipalities.

Yang Li, Jianjun Zhang, Yawei Hu et al.

Flow discharge, slope gradient, and erosion time are widely recognized as crucial factors in determining rill erosion and its morphological characteristics. However, the relative importance of these three factors needs to be further elaborated to refine the understanding of rill erosion. In the current study, scour experiments were done under various conditions, including five flow discharges (0.5, 1.0, 1.5, 2.0, and 2.5 mm/min), five slope gradients (5°, 10°, 15°, 20°, and 25°), and durations of 20, 40, and 60 min. The resulting rill erosion process and its related morphological characteristics have been documented and analyzed. The results demonstrate that the average soil loss rate increased significantly with the increase inflow discharge and slope gradient. The individual effect of flow discharge (38.35%) was more pronounced than that of slope gradient (18.38%). Increasing flow discharge, slope gradient, and scouring time intensified the occurrence of headward erosion. Over extended erosion durations, rill length, width, depth, and volume all experienced increases. Additionally, with higher flow discharge and steeper slope gradient, the rill width-depth ratio decreased, indicating that rills became narrower and deeper. The individual effect of flow discharge on all rill morphological characteristics was more pronounced than that of slope gradient and scouring time. Except for rill length, the slope gradient had a greater impact on rill morphological characteristics than scouring time. Importantly, a significant portion of the runoff's potential energy was channeled into soil erosion rather than kinetic energy in sediment-laden flow. Based on the principle of energy conservation, the occurrence of rills reduced the energy required for soil erosion from 83.84 to 598.96 J/kg to 2.22–37.53 J/kg. The current study deepens the understanding of rill erosion mechanisms on the Loess Plateau in China and provides a scientific foundation for soil erosion control.

Pasquale Perrini, Vito Iacobellis, Andrea Gioia et al.

Abstract Flood hazard is a dynamic nonstationary phenomenon, which can be categorized based on the origin of the inundation. Inland flood hazard arises primarily from pluvial and fluvial inundations, typically modeled separately with respect to the pertaining spatial domains of the assessment, namely the urban areas and the riverine floodplains. When modeling is based on the catchment‐scale hydrological‐hydrodynamic approach, the inundations such as those resulting from pluvial and fluvial processes are usually not discerned, even though disparities in normative flood risk management exist in different countries. This paper establishes a tracer‐aided criterion to discretize between pluvial and fluvial flooding at a catchment scale, relying on the advection process of a conservative tracer. Applied to a small urban catchment for multiple probabilistic rainfall scenarios, our physically based methodology shows that the incorporation of a transport equation within a shallow water model can be used to define the inundation sources. We highlight the advantages of the proposed approach compared to commonly employed modeling techniques for mapping fluvial inundations, while emphasizing the significance of mapping and regulating pluvial hazards in urban areas. The study shows the potential role of an abstraction of the tracers' transport toward identifying the hazard sources in a catchment‐scale 2D numerical framework.

Risha Singh, Jenny B. Mason, Jahangeer Jahangeer et al.

ABSTRACT In the United States, research to date has primarily focused on mitigating urban coastal flood risks, with limited knowledge available on the planning capacity and effectiveness of flood mitigation in rural inland areas. This study addresses the gap by analyzing 162 publicly accessible local comprehensive plans from local jurisdictions across Nebraska, evaluating their preparedness for managing floodplains and reducing flood risks. The research examines how well Nebraska's communities, particularly rural ones, are prepared for flood risk reduction and whether they have adopted more proactive measures following the historic 2019 flood disaster. The evaluation criteria focus on three key areas: vulnerability assessment, policy toolkits, and coordination mechanisms. The findings reveal a mix of strengths and weaknesses across these categories. Overall, vulnerability assessment is generally low, with a score of 26.7%, indicating limited awareness and inadequate use of federal and state floodplain datasets to support rural planning. Policy toolkits, scoring 58.7%, are moderately available, suggesting that local communities have taken broader steps to address local flood risk reduction. Coordination mechanisms are relatively well‐established within local planning frameworks as found in 74.5% of the plans, showing promise for collaborative flood risk reduction efforts. In rural communities, particularly, the quality of plans is lower compared to urban communities. However, following the 2019 floods, rural communities have shown some improvement in enhancing floodplain management and planning. This research contributes to resilience planning theories, particularly for resource‐limited and disadvantaged rural communities in the United States.

Mehdi Bagheri‐Gavkosh, Diego Panici, Alan Puttock et al.

ABSTRACT Natural flood management strategies (NFMs) encompass a variety of measures implemented across catchments to mitigate flood risks while providing multiple benefits. In recent years, NFMs have gained increasing attention from researchers and policymakers. However, despite the growing body of research, there remains a lack of a critical review that quantitatively synthesises the reported performance of different NFMs by analysing their effects on key hydrological parameters. To address this gap, we conducted a systematic review of NFMs based on 145 peer‐reviewed papers covering 216 case studies across 37 countries, following the preferred reporting items for systematic reviews and meta‐analyses (PRISMA) guidelines. Our analysis moves from a descriptive overview of the evidence base to a novel, quantitative investigation of three critical themes: the characteristics of studied NFM schemes, the methodologies used for their assessment, and their quantitative hydrological performance and its influencing factors. Results indicate that 31% of the studies identified flood peak reduction as the most commonly targeted hydrological objective. A significant positive correlation was found between intervention diversity and intensity (Spearman's ρ = 0.53). Furthermore, our methodological analysis reveals a critical trade‐off in the literature, with empirical monitoring typically used in small catchments over shorter durations, while modelling is used to assess a greater diversity of interventions at larger scales, with truly combined approaches being notably rare (11%). Notably, river and floodplain management (RFM) demonstrated higher effectiveness, achieving an average flood peak reduction of 30%, particularly in larger catchments. Bearing the often multi‐faceted aims of NFMs in mind, this paper provides key suggestions for future research.

Venera Hajdari Llapashtica, Laura Kusari, Lavdim Osmanaj et al.

Suman Kumar Padhee, Giriraj Amarnath, Yakob Umer

Luc Anh Tuan, Can Thu Van, Doan Van Binh et al.

AbstractThe problem of flooding in Central Vietnam in general and the lower Ba River in particular is one of the natural disasters that frequently threatens people's lives and socioeconomic development in the region. Especially, climate change is becoming ever more prominent and hotter, making extreme natural disasters more unusual and unpredictable. In this research, MIKE‐FLOOD—a model that connects a 1‐dimensional (1‐D) MIKE 11 Hydrodynamics (HD) model with a 2‐dimensional (2‐D) MIKE 21 HD model—was used to set up. The model was calculated for three floods: (1) flood in October 1993, (2) flood in November 2003, and (3) flood in November 2007; these are floods with high frequency and relatively large magnitude. The results show that the 1993 flood rose and receded quickly. The flood peak inundated an area of 22,600 ha, accounting for 52% of the natural area. The flooded areas deeper than 1, 2, 3, 4, and 5 m were 16500, 11,000, 7000, 4200, and 2200 ha, respectively. In the center of Tuy Hoa city, the flooded area at the time of maximum water level was almost 100%.

Hany F. Abd‐Elhamid, Martina Zeleňáková, Tatiana Soľáková et al.

Abstract Flood and drought are natural phenomena whose probability of occurrence increases with changing weather conditions. Climate change has affected the hydrologic cycle's parameters and led to changes in temperature and precipitation pattern, which may increase the probability of occurrence of floods and droughts. Arid and semi‐arid areas are subject to extreme weather conditions and water resources scarcity. This study aims to assess drought and flood in Syria using remote sensing data. Monthly precipitation data have been collected from 10 land stations in the western part of Syria for the period (1991–2009) and satellite images for monthly precipitation from 1983 to 2020 were collected. The land stations data were used to correct the satellite images and correction equation was developed for each station. Standardized Precipitation Index (SPI) is used for analysis of drought and flood. Also, the main parameters for drought and flood, severity, intensity, duration, and the average return time were estimated. The results showed extreme flood events were recorded in 1988, 2002, 2012, and 2019 and extreme drought events were recorded in 1990, 2014, and 2016. The highest severity of drought and flood were recorded in 2014 and 1988 respectively. However, the highest intensity of droughts and floods was recorded in 2016 and 1988, respectively. If land station data are unavailable, as in the case of Syria owing to the protracted war, satellite images may be a useful source of data for drought and flood analysis after correction. This methodology can help in drought/flood analysis and estimate severity, intensity, duration, and the average return time of flood and drought in other locations of the world. The results proved that SPI is a useful tool to predict the time of occurrence of both flood and drought that could help decision‐makers for putting efficient plans for flood and drought risk management that could mitigate the impacts of such risks.

Thi Thao Nguyen Huynh, Nynke Hofstra, Hong Quan Nguyen et al.

Abstract Microbial pathogens in urban floodwaters pose risks to human health, potentially causing diseases such as diarrhea. However, the disease burden related to urban traffic exposure from citizens passing through floodwaters is not easily quantified and therefore not included in many studies. Notably, this problem has received little attention in low‐to‐middle‐income countries, with frequent flood events and the heavy diarrheal disease burden. This article calculates the infection risks and disease burden, considering traffic associated with exposure to floodwater contaminated with rotavirus for the first time in Ninh Kieu District, Can Tho city. Can Tho city in the Vietnamese Mekong Delta is well known to have many flood events every year, with many diarrheal cases during the flood season. The methodology comprises two steps. First, we applied quantitative microbial risk assessment that proposes the inclusion of exposure to traffic due to rotavirus in floodwater. Second, the disease burden was expressed in disability‐adjusted life years (DALYs). The exposed groups are child pedestrians, adult pedestrians, motorcyclists, and cyclists. We used video footage to monitor the traffic. The results show that total DALYs per flood event were 1.35 × 104 for 63,390 exposed people (i.e., 2129 DALYs per 10,000 cases). Motorcyclists are the strongest contributors to the DALYs (95%), followed by cyclists (2.8%), adult pedestrians (2%), and child pedestrians (0.2%). The population in Ninh Kieu District may suffer from waterborne diseases through traffic activities during flooding times. Our approach can be applied in other areas worldwide and helps identify main risk groups and focus areas for interventions.

William Paul Chilton, Robert Weiss, Jennifer L. Irish

Abstract The development of a basin‐specific comprehensive flood record using publicly available data for the James River Basin, Virginia. Using mixed surface analysis maps (NOAA, NWS), historical hurricane records (IBTrACS, HURDAT2), and flood and river gauge records (NWS, USGS), a database is created for analysis. Related to creating this database, a novel classification of six unique weather systems (non‐tropical and tropical) responsible for flooding is presented. The analysis includes Two‐Way tables with observed marginal and joint probabilities in various potential flood, storm, and regional combinations. Results show 233 tropical systems passed within the 500‐km study area, with 12.4%, or 29 systems of those systems causing flooding within the basin. An additional 713 events were non‐tropical, composing the majority of flood sources in the basin. Non‐tropical systems are responsible for 84% of the worst floods recorded, leading to an increased frequency of 6% yearly since 1941 and nearly 770% between 2014 and 2018. The findings of this study will be the basis for assessing land use and population patterns in the area, along with a future compound flooding model for the lower James River Basin.

مجید کاظم زاده, زهرا نوری, محمد جهان تیغ

مقدمه یکی از بلایای طبیعی که مناطق مسکونی و محورهای جاده‌ای را در مناطق کوهستانی تهدید می‌کند، ریزش‌های دامنه‌ای شامل ریزش سنگ، وقوع بهمن و لغزش است. بهمن، یک حجم عظیمی از برف، سنگ، یخ و واریزه‌ها را به پایین‌دست مناطق کوهستانی حمل می‌کند. وقوع بهمن در مناطق کوهستانی، یکی از مهم‌ترین مخاطرات طبیعی است که خسارت‌های جانی و مالی بسیاری را ایجاد می‌کند و مطالعه عوامل مؤثر در وقوع بهمن و شبیه‌سازی آن جهت مدیریت این پدیده از اهمیت زیادی برخوردار است.   مواد و روش‌‌ها در این پژوهش، به تحلیل شاخص‌های مؤثر بر وقوع بهمن (شاخص‌های زمینی و هواشناسی) و شبیه‌سازی وقوع بهمن و مؤلفه‌های آن با استفاده از مدل RAMMS در جاده ولایت رود البرز مرکزی (جاده دیزین)، استان البرز پرداخته شده است. شاخص‌های توپوگرافی و ژئومورفولوژیکی ازجمله شیب، جهت، انحنای دامنه (Curvature)، شاخص موقعیت توپوگرافی (TPI)، شاخص ناهمواری زمین (TRI) و شاخص رطوبت توپوگرافی (TWI) با استفاده از مدل رقومی ارتفاع (DEM) با اندازه پیکسل 6 × 6  سانتی‌متر مربع با کمک پهباد تهیه شد. از شاخص‌های هواشناسی نیز بارش، دما و باد مورد بررسی قرار گرفت. سپس، با استفاده از مدل شبیه‌سازی RAMMS مؤلفه‌های بهمن ازجمله سرعت، فشار و ارتفاع بهمن در منطقه مورد مطالعه برآورد شد.   نتایج و بحث نتایج نشان داد که مقدار و جهت شیب و شاخص‌های توپوگرافی تأثیر زیادی بر روی شکل‌گیری و وقوع بهمن داشتند. مهم‌ترین گذرگاه بهمن با مساحت 5.7 هکتار و 54.6 درصد از منطقه موردمطالعه که شامل منطقه تجمع و گذرگاه اصلی با شیب 60 تا 120 درصد و جهت شمال شرقی است که بیشترین پتانسیل ایجاد بهمن را دارد. همچنین، نتایج مدل شبیه‌سازی RAMMS نشان داد که سرعت متوسط و حداکثر سرعت بهمن در منطقه 5.3 متر بر ثانیه و 16 متر بر ثانیه بوده است. متوسط فشار مؤثر بهمن هفت و حداکثر فشار بهمن در منطقه نیز 45 کیلو پاسکال بوده است. برآورد ارتفاع بهمن در منطقه نیز نشان داد که متوسط ارتفاع بهمن در منطقه توقفگاه (مناطق مسکونی) 4.5 متر و حداکثر ارتفاع بهمن در منطقه 10 متر است که جز بهمن‌های بزرگ طبقه‌بندی می‌‌شود.   نتیجه‌گیری شناخت بهمن و ویژگی‌های دینامیک بهمن، یکی از عوامل بسیار مهم در پیش‌بینی و کنترل این پدیده طبیعی و خطرناک است. همچنین، شناسایی نوع بهمن (مرطوب، قطعه‌ای و پودری) می‌‌تواند کارشناسان را تا حد بسیاری زیادی در مدیریت و پیشنهاد روش‌های کنترل آن راهنمایی و کمک کند. در این پژوهش، با استفاده از نقشه‌ها و اطلاعات پایه‌ای و هواشناسی و عامل‌های ژئوموروفولوژیکی مانند انحنای دامنه، شاخص موقعیت توپوگرافی (TPI)، شاخص ناهمواری زمین (TRI) و شاخص رطوبت توپوگرافی (TWI) به‌همراه بازدیدهای میدانی، مناطق تجمع، گذرگاه عبور و توقفگاه بهمن شناسایی شد. سپس، مهم‌ترین شاخص‌های مؤثر در ایجاد و وقوع بهمن در منطقه تعیین شد. شیب بالای منطقه بین 120-60 درصد و همچنین، جهت دامنه (شمالی و شمال شرقی) و عوامل اقلیمی مانند بارش و دما، مهم‌ترین عوامل وقوع بهمن در منطقه موردمطالعه بوده است. متوسط ارتفاع بهمن در منطقه توقفگاه (مناطق مسکونی)، 4.5 متر و حداکثر ارتفاع بهمن در این منطقه 10 متر بوده است. با توجه به پژوهش حاضر، احتمال وقوع بهمن و خسارت در منطقه موردمطالعه بسیار بالا بوده و نیازمند ارائه و اجرای برنامه‌‌های مدیریتی و کنترلی برای جلوگیری از خسارت احتمالی است.

Leslie F. Mooyaart, Alexander M. R. Bakker, Johan A. van denBogaard et al.

Abstract Storm surge barriers are large movable hydraulic structures which close during a storm surge to prevent coastal floods. In the regions they protect, a failure to close the barrier is often the most likely cause for a catastrophic flood. Nevertheless, flood risk assessments usually only focus on raising flood defences behind the barrier. Despite its importance, there is no general method to assess the costs and benefits of improving the closure reliability. This paper presents a model that optimises investments considering both closure reliability improvements and raising flood defences behind the barrier, using the region protected by the Maeslant barrier as a case. We substantiate that constructing the Maeslant barrier was an optimal economic decision. Moreover, we demonstrate large investments such as a redundant barrier already being economically sound with a few decimetres of sea level rise. Based on our experience with this case study, we expect the model is useful in finding strategies to adapt to rising sea levels and other developments that cause coastal flood risk to rise worldwide.

Xiangfu Kong, Jiawen Yang, Jiandong Qiu et al.

Abstract Dynamically updated and fine‐grained flooding maps are critical for situational awareness and decision support. However, traditional methods, such as eyewitness reports, remote sensing, and hydrology models, may fail to correspond with the rapidly changing urban hydrological environment. The presence of crowdsourced data (such as social media data) allows for timely and cost‐effective monitoring of flood hazards through collective observations; however, such data can be unreliable due to sample bias and low spatiotemporal resolution. Therefore, new measures to identify flood‐affected roads are desirable. In this study, we propose a methodology that leverages taxi GPS data to support post‐event flood mapping for the road network. This method can identify whether a significant reduction in the taxi passing rate for a road segment was related to precipitation, and automatically recognize the flood‐affected roads based on a logistic regression model. Using taxi GPS data in Shenzhen as an example, we derived the flood map of the road networks, and compared and validated the results. This study demonstrated the usefulness of taxi GPS data in generating high‐quality flood maps and the value of incorporating multiple data sources for sensing near real‐time flood in the city.