NH1.4 | Enhanced flood risk management in urban environments
EDI
Enhanced flood risk management in urban environments
Convener: Maria Pregnolato | Co-conveners: Reza Ahmadian, Chiara Arrighi, María Bermúdez
Orals
| Tue, 25 Apr, 08:30–10:15 (CEST)
 
Room C
Posters on site
| Attendance Tue, 25 Apr, 10:45–12:30 (CEST)
 
Hall X4
Orals |
Tue, 08:30
Tue, 10:45
Floods are considered as one of the most devastating natural hazards globally and their impact is expected to increase as a result of climate change. Particularly, flooding in urban areas will result in greater impacts due to increased population residing in cities which is expected to be about 70% by 2050. There have been various enhancements in urban flood risk management in the last decade creating the opportunity to reduce risk to life and properties in cities. This special session is focused on these - advances in urban flood risk management, including but not limited to:
- improved representation of risk and its management (e.g. dynamic consideration of hazard and exposure);
- evacuation modelling and management;
- impact modelling to critical urban infrastructure, including cascading effects;
- new modelling techniques in flood risk management (such as application of emulators);
- new application and use of new data sources in flood modelling (such as remote sensing and real-time data, crowd-source data);
- application of nature-based solutions for urban stormwater management.

Orals: Tue, 25 Apr | Room C

Chairpersons: Reza Ahmadian, Chiara Arrighi
08:30–08:35
08:35–08:45
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EGU23-12624
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Highlight
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Virtual presentation
Alexia Tsouni, Stavroula Sigourou, Panayiotis Dimitriadis, Vasiliki Pagana, Theano Iliopoulou, G.-Fivos Sargentis, Romanos Ioannidis, Efthymios Chardavellas, Dimitra Dimitrakopoulou, Nikos Mamasis, Demetris Koutsoyiannis, and Charalampos (Haris) Kontoes

Flood risk assessment in vulnerable areas is crucial for efficient flood risk management, including the analysis and design of civil protection measures and the implementation of studies with proper interventions towards mitigating flood risk. This is even more crucial in highly dense urban river basins such as the ones in the region of Attica, which is hosting Athens, the capital of Greece, as well as critical infrastructures and important social economic activities. In the framework of the Programming Agreement with the Prefecture of Attica, the Operational Unit BEYOND Centre of EO Research and Satellite Remote Sensing of the Institute of Astronomy, Astrophysics, Space Applications & Remote Sensing (IAASARS) of the National Observatory of Athens (NOA), in cooperation with the Research Group ITIA of the Department of Water Resources and Environmental Engineering of the School of Civil Engineering of the National Technical University of Athens (NTUA), study five flood-stricken river basins in the region of Attica, which affect 23 Municipalities. The research teams collect all available data, conduct detailed field visits, run hydrological and hydraulic models, and assess flood hazard, flood vulnerability and eventually flood risk in every area of interest. Furthermore, high-risk critical points are identified, and mitigation measures are proposed, both structural and non-structural, in order to achieve effective crisis management for the protection of the population, the properties and the infrastructures. In addition, the BEYOND Centre has developed a web GIS platform where all the collected and produced data, the flood hazard, vulnerability and risk maps, as well as the identified critical points, the refuge areas and escape routes are stored and made available. All the relevant stakeholders and the competent authorities, who are directly or indirectly involved in civil protection, participate in dedicated workshops designed for their needs, and moreover, the studies’ general outcomes are disseminated to the wider public for raising awareness purposes. The response of the end users is very positive, and their feedback very constructive. The methodology and the outputs of the project are in line with the requirements for the implementation of the EU Floods Directive 2007/60/EC, the Sendai Framework for Disaster Risk Reduction, the UN SDGs, as well as the GEO’s Societal Benefit Areas.

How to cite: Tsouni, A., Sigourou, S., Dimitriadis, P., Pagana, V., Iliopoulou, T., Sargentis, G.-F., Ioannidis, R., Chardavellas, E., Dimitrakopoulou, D., Mamasis, N., Koutsoyiannis, D., and Kontoes, C. (.: Multi-parameter flood risk assessment towards efficient flood management in highly dense urban river basins in the Region of Attica, Greece, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12624, https://doi.org/10.5194/egusphere-egu23-12624, 2023.

08:45–08:55
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EGU23-7707
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ECS
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Highlight
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On-site presentation
Stefan Reinstaller, Albert König, and Dirk Muschalla

A city-wide approach to reduce the uncertainty regarding the spatial variability of urban flooding events is required in urban catchments. The goal of this study is the development of a modelling framework independent of the spatial scale to address the most hazardous areas in the current state and the future. The framework starts with the definition of the study objectives (e.g. reducing flood risk), which have a direct impact on the spatial and temporal scale, the used model approach, the data requirement and the level of detail. Furthermore, potentially hazardous areas will be identified with the potential flood risk index (PFRIi). The determination of this is a risk-based approach (R=E*V*H) which combines the exposition (E) with the vulnerability (V) and the hazard (H). The population density of each object and the total number of persons in the catchment will quantify the exposition. The vulnerability includes the number of past damage events and the object use. How accurate the modelled hazard is considered, depends on the used model approach: i) GIS-based; ii) only 1D; iii) only 2D; iv) 1D/2D models. The combination of H and V resulted in the risk factor (RFi) in four levels of detail depending on the used model approach. This allows both, the quantification of hazardous areas at the current state and the change of the PFRIi by future scenarios such as climate change and urbanization.

PFRIi = nP,k * RFi / (Ak * ∑P)                                                                                                                                                                                     

PFRIi=Potential Flood Risk Index; nP,k= number of Persons on a private ground k; Ak=total object area; =total number of persons in the catchment; Rfi= risk factor depending on the used model approach k

The GIS-based flow path analysis as the first level of detail can be used to identify the urban flooding hot spots. This allows the identification of hazardous sub-catchments in a city or high-risk private ground in a catchment quantified by the PFRIGIS. This is useful for further detailed analysis with other model approaches (e.g. 1D/2D model). The next steps are the implementation of the demonstrated framework for each level of detail in the city of Graz in Austria. Furthermore, the framework will integrate different climate scenarios based on a high-resolution climate model to address the impact of climate change on the urban drainage system quantified by the PFRIi.


Keywords: urban flooding, urban flood modelling, risk assessment, future changes

How to cite: Reinstaller, S., König, A., and Muschalla, D.: A modelling framework to assess urban flood risk on the city scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7707, https://doi.org/10.5194/egusphere-egu23-7707, 2023.

08:55–09:05
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EGU23-17553
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ECS
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Highlight
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Virtual presentation
Bernard Majani, Bruce D Malamud, and James Millington

This research develops a methodology to examine the change over time of urban textures for Nairobi in relation to flood hazard impact on infrastructure. We use three Landsat 7 (30 m resolution) images of Nairobi (2008, 2013, 2018). ‘Urban textures’ are the spatial distribution, shape and relative arrangement of urban elements such as green spaces, trees, roads and height of buildings and their geometry in a given urban city. Here, revising Stewart and Oke’s classifications for built-up areas and land cover types, we classify each of the three Landsat images into 14 urban textures using maximum likelihood under supervised classification. The building structure types were then examined using local knowledge, YouTube videos, Google Street View and ground truthing. We find that from 2008 to 2018 the urban textures with the largest total increases in area were compact mid-rise by 49.9km2 (6.9%) and compact high-rise by 11.3 km2 (1.5%). In contrast, the compact low-rise residential urban texture decreased greatly (29.2 km2). This suggests that for non-industrial land uses, Nairobi has grown upward. Accuracy assessments for the 2008 [2018] map were 83.6% [87.9%] with 95% confidence interval of 75.4–90.0% [80.6–93.2%] and kappa statistic 0.777 [0.834]. We then examine the spatial temporal change of intensive (high severity – low frequency) and extensive (low severity – high frequency) flood hazard events in terms of pattern, trend and impact in relation to rainfall, elevation, and urban textures. We find that urban textures for 2018 have reduced area coverage of the urban texture lightweight low-rise, having partly changed to compact midrise. The impact of change in land use through the development of urban areas greatly affects flooding and impacts in terms of severity. Flooding is more prevalent close to the major rivers in Nairobi, some of which occur in the non-informal settlements. Flood water flows from the higher areas of Ngong and Kikuyu towards the town centre, Nairobi west into industrial area going towards east lands. Rivers in Nairobi regularly overflow their banks and inundate low-lying areas like T-Mall, Nairobi west, industrial area and Mathare valley. These are the flood hotspots of Nairobi that also have high severity of fatalities and impact on infrastructure. We believe that our methodology of examining urban textures over time, using remote sensing images, combined with flood hazard impact information, will help scientists and hazard managers better understand, and prepare for, the interlinked nature of urban change with the flood hazard.

How to cite: Majani, B., Malamud, B. D., and Millington, J.: Urban textures and flood hazard impacts from 2008 to 2018 in Nairobi, Kenya, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17553, https://doi.org/10.5194/egusphere-egu23-17553, 2023.

09:05–09:15
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EGU23-16291
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Highlight
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On-site presentation
Eleni Tzanou, Antonios Chatzigiannis, and Michael Piliouras

Urban flooding occurs to  populated and build environments when there is excess water due to intense rainfall, extreme river flows, or storm occurance. Flood protection procedures and processes are  important and critical tools in flood-vulnerable and flood-prone areas. The consequences of the occurrence of such phenomena can have a seriously negative impact on a social, economic and environmental level. The first two categories are particularly affected in urban environments, where flooding might lead to severe casualties. The assessemnt for  optimal use of mobile systems of mobile flood protection dams/barrires as  short-term flood prevention and non-permanent/ nonstructural measures in combination with the permanently existing protection works and infrastructures in the urban environment is the subject of this study.

As a field of application (case study) of this research and the evaluation of different flooding and intervention scenarios, a stream section of an important transboundary watercourse that flows through the city of Serres, Greece was chosen. For this stream, the river bed and the surrounding areas as well as the built environment and all the technical works along the stream were measured by land observation methods (topographic and remote sensing data).

In order to draw into conclusions, the assessment of the hydrological characteristics and the water flow characteristics of the stream and the catchment area was carried out. Then, the simulation of the hydraulic characteristics for the current state of the stream and for various different flooding scenarios through the use of mobile flood barriers/small dams of different types and geometrical characteristics was applied.

The result of the study has led to a “roadmap” of how, when and where non-permanent protection measures and can be implemented in urban environments, useful to local authorities and civil protection in charge.

The evaluation of the capacity and performance of mobile barrier systems (based on their characteristics) was carried out, in order to be  effectively used in varying flooding events, with different characteristics and in  site-specific locations in various scenarios, through hydraulic simulations. The results of the hydraulic simulations resulted in the barrier systems’ evaluation and the formation of a methodology, which concerns their application efficiency and their inter-operability in the pilot area, while determining the optimal management and the overall cost at the same time.

How to cite: Tzanou, E., Chatzigiannis, A., and Piliouras, M.: Pilot-scale application of mobile barrier systems for flood protection of urban areas. Assessment and evaluation of their interoperability in the urban area of Serres, Greece., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16291, https://doi.org/10.5194/egusphere-egu23-16291, 2023.

09:15–09:25
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EGU23-738
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ECS
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On-site presentation
Raviraj Dave and Udit Bhatia

Flooding is among the most prevalent natural hazards worldwide, with increasing frequency and devastating impact. Urban floods are severe in Indian cities due to the culmination of changing climate, rapid urbanization, and intensive population growth. Transport infrastructure such as roads underpins economic activity enabling goods and human mobility. Evaluating the response against urban flooding is critical as disruption of the road system can result in cascading effects. The recent advancements in assessing the direct impact of urban flooding on road infrastructure are well explored. However, we lack a systematic approach to model and evaluate the direct, intangible, and indirect effects of extreme precipitation-induced urban flooding on road infrastructure systems in urban areas with unplanned drainage systems. Here in this study, we model the interaction between urban flooding and road transportation systems by integrating a hydrodynamic model with a network science approach for the coastal city of Kozhikode, India. We evaluated the response of the combined sewer drainage system against extreme precipitation events through the 1D-2D coupled flood model. While also identifying the resulting flood inundation characteristics- extent, propagation, and depth. Flood modeling results indicate the inundated roads and functionality loss of the road system for extreme precipitation events. Our initial assessment highlights that highly localized road network submergence due to flood inundation has a widespread and prolonged disruption in the system. The integrated framework and network functionality measures could help in future resilience assessment and in devising effective planning strategies for hazard mitigation in urban areas.

How to cite: Dave, R. and Bhatia, U.: Investigating the impact of extreme precipitation induced urban flooding on road network disruption, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-738, https://doi.org/10.5194/egusphere-egu23-738, 2023.

09:25–09:35
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EGU23-15092
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ECS
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On-site presentation
Ibrar Ullah, Gabor Kovacs, and Tibor Lenner

Urban flooding has gained great attention in recent years since population in urban areas have become more vulnerable to climatic extremes. The rate of urban flooding has increased around the globe mainly due to climate change. To cope with an increasing flooding issue, there has been an increased effort to manage flood management in urban areas. Similarly in this study, an attempt was made to develop a GIS based map to access flood resilience for the Gyor city. The Gyor city is particularly vulnerable to flooding due to its geographical proximity at the confluence of Raba, Rabca, Mosoni, Marcal and the great Danube rivers. Three elements i.e., hazard, Exposure, and coping capacity with each having pre-determined parameters were selected and processed through Analytic Hierarchy Process (AHP) technique. The product value map was then analyzed in ArcGIS using Specialized Flood Resilience Model (S-FRESI). The resultant product map shows that the majority of Gyorszentivan, Menfocsanak and Ipari Park districts have the very high resilience to floods, while most area of the  districts of Kismegyer, Nadorvaros,  Sziget, and Belvaros have very low resilience to floods. Similarly, the districts of Bacsa, Saras, Pinnyed, Gyimot and Likocs have most of the areas in medium resilience, while the remaining 6 districts possess areas with low, medium and high resilience. The study is very beneficial for future studies in assessing the areas that are more vulnerable to flooding and have low resilience and can help the decision makers to prepare a better urban flood management system.

How to cite: Ullah, I., Kovacs, G., and Lenner, T.: Urban Flood Resilience Assessment Using Arc GIS Based AHP Approach: A Case Study of Gyor City, Hungary, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15092, https://doi.org/10.5194/egusphere-egu23-15092, 2023.

09:35–09:45
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EGU23-1800
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ECS
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Highlight
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On-site presentation
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Yuhan Yang

Increasing urban pluvial flood disasters due to climate change and rapid urbanisation have been a great challenge worldwide. Timely and effective emergency evacuation is important for reducing casualties and losses. This has become a bottleneck for emergency management. This study aimed to develop a commonly used Agent-Based Mode (ABM) for pluvial flood emergency evacuation at the city scale, exploring the cascading impacts of pluvial flooding on human behaviour and emergency evacuation. The July 2021 pluvial flood event in Zhengzhou, Henan Province, claiming 380 lives and 40.9 billion yuan in direct losses, was selected as this case study. A raster-based hydraulic model (ECNU Flood-Urban) was used to predict flood inundation (extent and depth) during an event in Zhengzhou’s centre. Moreover, a comparative analysis of emergency evacuations was conducted before and after the pluvial flood event. The results showed that crowd behaviour plays an important role in emergency evacuation, and extensive flooding leads to an 11–83% reduction in the number of evacuees. This study highlights the importance of risk education and contingency plans in emergency response. The ABM model developed in this study is proven to be effective and practical and will provide support for decision-making in urban flood emergency management.

How to cite: Yang, Y.: ABM-based emergency evacuation modeling during urban pluvial floods: A “7.20” pluvial flood event study in Zhengzhou, Henan Province, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1800, https://doi.org/10.5194/egusphere-egu23-1800, 2023.

09:45–09:55
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EGU23-5027
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ECS
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On-site presentation
Hsiao-Ping Wei, Yuan-Fong Su, Chih-Hsin Chang, and Keh-Chia Yeh

A report from World Bank in 2022 reveals that about 1.81 billion people (23% of the world population) are directly exposed to flood with depths greater than 0.15 meters. In this study, we evaluate the impact of extreme rainfall events on population in urban areas in Taiwan using SOBEK models. The validation results of the SOBEK models are promising with photos collected from social media for historical storm events. To further assess the impact of extreme rainfall events, we used design rainfall with hourly rainfall of 80mm/hr, 90mm/hr, and 100mm/hr derived from Simple Scaling Gaussian Markov (SSGM) method for single rainfall gauge within major urban area. These results are provided for disaster prevention authority to reinforce the flooding management in urban area.

How to cite: Wei, H.-P., Su, Y.-F., Chang, C.-H., and Yeh, K.-C.: Flood Simulation and Population Impact Analysis of Short-Duration Intense Rainfall in Urban Area, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5027, https://doi.org/10.5194/egusphere-egu23-5027, 2023.

09:55–10:05
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EGU23-5522
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ECS
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On-site presentation
Kyewon Jun, Sunguk Kim, Minjin Jung, and Seunghee Lee

Due to climate change, the scale of flood damage by localized torrential rains in urban areas is on an increase. Meanwhile, the existing flood runoff analysis methods do not consider buildings in urban areas, resulting in an overestimation of the degree of flood damage. Therefore, this study presents a method to consider buildings when applying XP-SWMM for flood analysis in downtown areas where buildings are concentrated, in order to accurately simulate the flood spread pattern around the building. To propose an optimal method which considers buildings, water depth, maximum flooded area, and the flow pattern around the building were compared according to whether or not the building was applied. As a result of the study, the average flooded area was 172,900㎡ when the building was set as an inactive area, which was 64% of the average flooded area (271,000㎡) when the building was not considered. The average water depth was 0.32m when buildings were considered, which was 1.78 times deeper than the average water depth (0.15m) when buildings were considered. This is the reflection of the blocking effect of the building in the model analysis, resulting in a significant reduction of the flooded area. In addition, since the flood simulation considered the flow rate of the same volume, flow velocity and average submerged depth relatively increased. This study is expected to contribute to the establishment of optimal downtown flood measures, by presenting a method for accurate flood analysis using the XP-SWMM model considering the influence of buildings in urban areas. For further improvement in the accuracy of flood analysis, it would be necessary to develop flood simulation methods suitable for different basins with flood records.

 

This research was support by a (2022-MOIS63-002) of Cooperative Research Method and Safety Management Technology in National Disaster funded by Ministry of Interior and Safety(MOIS, Korea).

How to cite: Jun, K., Kim, S., Jung, M., and Lee, S.: 2D Flood Analysis considering Buildings in Urban Areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5522, https://doi.org/10.5194/egusphere-egu23-5522, 2023.

10:05–10:15
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EGU23-11379
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ECS
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Virtual presentation
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Mrunalini Rana, Dhruvesh Patel, and Vinay Vakhria

The most frequent catastrophic natural disaster is thought to be flooding. Due to climatic uncertainty, variable rainfall, a lack of river carrying capacity, illegal settlement along river banks, and dense population, flood magnitudes and vulnerabilities increased in the past ten years globally. There are 11,356 records of hydrological and meteorological occurrences from 1900 to 2020, according to the United Office of Disasters Risk Reduction's (UNDRR) International Database, with 8.6 million fatalities and 2600 million US dollars in economic damage. In the current climate, floods cannot be prevented, but their damages can be reduced with a thorough flood assessment. The identification of the flood inundation area, flood arrival time, and flow velocity in flood-prone areas can be accomplished using a variety of hydrodynamic models; however, the limited resolution of DEM (Digital Elevation Model) makes it impossible to determine the actual flooding state. To remedy this shortcoming, we developed a high-resolution DEM from UAV (Unnamed Aerial Vehicle) for this case study, which involves the well-known Sabarmati of Gujarat State, one of India's principal west-flowing rivers with a length of 371 kilometres, which was impacted by a flood in 2006. The 4RTK (Real-Time Kinematic) Phantom, a UAV survey, was used to acquire aerial pictures of a portion of the river Sabarmati. The image was then processed with 75% mosaicking using the Pix4D mapper tool for better accuracy. Later, with the aid of Global Mapper, various DEMs with grid sizes ranging from 0.5 m x 0.5 m to 10 m x 10 m are created with near precision of 3 cm spatial resolution. These generated DEMs are then used as input for the hydrodynamic simulation using Civil Geo-HECRAS. Hence, the hydrological data required for the hydrodynamic model has been assumed from past floods and the geometrical data for the study is derived from the UAV survey with four Manning's roughness coefficients—0.025, 0.030, 0.033, and 0.035 have been assumed for this case study considering the local conditions. The analysis of Manning's roughness value's influence reveals that when roughness increases, discharge reduces, and velocity and Froude's number decrease.

Keywords: Flood, DEM-Digital Elevation Model, UAV-Unnamed Aerial Vehicle, Hydrodynamic modeling, Manning’s roughness

How to cite: Rana, M., Patel, D., and Vakhria, V.: UAV based High-resolution DEM for 1D Hydrodynamic modeling - A case of Flood Assessment of Sabarmati River, Gujarat, India., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11379, https://doi.org/10.5194/egusphere-egu23-11379, 2023.

Posters on site: Tue, 25 Apr, 10:45–12:30 | Hall X4

Chairpersons: Reza Ahmadian, Chiara Arrighi
X4.13
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EGU23-3616
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ECS
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Florence Mainguenaud, Usman T Khan, Laurent Peyras, Claudio Carvajal, Bruno Beullac, and Jitendra Sharma

Urban areas are frequently built along rivers and earthen levees are commonly used to protect areas from fluvial floods. Levees are designed to protect assets from flooding, however, they deteriorate over time. Maintenance checks are required to maintain their efficacy but even in good condition, a levee structure may fail during a flood, hence flood risk assessments in fluvial areas require an investigation of levee failures, e.g. by overtopping, erosion, or sliding. In this research, we investigate the failure probability due to backward erosion of an adapted levee in the Etobicoke Creek watershed, in Toronto, Canada. The study proposes an adapted levee as the residential area is often flooded. Backward erosion is the most probable and challenging failure mechanism for our case study based on the levee shape and soil type. For this probabilistic study, the levee was modelled using GeoStudio, which produces seepage analysis from geotechnical and hydrological parameters. The seepage analysis provides hydraulic gradients from which we determine the failure probability of backward erosion based on a critical hydraulic gradient value. To obtain the flood hazard, we use a steady flow hydraulic model (HEC-RAS) to simulate the 350-years return period flow through the River. We compare two backward failure scenarios: one with a levee breach and one without, to better understand how failure of the levee will impact flood risks, and therefore, highlighting the importance of on-going levee maintenance. To obtain flood risk maps, the flood hazard (i.e., flood extent) is combined with flood exposure. The flood exposure includes land-use type (residential, commercial, etc.) and demographic information. Flood hazard and exposure data are combined using ArcGIS. The flood hazard and exposure rasters are reclassified in a new scale to determine flood risk. We then overlay the rasters to determine the spatial distribution of flood risk for both scenarios. We compare the resulting flood risk maps and calculate the change in flood risks for the area protected by the levee. Accounting for potential failure of infrastructure in flood risk mapping results in more accurate risk estimations. We also demonstrate the positive impact of the levee.

How to cite: Mainguenaud, F., Khan, U. T., Peyras, L., Carvajal, C., Beullac, B., and Sharma, J.: Mapping the impact of levee failure on flood risks: A Toronto case study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3616, https://doi.org/10.5194/egusphere-egu23-3616, 2023.

X4.14
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EGU23-3883
Sheng-Hsueh Yang, Der-Ren Song, Jyh-Hour Pan, Xi-Jun Wang, Sheau-Ling Hsieh, Keh-Chia Yeh, Cheng-Wei Li, and Wen-Feng Wu

Urban areas are gradually being affected by climate change. It is difficult to avoid urban flooding caused by heavy rainfall. Especially road flooding occurs 2-3 times a year in urban areas in the summer of Taiwan, when the regional weather is convective rainfall strong, it is difficult for general weather forecasting models to predict the amount of rainfall in the city in a short period of time. Rainfall areas in urban areas are prone to road flooding. Therefore, the intensity management value (>50dBz) of the radar reflectivity around the city is used to estimate the rainfall and urban flood warning, and the IoT water level monitoring instrument can monitor the water level in the urban rainwater sewer and set the urban flood warning based on the management value. The local low-lying areas of the city can also use CCTV images to identify flooding situation as a tool through AI's CCN deep learning technology and CCTV's flooding big data database that according to CNN's learning, training, and testing, after the completion, CCTV inspection and flood image recognition can be used for urban disaster prevention and relief. Finally, the monitoring data related to urban flooding is collected and displayed through the urban smart flood prevention platform, which provides efficient data collection, increases the response time for disaster relief, and quickly eliminates road flooding in the city. This study takes the urban smart flood prevention platform in New Taipei City, Taiwan as an example.

How to cite: Yang, S.-H., Song, D.-R., Pan, J.-H., Wang, X.-J., Hsieh, S.-L., Yeh, K.-C., Li, C.-W., and Wu, W.-F.: Smart city disaster prevention platform information integration displays and practical application in New Taipei City Taiwan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3883, https://doi.org/10.5194/egusphere-egu23-3883, 2023.

X4.15
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EGU23-9359
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ECS
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Daniel Lassiter, Julianne Quinn, and Daniel Wright

The central challenge to flood risk management is in designing flood mitigation practices and strategies that avoid the human and economic costs of under- and over-investment. Designing to avoid these costs requires accurate recurrence probability estimates for decision-relevant flood impacts such as water depths, financial damages, and water volumes. The challenge of estimating flood impact probabilities is exacerbated in coastal settings with non-independent compound flood drivers such as rainfall and storm surge. While techniques for compound flood impact probability assessments have been proposed, insight into the decision relevance of the choice of methodology has not been explored. Our work begins to address this gap by comparing flood-volume exceedance curves resulting from three approaches in a 1.9km2 coastal urban watershed in Norfolk, Virginia. Watershed runoff and storm sewer flow are represented by 1144 links, 1128 nodes, and 869 subcatchments in a U.S. Environmental Protection Agency Stormwater Management Model (SWMM).

The first flood impact probability assessment technique follows a traditional design storm approach in which the joint probability of storm surge and rainfall are mapped directly onto the modeled flood volumes. In contrast, the second and third techniques involve modeling many years of stochastically generated rainfall and storm surge time series and empirically estimating the probability distribution of the resulting flood volumes. These two techniques differ in their approach to stochastic weather generation, one fitting a probability distribution to local rainfall observations to allow for extrapolation outside the record, and the other using only historical rainfall observations but across a wider regional domain. Each approach is grounded in statistical and physical theory but leads to different estimates in flood-volume exceedance curves and their associated uncertainty. Since these estimates would influence flood mitigation design, we show that the choice of technique has design implications.

How to cite: Lassiter, D., Quinn, J., and Wright, D.: Evaluating the design relevance of the choice of flood frequency analysis technique in an urban coastal watershed, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9359, https://doi.org/10.5194/egusphere-egu23-9359, 2023.

X4.16
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EGU23-10415
Sunguk Kim, Kyewon Jun, and Minjin Jung

In recent years, the frequency and intensity of localized torrential rains in Korea have increased due to climate change, thereby increasing human and property damage through frequent urban flooding. Research on urban flood forecasting is mainly focused on numerical modeling and rainfall-based flood prediction, but the analysis technology of quantitative flood measurement data is lacking. In addition to flood mapping and verification of flood prediction results, it is necessary to develop urban flood management technologies using sensor-based quantitative flood depth measurements. The existing flood sensors have different management regulations depending on the development entities, and there are no set standard or basic performance standards, causing inefficiency in their budget and maintenance. Therefore, in order to improve the efficiency and prevent trial and error, this study proposes the performance standards and installation methods as guidelines, necessary for the installation and operation of flood sensors. To this end, firstly, domestic and foreign cases for urban flood sensors were reviewed for their installation procedures, installation location selection, measurement intervals, inspection and management plans, etc. The table of contents of the guidelines was derived through case analysis, consisting of a standard model installation plan that describes the detailed composition and operation principle of flood sensors, sensor installation plans for each measurement point such as the surface and sub-surface, on-site installation procedures, and instructions on a test run. These guidelines are expected to be followed to strengthen a proactive urban flood response system by effectively operating flood sensors.

 

Acknowledgment: This research was support by a (2022-MOIS63-002) of Cooperative Research Method and Safety Management Technology in National Disaster funded by Ministry of Interior and Safety(MOIS, Korea).

How to cite: Kim, S., Jun, K., and Jung, M.: Development of Guidelines on the Application of Urban Flood Sensors, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10415, https://doi.org/10.5194/egusphere-egu23-10415, 2023.

X4.17
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EGU23-15752
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ECS
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Daniela Rodriguez Castro, Solène Roucour, Pierre Archambeau, Christophe Dessers, Sébastian Erpicum, Michel Pirotton, Mario Cools, Jacques Teller, and Benjamin Dewals

In July 2021, the Bernd low-pressure system induced disastrous floods over part of Germany, the Netherlands and Belgium. Relatively small catchments were mostly affected. In Belgium, nine out of the ten most impacted municipalities are situated in a single catchment, namely river Vesdre (700 km2). Considering this catchment as a case study, we investigate whether available data enable detecting surprise and levee effects and, if so, whether the distribution of such effects shows a particular spatial pattern.

To explore this, we apply relatively simple data analysis based on official flood hazard maps, field surveys, as well as outcomes of hydrological and hydrodynamic modelling. The field surveys are twofold. On one hand, inundation depths were registered for 8,000 buildings and infrastructures in the considered catchment. On the other hand, detailed interviews were conducted with flood victims. Information was collect on: flow characteristics, building features, damage and monetary losses, as well as implemented precautionary measures and warning.

Data analysis shows that the mismatch between the observed inundation extent and the official hazard maps varies strongly from one section of the river to another, particularly between municipalities. These variations could be related to the presence of flood defense constructed along specific sections of the river, and the associated levee effects. Another quantity which varies enormously from one municipality to another is the ratio between the number of flooded buildings in a municipality to the total number of buildings in the same municipality. This quantity may reflect the degree of overwhelming of local authorities and first respondents, though it is not accounted for in current flood damage modelling.

The outcomes of the data analysis contribute to explain differences in how local authorities and communities reacted during this unprecedented flood. Overall, the results highlight the relevance of initiatives undertaken since the event for updating the official flood hazard maps based on more extreme scenarios aiming at enhancing risk awareness. It also emphasizes the need for improved management of residual risk in the case of channelized rivers, or rivers equipped with high-standard flood defences.

We are currently exploring to which extent the differences in the level of surprise and levee effects contribute to explain differences in damage and monetary losses between municipalities.

How to cite: Rodriguez Castro, D., Roucour, S., Archambeau, P., Dessers, C., Erpicum, S., Pirotton, M., Cools, M., Teller, J., and Dewals, B.: Contrasting levels of surprise and levee effect between municipalities in the 2021 flood in Belgium, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15752, https://doi.org/10.5194/egusphere-egu23-15752, 2023.

X4.18
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EGU23-17580
Hyunsuk Lee, Ki-Won Lee, and Ho-Jeong Jo

The water level observation technology, which converts the change in weight due to buoyancy into the water level, has a long history of Archimedes' buoyancy experiment. A buoyancy type water level gauge that can provide a resolution of 0.1mm or more using Archimedes buoyancy was developed by Lee (2001) under the model name BYL-EV250. Currently, the above technology has been used since 2013 for the purpose of observing evaporation from the water surface with a resolution of 0.03 mm or more. Recently, various observation techniques have been developed to quantitatively monitor urban flooding. The Department of Homeland Security (DHS) Science and Technology Directorate (S&T) (2020) provides guidelines for the use of low-cost urban flood monitoring sensors. In this study, the element technology necessary for urban flood monitoring was developed. The first is a waterproofing technology developed to minimize equipment damage even when the equipment is completely submerged as urban flooding progresses. The second is a power-saving technology developed to provide smooth monitoring power while minimizing installation space. In addition, case protection technology that can provide smooth communication while protecting the device has been developed. In the future, these technologies can be used for developing technologies to minimize damage and prevent disasters by quantitatively monitoring urban flooding.

How to cite: Lee, H., Lee, K.-W., and Jo, H.-J.: Development of Buoyancy Type Urban Water Level Gauge, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17580, https://doi.org/10.5194/egusphere-egu23-17580, 2023.