Flood Incident Management Research Articles

Climatic and Hydrological Factors Affecting the Assessment of Flood Hazards and Resilience Using Modified UNDRR Indicators: Ayutthaya, Thailand

This research aims to investigate the effect of climatic and hydrological factors on flood hazards and assess flood resilience in Ayutthaya, Thailand, using the 10 essentials for making cities resilient modified by the United Nations Office for Disaster Risk Reduction (UNDRR). Flood resilience assessment was performed based on a multi-criteria decision-making approach or the analytical hierarchy process (AHP) of pairwise comparison. The results indicate that runoff is considered the most influential factor in flood hazards, followed by land use, rainfall, and historical flood events, sequentially. Regarding the flood incident management concept, a questionnaire survey (n = 552) was conducted to understand the impacts of flood on local communities. The findings reveal that 50% of respondents had never received any flood information or participated in training sessions on flood preparedness. Most reported their concerns about the inadequate supply of drinking water during a flood. Spearman’s correlation coefficient shows positive correlations between flood disaster relief payments, preparedness training, access to flood hazard mapping, emergency health services, and their flood preparation actions. According to the modified UNDRR indicators, the top three highest AHP values in building community resilience to flood hazards in Ayutthaya are flood risk scenario identification, the effectiveness of emergency flood disaster response, integrated urban planning, and disaster risk reduction. The policy implications of this research include the need for national authorities to better understand the role cities can play a vital role in supporting both national and international climate resilience frameworks, especially Thailand’s National Disaster Management Plan, the Sendai Framework for Disaster Risk Reduction (SFDRR), and the global Sustainable Development Goals (SDGs).

Improving Urban Flood Mapping by Merging Synthetic Aperture Radar-Derived Flood Footprints with Flood Hazard Maps

Remotely sensed flood extents obtained in near real-time can be used for emergency flood incident management and as observations for assimilation into flood forecasting models. High-resolution synthetic aperture radar (SAR) sensors have the potential to detect flood extents in urban areas through clouds during both day- and night-time. This paper considers a method for detecting flooding in urban areas by merging near real-time SAR flood extents with model-derived flood hazard maps. This allows a two-way symbiosis, whereby currently available SAR urban flood extent improves future model flood predictions, while flood hazard maps obtained after the SAR overpasses improve the SAR estimate of urban flood extents. The method estimates urban flooding using SAR backscatter only in rural areas adjacent to urban ones. It was compared to an existing method using SAR returns in both rural and urban areas. The method using SAR solely in rural areas gave an average flood detection accuracy of 94% and a false positive rate of 9% in the urban areas and was more accurate than the existing method.

Floodwater detection in urban areas using Sentinel-1 and WorldDEM data

Remote sensing using synthetic aperture radar (SAR) is an important tool for emergency flood incident management. At present, operational services are mainly aimed at flood mapping in rural areas, as mapping in urban areas is hampered by the complicated backscattering mechanisms occurring there. A method for detecting flooding at high resolution in urban areas that may contain dense housing is presented. This largely uses remotely sensed data sets that are readily available on a global basis, including open-access Sentinel-1 SAR data, the WorldDEM digital surface model (DSM), and open-access World Settlement Footprint data to identify urban areas. The method is a change detection technique that locally estimates flood levels in urban areas. It searches for increased SAR backscatter in the post-flood image due to double scattering between water (rather than unflooded ground) and adjacent buildings, and reduced SAR backscatter in areas away from high slopes. Areas of urban flooding are detected by comparing an interpolated flood level surface to the DSM. The method was tested on two flood events that occurred in the UK during the storms of Winter 2019–2020. High urban flood detection accuracies were achieved for the event in moderate density housing. The accuracy was reduced for the event in dense housing, when street widths became comparable to the DSM resolution, though it would still be useful for incident management. The method has potential for operational use for detecting urban flooding in near real-time on a global basis.

Testing the impact of direct and indirect flood warnings on population behaviour using an agent-based model

Abstract. This paper uses a coupled hydrodynamic agent-based model (HABM) to investigate the effect of direct or indirect warnings in flood incident response. This model uses the LISFLOOD-FP hydrodynamic model and the NetLogo agent-based framework and is applied to the 2005 flood event in Carlisle, UK. The hydrodynamic model provides a realistic simulation of detailed flood dynamics through the event, whilst the agent-based model component enables simulation and analysis of the complex, in-event social response. NetLogo enables alternative probabilistic daily routine and agent choice scenarios for the individuals of Carlisle to be simulated in a coupled fashion with the flood inundation. Specifically, experiments are conducted using a novel “enhanced social modelling component” based on the Bass diffusion model. From the analysis of these simulations, management stress points (predictable or otherwise) can be presented to those responsible for hazard management and post-event recovery. The results within this paper suggest that these stress points can be present, or amplified, due to a lack of preparedness or a lack of phased evacuation measures. Furthermore, the methods outlined here have the potential for application elsewhere to reduce the complexity and improve the effectiveness of flood incident management. The paper demonstrates the influence that emergent properties have on systematic vulnerability and risk from natural hazards in coupled socio-environmental systems.

Long term investment scenarios and an opportunity to collaborate

In December 2014 the Environment Agency published Long Term Investment Scenarios (LTIS) for flood and coastal erosion risk management in England. It sets out the future costs and benefits of managing flood and coastal erosion risk in England in a range of different scenarios. Its major achievement in long-term risk-based resource allocation is to incorporate a rigorous national economic optimisation based on an aggregation of 3,000 flood defence systems covering the entirety of England’s floodplain. The analysis is based on the Environment Agency’s national assessment of flood risk from rivers and the sea, along with the risk of properties flooding from surface water. The risk information informs an innovative economic model to assess optimal levels of investment both in maintaining and improving the defence infrastructure, and is combined with a high level appraisal of investment in broader risk management activities (such as flood incident management). The headline results describe optimal investment profiles in the short and long term, and compare these with planned investment levels by government and external contributors. The potential to reduce flood risk in the long term is described in the context of the efficiencies required to reduce and hold down costs, the benefits of maintaining control over development in the floodplain, and the effects of climate change. There are constraints in the economic optimisation approach, as well as in the broader, inclusive overview of risk management activities, and the Environment Agency is now seeking a more open, collaborative approach – working with industry and academic partners – to develop LTIS and strengthen it further as robust, independent, world-leading evidence.

Keep it simple: user-focused flood risk visualisation

From complex server-dependent geographic information systems to simple sheets of paper, there is a myriad of flood risk visualisation approaches available, each with specific strengths and weaknesses. This paper discusses existing methods and tools to identify both common and novel features, and investigates how these traits affect their suitability for satisfying the requirements of different users and their technical requirements. The paper introduces a flexible web-browser-based tool focusing on delivering flood extents and key additional information (including critical infrastructure) in a user-friendly and resilient manner, without the need for network access or the installation of specialist software. Its development and implementation in the Midlands region of the UK's Environment Agency is discussed and its impact in use on flood incident management is investigated with the aid of user feedback.

Hydrological ensemble prediction systems

Hydrological ensemble prediction systems

Probabilistic flood forecasting and decision-making: an innovative risk-based approach

Flood forecasting is becoming increasingly important across the world. The exposure of people and property to flooding is increasing and society is demanding improved management of flood risk. At the same time, technological and data advances are enabling improvements in forecasting capabilities. One area where flood forecasting is seeing technical developments is in the use of probabilistic forecasts—these provide a range of possible forecast outcomes that indicate the probability or chance of a flood occurring. While probabilistic forecasts have some distinct benefits, they pose an additional decision-making challenge to those that use them: with a range of forecasts to pick from, which one is right? (or rather, which one(s) can enable me to make the correct decision?). This paper describes an innovative and transferable approach for aiding decision-making with probabilistic forecasts. The proposed risk-based decision-support framework has been tested in a range of flood risk environments: from coastal surge to fluvial catchments to urban storm water scales. The outputs have been designed to be practical and proportionate to the level of flood risk at any location and to be easy to apply in an operational flood forecasting and warning context. The benefits of employing a benefit-cost inspired decision-support framework are that flood forecasting decision-making can be undertaken objectively, with confidence and an understanding of uncertainty, and can save unnecessary effort on flood incident actions. The method described is flexible such that it can be used for a wide range of flood environments with multiple flood incident management actions. It uses a risk-based approach taking into account both the probability and the level of impact of a flood event. A key feature of the framework is that it is based on a full assessment of the flood-related risk, taking into account both the probability and the level of impact of a flood event. A recommendation for action may be triggered by either a higher probability of a lower impact flood or a low probability of a very severe flood. Hence, it is highly innovative as it is the first application of such a risk-based method for flood forecasting and warning purposes. A final benefit is that it is considered to be transferrable to other countries.

The European Flood Alert System and the communication, perception, and use of ensemble predictions for operational flood risk management

AbstractAlthough ensemble prediction systems (EPS) are increasingly promoted as the scientific state‐of‐the‐art for operational flood forecasting, the communication, perception, and use of the resulting alerts have received much less attention. Using a variety of qualitative research methods, including direct user feedback at training workshops, participant observation during site visits to 25 forecasting centres across Europe, and in‐depth interviews with 69 forecasters, civil protection officials, and policy makers involved in operational flood risk management in 17 European countries, this article discusses the perception, communication, and use of European Flood Alert System (EFAS) alerts in operational flood management. In particular, this article describes how the design of EFAS alerts has evolved in response to user feedback and desires for a hydrographic‐like way of visualizing EFAS outputs. It also documents a variety of forecaster perceptions about the value and skill of EFAS forecasts and the best way of using them to inform operational decision making. EFAS flood alerts were generally welcomed by flood forecasters as a sort of ‘pre‐alert’ to spur greater internal vigilance. In most cases, however, they did not lead, by themselves, to further preparatory action or to earlier warnings to the public or emergency services. Their hesitancy to act in response to medium‐term, probabilistic alerts highlights some wider institutional obstacles to the hopes in the research community that EPS will be readily embraced by operational forecasters and lead to immediate improvements in flood incident management. The EFAS experience offers lessons for other hydrological services seeking to implement EPS operationally for flood forecasting and warning. Copyright © 2012 John Wiley & Sons, Ltd.

An aggregative fuzzy risk analysis for flood incident management

Mitigation of loss or damage is the prime focus in flood incident management (FIM). Emergency response program, a key element in flood incident management can fail in multiple ways; however it can be mainly attributed to failure of infrastructure and/or failure of human institutions. Characterization and quantification of various risk factors in emergency response is a difficult task because responses to floods are complex and dynamic in nature. For these reasons, high level of uncertainties are inherent in the estimation of risk associated with the emergency response and may warrant the usage of a quantitative–qualitative risk assessment framework. In this paper, a multi-stage hierarchical model is developed to estimate the aggregative risk associated with the failure of emergency response system in case of flood. Each risk item is defined by the product of the likelihood of a failure event and associated consequences. Both likelihood and the consequences of a failure event are defined using fuzzy numbers to capture vagueness in the concept of relevant risk factors. An analytic hierarchy process is used for estimating the priority matrix (weights) for grouping risk attributes. Utility of a proposed model is demonstrated through a simplified risk hierarchy representing emergency response system failure of a FIM.

An agent-based model for risk-based flood incident management

Effective flood incident management (FIM) requires successful operation of complex, interacting human and technological systems. A dynamic agent-based model of FIM processes has been developed to provide new insights which can be used for policy analysis and other practical applications. The model integrates remotely sensed information on topography, buildings and road networks with empirical survey data to fit characteristics of specific communities. The multiagent simulation has been coupled with a hydrodynamic model to estimate the vulnerability of individuals to flooding under different storm surge conditions, defence breach scenarios, flood warning times and evacuation strategies. A case study in the coastal town of Towyn in the United Kingdom has demonstrated the capacity of the model to analyse the risks of flooding to people, support flood emergency planning and appraise the benefits of flood incident management measures.

National/local policy tensions in flood risk management: An international comparison

In recent years, both the French and the English states have played an important and newly enhanced role in flood hazard response. Planning Policy Statement (PPS) 25 and Plan de prévention des risques (PPR) policies exemplify the shift towards a strategic and multi-method approach to land and water management—a flood risk management approach. However, evidence from 72 semi-structured interviews suggests that these new policies are not properly implemented at the local level, as can be clearly seen in Seine-Amont, France and East London, UK. Flood management is not a priority on local planning authorities' agendas and there are often tensions and even conflicts between national and local levels as far as flood management is concerned. The analysis of these tensions shows that effective flood governance at all levels of the planning system could be better achieved by a ‘bottom-up’ approach to flood management, in which central government gives the local authorities the opportunity to build resilient places better able to cope with the flood hazard in the longer term. Such an approach requires better coordination between stakeholders, more clarity and transparency in hazard assessment, and proper integration of emergency issues into flood incident management. Regeneration areas offer the opportunity to tackle these issues from the early stages of development projects.

Risk communication in emergency response to a simulated extreme flood

Risk communication in flood incident management can be improved through developing hydrometeorological and engineering models used as tools for communicating risk between scientists and emergency management professionals. A range of such models and tools was evaluated by participating flood emergency managers during a 4-day, real-time simulation of an extreme event in the Thamesmead area in the Thames estuary close to London, England. Emergency managers have different communication needs and value new tools differently, but the indications are that a range of new tools could be beneficial in flood incident management. Provided they are communicated large model uncertainties are not necessarily unwelcome among flood emergency managers. Even so they are cautious about sharing the ownership of weather and flood modelling uncertainties.