CONFIGURE: An Optimisation Framework for the Cost-Effective Spatial Configuration of Blue-Green Infrastructure

This paper develops a Blue-Green Infrastructure (BGI) performance evaluation approach by integrating a Non-dominated Sorting Genetic Algorithm II (NSGA-II) with a detailed hydrodynamic model. The proposed Cost OptimisatioN Framework for Implementing blue-Green infrastructURE (CONFIGURE), with a simplified problem-framing process and efficient genetic operations, can be connected to any flood simulation model. In this study, CONFIGURE is integrated with the CityCAT hydrodynamic model to optimise the locations and combinations of permeable surfaces. Permeable zones with four different levels of spatial discretisation are designed to evaluate their efficiency for 100-year and 30-year return period rainstorms. Overall, the framework performs effectively for the given scenarios. The application of the detailed hydrodynamic model explicitly captures the functioning of permeable features to provide the optimal locations for their deployment. Moreover, the size and the location of the permeable surfaces and the intensity of the rainstorm events are the critical performance parameters for economical BGI deployment.Comment: Paper submitted for publication in Environmental Modelling and Software. 26 pages, 11 figure

Exploring new technologies for simulation and analysis of urban flooding

Eng.D ThesisRegulatory drivers, climate change and urbanisation put pressure on urban water managers to find sustainable solutions protecting people and properties from floods now and in the future. For this purpose flood model simulations and analysis are conducted to assess impacts of change on existing systems and to test options for adaptation. Recent developments in hydrodynamic models like CityCAT offer innovative concepts for effective and efficient integrated urban flood modelling. The application of new developments however is met by constraints related to the legacy of established modelling strategies, the modelling tools applied, data availability and the specific duties and responsibilities of stakeholders. The aim of this thesis is to explore new technologies for the simulation and analysis of urban flooding and outline a programme for delivering practical solutions for end-users which addresses these constraints. To address the important practical challenge of missing and inadequate data, a method for generating synthetic networks of storm drain inlets was developed and demonstrated. Tested in fully coupled CityCAT models to link the surface and sub-surface drainage domain, results have shown that synthetic networks of storm drain inlets provide satisfactory results compared with surveyed inlet networks. The results also highlight the sensitivity of the inlet drainage performance related to their location and elevation. Additionally, a generic, open-source flood exposure analysis tool was developed. Detailed hydrodynamic model results and exact building geometries are used to assess the potential internal flooding of buildings for entire cities. Newly developed mapping scripts combine exposure results with hydrodynamic model results to assess cause and consequence of floods. The third part of the thesis presents a strategic-level options appraisal highlighting the practical and financial benefits in relation to a potential industrial application of the new developments. With the availability of open architecture modelling software, this section demonstrates that the model building, simulation and analysis process can be optimised through the application of automated, generic algorithms and cloud computingScottish Water and EPSRC for co-funding

Reliable and Resilient Surface Water Management through Rapid Scenario Screening

Surface water flooding causes significant damage, disruption and loss of life in cities, both in the UK and globally. These impacts have historically been managed through application of conventional urban drainage systems designed to meet specified design standards. Conventional strategies have performed well in the past, but are becoming increasingly unfit for purpose due to intensifying hazards caused by several emerging challenges, including climate change, urban growth and aging drainage infrastructure. In response, an extensive range of alternative novel interventions has been developed. These have been successfully applied across many case studies and their performance to meet design standards on specific sites is now well understood. However, application is still limited and challenges exist regarding how to maximise performance at the urban catchment scale and incorporate resilience to extreme rainfall events within design. This thesis addresses these challenges through evaluating intervention performance using a rapid scenario screening framework. This framework delivers insight into the complex permutations of intervention strategies at a catchment scale through evaluating alternatives, scales, spatial interactions and responses to a range of rainfall events. The study achieves novelty through developing a new modelling methodology which applies cell parameterisation to represent urban drainage systems and interventions using an existing cellular automata model. The framework is applied at a high level to screen intervention performance using easily accessible data and simplified intervention strategies, it is envisaged that this style of analysis is appropriate for initial catchment assessment to evidence and direct future flood management actions. The research finds intervention scale, distribution and placement to be important factors in determining performance within the context of initial catchment screening using theoretical modelling parameters. Although localised interventions provide benefit at a smaller scale, catchment based strategies are required to substantially reduce estimated annual damage costs across urban areas. The most effective intervention was consistently found to be extensive application of decentralised rainfall capture, which reduced expected annual damage in a UK case study by up to 76%. Intervention distribution and placement are also demonstrated to significantly influence cost effectiveness of strategies, with a wide range of ratios predicted, ranging from £0.10 to £26.0 saved per £1 spent. The most cost effective interventions across the case studies investigated were found to be high volume local drainage interventions targeted in areas of intense flooding. Results demonstrate significant variation in strategy performance depending on rainfall intensity and duration. Analysis across events ranging from 2 to 1000 year return periods found many interventions which performed well during design standard events demonstrate substantial decreases in effectiveness during higher magnitude rainfall. Of particular note are interventions with finite storage capacities, which exhibit considerable decreases in performance at certain threshold levels. The implications of this finding are that designing interventions with resilient performance requires simulation of many rainfall scenarios, and that interventions with resilient properties, such as green infrastructure, do not necessarily achieve resilient performance. The research also identifies that rapid screening frameworks contribute an adaptable and useful tool for stakeholder engagement, intervention design and scenario exploration. Case study application of the framework alongside catchment stakeholders in Melbourne, Australia, facilitated an efficient and collaborative design screening process which benefitted from enhanced communication across a wide range of expertise. The simplified development of intervention strategies provided a clear communication tool which supported the multi-disciplinary investigations required for urban planning in a complex environment. Analysis of many strategy permutations highlighted the advantage of multiple smaller intervention strategies accumulating towards catchment scale benefits, a possibility which is advantaged through stakeholder communication tools, such as this framework. Overall, this thesis demonstrates that reliable and resilient surface water management can be achieved through decentralised catchment scale implementation of interventions, complemented by targeted and cost effective high volume measures. Complexity and variation of outcomes across a range of scenarios indicates the importance of encapsulating the complex permutations of options when evaluating interventions and provides justification for future application of rapid scenario screening frameworks.Engineering and Physical Sciences Research Council (EPSRC

Advancing the Unit Flood Response Approach for Urban Flood Management

Flooding is the most frequent natural disaster that causes significant, societal, economic, and environmental damage. The processes involved in flooding are shaped by spatial and temporal factors including weather patterns, topography and geomorphology. In urban setting, where landscapers are dynamic, land cover, green spaces, and drainage play a crucial role. Recognising flood source areas (FSAs) is pivotal for strategic flood risk management (FRM). Although FSA identification is not novel concept, recent advancements in flood modelling research, driven by technology and methodology improvements have extended beyond traditional methods. Emerging modelling approaches in FRM propose innovative methodologies for flood risk mitigation focusing on understanding and addressing flooding at its source. This thesis offers a review of current modelling approaches used to identify FSAs, specifically the Unit Flood Response (UFR) approach. The approach is a spatial prioritisation method for flood defences and mitigation. Traditionally, reliant on hydrological modelling and streamflow routing, this these instead uses rain-on-grid models (TUFLOW and HEC-RAS 2D) to assess the importance of model choice for the UFR approach for a catchment in the UK. The thesis further developed the UFR methodology by using a Hazard Index (HI) and Building Exposure Index (BEI) to show the significant differences between the model outputs, as well as emphasising on the computational costs associated with these methodologies. Additionally, recognising the important role of drainage systems in urban infrastructure, this thesis addresses the limited body of work available on drainage representation in flood models by introducing the Capacity Assessment Framework (CAF) to be used for drainage representation. By applying the CAF to assess and represent the drainage system in Leeds, the thesis draws a direct link between spatial prioritisation of flood defences and drainage system performance. The thesis introduces the application of the CAF outputs in flood models, demonstrating a more explicit representation of spatially varied drinage capacity. By comparing the national average removal rate (NARR) of 12 mm/hr with CAFderived rates, the significant of realistic drainage representation in flood models is highlighted. Lastly, the UFR approach coupled with 2D rain-on-grid modelling is used to investigate the impact of climate change and drainage representation in the Lin Dyke catchment. This approach considers three scenarios (Baseline, Baseline+Climate Change, and Baseline+Climate Change+Drainage) to establish hazard and building exposure indices. Results highlight the importance of incorporating climate change projections and drainage representation in the UFR methodology for a thorough urban flood risk assessment. In synthesis, this thesis investigates the multiple factors of flood risk management, offering insights and innovations across various dimensions. The Unit Flood Response (UFR) emerges as promising tools for identifying flood source areas (FSAs), emphasising the need for adaptive decision-making in flood risk management (FRM). Our investigation extends beyond affected areas, focusing on understanding, and addressing flooding at its source. Moreover, the introduction of the Capacity Assessment Framework (CAF) provides a novel methodology for representing drainage systems in flood models based on their realistic performance in urban environments. By incorporating realistic representations of spatially varied drainage capacities in flood models, this thesis highlightsthe importance of considering multiple factors in the assessment for effective urban flood risk management. As climate change and urban development exert increasing pressures, the findings in this thesis underscore the importance of integrating these factors into flood risk models to ensure resilience and relevance in the face of evolving challenge

Nature-based solutions efficiency evaluation against natural hazards: modelling methods, advantages and limitations

Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS

Nature-based solutions efficiency evaluation against natural hazards: Modelling methods, advantages and limitations

Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS

The blue-green path to urban flood resilience

Abstract Achieving urban flood resilience at local, regional and national levels requires a transformative change in planning, design and implementation of urban water systems. Flood risk, wastewater and stormwater management should be re-envisaged and transformed to: ensure satisfactory service delivery under flood, normal and drought conditions, and enhance and extend the useful lives of ageing grey assets by supplementing them with multi-functional Blue-Green infrastructure. The aim of the multidisciplinary Urban Flood Resilience (UFR) research project, which launched in 2016 and comprises academics from nine UK institutions, is to investigate how transformative change may be possible through a whole systems approach. UFR research outputs to date are summarised under three themes. Theme 1 investigates how Blue-Green and Grey (BG + G) systems can be co-optimised to offer maximum flood risk reduction, continuous service delivery and multiple co-benefits. Theme 2 investigates the resource capacity of urban stormwater and evaluates the potential for interoperability. Theme 3 focuses on the interfaces between planners, developers, engineers and beneficiary communities and investigates citizens’ interactions with BG + G infrastructure. Focussing on retrofit and new build case studies, UFR research demonstrates how urban flood resilience may be achieved through changes in planning practice and policy to enable widespread uptake of BG + G infrastructure.EPSR

Achieving urban flood resilience in an uncertain future

Preliminary results of the UK Urban Flood Resilience research consortium are presented and discussed, with the work being conducted against a background of future uncertainties with respect to changing climate and increasing urbanization. Adopting a whole systems approach, key themes include developing adaptive approaches for flexible engineering design of coupled grey and blue-green flood management assets; exploiting the resource potential of urban stormwater through rainwater harvesting, urban metabolism modelling and interoperability; and investigating the interactions between planners, developers, engineers and communities at multiple scales in managing flood risk. The work is producing new modelling tools and an extensive evidence base to support the case for multifunctional infrastructure that delivers multiple, environmental, societal and economic benefits, while enhancing urban flood resilience by bringing stormwater management and green infrastructure together.</jats:p

Spatial and Temporal Risk Assessment for Water Resources Decision Making

Water resources systems are vulnerable to natural disasters such as floods, wind storms, earthquakes, and various meteorological events. Flooding is the most frequent natural hazard that can cause damage to human life and property. A new methodology presented in this thesis is capable of flood risk management by: (a) addressing various uncertainties caused by variability and ambiguity; (b) integrating objective and subjective flood risk; and (c) assisting the flood risk management based on better understanding of spatial and temporal variability of risk. The new methodology is based on the use of fuzzy reliability theory. A new definition of risk is used and described using three performance indices (i) a combined fuzzy reliability-vulnerability, (ii) fuzzy robustness and (iii) fuzzy resiliency. The traditional flood risk management relies on either temporal or spatial variability, but not both. However, there is a need to understand the dynamic characteristics of flood risk and its spatial variability. The two-dimensional (2-D) fuzzy set that relates the universe of discourse and its membership degree, is not sufficient to address both, spatial and temporal, variations of flood risk. The theoretical contribution of this study is based on the development of a three dimensional (3-D) fuzzy set. The spatial and temporal variability of fuzzy performance indices – (i) combined reliability-vulnerability, (ii) robustness, and (iii) resiliency – have been implemented to (i) river flood risk analysis and (ii) urban flood risk analysis. The river flood risk analysis is illustrated using the Red River flood of 1997 (Manitoba, Canada) as a case study. The urban flood risk analysis is illustrated using the residential community of Cedar Hollow (London, Ontario, Canada) as a case study. The final results of the fuzzy flood reliability analysis are presented using maps that show the spatial and temporal variation of reliability-vulnerability, robustness and resiliency indices. Maps of fuzzy reliability indices provide additional decision support for (a) land use planning, (b) selection of appropriate flood mitigation strategies, (c) planning emergency management measures, (d) selecting an appropriate construction technology for flood prone areas, and (e) flood insurance