The role of model complexity in assessing water supply system resilience

Assessing water supply system resilience is becoming increasingly important as system pressures, including climate change and population, increase. The resilience of water supply systems in the UK to droughts of differing intensity and duration is now assessed through the simulation of a range of extreme droughts using water resource models. This process can be time consuming, data intensive and in some cases, may not be proportionate to the system response. The drought response surface has become a useful tool in UK water resources planning to quickly visualise modelled outputs, and therefore resilience, to droughts of differing intensity and duration. Work undertaken as part of the NERC Historic Droughts project has sought to compare results within the drought response surface framework to different levels of modelling complexity. Models of increasing complexity were developed that are rapid, accommodate varying data quality and provenance, and can be applied worldwide. Droughts were characterised for a range of reservoir systems based on duration and system response in the historic record. Flexible linear and polynomial regression models were trained on historic storage data and increasingly complex inputs – firstly rainfall, then site-translated historic reconstructed streamflow, and finally site-specific historic reconstructed streamflow – to hindcast reservoir storage to 1891. System understanding was important in drought duration selection, which was dependent on the length and distribution of reservoir storage in the observed record. The models permit the input of fuzzy data points, accommodating anecdotal evidence related to drought intensity and duration. Extreme value analysis of storage allowed for water company levels of service to be considered, therefore providing a description of the system response of an event in terms of the customer experience. Drought response surfaces produced under increasingly complex inputs were compared with those produced through water resource modelling to demonstrate the implications of different levels of modelling complexity. While simple, statistical modelling approaches that do not incorporate physical parameters should not replace deterministic system modelling, they allow for identification of periods and systems of interest that can focus further, more detailed analysis using more complex models and may have particular applications in data and model poor regions

Application of machine learning techniques to support decision making under uncertainty in water resource management

Water companies in the UK are required to produce long-term plans of water resources for their supply area every five years, detailing how they will maintain secure, sustainable supplies , taking account of social and environmental impacts as well as economic costs. Extensive ensemble modelling of water resource systems underpins the production of these reports and the resulting investments chosen to maintain supplies into the future. Adoption of new guidance on the use of advanced Decision Making Methods (DMMs) and Risk Based Planning has demanded a more comprehensive modelling approach. Modelling and analytical efficiencies are increasingly required for their use and to realise their full benefits. Existing water resources, hydrological, groundwater, and demand models traditionally used by water companies are often not ideally suited for use in these DMMs. Consequently a toolset of approaches is evolving to enable UK water companies to undertake this more complex decision making. Key elements of this toolset include emulation modelling to complement computationally more expensive process models, machine learning techniques for groundwater assessment and to optimise reservoir control curves considering multiple objectives, and agent based models to explore the spatial and temporal pattern of demand over ensembles of plausible futures. These methods support the rapid simulation times required for applying the DMMs to provide a holistic view of system behaviour under large supply-side, demand-side and policy uncertainties. User-friendly tools and dashboards are being used to explore and communicate the outputs and facilitate effective decision-making, involving all stakeholders. This toolset of approaches is being increasingly adopted in the UK, demonstrating the potential for innovative methods to interpret and present complex modelling results. Due to the flexible structure of the tools, and the generic approaches used, these techniques can readily be applied to a wide range of settings. However, the absence of physical process representation in some of these methods, and associated implications, must be considered in their application and by planners when interpreting results. Methods in themselves are not a replacement for diligent water planning, but a tool to support it

Use of agent-based modelling to validate hurricane evacuation planning

Justification for evacuation and evacuation planning is sometimes questioned and there is a need develop approaches which justify the planning and associated expenditure. To this end, it was decided to carry out a pilot evaluation of the impact of a Hurricane Storm surge flooding on Brunswick, GA using a dynamic Agent Based Model that represents people's interaction with a flood and provides estimates of the number of people that are likely to be killed as a result of a flood event, as well as the time that is required for them to evacuate the area at risk. Climate change increase of 3ft in mean sea level would increase the population at risk in Brunswick by 20% for a category 4 hurricane. The modelling shows that for a category 4 hurricane managed evacuation can significantly reduce the number of fatalities

FRMRC presentations to practitioners workshop

Practitioners workshop introduction - Infrastructure management Channels and their management Estimating blockage potential at culvert trash screens Fragility curves Predicting breach Simplified tools for risk assessment 2nd generation asset inspection techniques Use of non-invasive measuring techniques in asset inspection Asset deterioration - Assessment and measurement Attributing risk to assets - Examples from pilot projects Practitioner workshop on asset managment Multi-objective optimisation of flood risk mitigation measures, including real options Next steps to implementation and future research need

Coastal defences: social utility, imagination and justice

New methods are being developed for the assessment of the condition of Flood and Coastal Erosion Risk Management (FCERM) defence systems in relation to their likely engineering performance and consequent fragility. However, it is being increasingly acknowledged that, in addition to their FCERM engineering utility, coastal defence systems can offer significant amenity and aesthetic value and contribute to wider ‘quality of life’ objectives. However, this can pose a challenge when seeking to deliver solutions which meet the requirements for flood and coastal defence but are also socially just. This paper sets out a theoretical framework within which these issues can be understood, drawing on literature and on interviews conducted by the author both with coastal engineering practitioners and with community members and activists. The framework – a trinitarian blend of Order, Imagination and Justice (Gorringe, 2002) – reflects both Vitruvius’ architectural principles (strength, utility and beauty) and insights drawn from key thinkers in sociology, psychology (Maslow) and philosophy. The paper sets out some initial thinking on how this framework might be applied in practice by engineers and what kinds of features might be important to include in designs. At the previous ICE breakwaters conference, Cruickshank et al (2005) presented a paper on their experiences with the design of a housing development on the south coast of England. In this, they reflected on the challenges of trying to integrate engineering and architectural thinking in the design of coastal defences. The present paper seeks to build on these earlier reflections. As well as examining various theories that might be used as the basis for inclusion of social dimensions in our engineering design, it draws on research data gathered in semi-structured interviews with both coastal residents and engineering practitioners

Direct action self-help (DASH) groups in UK flood risk management

This paper presents an analysis of the nature and effectiveness of community direct action self-help (DASH) groups and includes a case study analysis of a river conveyance management group and a sea wall management group. DASH groups are found to be motivated by the need to deal with increasing flood risk in the face of reduced public funding, alongside sense of stewardship and community solidarity. Channel maintenance work by a DASH group can be effective and efficient at reducing some aspects of local fluvial flood risk for lower order flood events. Maintenance of existing sea walls by a DASH group may be less efficient because of the need for significant expenditure on materials and only efficacious if the engineering is quality-controlled; its longer term effectiveness is also limited by sea level rise. DASH groups require nurture to be sustainable but can deliver community benefits. Professional FCRM coordination and support of DASH activity was examined using a case study of an Environment Agency (EA) area coordinator and comparisons with alternative approaches. Support of DASH groups by FCRM professionals was found to be essential to avoid unwise activities and involves not only controlling consents, but also providing advice on the nature and extent to which DASH activity might be appropriate and arranging practical support and seed-corn funding. The most effective form of DASH facilitation requires a quality and quantity of involvement that cannot readily be supplied by dispersed arrangements from a number of individuals