The Use of Probabilistic Climate Scenarios in Decision Making for Adaptation of Building and Property Drainage

Climate change predictions from UKCIP02/08 clearly indicate an increase in short duration high-intensity rainfall events. Such events are already causing incapacity problems for those who design, maintain and manage local drainage systems. The purpose of this research is to realise the potential benefits to building and small-scale drainage design and adaptation facilitated by the availability of the probabilistic-based data to be generated by UKCIP08. By using probability density functions (PDFs) to determine anticipated changes in precipitation, the loading imposed upon these drainage systems can be more accurately defined. Coupled with the ability to assess the flow interactivity of component networks, this means that exceedance threshold levels that can result in flooding can be determined. The ability to identify failure locations and the extent of any flooding will then allow the development of a decision-making tool to facilitate cost-effective design and adaptation of building and property drainage systems in response to predicted changes in climate.The tool will contain the following components:1. As input, UKCIP08 probabilistic precipitation and wind data, with appropriate temporal disaggregation of rainfall figures to facilitate flow modelling 2. a simulation interface to allow the input of PDF-derived rainfall data 3. the alignment of a suite of existing flow simulation models, to holistically evaluate the performance of building and property drainage systems 4. numerical model output 'flags' that will identify coincidental flows and surcharge events at critical conveyance nodes where flooding may be induced 5. building and/or drainage system strategic adaptation proposals, prioritised in terms of flood risk reduction and costThe proposed decision-making tool will be made available via an online portal and will also yield outputs that will be directly disseminated across a broad spectrum of beneficiaries. Two types of application of project outputs are envisaged. Firstly, the performance of existing systems subject to PDF-derived UKCIP08 precipitation figures can be assessed. If under-capacity is identified, then information on potential adaptation strategies and their effectiveness will be provided. Secondly, information can be used at the design stage, where matrices in the form of 'look-up' tables will be established from an extensive series of simulations undertaken as part of the proposed project. These will provide performance indicators categorised by building typology, curtilage dimensions and PDF-based climate change scenarios, and will similarly propose adaptation strategies. This form of output will be made available both electronically and as a hardcopy. Project deliverables will hence benefit designers, consultants and contactors operating across the spectrum of built environment activities, from pipework sizing and installation to planning and land management. Support for the project is extensive, and a number of partners have committed to the provision of access for system monitoring and case study investigations. Other project partners will assist with dissemination. Novelty is introduced on three fronts. Firstly, through the use of UKCIP08 climate change data as a basis for performance assessment, thereby allowing a comparison with current practice. Secondly, through the presentation of rainfall information in probabilistic terms, thereby facilitating realistic predictions and avoiding over design to accommodate climate change. Thirdly, through the ability to holistically simulate the time-dependent interactivity of the various drainage components that, when subject to high intensity rainfall, present a significant risk of flooding. The development of the proposed decision-making tool thus facilitates an exciting opportunity to implement practical, efficacious and cost-effective adaptation strategies for flood mitigation.