Decision support framework to incorporate river bank stability in pipeline crossing risk assessment

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Scottish Water has identified the need to develop their approach to dealing with uncertainty when assessing the risk of river erosion at pipeline crossings. In particular, there is a need to develop and pilot methods that can use data from initial asset inspections to quantify risks and uncertainties in making decisions on where to invest additional resources in more detailed inspections, for assets deemed to be at greater risk from river bank erosion or scour around bridge abutments. This challenge arises from the reality that, over the past 10-15 years, pipeline crossing inspections have been undertaken in an ad-hoc manner. The aim of this proposal is, therefore, to develop a decision support framework to incorporate river bank stability in pipeline crossing risk assessment. This will be used immediately during 2016 in Scottish Water's first, national-scale pipeline bridge asset inspection programme. The specific objectives are to: (i) evaluate uncertainty in the existing low-cost app-based inspection database that is used to screening risk; (ii) assess the uncertainty that arises from the initial desk-based phase of river bank stability assessment; (iii) develop a pipeline crossing scour assessment framework for analysing river bank stability at the screening phase and determining appropriate analysis for the initial assessment phase; and (iv) recursively test the risk assessment framework. To address these objectives there will be three methodological phases, results from which will be progressively reported. First, a sample of the pipeline crossings will be re-surveyed using a replicate inspection app. Results will enable evaluation of uncertainties in data capture and their consequences for river stability decision making at the screening stage of risk management. Second, uncertainty in assessing bank erosion will be assessed considering data from the asset inspection app, Google Earth imagery, high-resolution aerial images commissioned by Scottish Water, and legacy LiDAR acquired by the Scottish Government. Evidence of river instability will be mapped from imagery. Change will be quantified using appropriate techniques to represent errors in digitising and topographic change analysis. Finally, results will be used to produce a framework to: (i) characterise risk during screening; and (ii) determine the most appropriate forms of desk based analysis for initial risk assessment. The framework will include a multi-criteria process for calculating risk after the initial assessment phase to determine whether a more detailed assessment phase is necessary and, if so, necessary actions. This framework will be tested at a further set of 20 sites. Project outputs will be operationalised and used to improve decision making. App-based data capture will be improved with enhanced data fields and training material for asset inspectors. Results from evaluating uncertainty in data and analysis will be input to a multi-criteria scoring framework that will improve decision making at the screening and initial assessment stages and will thus enable scarce resources to be prioritised for desk-based river bank stability analyses. The framework will be used in the current drinking water pipeline crossing inspection programme and will also be of value for a future waste water pipeline crossing inspection programme. The project will last 12 months which will enable evaluation of uncertainty in a sufficiently large sample of data, analysis approaches and sites. The total cost (80% FEC) of the project is £89,707. This includes staff costs for Williams and Hoey, 9 months research assistant time, computer hardware, and travel.