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Halcrow implements flood mitigation solution

by Brian Sims

Halcrow has implemented risk analysis software from Palisade as an element in its programme to mitigate the consequences of severe flooding in the UK. The package is used to quantify the uncertainties in Halcrow’s process that determines the risk faced by critical assets such as water treatment works and pumping stations, and weighs it up against the cost of appropriate preventative measures. Halcrow identifies the likelihood that a site will be subject to fluvial flooding and quantifies the vulnerability and consequence of failure for each asset. Recommendations to improve flood resilience may include adaptive solutions, such as designing structures to reduce the consequences of flooding by facilitating recovery from it. Alternatively, resistance, which aims to prevent flooding in the first place, might be more appropriate for some sites. The @Risk solution plays a key role in quantifying the certainty with which forecasts can be made. Rectifying the consequences of a flooded water treatment plant can be very expensive. Physical damage to pumps and equipment needs to be repaired, and there are additional costs that may be incurred, such as bottled water supply while the plant is out of action, and customer compensation for lack of service. Working out the costs of these consequences helps determine the right solution for the individual site. However, it is difficult to quantify the exact costs so @Risk is used to quantify the variations in the figures. The software is also used to measure levels of uncertainty for other key aspects that have a bearing on the eventual outcome. For example, there are uncertainties around the direct damage costs and the expense of responding to customer contacts associated with the incident. At the same time it is important to understand the level of uncertainty in the costs of intervention, such as building a floodwall. Fluctuations in the cost of borrowing money must be accounted for as these may have a significant impact on the final expenses. Using @Risk, Halcrow can demonstrate how decisions on the best course of action to take for a critical water industry asset can be informed by quantifying the uncertainty. ‘Serious flooding having a major impact on water services is a very real possibility in some areas in the UK” and this has been demonstrated in recent years,’ stated Alec Yeowell, asset management engineer at Halcrow. ‘We set out to understand what it was realistic to mitigate against and achieve in terms of the costs and benefits of improving the current levels of resilience. The nature of the task means that each stage of the calculation is subject to uncertainty.’

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