Water & Wastewater Treatment

TECHNICALLY SPEAKING Flood management: making more of less As the cuts to flood management budgets bite, David Keiller, technical director, Black & Veatch Europe, Middle East, India & Africa, says public engagement and focussing spend on highest value assets are two ways to stretch funds I n an age of austerity, when public funding for flood defences is being stretched as far as possible, are there ways of cutting expenditure and providing a more sustainable future? The answer is - yes, in the right circumstances. Flood defences need regular maintenance and occasional major investment to ensure their effectiveness. For earth embankments, this is especially important: the grass needs to be cut to develop a good sward (upper soil layer) and control growth of shrubs and trees. Banks need to be inspected and damage by cattle trampling down the crest or animals burrowing into the bank needs to be repaired. Erosion protection needs to be checked and kept in good repair. Concrete and steel defences require less frequent maintenance, but repair and replacement when eventually needed is usually more expensive. Neglect When maintenance is withdrawn by a public authority all these activities stop; banks are allowed to become overgrown and when damage occurs through storm, corrosion, accident or vandalism it is not repaired. When a defence breaches it is left unrepaired. This policy allows nature to take its course, and can provide environmental benefits. Alternatively, withdrawal of public maintenance can spur on those who benefit from the defence to take responsibility for its upkeep. Withdrawal of funding from low-value defences allows the available public funds to be concentrated on maintaining and enhancing the higher value defences that better protect communities and important national assets. Withdrawing public funding from a flood defence is rarely going to be popular with those who benefit from the defences. They expect 'the government' to continue to support them in the manner they have become accustomed to. However, most people grumble about the high level of taxes they pay to support activities they consider less deserving. 28 Water & Wastewater Treatment January 2014 Case study: Isle of Axholme The 376km2 Isle of Axholme pump-drained catchment, alongside the River Trent in Nottinghamshire, offered opportunities to minimise maintenance costs by understanding how maintenance affects flood risk. The catchment has 57 pumping stations of various sizes and more than 90km of embankments, which cost more than £1M per annum to maintain. Black & Veatch identified that there was an economic case to maintain the defences that prevent the River Trent flooding the land; and also to maintain the two principal land drainage pump stations and drainage routes. Analysis found there were significant communities in the catchment that would be flooded permanently if this was not done. However, the benefits from managing the second and third tier drainage system, embankments and pump stations, were almost exclusively experienced by the local farming community, who relied on the drainage system to improve their farm incomes. In this case these beneficiaries either individually or through the local Internal Drainage Boards were best-placed to decide the correct balance between drainage efficiency and the cost of maintaining the system, following the 'beneficiary pays' principle Hydraulic and GIS analysis at Axholme helped identify communiti In the Isle of Axholme catchment, beneficiaries are being involved wwtonline.co.uk

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