2019-08-07 

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Local Knowledge Crucial to Minimising Future Flood Risk

Devastating flood damage caused by sudden bank breaches can be minimised by tapping into local knowledge and resources, while also helping to manage water levels and create availability during times of drought, says a major risk management authority.

“Climate change is a reality, and we have to accept that with more extreme weather conditions, there will be increased frequencies of river bank overtopping,” explains Innes Thomson, chief executive of ADA (Association of Drainage Authorities), the organisation representing drainage, water level and flood risk management authorities in the UK.

The discharge of water from the Steeping River into the Bellwater Drain which is within W4DIDB’s system and managed and maintained by them. The water is being pumped using one of the EA’s high-volume pumps mounted on the road bridge over the Steeping River at Thorpe Culvert.

The discharge of water from the Steeping River into the Bellwater Drain which is within W4DIDB’s system and managed and maintained by them. The water is being pumped using one of the EA’s high-volume pumps mounted on the road bridge over the Steeping River at Thorpe Culvert.

“It is all about resilience, and we must ensure embankments can withstand overtopping without failing,” adds Mr Thomson. “The local knowledge of public bodies such as Internal Drainage Boards (IDBs), alongside others including the local Environment Agency offices, Local Authorities, Parish Councils, is key to providing a local service in managing water where it really matters, to the people and the environment,” Mr Thomson adds.

Citing the example of the sudden bank failure on the Steeping River in June, causing flooding devastation to the Lincolnshire village and community of Wainfleet, ADA warns that it is essential that when water does breach embankments, the infrastructure is in place to get rid of that water.

“The first priority is to ensure embankments are resilient to avoid dangerous breaches, and local IDBs are best placed to identify any concerns within their own drainage district, due to local knowledge and surveying of risk areas,” continues Mr Thomson.

“When water does overtop embankments, it is essential to have the infrastructure in place, with well-managed and maintained sluices and pumping stations to divert water and relieve pressure.”

Mr Thomson flagged up the recent £1.8 million sea defence project at Wrangle Banks, on the Lincolnshire coast north of Boston, funded by Defra, with European Regional Development Fund (ERDF) support via Lincolnshire County Council. Here sea defences were raised and re-profiled to increase their resilience in an area of the Wash shoreline previously viewed as potentially catastrophic.

Headed up by Witham Fourth District IDB (W4IDB) as the lead risk management authority, this partnership project protects 3,400 hectares of prime grade one farmland and 460 domestic and industrial properties.

The project involved re-profiling the sea banks and raising them to over 7 metres high, with a slope leading to a soke dyke to cope with future over-topping. The project created a maintenance strip behind the bank and larger soke dykes. During high tides, these accommodate the water that permeates up through the ground and during heavy rainfall, they enable surplus water to flow to the W4IDB managed pumping stations.

This is a prime example of a co-ordinated effort, and highlights the importance of landowners and communities working together with local risk management authorities.

One example where working together brings obvious benefits, is in balancing environmental and habitat demands with the need to manage water level and flood risk requirements. Burrowing animals, for example, can have a significant impact on the resilience of a flood embankment, and this needs to be carefully managed. It is essential, therefore, that IDBs and other risk management authorities work closely with the Environment Agency and Natural England to address problems with the right balance.

While the lasting memories for many of the viewing public, watching coverage of the devastating Wainfleet flooding, may well be the two RAF Chinooks and a Puma helicopter dropping 342 one tonne bags of aggregate to plug the breach, what was going on behind the scenes was more engaging for the local communities.

Recognising the incredible response from all the emergency services and authorities involved, Lindsey Marsh Drainage Board were at the heart of the operation, the IDB’s Thorpe Culvert pumping station moving 430,000m3 per day out of the flood cell and back into Steeping River. When water levels threatened breaching the sub-station, the IDB team were joined by members of the local community, the emergency services, the Environment Agency and others, battling to keep flood water out of the station’s structure by building temporary defences, using over a thousand sandbags. 

Witham Fourth District IDB also played a decisive role by taking water into their neighbouring system, from the Steeping River. They diverted water 17 miles through a well maintained drainage network and two pumping stations to get to the Wash, helping to relieve pressure on the Steeping River system.

The heroic urgent intervention of all those teams working together remarkably kept the station operational throughout. Its loss would have resulted in a larger number of homes being affected in and around Wainfleet. In total, the station shifted in excess of five million cubic metres of water from the flooded area over 11 days.

Both these examples, very much replicated in lowland areas at risk across the country from the Fens to the Somerset levels, demonstrate the positive and proactive role of IDBs. Often however, there appears to be some disconnect between what happens on the ground, and the public perception.

Ultimately, IDBs are often best placed due to their connection to the local community. Public consultations help raise awareness, avert or reassure concerns but also justify expenditure and levy payments in internal drainage districts.

Mr Thomson concludes,
“Working in close collaboration with the Environment Agency and other authorities and voluntary groups, IDBs provide a cost-effective, efficient, local service in managing water where it really matters to people and the environment. The Wainfleet event demonstrated how professionals can come together in a very effective way behind the scenes. It is increasingly important, however, to publicise that joint service provision more and allow people to understand and support the work being done to reduce the risks of their lives being affected by flooding and drought.”

ADA

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