Dredging doesn’t work says Pow
It is barely 6 years since the waters subsided from the Levels after the devastating floods of 2012-2014. Yet politicians do not, it seems have very long memories. Taunton MP, Rebecca Pow whose constituency includes many of the areas worst hit by the floods is no exception.
During the floods residents of the Levels called out for dredging to be carried out after the Environment Agency had given up on it. In a Leveller exclusive in 2014, we revealed that not only did the EA have no intention of dredging, but they had sold all their dredging equipment off.
That was then.
Since 2014 the EA working with the newly formed Somerset Rivers Authority has dredged the River Parrett system regularly and carried out major improvements to the capacity of the River Sowy too. As a result, the floods that have happened since have been carefully managed and done little damage.
Now Rebecca Pow is saying dredging is simply not economically viable. And what she thinks today really matters as she is the Minister responsible. Whilst she acknowledges the progress made in the River Parrett basin, residents of the Levels have seen this all before.
The last paragraph of her statement sounds encouraging. At least new ideas are being trialled in Somerset. But if the Minister considers dredging is not economically viable, weare heading right back to the same place we were in 2012. The Leveller® simply asks whether lives have to be lost before this Conservative government will take flooding seriously?
In a written statement in reply to the MP for Tewkesbury this is what the Taunton MP had to say…
The Environment Agency (EA) refers to dredging as the removal of accumulated material in a river. It is often done to maintain channel conveyance and ensure water can flow freely. Dredging also includes ‘de-silting’ which removes material like gravel or soil washed into rivers, as well as rocks and plant life.
To protect people and properties from flooding the EA prioritises activities that achieve the greatest benefit. Dredging and clearing channels are important parts of the EA’s maintenance regime when they improve the channel’s ability to carry increased river flows and manage flood risk. Over each of the past three years the EA has spent between £45 million and £55 million per year on channel maintenance, and between £5 million and £11 million of that is spent on dredging.
In 2010, the EA carried out a comprehensive series of trials to review and update the understanding of the benefits and effectiveness of dredging. It showed dredging can reduce flood risk, but its effectiveness and value-for-money varies significantly depending on location. Historic records and modelling also show that dredging in some locations can increase erosion and flood risk for communities downstream.
Since then, further studies such as the Thames bathymetry review have validated the results of the 2010 trials. In many cases, rivers naturally and quickly return to their pre-dredged state. Therefore any flood risk benefits are so short lived that the work cannot be economically justified.
The Somerset Rivers Authority and internal drainage boards (IDBs) have trialled alternative methods for dredging. These included both cutter suction and water injection dredging, and a full-scale 5 km trial using water injection dredging on the River Parrett. The trials demonstrated some potential to reduce costs of dredging in tidal rivers. The Environment Agency uses the results of such trials and studies to decide where and how dredging will be effective, on a case-by-case basis.