Local pressure following floods sparked U-turn on dredging, study reveals

A new study has found local pressure in response to flooding in Somerset led to the Environment Agency to resurrect a policy abandoned 20 years ago – the dredging of rivers. But there remain uncertainties over its long-term viability due to funding constraints and debates over its effectiveness.

In the UK, more than five million people and two million properties are at risk from flooding. Flooding events are also expected to increase as a result of climate changes.

Historically, flood defences and other ‘hard’ engineering solutions have been widely used. Dredging – the widening or deepening of waterways to allow more water to pass through the channel – is an example of such an approach. However, dredging has fallen out of favour as a policy due to its expense, questions over its efficiency and concerns over its impact on wildlife.

More recently, flood defence has shifted towards flood management and ‘softer’ measures designed to work with nature. This change is reflected in the UK government’s most recent flood strategy, Making Space for Water. There has also been a shift towards more local decision-making, giving those affected a greater say in how flood risk is managed. This is reflected in the UK Flood and Water Management Act 2010, which gives local authorities lead responsibility for coordinating flood management.

A study by researchers from the University of Leeds and Leuphana University of Lüneburg focused on recent flooding. The winter of 2013–2014 was the wettest on record, and the Somerset Levels and Moors, an area of 650km2, was subjected to severe flooding with more than 115 km2 of land under water.

A 20-year action plan was produced in response to the flooding, which included new tidal barriers, sluice gates (sliding gates that control the flow of water) and extra pumping stations to remove water at a cost of approximately £100m.

The Environment Agency (EA) also reversed its flood policy and agreed to dredge the Rivers Parrett and Tone, and included dredging in the 20-year plan, marking a victory for local campaigners who had fought for several years for dredging to be reinstated. Prior to the flooding, dredging had not been used in the region for 20 years.

Researchers analysed national and local newspaper reports and interviewed key stakeholders to examine the policy shift. The study used a framework designed to unpick how particular policies gain prominence above others. The researchers analysed 275 newspaper articles from four national broadsheets and 12 local newspapers from 1994–2014, assessing how often media mentioned river dredging in Somerset. To supplement the newspaper review, interviews were conducted with 10 stakeholders, including local government officials, EA staff, professional engineers and residents affected by the floods.

The newspaper analysis indicated that prior to 2012 dredging was a low-key topic in the media, mentioned in fewer than 12 articles. Of these, 56% were broadly positive regarding dredging whereas 33% focused on the negative environmental impacts, such as the loss of the local mussel population. Following the 2013–2014 flooding, the number of articles grew tenfold, to 120 articles.

Reports were mostly positive in relation to dredging; for example, of the 35 local articles published from January 2014, 77% supported dredging. In the national newspapers, 67% of articles focused on the benefits of dredging during this period and only 15% flagged any concern with dredging.

Findings from press analysis and interviews were that criticism towards flooding policy over this period focused on the EA not dredging rivers, as well as on national government funding cuts. Local politicians, residents, farmers and drainage engineers all called on the government and the EA to invest in dredging. The study attributes the policy change to the work of campaigners and extensive newspaper reports highlighting the reduced channel capacity of the Rivers Parrett and Tone (which were at 65% of 1960s levels).

The other main factor was local public opinion, particularly via the creation of the local campaign group Flooding on the Levels Action Group, which pressurised the government and EA to justify its flood defence spending and the anti-dredging policy.

Despite the policy reversal in this case, the long-term viability of reinstating dredging is uncertain. Dredging is an expensive process (costing up to €23 700 per km on the Parrett River) and must be repeated every five to 10 years as riverbeds naturally accumulate silt and narrow again.

The EA’s modelling of flood risk in the area following the flooding also indicated that, while dredging would have reduced the level and duration of previous flooding in 2012, it would not have prevented it. These concerns were reflected in interviews with EA staff and flood experts.

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