Broads flooding study says dredging won't help stop problem

The Environment Agency (EA) and Broads Authority (BA) have published the findings of a probe which used modelling technology to determine if removing silt from the lower River Bure, near Great Yarmouth - known as the Bure Hump - would alleviate problems.

It found while there may be small reductions in river levels for certain areas around the northern rivers, it would not be worthwhile due to the high costs and the risk it would make flooding worse downstream.

The findings come after farmers were left swamped, homes backed up with sewage and boat firms struggled due to persistent high water levels that lasted for several months last winter.

However, critics remain sceptical, believing the study relies on inaccurate data of the river depths.

Broads Authority dredging the River Bure in 2015 (Image: Broads Authority)

BURE HUMP

The study was triggered following speculation that the Bure Hump - a 1.5 mile stretch of the river just before it reaches Yarmouth, where it flows into the Yare - had become silted up, restricting the flow of water out into the sea. 

It has become a growing focal point in recent years as flooding has got worse on the waterways.

Many people on the Broads have suspected that a build-up of silt means the rivers upstream cannot 'empty' quickly enough, leading to flooding on the northern rivers, especially at places like Potter Heigham, Hickling, Horning and Wroxham.

The section of the River Bure, part of which has become known as the Bure Hump (Image: Google)

The £13,000 investigation used hydraulic computer modelling of different possible scenarios to determine the effect of deeper dredging.

Currently, that section of the river is only dredged to depths to ensure it remains navigable by boat, rather than to prevent flooding.

The BA is responsible for maintaining navigation, whereas the Environment Agency has responsibility for dredging to prevent flooding.

READ MORE: Little-known silted-up waterway named as Broads Authority's top priority for dredging

FLOODING FINDINGS

Experts have concluded that deeper dredging of the lower Bure where the supposed 'hump' is found - a section also known as the Bure Loop - would not reduce the risk of flooding upstream.

Instead, it may increase the risk of tidal flooding at the lower end of the river.

However, the report does find that areas in the upper Thurne would see a small benefit.

Flooding at the marshes around Hickling and Martham (Image: Mike Page)

Jacobs, the engineering firm that conducted the study, said: "Dredging will increase the volume of water that can transfer in and out of the Broads river system, but for upstream locations such as Potter Heigham peak water levels during fluvial and tidal event are largely unchanged in both scenarios."

The EA determined that the lack of significant benefits would not make it cost-effective - estimates for the additional work range from £2.7m to £4.6m.

This means it would be unlikely that extra government funding would be approved.

In addition, dredging could also harm the environment, due to greater volumes of saltwater flowing in with the tide, which is harmful to freshwater fish and other wildlife in the Broads.

A boat travelling on the River Bure at Stokesby (Image: Newsquest)

Graham Verrier, the East Anglia area director for the Environment Agency, said: "If dredging isn’t the right solution, or costs more than the flood risk benefit it provides to properties, we will help communities and partners to look at other options to manage the risk of flooding.”

The EA says funding would be better targeted at other flood risk interventions, such as maintaining the crest height of raised embankments.

SCEPTICISM REMAINS

The Broads Reform Action Group - campaigners calling for changes in the governance of the Broads Authority - has previously raised concerns about the need for dredging of the Bure Hump to alleviate flooding.

It believes navigation charts and measurements of the depths of the river, which were used to inform the study, are incorrect.

To support their claims, members point to the high number of boats running aground on this stretch of river in recent years - which they say shows it is shallower than the officials believe.

READ MORE: Broads Authority hit back at critics over lower Bure dredging row

Sheep on the riverbank along the River Bure (Image: Denise Bradley)

Colin Chettleburgh, chairman of the group, said: "We have significant concerns about the report's content.

"It contains omissions and inconsistencies and relies on data we believe to be inaccurate.

"We do not accept its conclusions and will continue to advocate for those affected by last winter’s prolonged flooding. The report raises more questions than it answers, and we will address these after a comprehensive review."

The BA has refuted claims its navigation charts are inaccurate and that they are based on regular hydrological surveys by independent contractors.

Senior members have previously called the claims "embarrassing."