Flood defences 'coped well'

STEPHEN PULLINGER Flooding which hit a large swathe of Norfolk and Suffolk last November resulted from the third highest tidal surge since the great flood of 1953. But new defences throughout the Broads coped well and prevented any major flood bank breaches, according to a new Environment Agency report.

STEPHEN PULLINGER

Flooding which hit a large swathe of Norfolk and Suffolk last November resulted from the third highest tidal surge since the great flood of 1953.

But new defences throughout the Broads coped well and prevented any major flood bank breaches, according to a new Environment Agency report.

It refutes claims that the Agency's multi-million-pound Broadland flood alleviation scheme may actually have increased the risk to some villages such as Brundall by stopping overtopping and channelling water upstream, stating that the flooding pattern correlated well with the hydraulic model used by project engineers Broadland Environmental Services Ltd (Besl).

The report, being presented to the Broads Authority's navigation committee next Thursday, said the working of the flood defences had successfully met the project aim of “not increasing water levels through maintaining the same frequency and pattern of overtopping in the system, while minimising the risk of a breach”.

It states: “Confidence in the hydraulic modelling has been further confirmed by comparing modelled results with actual levels observed during the event.

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“This comparison shows good correlation, and Besl is currently working with the Environment Agency to use this tool to advance flood forecasting within Broadland.”

Report author Adrian Clark notes that the surge which caused the flooding resulted from a depression that developed north-west of Scotland on Monday, October 30. This depression deepened and joined a second depression heading south from Scandinavia the following day.

As the surge travelled into the shallower southern North Sea early on November 1, water levels rose with maximum surge levels recorded at Yarmouth of 1.75m above the predicted tide.

Fortunately, a significant band of high pressure then quickly pushed the offending weather system into the continent bringing water level quickly back to normal.

The report notes that the surge produced the third highest water level at Yarmouth since 1953 - when a 2m surge was recorded - and that peak water levels through the Broads system were also comparable with the other major events in January 1976, February 1983 and January 1993.

The only areas where there were significant breaches of floodbanks were on the River Waveney, near the A143 road bridge on Haddiscoe Cut and on Suffolk Wildlife Trust's Carlton Marshes nature reserve - both these areas had yet to receive flood defence improvements through Besl's project.

The Environment Agency undertook extensive monitoring of rising salinity levels throughout the flood, which will help to inform management of future incursions.

Field observations suggest that several thousand fish perished during the event in the lower Thurne, Ant, Yare and Bure but no long-term effects are anticipated given the size of the fish stocks.