The Scheme

The Problem

As a result of the naturally occurring high ground to both north and south banks, the flood plain of the River Stour narrows significantly as it passes through Blandford. When, periodically, large flows are transmitted downstream towards Blandford, those areas of Blandford Forum and Blandford St Mary which were historically developed within the flood plain have suffered severe flooding conditions.

Planning The Scheme

Planning the flood alleviation works began after the flooding of over 100 properties, some of them twice, in 1979. Around 180 properties, mainly shops and houses, were found to be potentially at risk from a major flood event which could happen at any time.

The Solution

Following the events of 1979 there were requests from many quarters to undertake major works which would protect life and property from future floods. The first stage of the work, the flood bank in Crown Meadows upstream of Blandford Bridge, was completed in 1986. Material from the former railway embankment across Langton Meadows was used to build the bank. The removal of the old embankment itself reduced flood levels. At the same time, flood defences were built south of the River Stour to reduce the flood risk at Blandford St Mary. The works between Blandford Bridge and Langton Meadows took much more planning. Not only do they have to keep out floodwater from the river, but they must deal with all the natural drainage from the town which runs towards the river. This includes the Pimperne Brook which meets the Stour at Langton Meadows. The flood wall required deep foundations to make sure that water from the river cannot leak through the ground

The Appearance

Through the town, the floodwall is built in reinforced concrete with brick facing. It crosses the Ham car park and follows a route across the lower part of a number of private gardens before emerging in the Gateway Supermarket car park. From here it takes a defined path diminishing in height until it disappears into the naturally high ground at Stour House. As the ground levels fall to the east of Stour House, the defence reappears ultimately crossing the Pimperne Brook and emerging into Langton Meadows where it connects once again into natural high ground. At its highest the wall is 2.5 metres high. The top of the wall is half a metre above the flood level reached in December 1979. Behind the flood wall a deep drain, one metre in diameter, has been installed.
High groundwater and all surface water drainage from the town flows into this drain and, under normal circumstances, discharges naturally into the River Stour. When the river level is high, the drain carries water to the new pumping station in Langton Meadows, from where it is pumped over the defence and into the river.

Conservation

Special effort has been made to design the wall so that it is in keeping with its surroundings. Planning and Conservation Officers from North Dorset District Council were consulted over the scheme's appearance. Brick facing was chosen to complement the existing walled gardens which are a feature of the area. The type of brickwork, and in some places, the flint panels in the wall, were chosen to reflect the character of Blandford, which is recognised as a fine example of Georgian architecture. The wall weaves its way between many of the mature trees on the site to give a degree of mature landscaping. In addition, many trees and shrubs have been planted, to provide visual and wildlife interest.
In Langton Meadows, grassed earth embankments were chosen for the defence. Once matured they will merge into their surroundings and be almost unnoticeable.

Scheme Facts and Figures

When the scheme was presented to the people of Blandford the most commonly asked questions were:

• Why is a flood alleviation scheme needed?
• But it won't flood again!.....
• Aren't floods in Blandford caused by high tide?
• Why isn't the river dredged or cleared out? Won't that solve the problem?
• So what will the flood wall look like
• But won't the flood water come up the drains?
• But won't the water come up through the ground?
• Has the National Rivers Authority taken proper advice on all of this?
• But it all seems very expensive…