Flood prevention scheme makes a splash

WORK on the next phase of a £4m flood prevention scheme on the River Don in Sheffield will begin this month.

Staff from the Environment Agency are aiming to reduce the impact of future flooding by removing trees, debris and silt from the riverbed in the city centre, which was particularly badly hit by the floods of summer 2007.

More than 150 trees that have self-seeded in and around the River Don are to be removed in the work, which will last around two months. Some of the trees are more than 50 feet tall.

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Riverside trees, branches and other vegetation are frequently a cause of flooding. When they fall into the water and get stuck under bridges or at pinch points, debris builds up behind them, creating an obstruction or dam that holds back water, which can then flood nearby properties and land.

Around 5,000 tonnes of debris and silt that has built up in the Don channel will also be dug out. Some will be recycled and some will go to landfill.

Jonathan Moxon, from the Environment Agency operations team, said: "We've done surveys in and around Sheffield and identified areas where trees, vegetation and other debris in the watercourse could be a cause of flooding.

"Working closely with Sheffield Council and other local organisations we will get as much of this out of the watercourse as we can, using cranes to pluck the tree trunks from the channel and then cutting them up so they can be taken away.

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"We also have to make sure that we manage our impact on the environment of the watercourse, and leave it in a good state for birds and aquatic wildlife."

The work will start at three sites along the river, at Nursery Street, Blonk Street and Effingham Street, with compounds for staff and equipment nearby.

It is planned to take place outside the coarse fish spawning season and before the start of the bird nesting season. A survey of has also been undertaken to identify important habitats for species such as brown trout, otters and grayling.

Once the trees, debris and silt have been removed, low-growing vegetation will be planted in selected areas. Any colonies of invasive non-native plants, such as Japanese knotweed, giant hogweed and Himalayan balsam, will be removed.

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Mr Moxon added: "We want to establish a maintenance programme for the river, and we are looking at developing river stewardship.

"This would involve a wide range of interested organisations and include the ecological, fisheries, recreational and amenity aspects of the watercourse and environment."