Whitesands project - dredging and removal of gravel islands
We were asked if work on the river itself, such as removing gravel build up or dredging, might help in a major flood.
Dredging
Lowering the bed of the river by dredging was modelled to see what the benefit might be.
Lowering the river bed by 100mm was shown to reduce water levels by only 50mm during a flood and this is considered an insignificant benefit.
Changes in habitat and environmental damage to lamprey and salmon, as well as to otters, again means it's very unlikely we'd be granted a licence to do the work.
Gravel islands
Removing the gravel islands would have a negligible impact on flood levels as they make up such a small area of the river. Even if they were completely removed, the reduction in water level during a severe flood would only be a few millimetres.
The islands are also otter habitat and, as a European Protected Species, we would have to be granted a licence to remove them. Given there is no flood risk management benefit in their removal, a licence could not be applied for on those grounds.
They also form quickly again with movement in the river and would need regular and expensive work to remove them.
