Tuesday, 27 December 2011

The Wensum: Going with the flow

Cost to Hellesdon 176

TO the untrained eye there appears little wrong with the River Wensum upstream of Hellesdon Mill on the northern fringes of Norwich. Lush vegetation grows underwater and the river’s banks are lined with a mixture of mature trees and fast-growing plants. Certainly it looked good enough from a canoe when I took this picture back in August.

But according to the experts, the Wensum could be in a lot better nick. Working out how to fix it is the job of a group of scientists from organisations like the Environment Agency and Natural England, working under the River Wensum Restoration Strategy umbrella. And according to their latest newsletter (scroll down the page from here) their latest trick has been to reduce the level of the river at Hellesdon in a three day experiment carried out back in September.

The mill might be long gone, say the experts, but the structures left behind still have quite an impact on the way the river behaves. With a higher water level, they describe the river as a “linear lake” – in other words a river without enough flow. But reducing the amount of water backed up at Hellesdon had a significant impact “with large sections of the river becoming free flowing upstream of the mill”.

This is just one of a number of fascinating experiments they’re conducting on the river. Another involves reinstating the river’s old meanders. Detective work on the ground means they can often track down the original river bed. And at Great Ryburgh, for example, they’ve discovered that the old bed was a mix of gravel and chalk – perfect conditions for the wildlife and vegetation they’re hoping to encourage.