The Environment Agency has finished essential improvements to fill in a breach at Woodmill on the River Itchen.
The breach, which first appeared as a small hole many years ago, had grown into a large gap taking half of the River Itchen flows. In response to the concerns about its increasing size the Environment Agency has filled in the hole with 30 tonnes of limestone boulders to reduce the flow through the breach.
This work will reduce the risk of flooding at Woodmill. There was a concern that the breach was effecting the automatic sluices at the end of the River Itchen. These fall and rise with the tide and help keep the water in the lower reaches of the river at the correct level. The amount of water being lost to the breach channel was making it difficult for the gates to find the correct level. Had the gates set the water level too high this could have increased the chance of flooding.
The reduced water flow through the breach channel should also encourage salmon and sea trout to use the fish pass at Woodmill Pool, designed to assist them upstream. Migratory fish such as salmon and sea trout are attracted to fast flowing water when travelling upstream. The size of the breach and the volume of water flowing through it was attracting the fish, leaving them more vulnerable to poaching as it flowed through a remote spot in the river.
The increased water flow downstream will help the various types of plant and animal life, which were previously trying to survive on half the amount of water needed. The limestone rocks have also been positioned in a way that will prevent further erosion but will still allow a flow of water over and through them. This will help retain the valuable instream and bankside habitat created by the breach.
By working closely with Southampton City Council, who own the Woodmill Activity Centre were the breach is, additional wetland habitat has been created. Several scrapes have been made in the low lying ground near the breach. This will encourage reeds to grow and also provide shallow pools for species such as frogs and dragon flies.
Heb Leman, Environment Agency Technical Officer, said of the project:
“The breach at Woodmill has been a concern for many years. It is satisfying to resolve the situation.
“The work we have done is one more step in the right direction at getting the famous River Itchen back into favourable status. By controlling the breach the main river will benefit from the increased amount of water. This will not only help the natural fauna and flora associated with this classic chalk river, it will also help create a better place for wildlife and for the local people that enjoy the river.”