River Restoration
The conservation and restoration of our rivers is at the heart of the work that we do at the River Lark Catchment Partnership.
River restoration projects usually seek to reduce the impact of high and low flows, create new or improved habitat, and prevent or reduce pollution.
Each of these objectives is focussed on one of the three pillars of river health: habitat; water quality; and water quantity. A well-functioning, healthy river has biodiverse high-quality habitats, consistent water flow without floods or droughts and clean unpolluted water.
Unfortunately, the River Lark struggles with all three of these key pillars and therefore requires direct action to help improve its condition.
Targeted action to help any one of these pillars will help restart natural processes. Effectively, the river works to improve its own overall health.
For example, in an over-widened river channel with very low flow, the river loses the ability to transport sediment and therefore deposits silt across the bed, which prevents fish and invertebrates from spawning. By narrowing the channel in places through the construction of brash shelves, we reintroduce variation in the flow, which enables the river to deposit sediment, encourages the development of river vegetation. There is increased flow in the narrowed section which scours sediment from the bed.
The resulting diversity in flow and sediment levels allows a much greater diversity of invertebrates, fish and other animals to thrive in the river.
Completed Projects
Starting in 2015, RLCP has undertaken a wide variety of river restoration projects mostly between Bury St Edmunds and Mildenhall. These have included the creation of:
- riffle and pool features using gravel to provide habitat for fish spawning.
- brash shelves to protect banks, trap silt and provide habitat diversity in the river channel.
- flow deflectors to create flow diversity and allow natural processes of erosion and deposition.
- natural habitat by planting riparian vegetation, both in-river and on banks.
- backwaters and vole runs to provide habitat diversity in wide river channels.
The aim now is to plan much larger scale projects over greater areas of the catchment.
Protecting a bank at Lackford Lakes.
This recently completed project at the Suffolk Wildlife Trust reserve at Lackford Lakes was designed to protect a high sandy river bank from being undercut and eroded by the river.
Large piles of of alder brash that had been coppiced by the reserve wardens were tied into 2m long bundles by our volunteers.
Stakes were driven into the river bed.
The bundles were wedged together, end to end, held in place by the stakes, and held down bwith poles secured at right angles to form a secure brash shelf.
The effect was instantaneous: the flow was deflected away from the bank by the brash shelf, which still allowed water to percolate through it. After only a couple of weeks, the brash was begining to get covered in silt that had dropped out of the water. The shelf will soon be colonised by reeds, and will provide a refuge for fish and invertebrates
