After the confluence of the rivers Fynn and Lark the combined river (the river Fynn) then passes under the A12. Between here and Post Office Lane, Martlesham is an area of river that has received intense focus over a number of years.

 

The Fynn and Lark Fly Fishing Club have the rights to fish this segment and have worked with the Wild Trout Trust, Environment Agency, Essex and Suffolk Rivers Trust and others to improve this section of river for fish habitat and water quality. Like most of East Anglia’s rivers, the Fynn has been modified to be straighter and wider than it naturally should be. It faces issues of sedimentation and damage to the banks.   

 

Work has been carried out by the fishing club and its partners since at least 2002 where the Wild Trout Trust undertook an advisory visit. It is likely some work was carried out before this time, though there is no mention of this.

 

See these links for the 2002 report and the follow up report from 2010.  

 

As a result of these visits, modifications were made to the channel (including some modifications upstream at Little Bealings and Playford, both by the ESRT). These modifications are woody mattresses and flow deflectors.

 

Woody mattresses are bundles of wooden infill, usually held in place with wire (or weaving) and stakes hammered into the channel bed. These are up against the bankside and produce a variety of affects. Over time, silt becomes trapped in them which gradually turns them into burm features, areas of bank just above the waterline. This, firstly, traps some sediment. Secondly, it changes the flow of the river, creating a narrow channel that keeps moving during times of low flow and that can be easily submerged during high flows, widening the channel, allowing more water to pass through this point and avoiding flooding. Thirdly, they protect the banks from erosion. These can also provide new habitat types for plant species and animals, especially invertebrates.

 

Flow deflectors are wooden barriers that extend up to around half way across the river channel, forcing the flow around them. Deflectors can be placed facing downstream, which can cause the bank down stream of them to erode. This is generally not a desirable effect though there may be times when this is a desired habitat. At Martlesham, the deflectors are all places facing upstream.

 

Upstream deflectors cause the flow around them to scour out a slightly deeper section of channel. This has the same effect as the mattresses, creating a narrow channel for times of low flow and a wider channel for high flows. Directly behind the deflectors, the river loses energy and drops sediment which build up. Again, this provides habitat for many species and makes the river less homogeneous. In a few places at Martlesham, there are two defectors, one on each side. This creates a fast flow of water and a deepened pool between them.

 

The consistent flow of water, as well as the repairs to the banks and the deposition of silt (and upstream work) mean that this section of river is now a habitat in which fish and other species thrive. Unlike most sections of fished river, the Fynn and Lark Fly Fishing Club no longer need to stock their river, such is the recovery of fish populations and the provision of fish habitats in the area.