To carryout works within the river Monnow catchment to reduce the amount of silt entering the rivers and reduce subsequent siltation of the rivers.

 

 

Where bank side trees have shaded out the native perennial plants and when combined with stock access the river banks are left bare and prone to erosion resulting in over widened streams in that locality and silt deposition downstream from the problematic site. Where streams become over widened they are no longer self cleaning because the flow is reduced and silt from upstream can drop out onto the river bed.

 

Where the riparian vegetation is denuded the natural buffer strip to run off from fields alongside the river is also lost so silt from them can enter the stream more easily.

 

Silt is recognised as a pollutant in its own right causing gravels and stones on the bed of the river to become compacted and smothering the bed of the river reducing the aquatic insect populations and reducing the spawning success of fish. Silt also holds and brings into the river with it phosphates and nitrates that cause eutrophication.

 

 

• Coppice and canopy lift a proportion of the riparian trees, principally multi stool alders to increase the light penetration to the banks.

• Lay in shrub and timber like trees to create living revetments to protect actively eroding areas of river bank.

• Fence livestock out to protect the coppice re-growth and remove grazing pressure from the river banks to allow the regeneration of grasses and native perennial species.

• Create silt traps close to the banks, where existing farm tracks adjoin the river and sky lighting these areas to improve regeneration of grasses.

• In areas of actively eroding river banks to install coarse woody debris to create living and dead soft revetments

 

 

• To identify high priority sites within the Monnow catchment where there is a high risk of current, actual and future sources of silt entering the river system.

 

• Obtain farmer and landowner approval for proposed works.

 

• Obtain all necessary legal consents for coppicing and river work.

 

• Carrying out Coppicing, fencing along the chosen sites and installation of water gates for drinking points and access.

 

• Carry out installation of silt traps as required.

 

• Install soft revetments to stabilise river banks.

 

• Obtain landowners’ written agreement to maintain the fences and watergates for a reasonable period.

 

 

• Stabilisation of the eroding river banks so reducing siltation.

 

• Increased marginal vegetation that will hold the river bank and trap further silt during floods and slow and trap field and track run off.

 

• Increased coarse woody debris that will stabilise eroding banks and trap further silt.

 

• Over time the narrowing of the river, increasing flows and reducing silt deposition.

 

• Allowing light onto the river bed will increase in stream plant populations, trapping further silt and providing a richer habitat for aquatic insects and cover for trout

 

• All of the above will improve the habitat of the river, increasing the food available to and providing additional habitat for the benefit of trout and grayling so increasing the amount of fish available to the visiting angler.

 

 

The Monnow Fisheries Association is an organisation committed to the improvement and maintenance of the Monnow catchment and one of its core objectives is to ensure that the habitat improvement work within the catchment, both future and already completed, will be maintained in a sustainable way.

This is being done by:

 

• encouraging visiting anglers, so increasing the income and capital values to farmers and fishery owners so that they are better able to and more prone to maintaining their own improved rivers.

 

• Carrying out and leading volunteers in maintenance works such as re-coppicing of alder re-growth particularly on small streams where there is little or no fishing interest but are of high importance for trout recruitment.

 

• Investigation of harvesting and sustainable use of coppice re-growth for woodfuel.

 

• Overseeing and inspections of work carried out to ensure that fences and water gates are being maintained and encouraging farmers to do this work and, where necessary providing funds and volunteer effort to carry this work out.

 

 

Both these sites are on Great Walkmill Farm, which is subject to high stocking rates of cattle and sheep combined with very deep shading causing significant erosion. The sites adjoin a length of the brook that was coppiced and fenced with great success in 2009. The farm is well known to the Ioan Williams and the completion of the coppicing and fencing along the rest of this farm is of high importance. The beat is already let under the Wye and Usk Foundation Roving Voucher Scheme.

 

The overall length is 780M and much of it is unfenced on both banks and the budgeted cost is £9750

 

 

This site is the three fields downstream of Ewyas Harold village and is heavily grazed with sheep and currently the fields are in stubble turnips and in previously the stubble turnips have been grazed during the winter months. There is no fencing and consequently there is erosion of the river banks and high risk of silt entering the river from the cultivated fields.

 

The overall length is 645M. The opposite bank is fenced and little felling on that bank needs to be done so only the subject bank needs to be coppiced and fenced. Over all cost is budgeted at £6560

 

 

This site is on the river Dore from the Elm Green road bridge down to the confluence with the Worm Brook. The two fields on either side of the river are run as one resulting in the stock, currently cattle using several “fords” to cross the river. Combined with high grazing pressure and substantial shading the banks are severely eroded in places.

 

Length 566M, expected costs £8380

 

 

This site is from the upstream of side of Elm Bridge. The right bank is a pony paddock with unfettered access and the opposite bank is fenced. The whole length is densely shaded and there is considerable bank erosion.

 

Length 190M, expected costs £4450

 

 

A combination of high grazing pressure and loss of mature trees in winter floods has resulted in the river starting to meander at an alarming rate resulting in many cubic metres of river bank being washed away in each flood. Currently the banks are so at risk of being lost that it is impossible to fence them for fear of loosing the fence. I recommend that three large areas of eroding bank have soft revetments installed, using nearby laid living willow, alder and coppiced material. These revetments will trap silt and debris and reform the banks over the next few years and, when stable fences can be installed either using MFA core funds or at the landowners’ expense.

 

Expected costs £2000

 

 

This site was subject to an inspection by Ioan Williams in 2009 when the field, with some steep slopes had been planted with stubble turnips and grazed off with sheep during the winter. Although the field is currently in grass it is still relatively heavily grazed and the banks are eroding due to grazing pressure and over shading. The opposite bank is fenced and only light coppicing to it would be required.

 

Total length 420M, expected costs £4900

 

 

This site is on the Olchon Brook, from its confluence with the Monnow. It is densely shaded. The first field is grazed and there is significant bank erosion. Upstream of the road bridge there is a high wooded bank and a sloping farm track of bare stone and soil that runs along the top of the bank and out into a sloping field. It is clear that at times of high rainfall the track acts as stream and that the silt washed from the fields currently makes its way directly down the bare banks into the river.

 

I recommend that the lower section is fenced and coppiced on the right bank, with light coppicing to the opposite bank, live hazel is laid into protect eroding banks and the field is fenced with the inclusion of a drinking point.

 

On the upper sections; that the wooded high bank is coppiced and a log silt trap is installed, where the silt from the track currently leaves it, to run down the bank into the brook.

 

Total length 260M, expected costs £2300

 

 

This field was grazed through out last autumn and winter by cattle, which have uncontrolled access to the stream causing severe erosion to banks and the bed of the stream. The opposite bank is fenced and only light coppicing would be required to that bank, whilst heavier coppicing and fencing is required to the subject bank.

 

This stream has a high proportion of spawning ravel and is extremely important to for juvenile recruitment to the Dore and Monnow catchment.

 

Total length 590M, expected costs £5160

 

 

The landowner liaison, obtaining all necessary permissions and over seeing of the proposed works will involve a considerable additional management role. That at my current charge out rate would cost in the region of £7500, including out of pocket expenses. However I am prepared to carryout the necessary work on the above project or a large proportion of it should not all the sites be included for £2000 to include all out of pocket expenses.

 

 

The total expected costs of the works as detailed above are £45,150.

 

Robert D B Denny MRICS
22nd September 2009