River Management Techniques. Upper Wharfedale Best Practice Project (Information Series No 6)

1.2. Gill habitat regeneration

1.2

LOCATION:
Swarthgill
Oughtershaw
SD 841825-842828
SD 843823-850822

AREA: c.2.47ha

DATE UNDERTAKEN:
Summer/Autumn 2000

COST: £9,100

BACKGROUND INFORMATION

A project to improve the existing limited gill habitat was carried out in 1997/98, when a gill in the immediate vicinity of the farmhouse was fenced off and tree planted.

Further work was needed to establish new native woodland in other gill sites to complement the work undertaken previously. The planting was to follow natural features on the land, which was generally steep rising from 360m to 500m above sea level, with limited cover ranging from rushy areas to steep grass slopes.

DESIGN

The project mainly involved fencing and tree planting but provision was also included for stock watering access to the stream. A total of 2,175 trees were planted in an area of about 2.47ha at an average spacing of 3m centres (between 1-5m). The shrub species element was concentrated at the edges of the planting, using wider spacing and protected with 0.75m tree shelters, with the exception of holly which was specified to have wider shrub guards. The fence was not rabbit proofed to allow for potential fence damage by deep snow falls. Tree protection was achieved by using individual tree guards. Consideration was given to landscape aesthetics and straight lines were avoided in the scheme. Fence lines were aligned within the land form of the gill so as not to be visually prominent. Tree planting within the gill was notionally split into three sections with the lowest section being relatively densely planted (70-90%), the middle section less so and the upper section sparsely planted (10-30%), thinning with altitude.

Approximately 1,050m of stockproof fence was used to secure the planted area, employing stock net and a barbed top wire. Where the fence line ran parallel to a public right-of-way a plain top wire was installed, in addition to the barbed wire, and placed on the path side of the fence to prevent accidental injury to walkers. The planted area was provided with a 1.2m galvanised steel gate for access through the fence line for future maintenance. A purpose-built stockwatering point was incorporated within the fenced off area. A water gate was used to close the fence line where it crossed the stream to exclude stock.

SPECIFICATION

Trees and shrubs

Tree planting stock was packaged and transplanted in accordance with BS3936 and delivered without delay prior to planting. The plants were protected against mechanical damage, extremes of temperature and drying out. 45cm-60cm transplants with a minimum root collar diameter of 5mm were obtained from an approved local source of northern provenance and delivered on site in co-extruded bags. All transplants were notch planted.

The trees were planted in species groups of 5-9 within the area to give a representation throughout the site, with the exception of sessile oak which was planted in deeper soil on the lower slopes within the gill.

All planting distances were random to create a natural appearance to the woodland. The species mix used was 25% downy birch Betula pubescens, 22% rowan Sorbus aucuparia, 15% ash Fraxinus excelsior, 10% alder Alnus glutinosa, 5% of each of sessile oak Quercus petraea, hawthorn Crataegus monogyna, hazel Corylus avellana, goat willow Salix caprea and grey willow Salix cinerea and 3% holly Ilex aquifolium.

Weeding was specified to be undertaken within a 1m diameter of the base of each tree. The area was to be maintained at least 80% weed free throughout the growing season. Application of the herbicides Kerb and Roundup was specified in winter and spring respectively.

Fencing

Stockproof woven wire fencing was erected. The stocknet was high tensile, medium to heavy duty, and galvanised. A single row of galvanised, high tensile barbed wire was placed along the top. Straining posts were at least 150mm top diameter, 2.1m long, and were provided at all changes of direction. Struts were between 75mm-100mm top diameter, 2.1m long and/or box struts. Intermediate posts were between 75mm-100mm top diameter, 1.65m long, and spaced at approximately 2-2.5m centres. Post and rails used were about 100mm by 40mm. All fixings used were galvanised, all wire was strained and all timber tanalised.

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