The aim of this study, undertaken for the Minch Project in collaboration with Scottish Natural Heritage, is to provide practical and viable guidance on how best to reinstate worked-out sand pits in the Minch area. This takes the form of general recommendations for reinstatement covering the range of sand pit types found in the study area, plus outline recommendations for three case study pits.
Sand pits in the Minch area are usually excavated in dune grassland and machair. As well as damaging landforms and habitats, unrestored and inappropriately restored pits can scar the landscape, create a safety hazard and, most importantly, possibly initiate large scale erosion of the machair.
However, the lack of significant amounts of fresh wind blown sand on the machair preclude the use of many of the techniques used in sand dune stabilization, such as Marram Grass planting, because of their reliance on sand trapping.
The techniques recommended in this report are therefore based on slope grading to reduce wind resistance, and so prevent undercutting, and on revegetation to create a turf sward. This will often result in a residual depression in the land surface, but it was found that once vegetated, these rarely have a significant visual impact. Infilling with rubble, scrap metal or other waste material, which has been carried out at a number of the sites studied, is not recommended as a technique because of the often occurring problems of re-exposure and wind scour. Furthermore, infilled pits near to the sea run the risk of being re-exposed should the coastline retreat.
The study highlights the necessity of identifying the need for reinstatement, that is, whether for erosion control, visual and ecological improvement, or safety reasons. Not all disused pits require reinstatement, particularly if they support naturally regenerated vegetation of nature conservation value.
Once the need for restoration is identified, an appropriate reinstatement strategy can be selected. This will be determined by the state of existing vegetation, site stability and shelter, and visual impact. Four options are recommended, a combination of treatments being possible at any one site:-
- "do nothing" - where existing natural regeneration is acceptable, or where conditions will allow its development
- cosmetic remedial measures - to remedy poorly carried out restoration, includes removal of dereliction signs and inappropriate capping
- landforming - cutting back or under-pegging undercut slopes, slope grading and pit widening to reduce wind funnelling
- revegetation - either seeding or encouraging natural regeneration, with the aid of mulches, such as peat and seaweed, fertilizer and, possibly, binders.
Restoration recommendations have to be very site specific. Ideally, treatment trials should be undertaken as it is impossible to give definitive specifications for any one site because of the difficulty in predicting erosion risk. Exclusion of grazing stock and rabbits is necessary and monitoring and aftercare are imperative.
Advance planning, to integrate reinstatement into pre-closure site operations, and also to carry out site selection according to geomorphological, visual and ecological sensitivity, would reduce problems arising from disused pits.
