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The Harnham Water Meadows Framework Management Plan - Contents
10. Drainage, water levels and flooding
10.1 ‘Yer lets the water on at a trot and off at the gallop’ as the Wiltshire saying goes. Priority will be given to drainage, particularly on the eastern meadows, but a review of exits from the western meadows is desirable. Indeed, progress has already been made in this respect. Careful consideration is needed when considering drainage from Ivy Mead (adjacent to the area of meadows presently a private garden), to Martin’s Mead and southwards, towards the SE tip of the ‘island’. For example, sediment and tree removal around the archaeologically significant ‘triple deck’ by Rose Cottage where the lower Great Mead drain badly needs silt removal and attention is required to an overhanging willow pollard.
10.2 Not only is the inundation of channels a comparative rarity due to low water levels, but there are also issues of control because ownership and management go beyond the purview of the Trust. It is probably best to start from the inlet side by the split in the Nadder channel, and work across site to eastern meadows.
10.3 The Conference endorsed:
Drain clearance should be established
Drain clearance protocols are needed, in respect of the SSSI and birds.
Protection of the Desmoulin’s whorl snail and water vole habitats.
Timings of operations need to be decided and carefully implemented.
10.4 Alteration of the ESA agreement remained open because of the option of changing to Higher Level Schemes in 2008 when new priorities are identified. The SSSI location is given in ANNEX IX, Drainage priority areas in ANNEX X.
10.5 Comparable watermeadow sites are increasingly abandoning clearance of drains where there is no immediate local problem for drainage. This will improve both possibilities for sediment trapping by the watermeadow systems and provide wet vegetated habitats.
10.6 Natural flooding is required by the SSSI and largely affects lower-lying areas that lack a viable floating infrastructure. The Trust can have no impact on flooding, but must recognise this as an important but random part of the overall management regime of the system. Ways of accommodating and taking advantage of natural flooding are central to the EA programme of Water Level Management Plans.
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