Carisbrooke Pond Feasibility Study 2007
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CARISBROOKE POND, IOW FEASIBILITY STUDY Environment Agency February 2007 Author - Jon Milliken Contents Page No. 1 Introduction 1.1 Background 2 1.2 Scope 3 1.3 Site Description 3 1.4 SINC Citation 5 1.5 Inlet and Outlets 5 1.6 Silt and water depth 7 2 The Lukely Brook 2.1 Connection with the Carisbrooke Pond 8 2.2 Water Quality 8 2.3 Biological Monitoring 9 2.4 Flow Data 9 2.5 Fish and Habitat survey 9 3 Carisbrooke Water Supply Works 3.1 Description 10 3.2 Vulnerability to Contamination 11 3.3 Previous Incident 11 3.4 Pond Enhancement and Risk to Abstraction 11 4 Waterfowl on Carisbrooke Pond 4.1 Problems associated with Artificial Feeding 12 4.2 Alternatives 12 5 Site Enhancement Options 5.1 Discussion 13 5.2 Terrestrial Areas 13 5.3 Pond Margins 15 5.4 Open Water 15 6 Protected Species 6.1 Discussion 16 6.2 Bats 16 6.3 Great Crested Newts 17 6.4 Water Voles 18 7 Heritage and Archaeology 18 8 Community ‘Ownership’ 8.1 Discussion 19 8.2 Opportunities for People 19 8.3 Residents Comments 20 9 Options 21 Appendices 25 Glossary 31 1 1.0 Introduction 1.1 Background There are currently estimated to be about 400,000 ponds in Britain, but some three-quarters (more than a million) of Britain's ponds have been lost over the last hundred years. Ponds are a unique biodiversity resource, an important part of our history and culture, a visual focus in many landscapes and an amenity for many communities. Carisbrooke Pond is a large body of water located in the heart of a community and surroundings rich in history and heritage. However it has been neglected in recent times and at present is a poor resource both in terms of its ecological potential and value to local people. An opportunity therefore exists to develop this potential. The creation of a marginal zone for wetland plants and some terrestrial planting would all contribute towards a richer diversity of habitats at this site. Bats, amphibians, wildflowers, insects, grasses, birds, mammals –all can flourish at this site through easily achievable improvements. But the true value of these improvements will be revealed through the link with the local community. For centuries this pond has been important to the local people. Stand on the banks and look around. This is a landscape created by people; archaeological remains pot mark the immediate surroundings. The pond, the buildings, the history and the people are inextricably connected. It is not through chance that the Carrisbrooke village has evolved to surround the pond and brook. Although, in modern times one might argue that the pond now merely exists within the landscape; its value, interest and use to the local people may be less now than at any point in the pond’s history. A fantastic opportunity exists to enhance the ecological potential, improve the visual attractiveness and provide an important amenity for the use of local people and visitors to Carisbrooke. Records show that the pond has been known as The Carisbrooke Pond, the Eight Bells Pond, the Mill Dam, Waterworks Pond and Priory Pond. This report will refer to it as the Carisbrooke Pond. Note that Carisbrooke Mill is situated upstream of this site and has a millpond which is sometimes referred to as Carisbrooke Millpond. 2 1.2 Scope The Newport Rivers Project is a collaborative project that has been running for the past 6 years. The aim of the project is to protect, enhance and restore the local rivers (Medina, Lukely Brook, and Gunville Stream) which flow through Newport for the benefit of people and wildlife. The Environment Agency is a key partner in the project, and has commissioned this Feasibility Study to identify the opportunities for the enhancement of the Carisbrooke pond (more recently known as the Eight Bells Pond). The pond is fed by the Lukely Brook. The pond and its environs is degraded due to siltation, nutrient enrichment and current management practice. It can be described as impoverished in terms of wildlife. Closely mown banks and lack of emergent and submerged aquatic plants provide little habitat for wildlife. The weir structures also present an impediment to fish migration. There have been serious concerns over the years with regard to the poor water quality and fish kills. However, it is an important amenity for the local community, and is designated as a Site of Importance for Nature Conservation (SINC), as it is recognised as an area provides foraging for bats. This report describes the existing pond and presents recommendations for enhancement taking into account constraints, risks and costs and most importantly the wishes of the local community. 1.3 Site Description Carisbrooke Pond is located at NGR SZ 488 881 and is a former mill pond and is believed to date back to Roman times. It is now owned by Southern Water Services. Water flows into the pond from the Lukely Brook in its southwest 3 corner, and discharges through two weir structures on either side of a waterworks building. The pond measures approximately 100m in length and 40m in width at its widest point. Carisbrooke pond On the north bank, the pond is bordered by a pub garden and residential properties. There is no public access on this bank except from the garden of the Eight Bells Pub from which the pond can be viewed and is a valued feature. On the south side an area of mown grassland extends along the entire length of the pond from inlets to outlets. This area falls within the ownership of Southern Water Plc who allows permissive public access from a pathway beside the pumping station. Gardens and an allotment lie alongside this grassland. A number of mature trees occur around the pond including horse chestnut Aesculus hippocastanum, alder Alnus Glutinosa, ash Fraxinus Excelsior and a weeping willow Salix chrysocoma. There is a small island in the southwest corner with a semi-mature ash. The grassland along the south side of the pond is regularly mowed. There are small areas of bankside vegetation consisting of bramble, nettle, hemlock water-dropwort, willowherb and greater pond sedge. The pond is a popular recreational area, and as a consequence is well populated with mallard ducks and black-headed gulls attracted by bread feeding. The grass area is used by local people to exercise dogs. A population of carp Cyprinus carpio exists in the pond. There is no evidence of rooted submerged aquatic plants but algae occur and are especially evident in the summer months. Anecdotal reports of blooms occurring have not been substantiated. However it is likely blooms may occur especially when low flow conditions coincide with warm weather and strong sunlight. 4 1.4 Site of Importance for Nature Conservation (SINC) A citation issued on 20 December 2006 designates the pond as a Site of Importance for Nature Conservation. The site description states that the pond is an important bat feeding site and is used by large numbers of daubenton’s bats (for which it is the best Island site), pipistrelles and sometimes serotine and noctule bats. The citation notes that Grey Wagtail has bred and wetland birds are regularly recorded and that bullheads occur in the stream. Although not formally assessed, the subjective view of the County Ecologist is that the site would be classified as ‘unfavourable’. Local people perceive that the numbers of bats using the site has diminished in recent years. A copy of the citation is included in Appendix 1. Two further SINCs exist nearby which are also situated on the Lukely Brook. Upstream, Plaish Meadows SINC at SZ480847 measures 9.46ha and is situated 0.75 km’s from Carisbrooke Pond. 0.5km downstream of the pond, the Lukely Brook SINC at SZ491886 measures 1.38ha. The Lukely Brook flows through each of these sites and may be considered to provide a river corridor link between them. 1.5 Inlet and Outlets The open channel of the Lukely Brook forms the inlet to the pond and is shown in photo. 1. Discharge from the pond is by two engineered outlets situated adjacent to the Southern Water Pumping Station and are described as follows in a report commissioned by the Environment Agency. These outlets are shown in photos 2 and 3. Structure Condition Estimated Comments Description Life Southern EXCELLENT 50 Structure is in excellent condition. Water Drop Several pipes entering internally. Structure Comprises a series of steps down to a level below high St. There is an estimated 2.5m drop just D/S of the weir. Sluice and VERY GOOD 25 It is not know if the sluice gate operates Side Channel properly. The sluice gate is the main Spillway structure prone to operational difficulty These structures are impassable to fish of all species. (Fish Habitat and population survey of the Lukely Brook, Environment Agency, January 2007) 5 Photo 1. Photo 2. 6 Photo 3. Comment – Fish movement prevented by these structures could be overcome by the construction of a fish pass. Such a proposal should be subjected to cost and benefit analysis. At the present time the absence of a brown trout population and general poor habitat on the Lukely Brook suggest that the installation of an expensive fish pass at the present time would have little value. However, future habitat improvements are planned for the Lukely Brook and populations of Brown Trout and Sea Trout may be restored. Consequently the construction of a fish pass at this site may become a viable and useful option in the longer term.