River Darent Catchment Management Plan Consultation Report
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NRA Southern 3 RIVER DARENT CATCHMENT MANAGEMENT PLAN CONSULTATION REPORT NRA National Rivers Authority Southern Region MISSION STATEMENT The N R A ’s mission is : "We will protect and improve the water environment by the effective management of water resources and by substantial reductions in pollution. We will aim to provide effective defence for people and property against flooding from rivers and the sea. In discharging our duties we will operate openly and balance the interests of all who benefit from and use rivers, groundwaters, estuaries, and coastal waters. We will be businesslike, efficient and caring towards our employees". Our Aims are to : Achieve a continuing overall improvement in the quality of rivers, estuaries and coastal waters, through the control of pollution. Manage water resources to achieve the right balance between the needs of the environment and those of the abstractors. Provide effective defence for people and property against flooding from rivers and the sea. Provide adequate arrangements for flood forecasting and warning. Maintain, improve and develop fisheries. Develop the amenity and recreation potential of inland and coastal waters and associated lands. Conserve and enhance wildlife, landscape and archaeological features associated with inland and coastal waters of England and Wales. Improve and maintain inland waters and their facilities for use by the public where the NRA is the navigation authority. Ensure that dischargers pay the costs of the consequences of their discharges, and, as far as possible, to recover the costs of environment improvements from those who benefit. Improve public understanding of the water environment and the NRA's work. Improve efficiency in the exercise of the NRA's functions and to provide challenge and opportunity for employees and show concern for their welfare. NRA Copyright waiver This document is intended to be used widely and may be quoted, copied or reproduced in any way, provided that extracts are not quoted out of context and due acknowledgement is given to the National Rivers Authority. © Crown Copyright Based on the 1990 Ordnance Survey 1:50,000 map with the permission of the Controller of Her Majesty’s Stationery Office. Published July 1994 River Darent Catchment Management Plan River Darent Catchment Management Plan Consultation Report CONTENTS Page Nos CONCEPT OF CATCHMENT PLANNING 2 SECTION A : GENERAL INFORMATION 3 A l.l INTRODUCTION 3 A1.2 THE DARENT CATCHMENT 3 A2. HYDROLOGY AND RAINFALL 5 A3. FUTURE DEVELOPMENT 7 SECTION B : USES 11 B1. PUBLIC WATER SUPPLY 11 B2. WATER SUPPLY FOR INDUSTRY AND AGRICULTURE 13 B3. USE OF THE WATER RESOURCE 15 B4. WATER QUALITY 17 B5. EFFLUENT DISPOSAL 19 B6. INTERMITTENT AND DIFFUSE POLLUTION 21 B7. FLOOD DEFENCE AND LAND DRAINAGE 23 B8. CONSERVATION 27 B9. FISHERIES 31 BIO. RECREATION AND AMENITY SECTION C : TARGETS 35 Cl RIVER FLOW TARGETS C2 WATER QUALITY TARGETS C3 RIVER TOPOGRAPHY TARGETS C4 RIVER MANAGEMENT TARGETS SECTION D : CATCHMENT ISSUES 39 SECTION E : MANAGEMENT OPTIONS 41 APPENDICES 49 -' i ^ f j g ! R ^'.‘ Authority 1 SUMMARY OF CATCHMENT DATA ..not- re 2 GLOSSARY OF TERMS AND UNITS 3 FURTHER READING ' o 1 ENVIRONMENT AGENCY Page 1 0 9 9 8 4 0 River Darent Catchment Management Plan CONCEPT OF CATCHMENT RUNNING The Water Act 1989 established the National Rivers Authority (NRA) as the "Guardian of the Water Environment”, a non-departmental government organisation with responsibility for regulating and managing water resources, water quality in coastal and inland waters, flood defence, salmon and freshwater fisheries, water recreation and, in some areas, navigation. An additional duty laid on the NRA was to further conservation of the natural environment, seeking opportunities for enhancement wherever possible. N RA Regions are defined by river basin catchments - singly, as in the Thames Region, or in geographical groups of individual rivers. With the exception of sea defence and coastal water pollution control, all the NRA’s functions are managed within this catchment framework, the need to resolve conflicts arising from differing functional objectives makes it essential to integrate the NRA’s planning in the same way. Catchment Management Plans relate firstly to the Authority’s own operations, including that of a statutory regulator controlling the actions of others. However, the Plans also offer an opportunity for input from the public to the development of NRA policy, and for the Authority itself to draw attention to its aspirations for the improvement of the water environment. The Plans concentrate on topics where the Authority has a direct interest and are focused mainly on the river corridor, although some functions such as water resource management and pollution control inevitably extend over the whole catchment area. Whilst they lack the status of statutory planning documents, it is hoped that Catchment Plans will make a positive input to the Town and Country planning process. The NRA consults widely with interested organisations and the general public before definitive Catchment Management Plans are published. This Consultation Report is the first stage of the process, your comments would be welcomed by The Catchment Planning Coordinator Guildbourne House Chatsworth Road Worthing West Sussex BN 11 1LD SECTION A : GENERAL INFORMATION TO THE NORTH TO ROCHESTER CULVERSTONE GREEN M20 TO MAIDSTONE RIVER THAMES RIVER DARENT TOPOGRAPHICAL CATCHMENT RIVER DARENT TOWNS MAJOR ROADS THE CATCHMENT River Darent Catchment Management Plan SECTION A : GENERAL INFORMATION A l.l INTRODUCTION The high yield and good quality of its chalk groundwater and the proximity of areas of high demand have led to the Darent catchment being heavily developed for public water supply, to the extent that groundwater levels are reduced and river flows may fail at times of low rainfall. In 1959, 1973, 1976, 1989, 1990, 1991 and 1992 the middle reaches of the River Darent dried downstream of Farningham, and in Dartford the water was static, with no outflow to the estuary. The NRA has identified the Darent as the most serious case of over abstraction amongst forty catchments in England and Wales requiring positive management for environmental improvement. Following extensive investigation, the Authority has agreed an Action Plan with the major abstractor for the management of water resources to reduce environmental problems and to enhance low river flows at times of drought. The Action Plan has been approved by the Department of the Environment and is being implemented - the purpose of this Consultation Report is to integrate this initiative with other management proposals for the Darent catchment. A U THE CATCHMENT The River Darent rises near Westerham and flows eastwards before turning north at Sevenoaks, where it cuts through the Chalk of the North Downs to flow through a wide valley and join the Thames estuary at Dartford. The greater part of the catchment is on the Chalk where surplus rainfall soaks underground, resulting in few permanent surface streams. As a consequence the River Darent has few tributaries other than the Honeypot and Watercress Streams which join the river north of Sevenoaks, and the River Cray which joins the Darent just below its tidal limit. The River Shuttle is an urban tributary of the Cray. The Darent valley has been a focus for human settlement and activity for many centuries. The catchment contains pre-Roman remains, Roman villas at Lullingstone, Farningham and Sutton-at-Hone, and mediaeval castles at Luliingstone and Eynsrord. The Cray and lower Darent catchments are highly urbanised and include the London suburbs of Dartford, Bexley, Bromley, Sidcup and Orpington, whereas the middle and upper reaches of the Darent are rural in character with several villages close to the river. In the past, some twenty five water mills along the course of the Darent produced flour, paper, fabric and gunpowder; many of these buildings survive, but are used as private houses or as industrial premises unconnected with milling. This intensive use of the river as a power source required the flow to be diverted down artificial channels leaving very little "natural" stream betweent mill ponds. There were once extensive water-meadows between Otford and Hawley, but much of this land has been developed for housing or gravel extraction. However, most of the gravel deposits in the lower Darent valley have now been exhausted leaving flooded pits which are used as nature reserves, fisheries, or sites for recreation. In the wider context, the Darent valley provides pleasant surroundings and historic interest for peaceful country walks, and many recreational users are attracted into the area from nearby London. Whilst the problems of low flows have received most attention in recent years, there has also been a history of flooding in the catchment. The exceptional flood of September 1968 damaged roads, bridges and riverside property, but subsequent work on the Rivers Cray and Shuttle, and on the Darent at Westerham, Chipstead and Dartford, has reduced the risk of damage from future floods. However, low-lying water meadows are still permitted to flood regularly, preserving their value as wetland habitats. The Dartford tidal barrier is operated by the NRA as a defence against flooding from exceptionally high Page 3 River Darent Catchment Management Plan tides, which threaten the low-lying land adjacent to the Thames estuary. A range of statistics for the Darent catchment is given in Appendix 1 at the end of this report. HYDROLOGY AND RAINFALL N NRA LEGEND RIVER THAMES RIVER DARENT TOPOGRAPHICAL CATCHMENT ESTIMATED GROUNDWATER CATCHMENT BOUNDARY PERENNIAL WATERCOURSE .GEOLOGY EPHEMERAL WATERCOURSE LOWER LONDON TERTIARIES TOWNS I | CHALK 660 MEAN ANNUAL RAINFALL (mm) | GAULT CLAY PRIMARY GAUGING STATION LOWER GREENSAND CATCHMENT HYDROLOGY 8c RAINFALL River Darent Catchment Management Plan A2. HYDROLOGY AND RAINFALL A2.1 Geoend This section considers the main features of the natural water resources within the catchment. Sections B l, B2 and B3 consider the use of these resources for water supply.