SUDS Options for Coy Pond Gardens

Option 1: in-stream pond 'A' upstream of Havelock Road

The construction of an in-stream pond at the most upstream part of the gardens, created by building a dam wall at its downstream end with simple controls for water flow during both normal and flood conditions.  Excavations would need to avoid electrical cables to the north and a water main to the south. 

Principal features of the pond being:

• a meandering channel with wetland areas which would be inundated to form a full pond during flood conditions;

• deeper 'deposition' pool area within the meandering channel;

• the construction of a gravel footpath around the perimeter with stream crossings at each end;

• wetland/reed bed planting along the meanders, and other perimeter planting.

Pros & Cons:  although option 1 would improve water quality for the rest of the stretch of the stream, and offers good access, it is quite remote from Coy Pond.  It's limited size would have only a moderate impact on improving water quality and flood water storage.  It does, however, allow an opportunity to remove existing concrete walls from the stream.

Option 2: removal of existing stream walls

Upstream of the pathway linking Havelock Road to Surrey Road is a 25m section of the stream which has been canalised.  Option 2 includes the removal of these walls and localised earthworks re-grading to reintroduce natural earth banks and in-stream meanders.

Pros & Cons: This option is relatively inexpensive and easy to engineer, whilst it's more natural profile provides different stream habitats, so is likely to offer greatest cost/benefit.  Nevertheless, there is limited water quality improvement when compared with other options.

Option 3: in-stream pond 'B'

Options 3 is another pond, more centrally located than option 1 and includes the same elements (see above).  The services again limited the width, but not the length of the pond, which might be up to 100m long.  Stream crossings at either end would improve access to the gardens.

Pros & Cons: the larger pond size would improve water quality to a greater extent and offer more habitat enhancements than option 1.  There is an opportunity for good flood water retention and the visual link to Coy Pond itself would attract more visitors.

Option 4: braided stream

Located entirely within the lower section of the garden, option 4 combines a number of elements, including:

• the construction of new meanders to the existing stream;

• construction of secondary channels to form a braided stream and island features;

• formation of a wetland garden in areas that are currently fenced off for safety reasons;

• the construction of a pathway (with a boardwalk in wetland area) linking across the islands created.

Pros & Cons: Option 4 would be highly visible from the road and has good access, so would draw visitors.  However it offers limited water quality improvements in a stretch of the stream that already benefits from meanders and reasonable habitats. It is also likely to be flooded when stream flows are high.