Sunnydale flood alleviation work
This map summarises what has been done and why. The most obvious changes are the re-routing of the stream to support more wildlife, and the major earthworks to relieve some of the risk of flooding that had been experienced in the past by houses further down the Cuttle Brook and down hill from the central cricket field in the park.
From below the brick bridge, carrying the drive to the allotments, the brook has been swung out one way and then the other and pools created, held back by natural-like weirs known as riffles, topped by stones to slow the water. The pools are designed with deeper areas, reeds and marginal plants to slow the flow and capture silt. The wetland pools are surrounded by wider areas that would hold more water in the event of a flood. The wetlands are intended to create a new habitat within the park to encourage more types of birds, insects, and amphibians. Great white egrets and herons seem to be more frequent visitors and kingfishers have been more frequently seen.
Between the wetland and the pond the path has been raised to help the flood control. The old pond itself has been extended a little and the bank replanted with marginals.
Beyond the pond something of a clay-pit has been excavated, creating a flat basin and sloping banks. In the event of heavier floods the basin would hold some of the water to be released more slowly, like a flood plain. The basin and banks have been planted with some standard pear trees and lots of native tree saplings, together with wildflower seeds appropriate to the habitat. These are to replace the wildflower meadow by the pond and the trees cut down when the clay-pit was excavated.
The wetlands and the clay-pit produced a huge quantity of earth. Some has been used to create earth banks (or bunds) around the central cricket field and much was carted off site. On the down-hill side of the cricket field a long bund has been formed to stop rain water run-off flooding houses in the closes off Nevinson Drive. Towards the central wood a large bund has been formed and sown with wildflowers to replace that previous meadow area. There is a shallow ditch through that bund to take water from the wood towards the pond. To help excess water run away a sunken drain has been installed topped with sand and eventually grass that leads to the Clay-pit, which together with other land drains collects water and channels it to the pond.
The other bund that stands alone opposite the children's play area has caused speculation as to its purpose - gun enplacement, helicopter pad, crowd seating for the cricket. The aggregate laid on the top is to encourage butterflies to bask and a different range of wildflowers to encourage different insects and maybe reptiles.
Beyond the central wood, where the Friends have worked many times to create a sheltered glade for butterflies, the Cuttle Brook scheme has tried to create new meadow areas and planted more trees. Beside the path from the Wilson Avenue entrance to where the Field Rise entrance leads in the triangle of grass has been sown with wildflower seeds. This is hoped to diversify the area of tussocky grass, left rough to support small mammals - field mice and field voles etc. - that support owls and kestrels.
On the Top Field, leading to Blagreaves Lane, over 200 trees saplings have been planted with some standard plum trees. The changing climate with longer drier summer periods are very challenging for saplings. Across the other side of the path a large area, over 8 thousand sq. metres, marked by posts has been sown with wildflower seeds to increase the biodiversity. When the council's maintenance teams don't mow the rest of the field it is apparent that there is a good basic variety of wildflowers waiting to grow and flower across the who area. In the winter and when the grass is low the field clearly has a system of ridge and furrows from the pre-industrial farming system. Archeologists have studied the arrangement of the ridges and consider that they were probably formed post-medieval period, so between 1500 and 1800 AD/CE.
The Cuttle Brook scheme has left a few areas still to be finished and there are more ideas for planting trees, installing benches and perhaps some other features to enhance the park.
