The Problem: -
The client has what used to be a series of commercial water-cress beds running through land to the rear of the property. Water flow is constant and regular being spring fed further up, serious water catchment is also directed locally to the stream during heavy rainfall. This volume of rainfall catchment coupled with changed local farming practices consequently led to runoff carrying huge volumes of inorganic suspended solids, this in turn was settling in the old water-cress beds leaving them heavily silted. Over the many years of flow after the cress production ceased the cress-bed channels had become much wider due to bank-side soil erosion and increasingly shallow as the channels themselves became more heavily silted. This created greater water velocity over a wider shallower surface area and further increased bank-side soil erosion, a perpetual scenario. The old cress channels were also very straight and formal leading to a rather bland aesthetic view, also lacking in marginal vegetation the channels were not particularly attractive to aquatic wildlife.
Solution: -
Initially Burley Aquatic Developments was asked to remove the silt from the channels which was achieved by a long-reach excavator. However it was very quickly apparent that with each major downfall of rain the channels became silted again.
An option was offered to the client based upon narrowing the channels using locally sourced and sustainable hazel faggots thereby increasing water velocity to create a slight scour effect reducing silt deposition. All the silt would be removed from the “new stream” bed and used as backfill behind the marginal faggots. An additional option was offered whereby the channel narrowing could be achieved in conjunction with creating more natural looking bends/meanders into the design; this would effectively give the impression of a more natural looking stream. A native marginal aquatic planting scheme was included in the design to help increase the overall natural look and increase marginal habitat diversity with the view that wildlife species diversity would also increase. Over time the roots from these plants also help with binding and protecting the bank-side soil and reducing/eliminating further marginal soil erosion.
The returning to the wild meandering stream creation now looks fantastic providing a superb show of mixed native marginal plants each spring and summer along the entire stream with Kingfishers regularly seen fishing for bull-heads. Returning the formal old cress beds into a more natural looking stream has greatly improved and increased the site’s aquatic habitat and consequently hugely increased the wildlife species diversity.
Occasional silt removal may still be a requirement in the future depending on seasonal rainfall, in dry years silt deposition will still occur due to lack of strong and regular water velocity. Bank-side and in-channel foliage control is now regularly a part of the stream maintenance regime.
