River Restoration – Soft Engineering
The River Cole, Oxford
The River Cole forms part of the
border between the counties,
Oxfordshire and Wiltshire. It is a
tributary of the River Thames and
joins it near Lechlade. Many mills
have altered the river by
straightening and polluting it. Much
of its upper course has been built
over due to urbanisation and so the
exact location of the source is
unknown. It also ?ows through
National Trust land.
The River Cole had become very
polluted and needed restoration.
Restoration is returning a river to its
natural state after arti?cial
alteration. The river needed
restoration in order to change the
water course, improve the water
quality and manage the bank-side
vegetation. In 1994, River
Restoration Project was set up in
order to show how contemporary
restoration techniques could help
damaged ecosystems thrive. The
project was run by the RRP (River
Restoration Project), the
Environment Agency, English
Nature, the National Trust, the
Countryside Commission and the
EU. Using the EU LIFE money,
three demonstration projects were set up, helping to restore over a 2km stretch of the River. The project was completed in 1996.
In order to bring the river bed back in line with the ?oodplain, the river bed below Coleshill Bridge was raised. More gravel rif?es (fast ?owing midstream ridges) were introduced, as well as some small weirs (small barriers allowing pools to form behind them). Due to the redevelopment of the river bed, it ran at a higher level than a large stretch of the river. A new meandering channel was cut allowing the water to travel at the same height. Parts of the old river were kept and acts as backwaters. During high ?ows, this provides shelter for ?sh, birds and insects, adding to the growing biodiversity of the river. The meanders also cause more regular ?ooding of the neighboring ?elds, creating water meadows and increasing agricultural productivity.
The ancient course of the River Cole has been able to be recreated. This is due to the ?oodwaters, caused by meandering, restoring the ?ood meadows along the western side of the Cole Mill. The Cole Mill is hoped to be put back into occasional operation by the
RRP. However, the water levels in the stream ?owing near the mill must be raised in order for this to be possible. They plan to develop the River Leat (the feeder stream – the tributary that empties in to the River Cole) into a long lake. The plan for wet pasture and reed beds along the sides of the river will accompany this development. These will contribute in cleansing the streams that have been polluted by silt, fertiliser and treated sewage.
The restoration has many bene?ts. It has allowed riverside organisms and wetland wildlife to thrive in the river and on the ?oodplain, playing a huge part in nature conservation. Fisheries now have an greater numbers of ?sh of different species. Due to installation of vegetation, there has been an increased interception of pollutants. Sediment has also been naturally settling on the ?oodplain and river bed. The restoration also acts as a ?ood defence. Due to the enlarged ?oodplain and the backwaters created by the old river, additional ?ood storage has been created. The restoration has also helped the attraction of recreational activities near the river. The natural landscape created by the restored river has received strong public support. Therefore, the River Restoration Project has been a success for the River Cole. This is thanks to the clear environmental bene?ts. Although the changes had to be paid for, there are economic bene?ts to the restoration. The surrounding landscape is now seen as a much more pleasant environment and so people are more likely to pay for recreational activities to do with the river. The social bene?ts are also clear. The cleaner waters of the river are both aesthetically and morally pleasing to general society. This leads to happier locals as their river is being taken care of.