Much of the landscape is relatively flat – the lower reach of the Colne forming the centre of the park. Almost all the land is only AOD, with a mixture of soils, including occasionally wet, loamy soils and clayey soils, and a small amount of naturally slightly acid heath. Passing through the park is the Colne Valley Trail or Colne Valley Way, which forms a major section of the London Loop and connects to the Hertfordshire Way north of Watford. East of the village of Denham, and west of the villages of Cowley and Harefield, and the town of Uxbridge, the Colne Valley regional park contains a mixture of farmland, woodland and water, of river and canal and over forty lakes, which help to regulate the flow of the major Thames tributary and provide fish for angling. The park is a regionally important place of recreation and is internationally important for wildlife. Large areas are open to the public or accessible through a network of paths. Paths stretch from Staines in the south to Rickmansworth in the north through the alluvialmeadows in the valley of the River Colne. Popular attractions include Black Park, Chiltern Open Air Museum and the conservation area of Little Britain by the Grand Union Canal, Cowley. Elevations nearby range from AOD on steep hillsides in Harefield, Denham and Rickmansworth, to at Staines Moor. In the south, the area includes Staines Moor, the Staines Reservoirs and the King George VI Reservoir. The reservoirs support nationally important wintering populations of tufted ducks, pochard, goosander and goldeneye.
HS2
In October 2017, activists set up a protest camp at Harvil Road to oppose the construction of High Speed 2. HS2 Limited plans to build the Colne Valley Viaduct which is long. The activists documented alleged environmental damage by HS2 workers over an eighteen month period, voicing concern about the destruction of wildlife habitats and the possibility that an aquifer supplying drinking water might be affected. The Woodland Trust called in May 2019 for the clearance of trees at Colne Valley to be halted. A prosecution against two women for aggravated trespass collapsed in July 2019 because HS2 Limited could not prove it owned the land in question. In January 2020, HS2 began evicting the protest camps. A couple living in a farmhouse on the route of the railway lost a seven year legal battle in July 2020 and were compelled to move out after HS2 Limited compulsory purchased their home on Dews Lane.
