The Loose Stream is the central feature of the conservation area and is responsible for the shaping of the valley. It rises from springs located at Langley and flows west and then north through the Valley until it reaches its confluence with the River Medway at Tovil.

Streams contain a range of features; the more varied, the greater the overall wildlife diversity. These features include shallow reaches, deeper pools, islands, eroding vertical banks and muddy margins with beds of emergent plants all of which are present on the Loose Stream.

The water quality of the stream has been classified by the Environment Agency as ‘very good’ close to its confluence with the River Medway at Tovil. Although no information regarding aquatic invertebrate species is available the combination of good water quality and the presence of a range of features is likely to result the in presence of a wide variety of species.

The Site of Nature Conservation Interest description states that the stream contained a "good range of common marginal and aquatic plants". This is likely to be due to the fast flowing water and lack of intensive agriculture on the surrounding riparian land.

Rivers and streams have been highlighted in the Kent Biodiversity Action Plan as a key habitat. The target is to ensure that they support the full potential range of flora and fauna.