Slade Brook

Also within

Gloucestershire County WYE VALLEY (England) Scenic Area

Condition (Natural England)

Habitats

Fast flowing river and stream

Geology & landscape

Geological Period: Carboniferous · Rock Type: Carboniferous Limestone, Limestone, Tufa

Landscape processes: Karst

Description

Description Slade Brook is nationally important for its active tufa forming stream system. The stream supports a series of tufa dams with associated plunge pools and connecting stream sections that are a result of the combination of a series of complex physical and chemical processes within the stream. This system of tufa dams forms the longest series of such structures representing this feature in Britain. General description Slade Brook is a small braided stream that rises in woodland on the Carboniferous Limestone in the Forest of Dean and flows for two kilometres to join the River Wye. The area is a kilometre section of the stream from its spring sources to a downstream point that includes the main area of tufa deposition. Rain water percolating down joints and sinkholes in the Carboniferous Limestone of the surrounding catchment area is enriched with dissolved calcium carbonate. On reemerging at numerous springs along the Slade Brook, removal of carbon dioxide from the water brings about the precipitation of calcium carbonate. The main deposition of calcium carbonate within the Slade Brook is as a series of dam like structures, constructed of tufa, within the channels. This formation takes place over a stretch of approximately 700 metres. Vegetation, including twigs and branches which fall into the stream, combined with the growth of the algae Vaucheria sp. and mosses for example Palustriella commutatum and Pellia epiphylla, are believed to assist in the deposition process and formation of the dam structures. The slowing of the flow of the water and the process of photosynthesis promote the removal of carbon dioxide from the water and the debris and vegetation thereby become the focus for accumulation of tufa. Actively forming tufa dams are rare features and their processes of formation and maintenance are poorly understood. However, they hold the key to understanding the origins of fossil tufa dams and the large number of dams present in this assemblage about 60 holds great potential for improving our current understanding of these features – both modern and fossil. Other information, The site lies within the Dean Plateau and Wye Valley Natural Area and within the Wye Valley Area of Outstanding Natural Beauty.

Species mentioned

Plant communities