I’m often asked “What is a chalk-stream?” It is a difficult question to answer quickly. Chalk-streams are created by geology, the geology of England is complex and chalk-streams vary so much in character. The important thing to understand is that while there might be chalk in other parts of the world, only in England and France do you find deep layers of chalk, close to and at the surface, polished clean but not worn away by glaciers and weathering. This creates the rivers we know as chalk-streams. The subtle differences amongst them are also determined by geological history: whether the river flows across clean chalk and then younger rocks and deposits (generally these streams flow south and east) or across older rocks (generally these flow north and west and are much shorter rivers), whether the river rises from chalk that was covered by glaciers (Yorkshire and Lincolnshire) or chalk that was on the very edge of the glaciers (Norfolk) or in the periglacial zone further south.
I was assisted on this index by Dr Haydon Bailey, a geologist with a keen interest in chalk, and we have started to sketch out some geological categorisations that help to shed light on those differences and show that what we have, in reality, is a spectrum of pure chalk-streams and chalk-influenced rivers.
The index is certainly not complete. Already I have been promised updates for Buckinghamshire. Please send feedback to me at the contact email on this blog and I will include corrections and additions and credit the contributors. In the meanwhile, I hope this index proves a useful resource for those who are interested in the conservation of English chalk-streams.
To make sense of the lay-out, please read the notes on the lay-out at the head of the index. You won’t get how it works otherwise!