Chalk streams are a globally rare habitat, confined to north west Europe and to the UK in particular. In fact more than 85% of all the chalk streams in the world, are found in England – many of them in Hertfordshire.
Chalk streams are important habitats for wildlife and support a massive range of plants and animals. They are home to some of our most threatened plants and animals, such as the water vole and brown trout.
You can find an account of the geology underlying chalk streams, and in particular two examples in East Hertfordshire, on the web site of the Friends of Rib & Quin.