Why is chalk important for the Chilterns?
Chalk streams are a characteristic and attractive feature of the Chilterns landscape. 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.
Which country has the most chalk streams?
Their pure, clear, constant water from underground chalk aquifers and springs, flowing across flinty gravel beds, make them perfect sources of clean water – and ideal for lots of wild creatures to breed and thrive. We’re lucky because the majority of the world’s chalk streams are found in England.
How many chalk streams are there in England?
Of the 210 rivers classified as chalk streams globally, 160 are in England.
Where are chalk streams in the UK?
Only 200 chalk rivers are known globally, 85% of which are found in the UK in southern and eastern England. Classic examples include the rivers Itchen and Avon in Wessex and the river Wensum in Norfolk.
Why are chalk streams special?
So, what IS so special about chalk streams? These distinct rivers originate from springs where chalk forms the bedrock. As chalk is permeable, water is able to percolate through the ground to the water table below resulting in chalk streams receiving little surface runoff.
How many chalk streams are in the Chilterns?
The Chilterns AONB (Area of Outstanding Natural Beauty) is home to nine significant chalk streams, see Figure two.
What is the largest risk to chalk streams?
There are a host of reasons why our chalk streams, and other rivers, are at risk. Agricultural pollution, a decline in native species and particularly invertebrates, the introduction of non-native invasive species, development and population growth, and the fact that we simply use, and waste too much water.
Is the river Lea a chalk stream?
While the lower Lea remains somewhat polluted, its upper stretch and tributaries, classified as chalk streams, are a major source of drinking water for London.
What is special about a chalk stream?
As chalk is permeable, water is able to percolate through the ground to the water table below resulting in chalk streams receiving little surface runoff. This provides them with beautifully clear water that contains little organic matter and sediment. Chalk streams are prominent features in our landscape.
How are chalk streams formed?
Chalk-streams form when rain falls on chalk down-land and seeps through fissures in the rocks, coalescing into trickles and rivulets. Where the fissures have widened with erosion the rivulets may even gather further to form underground streams.
How do chalk streams form?
Chalk-streams form when rain falls on chalk down-land and seeps through fissures in the rocks, coalescing into trickles and rivulets. Layers of marl and flint interrupt the chalk, and where they do water can flow laterally along these seams for miles. The seams may run counter to the hills above ground.
What is special about chalk streams?