Dry valley

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A dry valley is a valley found in either Karst (limestone) or chalk terrain that no longer has a surface flow of water. There are many examples of the latter along the North and South Downs in southern England. Examples include the Alkham Valley near Dover, and the Hartley Bottom and Fawkham valleys near Dartford in north Kent.details

There are two theories as to how they were made, the first that the water table was once much higher, while the other is that during the ice age the area had tundra like conditions. The normally permeable chalk would have been made impervious by permafrost, thus allowing rivers to flow.

During the ice age the water was not able to flow through the limestone because it was frozen. But when the ice melted, the water on the surface of the land carved wide valleys. Today these valleys don't have any rivers because it sinks through into the limestone and flows underground in caverns. Hence why they are called 'Dry Valleys'

There are many examples in the Peak District. A notable example is the valley of the River Manifold which is dry, except in spate, from Wetton south for several miles.