A dry valley is a valley found in either karst

KARST

Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...

 (limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

) or chalk

Chalk

Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

 terrain that no longer has a surface flow of water.

There are many examples of the latter along the North

North Downs

The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. The North Downs lie within two Areas of Outstanding Natural Beauty , the Surrey Hills and the Kent Downs...

 and South Downs

South Downs

The South Downs is a range of chalk hills that extends for about across the south-eastern coastal counties of England from the Itchen Valley of Hampshire in the west to Beachy Head, near Eastbourne, East Sussex, in the east. It is bounded on its northern side by a steep escarpment, from whose...

 in southern England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. Notably the National Trust-owned Devil's Dyke

Devil's Dyke, Sussex

Devil's Dyke is a V-shaped valley on the South Downs Way in southern England, near Brighton and Hove. It is part of the Southern England Chalk Formation.Devil's Dyke is on the way to Brighton and is a big hill at the side of the road.-Geological history:...

 near Brighton

Brighton

Brighton is the major part of the city of Brighton and Hove in East Sussex, England on the south coast of Great Britain...

 covers some 200 acre (0.809372 km²) of downland scarp, and includes the deepest dry valley in the world - created when melting water eroded the chalk downland to the permafrost layer after the last ice age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

. The three-quarter mile long curved dry valley is around 700 feet (213.4 m) in height and attracts tourists with its views of Sussex, Hampshire and Kent.

Other examples include the Alkham Valley

Alkham Valley

The Alkham Valley is in the Kent Downs , an Area of Outstanding Natural Beauty, in South East Kent, England. The valley, a lies between Folkestone and Dover....

 near Dover

Dover

Dover is a town and major ferry port in the home county of Kent, in South East England. It faces France across the narrowest part of the English Channel, and lies south-east of Canterbury; east of Kent's administrative capital Maidstone; and north-east along the coastline from Dungeness and Hastings...

, and the Hartley Bottom and Fawkham valleys near Dartford

Dartford

Dartford is the principal town in the borough of Dartford. It is situated in the northwest corner of Kent, England, east south-east of central London....

 in north Kent.

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

Tundra

In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...

 like conditions. The normally permeable chalk would have been made impervious by permafrost, thus allowing rivers to flow without carving into it. Today these valleys don't have any rivers because water sinks through into the limestone and flows underground in caverns.

There are many examples in the Peak District

Peak District

The Peak District is an upland area in central and northern England, lying mainly in northern Derbyshire, but also covering parts of Cheshire, Greater Manchester, Staffordshire, and South and West Yorkshire....

 and the Yorkshire Wolds

Yorkshire Wolds

The Yorkshire Wolds are low hills in the counties of East Riding of Yorkshire and North Yorkshire in northeastern England. The name also applies to the district in which the hills lie....

. A notable example is the valley of the River Manifold

River Manifold

The River Manifold is a river in Staffordshire, England. It is a tributary of the River Dove ....

 which is dry, except in spate, from Wetton

Wetton, Staffordshire

Wetton is a village in the Peak District National Park, North Staffordshire, at the top of the east side of the Manifold Valley. The population recorded in the 2001 Census was 157. This article describes the location, some of the main features of the village, and a number of places of historical or...

south for several miles.