Ecosystems at Risk: Limestone caves
4c. Catchments

Karst is the term used for the distinctive landforms of catchments on limestone and other soluble rocks. Karst landforms are formed by solution processes and are characterised by underground drainage where water has dissolved the rock forming caves but the general surface landform is dominated by gorges and sink holes which capture surface streams leaving dry valleys. The topographic map below displays some of these features with a gorge in the area of the Natural Bridge (a cave where all of the Yarrangobilly River runs through a hillside) and sink holes capturing creeks.

		Scale: each grid is one kilometre contour interval 10 m Source: © Land and Property Information Panorama Avenue Bathurst 2795
Above: Gorge and cave just upstream of the Natural Bridge. Right: Gorge downstream of the map area. The Yarrangobilly River has formed the gorge by cutting through the limestone bedrock through the processes of dissolving the limestone (chemical weathering), undercutting the gorge walls on the outside of meanders and the removal of material by the river (erosion).
	Sink hole, Glory Hole Cave, Yarrangobilly.     ecology