River caves are caves containing a cave river. Although they are much harder to explore than dry caves (because of the cold water) some of the most famous early cave explorations were made into river caves. The idea of those explorers was often, to discover the subterranean path of the water. This sometimes had financial and political background, as knowledge about the water was necessary for drinking water supply, for water mills and for fishing.
The first modern cave exploration was made 27-JUN-1888 by Eduard Alfred Martel. and is often called the birthday of Speleology. It was the exploration of the underground river of the Abîme de Bramabiau. Martel made the first through-crossing of the plateau de Camprieu in Southern France, following the cave river.
The water of the river works on the erosion of the rock. Sand and gravel in the water is transported away, but while it is pushed around it works like sandpaper, polishing the rock. Bulders up to the size of a head are carried away by the water, turned around by whirling water, and hit against the walls and the cave floor. The result looks similar to gorges: round forms, dolly tubs and narrow, high, irregular passages.
Water erosion is a typical mechanism in the forming of karst caves. But it is based on mechanical destruction, not on the chemical dissolving of water, thus it is not dependent on soluble rocks. River caves can be formed in non soluble rocks, although this is rather rare.
The cave river was once seen as the main cave forming mechanism, so caves with a river were called active caves in many languages, expressing that they are in the first stage, the stage of formation. Today the theory of cave formation by flowing water is a little outdated. It is still an important mechanism, but because of the impressive surfaces it produces, its importance was exaggerated.
Caves start their formation below ground water level based on chemical solution. The second stage in cave development is the river cave stage. Then, in the third stage, the cave becomes dry and gets filled with speleothems.