Rivers lose stream flow to underground regimes through dolines (sinks) or other defects in the rock. As more water enters the underground systems, the solution action increases the size of the opening and more water is lost. On the surface downstream from this sink the surface river will not flow unless flooding or high runoff create some intermittent flow through the valley. Such a valley is called a semi-blind valley.
Once the river cuts deep enough so that all water flows into the sink, the stream no longer produces any intermittent flooding and the term used is blind valley.