How does a normal stream valley develop into a dry valley in fluviokarst terrain?

In fluviokarst terrain, a normal stream valley evolves into a dry valley through the progressive diversion of surface water into underground drainage systems.1

The process follows these stages:

• Initial Downcutting: A stream gradually deepens its channel until it intersects underlying limestone or dolomite beds.1
• Subsurface Diversion: Water begins to leak into the bedrock through joints and fractures, which slowly enlarge into cave systems.1
• Flow Reduction: As these cave passages grow, they capture an increasing portion of the surface stream's flow. Initially, the stream may only run dry during low-flow seasons.1
• Total Abandonment: Over time, the cave system expands sufficiently to carry even major flood waters. The surface channel remains dry year-round, and because no water flows through it to continue erosion, the valley ceases to deepen.1

Once a valley becomes dry, its banks may collapse, the channel becomes overgrown with vegetation, and shallow sinkholes often develop on the valley floor.1