1.

The term fluviokarst is used to describe a karst landscape in which the dominant physical landforms are valleys initially cut by surface streams that have been partly or completely diverted underground by subsurface conduit piracy.

Field, 2002

2.

fluviokarst : A predominantly karst landscape in which there is much evidence of past or present fluvial activity.

Monroe, 1970

CAUSE past or present fluvial activity
CONTAINS the dominant physical landforms are valleys