[Billy Wobble Dagger]

Certainly the water vole and their burrows are protected by law. The Scottish wildlife trust should be informed quickly so they can carry out surveys to find the extent of the water vole colony. Unfortunately this alone won't save the meadow. Good land management for water voles says keep a minimum of 3m from the river bank untouched or fenced off.
Check to make sure the field isn't a SSSI, they can be as small as a field and if there are some rare plants in the meadow they maybe protected, unfortunately as we've seen with the SSSI and the golf course in Aberdeen even these aren't safe. Finally public opinion and outcry might save the day. Certainly inform the wildlife trust though

Good luck and welcome to WAB.

BWD