If Devils Lake rises and overflows through the Tolna Coulee and into the Sheyenne RAiver, the Tolna Coulee could erode, causing flooding downstream.
How much flooding and how Valley City, ND and other communities will be affected remains unclear. Also, if the Couldee Erodes as Devils Lake Falls, what will the final elevation of Devils Lake be? Athe Corps’ operating plan will determin the elevation of Devils Lake.
After the erosion of the Tolna Coulee, Devils Lake might end up at an elevation 1450′ MSL. or the lake may fall to 1448′ MSL.? How about 1446′ MSL?
To understand how the Tolna Coulee will be operated, read the Corps’ “standing instructions” for the operation of the Tolna Coulee control structure.