The park's used to periodic flooding, after getting hit in 1996 and 1972, which is evident in the oddly-cheerful report on their site. "Oh Yeah! We've got a bit of water right here at Knoebels!"
The Knoebel family is nothing if not resilient and optimistic, though. While the park's "closed indefinitely" at this point, Dick Knoebel has already said he's looking to get as much open as he can for this weekend (the all-important Fourth weekend!)
Knoebels has always been known to take their misfortunes and turn them into something good. After the 1972 flood, the floor of the park's roller skating rink was too warped and buckled to restore, so the park took the building, bought some dark ride stunts from other parks, and built their Haunted Mansion ride. The Haunted Mansion is excellent. Currently the park's major project is a new build of an old design: The Flying Turns bobsled ride. I wonder how the flood will affect the construction plans.
I love Knoebels, and as I can't see actually getting out there any time soon, I miss the park and its amazing charm. But I hope they get all the stuff out of the muck and water real quick. Sounds like they know they can.