What I've heard in the past is that the park can't expand the dikes without permission from the U.S. Fish and Wildlife Service since the park borders the MN River Valley National Wildlife Refuge, and that permission is unlikely to be forthcoming since expansion of the dikes would affect something related to the waterfowl that inhabit the river in the area by the park (I can't remember exactly what). Expanding the dikes is probably the single best thing the park could do with regards to long-run planning but it's probably impossible. It's frustrating since without the flooding issues, VF has one of the biggest expansion potentials of any park in the chain (and maybe the country) in terms of the unused land around it that CF owns.