Here are a couple possibilities of the restrictions that may be on the land:
First, there could be county zoning ordinances based on the designation of a wetland or a floodplain. Where I am in Indiana, floodplain land is treated similarly to ag land, but with a bunch more restrictions on what you can build.
Second, the
state water department may place restrictions on the land. In my experience, these primarily focus on making sure you have "compensatory water storage" if you do any filling/digging on your property. They don't want you to fill in your flooded property and cause the people downstream to flood.
Third, the property might be in the federal
wetlands reserve program. In that case there might be a permanent or 30 year easement on the property that limits what you are able to do with it.