Some food for thought...
One of the dozens of properties that we researched for a pond was a similar situation. The pond would be adjacent to a creek. The issues came up relative to the hydrology of the soils in the bottom land. The NRCS checked the maps and said that the entire area at the level of the creek was mapped as wetland. It ran up into the surrounding region at elevations higher than the creek. Since the pond dam required reaching down close to the creek area, it would have been into the higher regions of what was mapped as wetland. I asked how soils that were 10 - 20 feet higher than the creek could be considered wetland? It all came down to hydrology. It gets complicated, but, in layman's terms, something to do with the amount of moisture in the soils for a given period thru the year. Anyway, they told me I was messing with stuff that would need DNR and likely ACoE approval. I made those phone calls to both the DNR and ACoE and it started gettin' scary: permits and mitigation of the affected wetlands (find another comparable area and convert it to wetlands). The potential hoops shut it down quickly for me.
