Doesn't appear Ohio follows that type of rule.  Under Ohio law, a riparian owner has no right to impede the natural flow of water by filling such portion of his or her land as is covered by the flowing waters of the stream at any stage which may be reasonably anticipated, thus narrowing the channel.  But, here, it wasn't Chris that did anything to impede the flow of water, it was the beavers.  I was unable to find any statute, or other law, that places a duty on a riparian owner to maintain the water-way for the benefit of downstream land owners.

Interestingly, there was a case in Ohio where a landowner, upstream, sued for the right to go onto the land of a downstream owner to remove a beaver dam that was causing flooding on his land.  He used a statute that gave such a right to landowners to clear out random, naturally accumulating soil deposits, debris, and the like. He lost - the court said that the beaver dam was not a random occurrence - it was the result of "busy beavers."  The statute has since been repealed, anyway. 

My friend was considering the possibility of a private nuisance suit, but that is a tort that requires an act that wrongfully interferes with another's interest, use, or enjoyment of land.  Absent an affirmative duty to maintain the stream, I don't think that a lack of action would be actionable.

There were also a few cases where land owners sued the Dept. of Natural Resources for introducing beavers into the wildlife population that caused flooding from the dams they built.  There, the introduction of the beavers into the habitat was an affirmative action, but the landowners lost those cases, too.  Mainly, I think it was due to problems proving causation.

Dam beavers!  (pun intended)

Best,
Robert A. Franco
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