Where legal descriptions say ‘to the center of the river’ or ‘to the riverbank,’ Larimer County considers that gradual changes redefine the shape of the parcel. But the sudden changes caused by a flood event do not change the parcel shapes and sizes.
From the Larimer County Assessor’s Office:
“When a property boundary is legally described by reference to a river, if the course of the river changes slowly over time it is called accretion and the boundary line moves with the river. On the other hand, a sudden or “violent” shift in the course of the river is called avulsion and the boundary line does not change. Changes in the course of a river due to a sudden flood event qualify as avulsion, and property boundaries are unaffected by the change in course.”