The WA Supremes are looking into a navigable waters case. Somebody filled/raised their land on Lake Chelan. At one time, it was all upland. Then, a dam was built that seasonally raised the lake to flood the land. So, the landowner filled the (former) upland so that it remained always upland, and therefore buildable. The state was sued for allowing this because it "took away navigable waters from the people and the state has a trust responsibility to protect the waters".

It gets really convoluted in streams that regularly wander across floodplains.