From the Daily Paul:
Since 1803 when the Louisiana Purchase was completed, there has been a controversy over the boundary between Oklahoma and Texas. The boundary is supposed to be the vegetation line on the south side of the Red River. But the River has moved over time. The problem is the definition of that boundary line - Oklahoma and Texas each use different semantics to define it. And the BLM is finding ways to use the disputed words to give them the ability to seize the land.
According to the BLM, the Red River is always Accretion (gradual accumulation of sediment) to the south, and always Avulsion (rapid formation of a new river channel) to the north. So according to the BLM, the boundary only moves one direction, never in the direction that favors the ranchers. They are looking to re-draw the entire portion of the Red River boundary. That includes 90,000 acres of land along a 116 mile stretch of the river.