Government surveys land all the time to set, clarify and verify boundaries. With respect to federal land this is no different. The river and the river bed is federal property. The definition of the bed itself is what's in question. This must be clearly defined to prevent private owners from being responsible for federal property. If there is an alternative motive behind this it will show after the survey is complete but the survey must be completed properly and be a consistent policy for all federal land and property.