The boundaries of river areas described in Appendix Q-6 of these regulations as a uniform distance from a river bank shall themselves wind and turn as the river does. Terminal boundaries shall be lines perpendicular to the flow, extending through the terminal points in Appendix Q-6.

The agency and the Commissioner of Environmental Conservation may, after public hearing, amend the boundaries of any river area located in the Adirondack Park. No public hearing is required in the case of boundary amendments occurring as part of approval of a local land use program or in connection with amendments clarifying or providing a more readily identifiable river area boundary and not materially affecting the river area.

Distances shall be measured horizontally from the mean high water mark of the river. Upon request of any person having a legal interest in property contemplating land use or development or subdivision thereon, the agency shall determine the river area boundary, or the the mean high water mark at relevant points of the river involved pursuant to the procedures set forth in section 571.3 of these regulations.