N.H. Rev. Stat. § 1:8
No person shall willfully or maliciously disturb or injure, or, except as herein provided, remove, obliterate, deface or cover up any monument or mark designating a boundary line between the state of New Hampshire and an adjoining state. Any person desirous of removing and/or replacing any such monument or mark may apply to the commissioner of the department of transportation. In addition, no person shall begin or attempt to begin any alteration or improvement of the banks or bed of the Connecticut river, the erection of any building, dam, or other structure upon the banks or bed of said river or any other operations which will affect the waters or flow of said river so as to make difficult the ascertaining of the location of the boundary line between this state and the state of Vermont without first applying to the commissioner of the department of transportation.
RSA 1:8
2000, 35:1, eff. Jan. 1, 2001.