All persons, associations and corporations engaging in improvement of the navigation of any river or watercourse, as authorized in ORS 780.010, may enter upon the lands adjacent to any river or watercourse for the purpose of cutting timber, taking rock, gravel, dirt and other materials necessary for the prosecution of the work of such improvement, and pass over adjacent lands with means of transportation proper for conducting the work contemplated by ORS 780.010, doing as little damage as possible, subject only to the payment of such damages as may be assessed according to law.
ORS 780.020