The county legislative body may, as often as necessary, appoint commissioners to:
(1) Examine the watercourses in the county, to see that the local erections allowed in the watercourses are conformable to law, and that one fourth (¼) of such watercourses, including the deepest portions, are left open for the free passage of fish;
(2) Lay off slopes of dams when necessary, determining the time they shall be left open; and
(3) Return a plan of the stream, and the falls, dams, and other erections on the stream, when deemed necessary.