Every such board of supervisors shall have power to make general rules and regulations as to the kind of bridges, and the mode of constructing the same over any such stream, as mentioned in section 21 of this act, when such stream shall not be navigable for boats or vessels of 15 tons burden, or to grant permission for building the same, without the notice or hearing above provided, in such manner as shall be judged proper with reference to the passage of boats, rafts and timber.