It shall be the duty of said board of directors to determine what work is necessary to be done, or levees to be constructed, to protect their district from overflow or inundations or from bank erosion, wash or cutting from rivers. Whenever said board of directors shall deem it necessary they shall cause accurate surveys, maps and profiles thereof to be made of levees or other works to be constructed or repaired, and estimates and calculation of the costs of such work to be made by some experienced, suitable and competent engineer, who shall make a written report of the same, showing the amount, character and kind of work to be done, the exact location and probable cost thereof, and return the same, with all plans and specifications, to the board of directors.