That the board of directors may appoint or employ one or more engineers and prescribe their duties, and may cause all such surveys, plats, estimates, specifications and reports to be made as may be required to determine whether the construction of any levee is necessary to prevent the overflow of any natural watercourse or other work or improvement should be done within the district, or to determine and fix the height and location of any pier, bridge or other structure permitted to be placed in or across such watercourse, or to direct and supervise any work or improvement ordered to be made.