For the purpose of preserving any ditch, drain, dyke, levee or other work constructed or erected under the provisions of this chapter the board of supervisors may appoint an overseer or overseers of the district who shall hold their positions at the will of the board. Such overseer or overseers shall keep the canals, ditches, drains, levees, dykes and other works of the district in good repair, remove all obstructions from canals, ditches, drains or watercourses within or without the district that may affect the works of the district and perform such other duties as may be prescribed by the supervisors.