The board of directors shall have charge of all embankments and other works or improvements constructed to prevent the overflow of any natural watercourse within their respective districts, and to protect and repair the same shall have power to employ guards and laborers, and to protect and superintend such work as may by them be deemed necessary, but all money expended for such purpose shall only be paid out of the general fund provided by the levy of a general tax on all the property of the district as hereinbefore authorized.