The board of supervisors of any county after having constructed improvements under this chapter is hereby authorized and empowered to operate and maintain such harbor facilities and to make and enforce all rules and regulations necessary for such operation and maintenance, and such board may also fix and collect charges for the use of such facilities and may, in its resolution or order directing the issuance of bonds under this chapter, irrevocably pledge to the payment of the principal of and the interest on such bonds the net income and revenue resulting from the operation of such facilities.