Whenever bonds are issued by the bridge and park commission under this chapter, an amount of the income, revenues or grants from all sources received by the commission, after the deduction of the necessary expenses of operating and maintaining the facilities and properties of said commission, shall be pledged in an amount sufficient for the purpose of the payment of the principal of and interest on said bonds as the same shall mature and accrue. The resolution authorizing such bonds shall contain such covenants as may be deemed necessary or advisable for the assurance of payment of the bonds thereby authorized and may contain such restrictions upon the issuance of additional bonds by the commission as may be deemed advisable. Such resolution may direct the depository in which funds of the commission are held to remit to the paying agent designated for such bonds specified periodic remittances without further direction or authorization by the commission and may provide for the establishment of funds for operation and maintenance, for depreciation, for the payment of principal and interest and for contingencies, and may provide for the setting aside of amounts over and above those necessary for current debt service so as to provide and produce a reserved fund to meet any possible deficiency in future years.