The Commissioner of Energy and Environmental Protection is authorized to provide for the payment by the state of the total cost of any flood or erosion control system when such system is for the benefit of state parks or state-owned land. When such system is for the benefit of municipally owned littoral or riparian property or littoral or riparian property held by the municipality under lease for a term not less than twenty-five years, the commissioner is authorized to pay two-thirds of the cost of the system and the remaining one-third shall be the obligation of the local authority. If the project will benefit privately owned littoral or riparian property, the cost shall be prorated on the basis of two-thirds of the total cost to such local authority and one-third of the cost to the state. If the system involves benefit to both municipally owned or leased and private littoral or riparian property, said commissioner shall determine the extent of the financial participation of the state as well as that of the local authority on a shorefront or stream-front percentage basis for each type of property benefited.