Wherever and whenever a river is or shall be the boundary line or part of the boundary line between two counties, or it, or its tributaries or outlet or part thereof, flows through parts of two counties, and the waters thereof have in the past been the cause of damage, by inundation or otherwise, to the roads, bridges or other public property situate in or to other public interests of both such counties, or the flow of such waters shall have alternated between the said counties so at one time or times such waters shall have caused damage to one county and at another time or times to the other county, and it shall be deemed by the boards of county commissioners of both counties to be for the public interests of their respective counties that the flow of such waters be definitely confined to a particular channel, situate in whole or in part in either county, in a manner calculated to prevent such alternation or to prevent or lessen damage in the future, it shall be lawful for the two counties, and their boards of county commissioners are hereby empowered, pursuant to resolution, to enter into a contract in writing in the names of the respective counties for the purpose of settling all disputes in relation to any such situation, and providing ways and means for the control and disposition of such waters. Any such contract may provide:
(1) That it shall be operative in perpetuity, or only for a term of years or other measure of time to be specified therein.
(2) The amount of money to be expended by each county during each year of the life of said contract, or such other method of determining the amount of expenditure or dividing the financial burden as may be agreed upon.
(3) That an annual tax shall be levied, at the same time and in the same manner as other county taxes are levied, each year during the life of the contract, by the county commissioners of each county. The annual tax herein provided for need not be levied at the same rate for each county, but shall be at such rate in each county as will produce annually the amount of money for each county as is required for the fulfillment of the contract on its part: PROVIDED, HOWEVER, That in no event shall any such tax levy by either county exceed twenty-five cents per thousand dollars of assessed value for any one year.
(4) That the general scheme for the improvement of such river shall be as stated in such contract, but by consent of the contracting parties, pursuant to resolution of each board of county commissioners, such scheme may be modified from time to time during the life of the contract. The contract may but need not provide the details of such scheme, but must designate the general purpose to be accomplished. So far as details are not specified in the contract, same shall be for future determination by joint action of the two boards of county commissioners. Any such contract may be subsequently modified or abrogated by mutual consent evidenced by separate resolution of both boards of county commissioners.