Where separate works or items are consolidated in River and Harbor Acts and an aggregate amount is appropriated therefor, any balances remaining to the credit of the separate works or items may be transferred to the credit of the corresponding aggregate amounts appropriated for the consolidated items, and the amounts appropriated or transferred shall, unless otherwise expressed, be expended in securing maintenance and improvement according to the respective projects adopted by Congress, after giving due regard to the respective needs of traffic. The allotments to the respective works consolidated shall be made by the Secretary of the Army upon recommendations by the Chief of Engineers. In case such works or items are consolidated and separate amounts are given with each project, the amounts so named shall be expended upon such separate projects unless, in the discretion of the Secretary of the Army, another allotment or division should be made of the same. Any balances remaining to the credit of the consolidated items shall be carried to the credit of the respective aggregate amounts appropriated for the consolidated items.