Any city acting under special charter, which is bounded in part or divided by a river, may improve said waterfront by constructing retaining walls, filling, grading, paving, macadamizing, or riprapping the same and may improve and beautify its waterfront and the river bank and nearby uplands and made and reclaimed lands in such city; and to pay for such improvements the council of such city is empowered to levy a tax of not exceeding six and three-fourths cents per thousand dollars of assessed value per annum on the taxable property thereof, the same when collected to be known as the levee improvement fund. The proceeds of such fund shall be used exclusively for said purposes.