Drainage systems shall have adequate capacity to convey the storm water runoff from all upstream tributary areas through the development under consideration for a storm of 100-year design period calculated on the basis of the upstream land in its present state of development. An allowance, equivalent to the reduction in flow rate provided, shall be made for upstream detention when such upstream detention and release rate have previously been approved by the Department of Planning and Building after review and recommendation of the Plan Commission and evidence of its construction can be shown.
(Ord. No. 1708, 6-13-07)