A. A development proposed for a one-hundred-year floodplain, where water surface elevations are available but no floodway is delineated, may not significantly increase flood velocities or depths or generally alter patterns of flood flow. The provisions of Sections 15.28.320, 15.28.330 and 15.28.340 shall apply to these areas. The floodplain administrator may require a permit applicant to furnish additional hydraulic data before acting on a permit application for such a floodplain. The data may include, but are not limited to, any of the following:

1. A hydraulic study documenting probable effect on upstream, downstream or adjacent property owners caused by the proposed development; or

2. The calculated increase in the one-hundred-year floodwater surface profile caused by the proposed development.

B. Permits for such proposed development may be modified or denied if the additional information shows that the proposed use would cause an additional flood hazard to adjacent property or significantly increase flood heights. A significant increase in flood heights is one-half foot unless existing or anticipated development in the area dictates a lesser amount of allowable increase. (Ord. 576 § 6(D), 1994)