Section 25.86.010 Findings of Fact.

Chapter 25.86 FLOOD PLAIN MANAGEMENT AND OVERLAY ZONES

1. The flood hazard areas of the City of Sioux City, Iowa are subject to periodic inundation which can result in loss of life and property and health; and, safety hazards, disruption of commerce and governmental services, extraordinary public expenditures for flood protection and relief, and impairment of the tax base; all of which adversely affect the health, safety, and general welfare of the community.

2. These losses, hazards and related adverse effects are caused by

a. The occupancy of flood hazard areas by uses vulnerable to flood damages which create hazardous conditions as a result of being inadequately elevated or otherwise protected from flood and

b. The cumulative effect of flood plain construction on flood flows, which causes increases in flood heights and flood water velocities.

3. This chapter relies upon engineering methodology for analyzing flood hazards which is consistent with the standards established by the Department of Natural Resources. This methodology consists of a series of interrelated steps including:

a. Determination of flood magnitudes and the corresponding flood frequencies by statistical and engineering calculations which permits a consideration of such flood factors as expected frequency of occurrence, area inundated, and depth of inundation.

b. Calculation of water surface profiles based upon a hydraulic engineering analysis of the capability of the stream channel and overbank areas to convey flood flows.

c. Computation and delineation of a floodway, an area which must be reserved (no obstructions) for conveyance of flood flows so that flood heights and velocities will not be substantially increased by future encroachment on the flood plain. (Ord. 89/T-7348)