17.30.040 Findings of fact.
(a) Flood Losses Resulting From Periodic Inundation. The special flood hazard areas of the City are subject to inundation which results in loss of life and property, 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 public health, safety and general welfare.
(b) General Causes of the Flood Losses. Flood losses are caused by the cumulative effect of development in any delineated floodplain causing increases in flood heights and velocities; and the occupancy of flood hazard areas by uses vulnerable to floods, hazardous to others, inadequately elevated, or otherwise unprotected from flood damages.
(c) Methods Used to Analyze Flood Hazards. The flood insurance study (FIS) that is the basis of this chapter uses a standard engineering method of analyzing flood hazards, which consists of a series of interrelated steps:
(1) Selection of a base flood that is based upon engineering calculations which permit a consideration of such flood factors as its expected frequency of occurrence, the area inundated, and the depth of inundation. The base flood selected for this chapter is representative of large floods, which are characteristic of what can be expected to occur on the particular streams subject to this chapter. The base flood is the flood that is estimated to have a one percent chance of being equaled or exceeded in any one year as delineated on the current effective Federal Insurance Administrator’s FIS, and illustrative materials documented in the interior drainage area maps of the Topeka levee certification package, and any future revisions thereto, and illustrative materials dated September 29, 2011, as amended and any future revisions thereto.
(2) Calculation of water surface profiles that are based on a standard hydraulic engineering analysis of the capacity of the stream channel and overbank areas to convey the regulatory flood.
(3) Computation of a floodway required to convey this flood without increasing flood heights more than one foot at any point.
(4) Delineation of floodway encroachment lines within which no development is permitted that would cause any increase in flood height.
(5) Delineation of floodway fringe, i.e., that area outside the floodway encroachment lines, but still subject to inundation by the base flood. (Ord. 20425 § 4, 6-20-23.)