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  1. Flood Losses resulting from Periodic Inundation

    The flood hazard areas of Douglas County, Nebraska, 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.
  2. General Causes of the Flood Losses

    These flood losses are caused by:

    1. The cumulative effect of obstructions in floodplains causing increases in flood height and velocities
    2. the occupancy of flood hazard areas by uses vulnerable to flood or hazardous to others, which are inadequately elevated or otherwise unprotected from flood damages.
  3. Methods Used to Analyze Flood Hazards: This resolution uses a reasonable method of analyzing flood hazards which consists of a series of interrelated steps.

    1. Selection of a regulatory flood which 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 is selected for this resolution. It is representative of large floods which are reasonably characteristic of what can be expected to occur on the particular streams subject to this resolution. It is in the general order of a flood which could be expected  to have a one percent (1%) chance of occurrence in any one year, as delineated on the Federal Insurance Administrations Flood Insurance Study, and illustrative materials dated March 19, 2007 as amended, and any future revisions thereto.
    2. Calculation of water surface profiles based on a hydraulic engineering analysis of the capacity of the stream channel and overbank areas to convey the base flood.
    3. Computation of the floodway required to convey this flood without increasing flood heights more than 1 (one) foot at any point.
    4. Delineation of floodway encroachment lines within which no obstruction is permitted which would cause any water surface increase along the floodway profile.
  4. Delineation of floodway fringe, i.e., that area outside the floodway encroachment lines, but which still is subject to inundation by the base flood.
     


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