1111.06 FLOOD AREAS AND STORM DRAIN DITCHES.
(a) Flood Plain Areas. All subdivisions shall conform to the City flood damage prevention ordinance or, if in unincorporated territory, to the Hancock County Flood Damage Prevention Regulations, as approved by the Hancock County Commissioners on May 9, 1991. Such Regulations are maintained by the Hancock County Engineer.
Whenever all or part of a proposed subdivision lies within an area of special flood hazard as identified in the most recent available mapping published by the Federal Emergency Management Agency (FEMA), approval of the subdivision plat shall be conditioned on the following:
(1) No encroachment by either fill material or future structures shall be permitted in the area identified as "floodway" on FEMA mapping. Modifications of floodway areas shall only be permitted if an engineering analysis demonstrates to the satisfaction of the City or County Engineer that such modifications will not result in detrimental impacts either up or downstream
(2) Development within flood hazard areas shall not result in any decrease in the flood storage capacity of the flood plain area. Therefore, any subdivision proposed in flood hazard areas shall be accompanied by a grading plan indicating how land balancing may be achieved, and how all building sites can be elevated above the base flood elevation for that location.
(3) If a subdivision is approved in a flood hazard area, the subdivider shall be required to post a performance bond guaranteeing execution of the grading plan. The grading plan shall be executed and the results certified by an engineer prior to the plat being signed by the City Engineer and submitted to the County Recorder. The plat shall be accompanied by restrictive covenants prohibiting the placement of any fill material in areas lying below the base flood elevation, and the subdivider shall be responsible for enforcement of the covenants until all lots in the subdivision have been conveyed to others.
(4) Development activities located in areas that are designated as flood plain areas, including floodway, will require an approval from the City Local Flood Plain Administrator and shall follow all requirements set forth in Chapter 1351 of these Codified Ordinances. All engineering analysis submitted to the City Local Flood Plain Administrator shall be conducted by a state registered professional engineer.
(5) No encroachment by either fill material or future structures shall be permitted in the area identified as “floodway” on FEMA mapping. Modifications of floodway areas shall only be permitted if such modifications follow all requirements found in Section 60.3(d) of the National Flood Insurance Program (NFIP) regulations and in Chapter 1351 of these Codified Ordinances. Modifications in the floodway shall not result in any increases in the base flood elevation, also known as 100 year flood elevation. All engineering analysis that certifies no increase in the base flood elevation shall extend a distance of one mile upstream and downstream of the development site to ensure no impact on the 100 year flood elevation.
(b) Areas of Poor Drainage. If a subdivision is located in an area having poor drainage or other adverse physical characteristics, the Commission may approve the subdivision provided the subdivider agrees to perform such improvements as will render the area safe for the intended use. In lieu of the improvements, the subdivider shall furnish a surety or certified check covering the cost of the required improvements.
(c) Flood Control and Storm Drainage Facilities. Flood control or storm drainage facilities shall be provided as follows:
(1) Access to flood control or storm drainage ditches and channels shall be by means of easements. Such easements shall be not less than thirty feet in width, exclusive of the width of the ditch or channel, and an easement of this type shall be provided on one side of a flood control or storm drainage ditch, channel or similar type facility.
(2) Flood control or storm drainage easements containing underground facilities shall have a minimum width of ten feet.
(3) Whenever a flood control or storm drainage ditch or channel has a depth of five feet or more, or a bank slope of two feet horizontal to one foot vertical or steeper, a five-foot high masonry wall or chain link fence may be required by the Commission.
(4) The basis for determining storm water conveyance shall be a 10-year storm. All storm water to be discharged from the platted area shall be detained based on a 100-year storm volume unless otherwise recommended by the Chief Engineer and approved by the City Planning Commission. The discharge rate for all detention-retention areas shall be equal to the 5-year pre-developed runoff from the site. Detention- retention calculations shall be reviewed by the Chief Engineer. All lots within recorded subdivisions shall be provided positive drainage so as to avoid areas of standing water.
Where a subdivision includes a pond, lake, basin or other physical facilities for storm water management, the restrictive covenants filed with the plat shall include measures to assure the continued maintenance of the facilities, placing the responsibility for maintenance with the owners of property in such subdivision.
(5) Provisions shall be made to provide an emergency overflow route, from the detention areas to the point of discharge, in the event a storm exceeds the 100-year detention capacity. The overflow route must not adversely impact adjoining properties.
(6) In any subdivision created after the effective date of this section, the subdivider shall be required to post a performance bond to guarantee the execution of the detention-retention area plan. The performance bond shall not be released until the actual conditions, certified by a professional engineer, are submitted and verified by the Chief Engineer.
(Ord. 2008-002. Passed 2-5-08.)