§ 7.5-154. Standards for development.

(a)

Definition of floodplain boundaries.

(1)

Studied "A" Zones, as identified in the FIS, shall be used to establish base flood elevations whenever available.

(2)

For all streams with a drainage area of one hundred (100) acres or greater, the future-conditions flood elevations shall be provided by the City of Cartersville. If future-conditions elevation data is not available from the City of Cartersville, then it shall be determined by a licensed professional engineer using a method approved by FEMA and the City of Cartersville.

(b)

Definition of floodway boundaries. The width of a floodway shall be determined from the FIS or FEMA approved flood study. For all streams with a drainage area of one hundred (100) acres or greater, the regulatory floodway shall be provided by the City of Cartersville. If floodway data is not available from the City of Cartersville, it shall be determined by a licensed professional engineer using a method approved by FEMA and the City of Cartersville.

(1)

Developments or subdivisions. If the request involves a development or subdivision, the developer or subdivider shall either pay for the city to conduct the study, or shall pay an impendent consultant to provide the data, provided that consultant is first approved by the city engineer. If floodway data is provided by the city, the developer or subdivider shall pay the pro rata share of the costs of the consultant to map the relevant basin.

(2)

Individual lots. If the request involves an individual lot not part of a larger common plan of development, or a pre-existing lot in an existing subdivision, then the individual shall consult with the city engineer. The city engineer shall make the determination whether to require additional floodway data at the applicant's expense, to expedite county mapping of the relevant area, or to accept the existing data as sufficient.

(c)

General standards.

(1)

No development shall be allowed within any area of special flood hazard or area of future-conditions flood hazard that could result in any of the following:

a.

Raising the base flood elevation or future-conditions flood elevation equal to or more than 0.01 foot;

b.

Reducing the base flood or future-conditions flood storage capacity;

c.

Changing the flow characteristics as to the depth and velocity of the waters of the base flood or future-conditions flood as they pass both the upstream and the downstream boundaries of the development area; or

d.

Creating hazardous or erosion-producing velocities, or resulting in excessive sedimentation.

(2)

Any development within any area of special flood hazard or area of future-conditions flood hazard allowed under subsection 7.5-154(a) shall also meet the following conditions:

a.

Compensation for storage capacity shall occur between the average groundwater table elevation and the base flood elevation for the base flood, and between the average groundwater table elevation and the future-condition flood elevation for the future-conditions flood, and lie either within the boundaries of ownership of the property being developed and shall be within the immediate vicinity of the location of the encroachment. Acceptable means of providing required compensation include lowering of natural ground elevations within the floodplain, or lowering of adjoining land areas to create additional floodplain storage. In no case shall any required compensation be provided via bottom storage or by excavating below the elevation of the natural (pre-development) stream channel unless such excavation results from the widening or relocation of the stream channel;

b.

Cut areas shall be stabilized and graded to a slope of no less than two (2.0) percent;

c.

Effective transitions shall be provided such that flow velocities occurring on both upstream and downstream properties are not increased or decreased;

d.

Verification of no-rise conditions (less than 0.01 foot), flood storage volumes, and flow characteristics shall be provided via a step-backwater analysis meeting the requirements of subsection 7.5-154(d);

e.

Public utilities and facilities, such as water, sanitary sewer, gas, and electrical systems, shall be located and constructed to minimize or eliminate infiltration or contamination from floodwaters; and

f.

Any significant physical changes to the base flood floodplain shall be submitted as a conditional letter of map revision (CLOMR) or conditional letter of map amendment (CLOMA), whichever is applicable. The CLOMR submittal shall be subject to approval by the City of Cartersville using the FEMA community concurrence forms before forwarding the submittal package to FEMA for final approval. The responsibility for forwarding the CLOMR to FEMA and for obtaining the CLOMR approval shall be the responsibility of the applicant. Within six (6) months of the completion of development, the applicant shall submit as-built surveys and plans for a final letter of map revision (LOMR).

(d)

Engineering study requirements for floodplain encroachments. An engineering study is required, as appropriate to the proposed development activities on the site, whenever a development proposes to disturb any land within the future-conditions floodplain, except for a residential single-lot development on streams without established base flood elevations and floodways. This study shall be prepared by a licensed professional engineer and made a part of the application for a permit. This information shall be submitted to and approved by the City of Cartersville prior to the approval of any permit which would authorize the disturbance of land located within the future-conditions floodplain. Such study shall include:

(1)

Description of the extent to which any watercourse or floodplain will be altered or relocated as a result of the proposed development;

(2)

Step-backwater analysis, using a FEMA-approved methodology approved by the City of Cartersville. Cross-sections (which may be supplemented by the applicant) and flow information will be obtained whenever available. Computations will be shown duplicating FIS results and will then be rerun with the proposed modifications to determine the new base flood profiles, and future-conditions flood profiles;

(3)

Floodplain storage calculations based on cross-sections (at least one (1) every one hundred (100) feet) showing existing and proposed floodplain conditions to show that base flood floodplain and future-conditions floodplain storage capacity would not be diminished by the development;

(4)

The study shall include a preliminary plat, grading plan, or site plan, as appropriate, which shall clearly define all future-conditions floodplain encroachments;

(5)

Detailed flood studies in areas where floodplain has been established but the base flood elevation (BFE) and/or the floodway has not been established and in areas beyond the limits of study on the FIRM, which may contain a watercourse, and have greater than one hundred (100) acres of surface drainage area above the property, shall be submitted showing the base flood elevations, future-conditions flood elevations, and the floodway. Approval of the study must be received before the final plat of the affected lots can be approved or a certificate of occupancy can be issued.

(e)

Floodway encroachments. Located within areas of special flood hazard are areas designated as floodway. A floodway may be an extremely hazardous area due to velocity floodwaters, debris or erosion potential. In addition, floodways must remain free of encroachment in order to allow for the discharge of the base flood without increased flood heights. Therefore, the following provisions shall apply:

(1)

Encroachments are prohibited, including earthen fill, new construction, substantial improvements or other development within the regulatory floodway, except for activities specifically allowed in subsection (e)(2) below;

(2)

Encroachments for bridges, culverts, roadways and utilities within the regulatory floodway may be permitted provided it is demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the encroachment will not result in any increase to the pre-project base flood elevations, floodway elevations, or floodway widths during the base flood discharge. A licensed professional engineer must provide supporting technical data and certification thereof; and

(3)

If the applicant proposes to revise the floodway boundaries, no permit authorizing the encroachment into or an alteration of the floodway shall be issued by the City of Cartersville until an affirmative conditional letter of map revision (CLOMR) is issued by FEMA or a no-rise certification is approved by the City of Cartersville.

(f)

Maintenance requirements. The property owner shall be responsible for continuing maintenance as may be needed within an altered or relocated portion of a floodplain on the property so that the flood-carrying or flood storage capacity is maintained. The City of Cartersville may direct the property owner (at no cost to City of Cartersville) to restore the flood-carrying or flood storage capacity of the floodplain if the owner has not performed maintenance as required by the approved floodplain management plan on file with the City of Cartersville.

(Ord. No. 04-15, § 1, 3-5-15)