§ 38-15. General standards.

(a)

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:

(1)

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

(2)

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

(3)

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

(4)

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

(b)

Any development within any area of special flood hazard or area of future-conditions flood hazard allowed under section 38-15(a) shall also meet the following conditions:

(1)

Compensation for storage capacity shall occur between the average ground water table elevation and the base flood elevation for the base flood, and between the average ground water 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;

(2)

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

(3)

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

(4)

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 section 38-19;

(5)

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 flood waters; and

(6)

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 Riverdale 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 months of the completion of development, the applicant shall submit as-built surveys and plans for a final letter of map revision (LOMR).

( Ord. No. 13-2016 , § 1, 11-14-16)