§ 1.2.6. Floodplain Delineations

A.

City of Austin.

1.

For purposes of this Drainage Criteria Manual, a drainage area of 64 acres or greater is required within a contributing watershed to create a "floodplain". For areas of flow with less than 64 acres of contributing area, no floodplain shall be defined unless the City or FEMA currently indicates the area as a floodplain. In all cases where a floodplain delineation is required, its determination shall be based on the projected full development of all properties contributing to the point of consideration. It is the responsibility of the design engineer to determine, based on the most accurate information available, what the floodplain delineation is.

2.

The design engineer may elect to utilize a floodplain delineation previously approved by the Director of the Watershed Protection Department, assuming the same is still applicable under present requirements and criteria. In so doing the engineer does not remove himself from the responsibility for the delineation's accuracy.

B.

Federal Emergency Management Agency.

1.

The Federal Emergency Management Agency (FEMA) maintains Flood Insurance Rate Maps (FIRM's) that depict floodplain boundaries. The floodplain boundaries depicted on FIRM's are based on existing conditions of development in the contributing area at the time the floodplain study that delineated the floodplain was completed.

2.

FEMA reviews and approves or denies all revisions or amendments to FIRM's. FEMA revises or amends FIRM's by approval of a Letter of Map Change (LOMC). FEMA establishes the process and fees necessary for review of an application for a LOMC.

3.

FEMA reviews the impact of proposed site developments and offers or denies conditional assurance that a FIRM may be changed by the proposed development. FEMA offers this assurance by a Conditional Letter of Map Change (CLOMC). The CLOMC is a conditional statement that the FIRM may be changed if (1) the development is constructed as proposed in the CLOMC application, and if (2) a complete LOMC is submitted after construction of the proposed development.

4.

As the local floodplain administrator, the City must review and acknowledge certain LOMC or CLOMC requests. The City establishes the process necessary for review of an application for a LOMC or CLOMC.

C.

Coordination of City of Austin and FEMA Floodplain Delineations.

1.

The 100-year floodplain as determined in accordance with this Manual is a standard for dedication of drainage easements. This floodplain is theoretically equal to or greater than the 100-year floodplain depicted by FEMA on the FIRM. If the floodplain on the FIRM extends beyond a drainage easement required by the Land Development Code, or offered by the applicant, then the floodplain depicted on the FIRM must be changed by FEMA. This requirement assures that floodplain boundaries and associated regulations are coordinated between the City of Austin and FEMA. Floodplain mapping may be changed due to updated analysis of the floodplain under existing conditions, or due to land development activities that alter existing conditions.

2.

If the floodplain depicted on the FIRM is required to be changed, pursuant to C.1. above, due to updated analysis of the floodplain under existing conditions, then the following requirements are applicable:

(a)

Prior to approval of a preliminary plan, the applicant must provide to the City a letter of acknowledgement by FEMA of receipt of a complete application for a LOMC.

(b)

Prior to approval of a final plat, the applicant must provide to the City evidence of approval by FEMA of the LOMC submitted under C.2.(a). If the final plat is approved before it is determined that a LOMC is necessary or desired, prior to release of a subdivision construction permit or site plan permit, the applicant must provide to the City a letter of acknowledgement by FEMA of receipt of a complete application for a LOMC.

(c)

Prior to final acceptance of the construction of the subdivision or issuance of building permits for buildings that are within the floodplain at the time of application, the applicant must provide to the City evidence of final acceptance by FEMA of the LOMC submitted under C.2.(a) above.

3.

If the floodplain depicted on the FIRM is required to be changed, pursuant to C.1. above, due to land development activities that alter existing conditions, then the following requirements are applicable:

(a)

Prior to approval of a preliminary plan, the applicant must provide to the City either: evidence that the proposed land development activities do not increase the level of the FEMA floodplain; or a letter of acknowledgement by FEMA of receipt of a complete application for a CLOMC.

(b)

Prior to approval of a final plat, the applicant must provide to the City either: evidence that the proposed land development activities do not increase the level of the FEMA floodplain; or evidence of approval by FEMA of the CLOMC.

(c)

If the final plat is approved before it is determined that a CLOMC is necessary or desired, then prior to approval of a subdivision construction permit or site plan permit, the applicant must provide to the City either: evidence that the proposed land development activities do not increase the level of the FEMA floodplain; or a letter of acknowledgement by FEMA of receipt of a complete application for a CLOMC.

(d)

Prior to final acceptance of the subdivision construction or site plan improvements or issuance of building permits for buildings that are within the portion of the FEMA floodplain affected by a required LOMC, the applicant must provide to the City evidence of final acceptance by FEMA of the CLOMC if required under C.3 above, and a letter of acknowledgement by FEMA of a complete application for a LOMC.

(e)

Prior to issuance of a certificate of occupancy for buildings within the portion of the FEMA floodplain affected by a required LOMC, the applicant must provide to the City evidence of final acceptance by FEMA of the LOMC.

4.

The applicant shall bear the cost of engineering services required to develop the application, respond to review comments, and obtain final approval of LOMCs and CLOMCs. The applicant shall bear the cost of any fees associated with review and disposition of LOMCs and CLOMCs that are established by FEMA.