127.9 Floodplain Management

Key Points

127.9.1 Introduction

127.9.1.1 Overview

Acting as the Federal Highway Administration’s (FHWA’s) agent, MoDOT must evaluate every project and determine whether it could have a negative impact on the base (100-year) floodplain or regulatory floodway. The Federal Emergency Management Agency (FEMA) and Federal Highway Administration (FHWA) guidelines 23 CFR 650 identify the base (100-year) flood as the flood having a one-percent probability of being equaled or exceeded in any given year. The base floodplain is the area of 100-year flood hazard within a county or community. The regulatory floodway is the channel of a stream plus any adjacent floodplain areas that must be kept free of encroachment so that the 100-year flood discharge can be conveyed without increasing the base flood elevation more than a specified amount. FEMA has mandated that projects can cause no rise in the regulatory floodway and no more than a one-foot cumulative rise for all projects in the base (100-year) floodplain.

A "No-Rise" Certification is signed and sealed by an engineer licensed to practice in Missouri that a project will cause no rise in the regulatory floodway of a given flooding source. The project will not create any increase to the 100-year elevations on said flooding source at published cross-sections in the Flood Insurance Study for a given community and will not create any increase to the 100-year flood elevations at unpublished cross-sections in the vicinity of the proposed development.

127.9.1.2 Laws and Regulations

• National Flood Insurance Act (42 U.S.C. 4001-4129 and 44 CFR 59-77) of 1968 provides previously unavailable flood insurance protection to property owners in flood-prone areas.
• Executive Order 11988: Floodplain Management (DOT Order 5650.2, 23 CFR 771, 23 CFR 650, Subpart A) of 1977 seeks “to avoid to the extent possible the long and short-term adverse impacts associated with the occupation and modification of floodplains and to avoid direct and indirect support of floodplain development wherever there is a practicable alternative.”
• National Environmental Policy Act (NEPA) of 1969.

127.9.2 Process

The district must complete and submit a Request for Environmental Services (RES) to the Design Division’s environmental section. Upon receiving an RES from the district, the environmental specialist will consult SEMA to determine whether the community or county in which the project is located has been mapped for floodplain and/or floodway. If the community or county has not been mapped, this is communicated to the district, along with the fact that no permits from SEMA will be required. If the community has been mapped, then the environmental specialist will identify the extent of encroachment, if any, into the 100-year floodplain and/or regulatory floodway, whether the community participates in the NFIP. If there is to be an encroachment into the regulatory floodway, MoDOT must issue a "No-Rise" Certification as required by SEMA to obtain a floodplain development permit that is needed for any encroachment into the 100-year floodplain, regardless of whether it also takes place within the regulatory floodway. The environmental specialist will, via the RES response, communicate this information to the district, which will then take the appropriate steps, often in consultation with Bridge, to obtain the necessary permit.

127.9.3 Project Development Milestones

127.9.3.1 Initial Screening Stage

At the initial project screening stage if maps are available, the environmental specialist will identify whether the project takes place in a county or community that participates in the NFIP and the extent of the encroachment into the regulatory floodway and/or 100-year floodplain.

The district initiates this process by submitting an RES to the Design Division. Any findings pertinent to the project will be relayed to the district in the RES response.

127.9.3.2 Location/Conceptual Plan Stage

At the location/conceptual plan stage if floodplain impact was not evaluated previously, the environmental specialist will identify whether the project takes place in a county or community that participates in the NFIP and initialize a floodplain/floodway encroachment study for the project.

The district initiates this process by submitting an RES to the design division. Any new findings pertinent to the project will be relayed to the district in the RES response.

127.9.3.3 Preliminary Plans Stage

At the preliminary plans stage if floodplain impact was not previously evaluated, the environmental specialist will identify whether the project takes place in a county or community that participates in the NFIP and initialize a floodplain/floodway encroachment study for the project.

The district initiates this process by submitting an RES to the design division. Any new findings pertinent to the project will be relayed to the district in the RES response.

127.9.3.4 Right of Way Plan Stage

At the right-of-way plan stage if floodplain impact was not previously evaluated, the environmental specialist will identify whether the project takes place in a county or community that participates in the NFIP and initialize a floodplain/floodway encroachment study for the project.

The district initiates this process by submitting an RES to the design division. Any new findings pertinent to the project will be relayed to the district in the RES response.

127.9.3.5 Final Design Stage

Floodplain impact should have been previously evaluated, as any required floodplain development permit and "No-Rise" Certification should be obtained before final design stage. If floodplain impact was overlooked and has not been evaluated by the final design stage, the environmental specialist will initialize a floodplain/floodway encroachment study for the project. However, the project may be delayed since any required floodplain development permit and "no-rise" certification must be obtained before letting.

The district initiates this process by submitting an RES to the Design Division. Any new findings pertinent to the project will be relayed to the district in the RES response.

127.9.3.6 Letting

Floodplain impacts must be known prior to letting as any required floodplain development permit and "No-Rise" Certification must have been obtained prior to letting. The project may be delayed until these permits are received.