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Oklahoma's Floodplain Management 101

Chapter 6: No Adverse Impact

A concrete trench that has collected runoff from upstream lots and surrounding areas

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Flooding has been a pervasive problem throughout history. The NFIP has had an impact on the problem. New buildings are better protected from damage and there is greater awareness of the consequences of infringing on floodplains. However, while the NFIP and participating communities have helped mitigate flood damage, flooding has certainly not stopped. The reason is that most communities adopt and enforce only the minimum national and state floodplain management requirements, which focus on protecting new buildings, not what the impact of that construction will do to others.

The "No Adverse Impact" (NAI) floodplain management approach is a concept developed by the Association of State Floodplain Managers (ASFPM) to address the shortcomings of the typical local floodplain management program.

Rather than looking at the minimum requirements of federal or state programs, NAI focuses on what communities can do that will actually protect property and prevent increased flooding, now and in the future. The NAI approach focuses on planning for and lessening flood impacts resulting from land use changes (see Figure 6-1). It is essentially a "do no harm" policy that will significantly decrease the creation of new flood damages. In essence, NAI means that your neighbor should build in such a way that does not increase the risk of flooding to your property or others. Examples of this “wise use” or the “most beneficial use” would be using the floodplain as dedicated open space for flood storage and low impact uses such as recreation.

In Oklahoma, the OWRB supports the concept of NAI, and although adopting higher standard ordinances is strictly voluntary, communities should be aware of the benefits of doing so. The following article from the Missouri State Emergency Management Agency Newsletter (vol. 49(4)) gives an overview of why communities should adopt and consider higher standard ordinances. Adopting a freeboard above the 1% flood event will provide more protection from flood damage and provide a cost savings for people that wish to purchase flood insurance.

Two Feet or Not Two Feet? What is the Answer? — L. Scott Samuels, P.E., Certified Floodplain Manager

By now, hopefully everybody knows that, the National Flood Insurance Program (NFIP) standard for new residential structures is that the lowest floor must be elevated "at or above the Base Flood Elevation (BFE)" - 44 Code of Federal Regulations (CFR) Part 60. But what most people don't realize is, that by adopting this minimum standard, one day there could legally be one foot of water above the lowest floor elevation or the current BFE.

How can that be? Simple, it's a direct result of how floodways are defined for NFIP purposes. After a detailed study has been performed on a stream reach and the floodplain boundaries and BFE have been determined, a floodway can be defined on that particular stream reach. A floodway is determined, by "squeezing" the boundaries of the floodplain together (reducing the cross-sectional flow area) until the calculated water surface elevations increase up to one (1) foot (see Figure 1) while still passing the base flood event. This floodway is referred to as a "1 foot surcharged floodway." There are other factors that are considered when determining a floodway. One factor is that the reduction in conveyance must be equal on both sides of the centerline of the stream. Hydraulically speaking, this means one side of the creek is not having more of a reduction in the conveyance of flows, than the other side. Also, the "squeezing" shall not go beyond the current stream banks and into the creek's channel, thus ensuring that the entire stream channel will always be preserved as an "open area" to pass the base flood. That is why it is so very important to regulate development in regulatory floodways. The higher development standards that apply to regulatory floodways ensure that any additional development in the regulatory floodway will not cause water surface elevations to rise during the base flood.

So why define a floodway in the first place if it allows the water surface elevations to increase by a foot? Because the positives results of defining a floodway far outweigh any negatives. Let me explain. The main positive features of having a floodway is that the floodway, when properly administered, reserves an area to pass the base flood that will be free from future obstructions, thus reducing future flood damages. It also allows for development in the floodway fringe without requiring every single project that is proposed, no matter how small, to perform a hydraulic analysis of the stream to determine the impacts of the project on the current flooding conditions. Not having a floodway designated would create a tracking nightmare for the local community and would substantially increase the cost of new single-family structures. The community would be responsible for tracking all development in the floodplain, deciding when the floodplain was "fully developed," and prohibiting any further development at that point in time. Developers or individual homeowners would bear the cost of engineering studies to determine these floodplain impacts.

So what can your community do? To fully realize the benefits of having a regulatory floodway defined, your community needs to adopt building standards greater than the NFIP minimum standards to truly provide some additional measure of protection, and I am not just talking about adopting a standard that requires the lowest floor to be "one foot above the BFE." If your community only adopts a "one foot above BFE" standard, then it is setting up the situation where homeowners think they have one foot of freeboard above the base flood, but if the floodway fringe is ever completely filled, then their lowest floor could be the same elevation as the base flood someday. People who have experienced flooding firsthand know that it doesn't take a great depth of water in a home to do a lot of damage. For these reason I recommend that communities adopt a standard requiring the lowest floor to be a minimum of two (2) feet above the BFE in Special Flood Hazard Areas (SFHA).

There are several great reasons for adopting the “two (2) feet above the BFE” standard in your community. First this standard takes into account the future rise due to development in the floodway fringe. Therefore, sometime in the future, when water surface elevations have legally raised one foot, the structure should hopefully still have that one foot of protection against the base flood. Another reason, even though detailed studies are based on sound engineering principles and practices, is that there is still an art in making floodplain and floodway analyses. Since floods don't read flood maps, the “two feet above the BFE" standard takes into account some of the uncertainty associated with floodplain calculations. This also might help mitigate any unforeseen circumstance that might occur during a flooding event such as floating flood debris blocking culverts, channels or bridge openings. These obstructions could cause a temporary rise in the base flood that the additional freeboard requirements could help mitigate since the FIRM does not identify these areas of temporary obstructions. And finally, by building the lowest “floor two feet above the BFE”, the structure would be eligible for a lower insurance rate. This could add up to a substantial savings on a homeowner's annual insurance premium over the life of the loan.

Hopefully this article has given you a better understanding, of what the squiggly lines and floodway boundaries represent on your community's FIRM. Even if you can't convince your governing body to adopt a higher standard, hopefully you will be able to explain to the developer or homeowner as the Floodplain Administrator, the advantages of elevating higher than your community ordinance requires. If you would like to talk about these issues with me, please feel free to contact me at 573.526.9119. Or if you like, comments can be sent to me via e-mail, at ssamuels@mail.state.mo.us

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Community Rating System

The NFIP has an incentive program called the Community Rating System (CRS) that reduces flood insurance premiums for communities that perform activities that exceed the minimum NFIP standards. The CRS has three goals: reducing losses due to floods, helping communities achieve an accurate insurance rating, and increasing the awareness of flood insurance.

For a community to be eligible, the community must be in full compliance with the NFIP and be in the Regular phase of the program. Communities in the Emergency phase of the program are not eligible.

All communities start out with a Class 10 rating (which provides no discount). There are 10 CRS classes: Class 1 requires the most credit points and gives the greatest premium reductions; Class 10 identifies a community that does not apply for the CRS, or does not obtain a minimum number of credit points and receives no discount. There are 18 activities recognized as measures for eliminating exposure to floods. Credit points are assigned to each activity. The activities are organized under four main categories: Public Information, Mapping and Regulation, Flood Damage Reduction, and Flood Preparedness. Once a community applies to the appropriate FEMA region for the CRS program and its implementation is verified, FIA sets the CRS classification based upon the credit points. This classification determines the premium discount for policyholders. Premium discounts ranging from 5 percent to a maximum of 45 percent will be applied to every policy written in a community as recognition of the floodplain management activities instituted. The following table demonstrates how the CRS premium discount is reflected on the application.

1 45%
2 40%
3 35%
4 30%
5 25%
6 20%
7 15%
8 10%
9 5%

Participation in the CRS is voluntary. If your community is in full compliance with the rules and regulations of the NFIP, you may apply. There's no application fee, and all CRS publications are free.

Your community's chief executive officer (that is, your mayor, city manager, or other top official) must appoint a CRS coordinator to handle the application work and serve as the liaison between the community and FEMA. The coordinator should know the operations of all departments that deal with floodplain management and public information. And the coordinator should be able to speak for your community's chief executive officer.

The first step in the application process is to get a copy of the CRS Coordinator's Manual, which describes the program and gives details on the eligible activities. The manual includes application worksheets and the formulas for calculating credit points. Computer software for completing the application is available at no charge. In addition, the CRS has a Short Form Application that may be more appropriate for your community. The Short Form is easier to complete than the regular worksheets, but it does not cover some of the more complicated activities you may be doing. Your designated CRS coordinator should fill out and submit your application. The CRS will verify the information and arrange for flood insurance premium discounts.

If you are interested in the CRS, and would like to visit with a community already participating, you are encouraged to contact one of the communities. For a current list of Oklahoma communities participating in CRS, please contact the OWRB. Additional information is also readily available on FEMA's website. FEMA provides a variety of tools to help make the application process go as smoothly as possible.

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