AMES, Iowa – Iowa communities have land use planning issues to deal with as they prepare for life after the floods of 2008, say Iowa State University (ISU) experts. Gary Taylor, ISU Extension specialist and assistant professor in Community and Regional Planning, and Doug Johnston, professor and chair in Community and Regional Planning and Landscape Architecture, answered questions related to floodplain zoning, floodplain mapping, flood insurance issues, related land use planning and zoning and other issues in the flood recovery process.

How were the 100-year floodplains determined? Have they changed over time?
Floodplains are determined along watercourses and are calculated based on surveys of the stream channel, geometries of the stream channel, and hydrologic simulation models based on assumptions about what’s going on upstream. From these data, flood heights are calculated based on historic heights of rainfall. It’s based on history. Now, if that history is changing due to climate change or other factors, then the 100-year flood no longer may be accurate. If it’s more than a 100-year flood, the flood is extending into areas beyond what was previously mapped. The 100-year floodplain is a little smaller than the 101-year floodplain and a little larger than the 99-year floodplain. It’s a continuum.

Does the Federal Emergency Management Agency (FEMA) have restrictions for building in a floodplain?
For communities participating in the National Flood Insurance Program, building, or the availability of insurance, is regulated based on the risk of flooding within different areas. 

What about a low-lying area that floods, but isn’t a part of the floodplain?
Floodplains are not calculated for other disconnected, low-lying areas – even though a disconnected, low-lying area may flood prior to, more than or after a floodplain.

What can a community do to prevent houses from being rebuilt in a low-lying area or floodplain?
Within a floodplain, if a community is part of the FEMA flood insurance rate program, then the city has to have adopted a floodplain management ordinance — a zoning ordinance that limits the types of structures that can be built and the placement of those structures.

FEMA gives the states some latitude in the types of floodplain regulations they can adopt. FEMA sets a minimum standard designed to protect the structure within the floodplain and establishes a base elevation. To build requires a permit and being 1 foot above the base elevation. Some Iowa communities have decided to go beyond those basic standards; they are more restrictive in terms of the types of structures that can locate in the floodplain, and the height above base flood elevation they must achieve in order to build. They may be using more low-density zoning, designating the floodplain for nonstructural uses such as golf courses, and/or actively acquiring property for parks and trails.

What about nonconforming use?
If a community wants to limit rebuilding in the floodplain, it can use the nonconforming use provisions in its zoning ordinance. (Many buildings in the floodplain were built prior to the 1970s, when most communities agreed to participate in the flood insurance rate program.  Many of those buildings don’t meet the minimum standards.) This allows a community to say “no” if the building is destroyed; the community can say the landowner is limited to the types of uses and building regulations as they now exist.  

Who is eligible for flood insurance?
Communities may choose to participate in FEMA’s National Flood Insurance Program. About 500 communities in Iowa participate in this system. If a community is participating, then the community has mapped its floodplain. The map shows several different zones designed to reflect the flood risks in a particular location. If you are a landowner in one of the zones that permits development within the floodplain, then you are subject to flood insurance purchase requirements. FEMA backs the insurer providing coverage in case of loss.

Are communities taking the next steps to change neighborhoods to avoid floods in the future?
Communities are cleaning up. Most are not to the “next steps” yet. Community conversations regarding how to avoid the same magnitude of loss due to flooding likely will start once cleanup is winding down, particularly since it’s now happened twice in 15 years.

The American Planning Association has emphasized hazard mitigation research and planning communities can take. Guidebooks are available to help communities think through hazard mitigation planning – so that the next disaster will not be as severe economically or put people’s lives in danger.

When should a community do disaster mitigation planning?
The time to make these decisions is BEFORE a disaster. If a community does not already have a disaster mitigation plan, get a plan in place now, to be ready for the next disaster.

-30-