Federal Flood Plain Regulations

Association of Construction and Development
February 15, 2013 — 1,786 views  

Floodplains are responsible for a variety of natural functions such as ground water recharging, prevention of soil erosion, temporary flood water storage, and maintenance of water quality. They also provide habitation to wildlife. The National Flood Insurance Program (NFIP) enjoys the participation of all the counties in Maryland and 92 odd municipalities. Under the National Flood Insurance Program, property owners in the participating social groups are endowed with flood insurance. In exchange, the local governments are required to employ ordinances to supervise developmental activities within the 100 year flood plains and reduce chances of flooding in the future. The Federal Emergency Management Agency (FEMA) publishes the floodway and flood insurance rate maps (FIRM) which are employed to demarcate the 100 year floodplain and earmark regulated land.

Types of Floodplain Zones

The floodway fringes and the floodways along creeks, streams, and rivers constitute the non-tidal floodplains. Areas exposed to coastal flooding by consistent on-shore winds, tropical storms, high tides, and hurricanes form the tidal floodplains. On the other hand, areas subject to tidal flooding and high velocity wave and wind occurrence are characterized as coastal high hazard areas.

Availing the Permits

Under the NFIP, towns and counties are required to authorize permits for any development activity in the 100 year floodplain. Development may be broadly defined as any human-induced modification to land, which may include dredging, grading, filling, extraction, storage, sub division of lands, and constructing or improving structures. However, the contemplated development should not aggravate flooding or worsen conditions during floods, particularly on another individual’s property. Permits are an important part of Federal Flood Plain Regulation requirements.

Setback for Protection

Flood damage can be reduced by ensuring that developments are setback at least 100 feet measured from the top-side bank of every Federal Emergency Management Agency designated water course and 50 feet from every unmapped stream. The setback may end near the floodplain periphery when the floodplain cannot meet the setback requirements. The setback area characterizes a “no construction” zone aimed at preserving the naturally occurring functions of floodplains.

Elevation and Elevation Certificates

Raising the lowermost floor of inhabited areas by one foot over the level of the designated 100 year floodplain can help in minimizing damage to improved floodplain structures. Enclosed spaces below this area should be judiciously used and vented to permit flooding without substantial damage. This is applicable to all electrical and plumbing devices and gas-powered appliances. These structures should be securely anchored to avoid flotation and lateral motion. Also helpful for added protection is freeboard, an additional degree of elevation above the 100 year floodplain elevation.

Freeboard can compensate uncertainties like floods bigger than the 100 year floor, rise in sea level, and errors in measurement, and thus provides increased protection. The above conditions need to be adhered to and an elevation certificate must be obtained. A professional engineer must certify that the structures fulfill the prescribed elevation standards, and issue this certificate. Towns and counties maintain these certificates as part of the permit record and the certificate must be obtained before the property is legally occupied.


Floodways must be designated to carry the deep, high-velocity waters during the 100 year flood. New buildings are not allowed in the floodway. Also prohibited are constructions that obstruct floodwaters or increase water surface elevations during 100 year floods. Existing buildings may be improved only within the stipulated footprint.


Federal flood plain regulation requires enclosed spaces below the 100 year flood level to be vented to facilitate free movement of water to even the pressure on both faces of the wall. For every foot of enclosed area below the flood level, a square inch of vent opening is needed. The spaces below the flood level can be used only for limited storage and parking of vehicles.

Accessory Buildings

Smaller accessory buildings like garages and sheds measuring 300 feet and below are not required to be completely elevated, provided they possess water-equalizing vents and a non-conversion agreement is in vogue. Larger accessory structures may be permitted sans the required elevation standards as long as a land restriction declaration is recorded to prevent conversion to habitable space.

Coastal Hazard Areas

Areas prone to added flood hazards owing to wave and wind action need special measures. This includes elevating buildings on columns or pilings such that the bottom part of the lowest floor is at minimum one foot over the earmarked flood level. Areas below can be opened up to permit free water movement under the constructed structure or may be fitted with breakaway walls meant to crumble without harming the support system.

Association of Construction and Development