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DAM SAFETY, FLOODPLAIN MANAGEMENT

Floodplain protection regulations

Floodplain definitions - Before getting too deeply into regulatory details of the floodplain program, it might be helpful to know what a floodplain is. Simply put, a floodplain is any land area susceptible to being inundated by water from any source. It includes the floodway and flood-fringe areas. Here are some related definitions.

Flooding or flood means

  • A general and temporary condition of partial or complete inundation of normally dry land areas from the overflow of inland or tidal waters, the unusual and rapid accumulation or runoff of surface waters from any source, or mudflows which are proximately caused by flooding
  • The collapse or subsidence of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels, or suddenly caused by an unusually high water level in a natural body of water accompanied by a severe storm, or by an unanticipated force of nature, such as a flash flood or an abnormal tidal surge, or by some similarly unusual and unforeseeable event that results in flooding.

The regulatory floodway means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. The floodway is the most dangerous part of the floodplain. It is associated with moving water. Development is generally prohibited in floodways.

The flood-fringe is the portion of the floodplain outside of the floodway, which is covered by floodwater during the 100-year discharge. The term, "flood-fringe" is generally associated with standing rather than flowing water. It is also that part of the floodplain wherein development is subject to a community's floodplain ordinance.

Base flood means the flood having a one percent chance of being equaled or exceeded in any given year.

Floodplain management means the operation of an overall program of corrective and preventive measures for reducing flood damage, including but not limited to emergency preparedness plans, flood control works and floodplain management regulations.

Special flood hazard area is floodplain land subject to a one or greater percent chance of flooding in any given year (a.k.a. the 100-year flood). The area may be designated as "Zone A" on the flood hazard map. After detailed rate-making has been completed in preparation for the publication of a flood insurance rate map, Zone A usually is refined into Zones A, AO, AH, A1-30, AE, A99, AR, VO, or V1-30, VE or V.

So...What are the regulations?

Floodplain regulations are meant to:

  • Protect life, health and property
  • Minimize public expenditures for costly flood control projects
  • Minimize rescue and relief efforts
  • Minimize business interruptions
  • Minimize damage to public facilities
  • Minimize the occurrence of future flood blight areas
  • Discourage the victimization of unwary land and homebuyers
  • Prevent increases in the regional flood from occurring

So, the floodplain consists of the flood-fringe and the floodway. What is allowed in each of these areas?

Floodway: Since this area is the most dangerous part of the floodplain, activities are strictly regulated here. Certain activities and uses are allowed here provided they meet these strict criteria:

  • No rise in the base flood elevation
  • Certain structures accessory to open space or historical areas
  • Campgrounds

Flood-fringe: Certain activities and uses are permitted in the floodway, provided they meet certain development standards:

  • Residential, commercial, manufacturing and industrial uses
  • Accessory uses (to those mentioned above)
  • Storage of materials
  • Public utilities and infrastructure and
  • Private sewage systems and wells

What is not allowed in these special areas?

Floodway:

  • Structures intended for human habitation
  • Storage of materials that are buoyant, flammable, explosive or injurious to human, animal, plant, fish, or other aquatic life
  • Sewage systems or wells
  • Solid or hazardous waste disposal facilities
  • Wastewater treatment pond or facilities except as otherwise permitted by Virginia Administrative Code and
  • Filling which would cause an obstruction to flow which is not otherwise permitted

Flood-fringe:

  • Solid or hazardous waste disposal facilities

Conditional uses (sometimes referred to as special exceptions) may be granted by the locality upon application and public hearing provided that provisions, purpose and objectives of the floodplain-zoning ordinance are met.

The local board of zoning appeals may grant variances or appeals upon application and public hearing provided that the application can meet strict criteria. However:

  • Variances may not permit a lower degree of flood protection in the floodplain area than the flood protection elevation; and
  • Variances may not permit uses that are strictly prohibited in the underlying use district (i.e. residential homes in a floodway).

Where can I find the regulations and model ordinances?

To view Virginia's laws regarding floodplain management, see Code of Virginia §10.1-602. Click here for model ordinances for Virginia's communities. Those with questions should contact the Virginia Floodplain Management Program staff: 804-371-6135, charleybanks@dcr.virginia.gov; 804-625-3978, charles.kline@dcr.virginia.gov; 804-514-3884, nabil.ghalayini@dcr.virginia.gov; 804-514-6478, melissa.hall@dcr.virginia.gov.