Hocking Conservancy District

Margaret Creek Subdistrict

Glossary of Terms

Bankfull Stage - The maximum stage or height at which stream flow can be contained within the natural channel throughout a given reach of a stream with no significant inundation of, or damages to, adjacent land or structures.

Flood - An overflow of lands not normally covered by water and that are used or usable by man. Floods have two essential characteristics: The inundation of land is temporary; and the land is adjacent to, and inundated by overflow from a river or stream or an ocean, lake, or other body of standing water.

Normally, a “flood” is considered as any unusual rise in stream flow or stage, but not the ponding of surface water. The adverse effects of floods may include damages from overflow of land areas, temporary backwater effects in sewers and local drainage channels, creation of unsanitary conditions or other unfavorable situations by deposition of materials in stream channels during flood recessions, rise of ground water coincident with increased stream flow, and other problems.

Flood Crest - The maximum (peak) stage or elevation reached by the waters of a flood at a given location.

Flood Peak Discharge - The maximum instantaneous discharge of a flood at a given location. It usually occurs at or near the time of the flood crest and is given in cfs (cubic feet per second).

Flood Plain - The relatively flat area or low lands adjoining the channel of a river, stream or watercourse or ocean, lake, or other body of standing water, which has been or may be covered by flood water.

Flood Stage - The stage or elevation at which overflow of the natural banks or a stream or body of water begins in the reach or area in which the elevation is measured.

Intermediate Regional Flood - A flood having an average frequency of occurrence on the order of once in 100 years, although the flood may occur in any year. It is based on statistical analyses of stream flow records available for the watershed, and analyses of rainfall and runoff characteristics in the “general region of the watershed”.

River Mile - Miles above the mouth. In this particular case, miles above the confluence of the Hocking and Ohio Rivers.

Standard Project Flood - A term applied to the largest flood that may be expected from the most severe combination of meteorological and hydrological conditions that is considered reasonably characteristic of the geographical region involved. It represents a standard against which the degree of flood protection selected, called the project design flood, may be judged in the interest of consistency in design of flood protection works.

Definitions of terms as used by the National Weather Service

Flash Flood Warning - issued to inform the public, emergency management, and other cooperating agencies that flash flooding is in progress, imminent, or highly likely.

Flash Flood Watch - issued to indicate current or developing hydrologic conditions that are favorable for flash flooding in and close to the watch area, but the occurrence is neither certain or imminent.

People who live near small streams/creeks should be very aware of the potential for flash flooding.

Flash flooding notes of interest:

  • Most flash flooding related deaths occur at night
  • Most people at risk are those in a automobile
  • 2’ of water can float most vehicles
  • 6” of moving water can knock you off your feet

Flood Watch - issued to inform the public, and cooperating agencies that current and developing conditions are such that there is a threat of flooding, but the occurrence is neither certain nor imminent.

Flood Warning - issued to inform the public of flooding along larger streams in which there is a serious threat to life or property. A flood warning will usually contain river stage forecasts.