Under the National Flood Insurance Program, a factor of safety, usually expressed in feet above a flood level, for the purposes of floodplain management. Freeboard tends to compensate for the many unknown factors that could contribute to flood heights greater than the heights calculated for a selected size flood and floodway conditions, such as the hydrological effect of urbanization of the watershed.
Related Topics: [ pond] [ structures] For a waterway, freeboard is the additional depth added to the design depth to provide an overflow factor of safety and for siltation during the useful life of the channel. Typically, a 10 percent freeboard (rounded to the nearest .1 ft with a minimum of .2 ft) is adequate. For a dam, freeboard refers to the height from the crest (bottom elevation plus the depth of flow) of the flood spillway to top of dam. This extra height provides for protection against wave action and frost. Frost looses the soil at the top of the dam, making it ineffective for holding water. Typical freeboards for agricultural ponds are .5 - 1.5 ft.
A factor of safety usually expressed as a height above the adopted flood level thus determining the flood planning level. Freeboard tends to compensate for factors such as wave action, localised hydraulic effects and uncertainties in the design flood levels.
Vertical distance between the top of a tank or surface impoundment dike and the surface of the hazardous substance contained therein. Freeboard is intended to prevent overtopping resulting from normal or abnormal operations, wind and wave action, rainfall, and/or run - on.
The vertical distance between the top water level and the crest of a bank, dam or similar structure. Freeboard is provided for in designing such structures to prevent overtopping due to surcharge or wave action. In an earth structure, freeboard should include an allowance for settlement.
the space from the top of an embankment to the highest water elevation expected for the largest design storm to be stored. The space is required as a safety margin in a pond or basin. A minimum of one foot is required.
A factor of safety expressed in feet above a design flood level for flood protective or control works. Freeboard is intended to compensate for the unknown factor which could increase design heights, such as wave action, floodway obstruction, or future changes in the watershed.
The vertical distance between the normal maximum level of the water surface in a channel, reservoir, tank, canal, etc., and the top of the sides of a levee, dam, etc., which is provided so that waves and other movements of the liquid will not overtop the confining structure.
The height of the watertight portion of a building or other construction, such as a ditch, above a given level of water. In the context of the Molycorp mine, freeboard refers to drainage ditches constructed around the tailings impoundments in Questa.
The reserve volume designed into a lagoon or earthen manure storage to minimize chances of the contents overflowing and causing contamination. Freeboard is typically sized to hold the water draining into the storage from the highest intensity 24-hour rainfall expected to occur within 25 years.
The vertical distance between a bed of filter media or ion exchange material and the overflow or collector for backwash water; the height above the bed of granular media available for bed expansion during backwashing; may be expressed either as a linear distance or a percentage of bed depth.
Freeboard, in sailing and boating, means the distance from the waterline to the upper deck level, measured at the lowest point where water can enter a boat or ship. A low freeboard is often found on racing boats, for speed. A higher freeboard will give more room in the cabin, but may compromise speed.