NPDP Dam Dictionary

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Term AKA Definition
Loess Wind-deposited silt.
Loessial Medium-textured materials (usually silt or very fine sand) transported and deposited by wind action. These materials may be deposited in depths ranging from less than 1 foot to well over 100 feet.
Log boom A floating structure used to protect the face of a dam by deflecting floating material and waves away from the dam. A device used to prevent floating debris from obstructing spillways and intakes.
Logbook A dated, written record of performed operation and maintenance items or observations pertinent to a structure.
Long-throated flumes Long-throated flumes control discharge rate in a throat that is long enough to cause nearly parallel flow lines in the region of flow control. Parallel flow allows these flumes to be accurately rated by analysis using fluid flow concepts. Long-throated flumes can have nearly any desired cross-sectional shape and can be custom fitted into most canal-site geometries. The Ramp flume, also considered a version of broad-crested weir, is an example of this kind of flume.
Longitude The longitude at the dam centerline as a single value in decimal degrees (e.g., -140.15).
Losing stream A stream or reach that contributes water to a zone of saturation.
Lotic Flowing water, such as rivers and streams.
Low density material A material having a low weight per unit volume either as it occurs in its natural state or after compacting it, such as loess with a density of 80 pounds per cubic foot or less.
Low hazard A downstream hazard classification for dams in which no lives are in jeopardy and minimal economic loss (undeveloped agriculture, occasional uninhabited structures, or minimal outstanding natural resources) would occur as a result of failure of the dam. This classification also applies to structures other than dams.