La. Admin. Code tit. 56 § III-705
Abutments- those portions of the valley sides which underlie and support the dam structure, and are usually also considered to include the valley sides immediately upstream and downstream from the dam.
Auxiliary or Emergency Spillway- a secondary spillway designed to operate only during unusually large storm events. Louisiana's Dam Safety Program defines "unusually large storm events" as being equal to the 100 year storm event or larger.
Baffle Blocks- blocks constructed in a stilling basin to dissipate the energy of fast flowing water.
Berm- a horizontal step in a sloping profile. The berm is usually constructed with a slight slope for drainage purposes. The berm is often referred to as a seepage or stability berm.
Blanket Drain- a horizontal pervious zone located downstream of the impervious core. This zone is often referred to as a sand blanket.
Breach- an eroded opening through a dam that drains the reservoir. A controlled breach is an intentionally constructed opening. An uncontrolled breach is an unintentional opening that allows uncontrolled discharge from the reservoir.
Chimney Drain- a vertical pervious zone located just downstream of the impervious core. The chimney drain is usually constructed with a sand material.
Cofferdam- a temporary structure enclosing all or part of the construction area so that the construction can proceed in the dry.
Conduit- a closed channel to convey discharges through or under a dam. The conduit can be a reinforced concrete pipe, a corrugated metal pipe or a single or multi-barrel reinforced concrete box culvert.
Crest Length of Dam- the length of the top of dam. This length includes the spillway(s) and other appurtenant structures. The crest length of dam is basically the length from where the top of dam terminates on one abutment to a similar point on the other abutment.
Cutoff Trench- an impervious barrier built into the foundation to reduce seepage under the dam. A cutoff wall or slurry wall could be used as a seepage barrier. The slurry wall is relatively thinner in the horizontal direction when compared to a clay core cutoff trench.
Dam- any artificial barrier, including appurtenant works, which does or will impound or divert water or any other liquid substance.
Downstream Slope- the inclined surface of an embankment dam that faces away from the reservoir.
Drawdown Structure- a low-level outlet which can be used to lower the reservoir below normal pool stage. This may be necessary for lake management purposes, routine repairs or dam safety purposes.
Earthfill Dam- a dam constructed predominantly of fine-grained material. Earthfill dams are also known as rolled fill dams where material is placed in layers and compacted by using rollers or rolling equipment.
End Sill- the area at the upstream and downstream end of the stilling basin base slab.
Foundation of Dam- the natural material on which the dam is placed.
Heel of Dam- the junction of the upstream slope with the foundation. The heel of the dam is often referred to as the upstream toe.
Impervious Core- a zone of low permeability material. This zone is the water or seepage barrier and is often referred to as the clay core.
Intake Structure- the structure placed at the beginning of an outlet works waterway. The intake structure establishes the ultimate drawdown level of the reservoir by the position of its opening(s) to the outlet works. Intake structures may be vertical or inclined towers (drop inlets).
Maximum Cross Section of Dam- cross section of a dam at the point where the height of the dam is at it's maximum.
Maximum Storage Capacity- the capacity at maximum storage is the volume in the reservoir in acre-feet when the level in the reservoir is at top of dam elevation.
Non-Overflow Wall- a wall which is usually constructed parallel to the spillway crest at an elevation equal to the top of dam elevation. This wall is not designed to be overtopped and are often referred to as a closed dam section.
Normal Pool Stage- the water level at the dam to which water may rise under normal operating conditions and for uncontrolled spillways is defined as the lowest crest elevation of the principal spillway. This does not include flood surcharge.
Outlet Gate- a gate on the drawdown structure or spillway which is used to control the outflow of water.
Piping- the progressive internal erosion of an embankment, foundation, or abutment material. The erosion (piping) begins on the downstream side and progresses upstream.
Primary or Principal Spillway- the first used spillway during flood flows.
Probable Maximum Flood (PMF)- the flood that may be expected from the most severe combination of critical meteorologic conditions that are possible in the region.
Retaining/Training Walls- walls which are usually constructed perpendicular to the spillway crest. Retaining walls are walls which support an overturning load. Training walls are walls which confine or guide the flow of water. In many instances, these walls serve both purposes and can be referred to as either a retaining or training wall.
Riprap- a layer of large uncoursed stones, broken rock or precast blocks placed in a random fashion on the upstream slope of the dam and stilling basin outlets. Riprap is a flexible type of slope protection which will deform if material is displaced from beneath.
Riser- a type of drop inlet spillway with a vertical section of metal or concrete pipe that allows the reservoir to rise to a predetermined level before water flows into the pipe.
Slope Protection- protection against wave action or erosion. The two most common types of slope protection, are riprap and soil cement.
Sluice- a low-level opening for releasing water from a dam.
Soil Cement- a well compacted mixture of soil, portland cement and water that produces a hard pavement. Soil cement is usually placed in horizontal layers. Soil cement is a rigid type of slope protection which attempts to span voids.
Spillway Crest- the overflow section or top of weir section of the spillway.
Stilling Basin- a basin constructed to dissipate the energy of fast flowing water. The stilling basin area is located just downstream of the spillway crest between the training/retaining walls.
Structural Height- the distance between the lowest point in the excavated foundation and the top of the dam.
Surcharge/Flood Surcharge- the volume or space between normal pool and the maximum design water level.
Tailwater- the level of water immediately downstream of the dam.
Toe of Dam- the junction of the downstream slope with the foundation. The toe of the dam is often referred to as the downstream toe.
Top of Dam/Crown- the uppermost surface of the dam. The top of dam can also be referred to as the crest of the dam. When the term "crest" is used, it must be specified that it is the "crest of the dam" and not the "crest of the spillway."
Uncontrolled or Ungated Spillways- spillways where the flows over the spillway crest are controlled only by the elevation of the spillway crest. This type of spillway is often referred to as a fixed crest spillway. Normal Pool Stage for uncontrolled spillways is defined as the lowest crest elevation of the principal spillway.
Upstream Slope- the inclined surface of an embankment dam that is in contact with the reservoir.
La. Admin. Code tit. 56, § III-705