Glossary of Terms for Dam Safety

A working level or step in a cut (from the Bureau of Reclamation Library Glossary).

A nearly horizontal step in the sloping profile of an embankment dam. Also, a step in a rock or earth cut (from the U.S. Mine Safety & Health Administration Dam Inspection and Plan Review Handbook).

Flood flows expected at a point on the river system below a dam at the same time a flood inflow occurs above the dam (from the United States Society on Dams Glossary).

Learn more about flood-type definitions at the National Weather Service Glossary.

Disclaimer: These may not apply to every agency.

Assessment that best describes the condition of the dam based on available information. 

• National Inventory of Dams DATA FIELD
• A dam safety deficiency is defined as a load capacity limit or another issue that can result in a failure of the dam or appurtenant structure.  It is a characteristic or condition that does not meet the applicable minimum regulatory criteria. 
• Normal operations are defined as loading on the dam resulting from day-to-day pool operations to achieve authorized purposes in accordance with minimum state or federal regulatory criteria. 

Source: National Inventory of Dams Data Dictionary

An emergency situation that threatens the integrity of the dam, or its components, that could result in an increased risk to the population but does not result in the catastrophic failure of the dam. An incident may also include operational releases from the dam (e.g., principal spillway, emergency spillway) that may result in flooding major roads, homes, or businesses.

Source: Emergency Operations Planning: Dam Incident Planning Guide

The full or partial removal of an existing dam and its associated facilities such that the statutory definition of a dam is no longer met or the structure no longer presents a downstream hazard (from the United States Society on Dams).

The highest qualified individual within the dam owning agency who is responsible for implementing all aspects of the Dam Safety Program. This person is typically a registered professional engineer with a civil engineering background with management abilities and is competent in areas related to the design, construction, operation, inspection, and evaluation of dams (from the U.S. Army Corps of Engineers).

The full or partial removal of an existing dam, reservoir, and their associated facilities or significant changes to the operations thereof, such that the structure no longer meets the regulatory definition of a dam (from the United States Society on Dams).

A material defect or load capacity limit that, if left unaddressed, could lead to a dam failure (from the U.S. Army Corps of Engineers).

Dam Safety Deficiency

A physical condition capable of causing the sudden uncontrollable release of reservoir water by a partial or complete failure of a dam, appurtenant structure, or facility (from the Bureau of Reclamation Library Glossary).

A dam safety deficiency is defined as a load capacity limit or another issue that can result in a failure of the dam or appurtenant structure.  It is a characteristic or condition that does not meet the applicable minimum regulatory criteria (from the National Inventory of Dams Data Dictionary).  
 

A method in which the chance of occurrence of the variable involved is ignored and the method or model used is considered to follow a definite law of certainty and not probability (from the United States Society on Dams Glossary).

An embankment to confine or control water, especially one built along the banks of a river to prevent overflow of lowlands; a levee. (2) A low wall that can act as a barrier to prevent a spill from spreading. (3) (Geology) A tabular body of igneous (formed by volcanic action) rock that cuts across the structure of adjacent rocks or cuts massive rocks (from the United States Society on Dams Glossary). 

Lowering of a reservoir's water level; process of depleting a reservoir or ground water storage. The drop in the water table or level of water in the ground when water is being pumped from a well. Vertical distance the free water surface elevation is lowered or the reduction of the pressure head due to the removal of free water. The difference between a water level and a lower water level in a reservoir within a particular time. The amount of water used from a reservoir (from the United States Bureau of Reclamations Glossary).

The rate of dissipation of head per unit of length in the area where seepage is exiting the porous media. 

Source: Engineering and Design - SEEPAGE ANALYSIS AND CONTROL FOR DAMS.

The ratio of the ultimate strength of the material to the allowable or working stress (from the Bureau of Reclamation Library Glossary).

Man-made deposits of natural soils and rock; an earth or broken rock structure or embankment. (2) The process of depositing material (from the United States Society on Dams Glossary).

The mineral by-product of the final, wet processing of coal, which is then transported to disposal as a slurry.  It consists primarily of silt and clay-sized particles but usually includes fine sand (from the U.S. Mine Safety & Health Administration Dam Inspection and Plan Review Handbook).