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USGS IN YOUR STATE
USGS Water Science Centers are located in each state.
The 1977 Toccoa Flood
Report of Failure of Kelly Barnes Dam Flood and Findings
by Federal Investigative Board
December 21, 1977
- A surface
or mass provided to withstand thrust such as at the ends of a
- acre foot
- A volumetric
measure of water equivalent to one acre covered to a uniform depth
of one foot.
to or composed of alluvium, or deposited by a stream or running
- A general
term for clay, silt, sand, or gravel or similar material
deposited during comparatively recent geologic time by a
stream or other body of running water.
- base line
- A reference
line used for measurements and surveys.
- Rock of
relatively great thickness and extent in its native
- A horizontal shelf
or ledge built into an embankment or other sloping
- biotite gneiss
metamorphic rock of coarse grain size, in which biotite is a
- A tarry hydrocarbon substance sometimes
used to coat metals to prevent oxidation.
- borrow pit
- An area
from which earth is taken to be used in the construction of an
- An opening made
by breaking down a portion of a solid body, such as a dike or
- A fine grained,
natural, earthy material composed primarily of hydrous aluminum
- Tests carried out to determine the
relationship between unit weight and water content of a
- A pipe, tube,
or tile through which water or other fluid passes or is
- core drilling
process of obtaining natural or undisturbed samples of soil or
rock by drilling.
- A point, line, or
surface with reference to which elevations are measured.
- The angle at which a
bed, stratum, or vein is inclined from the horizontal.
- The rate
of flow of water in a stream, conduit, or other channel,
usually measured in cubic feet per second (cfs).
- A dispersive soil is a clay soil that
behaves as a single grain soil and is highly erodable when
subjected to water forces.
- drainage area
area of a drainage basin, or catchment area.
- earth fill dam
dam built of gravel, earth, broken rock, sand, or silt, and
usually containing an impervious clay core or facing.
structure, usually of earth or gravel, constructed above the
natural ground surface and designed to hold back water.
- factor of
- The ratio allowed for in design, between
the ultimate breaking strength of a material, to the force
exerted against it. A factor of safety of one means a material
will fail when the force exerted against it equals the ultimate
breaking strength of the material.
- field density
- Tests carried out under site conditions
to determine the density of soils.
- See stop
- A wall, collar, or other structure
intended to reduce percolation of water along
surfaces or porous strata.
vertical distance between water level and the crest of a dam or
the top of a channel.
- A cementitious
material of high water content, fluid enough to be poured or
injected into spaces and thereby fill or seal them.
- A wash line, seed line, mud line, trash
line, or other debris line formed at the highest level reached
by a stream or body of water.
- A graph
to show the relation with time of the level, flow, or velocity
of water in a lake or stream.
- internal drain
means of draining water from the interior of an embankment to
prevent water from entering the soil and causing it to soften
and endanger the embankment.
- The bottom, or
lowest part, of the internal cross section of a conduit or
- A surface of
actual or potential fracture or parting in a rock without
- left or right
direction designated as one faces in a downstream
process of becoming liquid; the sudden large decrease of the
shearing resistance of a cohesionless soil.
- An analysis of the physical and
mechanical properties of metal.
- Silt containing mica.
- National Geodetic Vertical
- Reference level, equivalent to mean sea
level datum, from which elevations are measured.
- normal pool
usual reservoir level during times not affected by drought or
of water over the top of a dam or embankment.
- A closed
conduit for supplying water to a water wheel or turbine.
of water, usually downward, through small openings in a porous
property of a porous rock or soil medium for transmitting a
fluid without impairment of the structure of the medium.
- phreatic line
upper free-water surface of the zone of seepage.
- A physiographical area lying along the
southern and eastern base of the Appalachian Mountains.
- pin hole dispersion
- Tests to determine dispersive properties
- Erosion by
percolating water in a soil resulting in caving and the
formation of conduits, tunnels, or pipes through the soil.
- A method of surveying whereby the
observations are plotted as the survey progresses. Used
extensively in topographic surveys.
- In soil
mechanics, a term used to define soils, usually clays, that are
capable of deforming plastically at varying water
- A method
developed by R. R. Proctor for measuring the degree of
compaction of a soil.
- return period
average period of time occurring between events.
- right or left
direction designated as one faces in a downstream
- rock crib dam
dam constructed of interlocking sections of timber or concrete,
forming cells which are filled with earth or broken rock.
- A computation
technique whereby a streamflow hydrograph for a specific site
can be transposed to another site.
- That portion of
rainfall that finds its way into streams as surface flow.
- An escarpment,
cliff, or steep slope along the margin of a plateau, terrace,
material settled from suspension in a liquid.
- The act or
process involving the slow movement of water or other fluid
through a porous material such as soil or rock.
- seepage collar
wall, collar, or other structure to reduce or prevent seepage
of water along the outside surface of a conduit or pipe.
- shear test
- Tests to
determine the shear strength of soils.
- Shelby tube
- A soil
sampling device consisting of thin-wall tubing which is driven
into a soil to obtain a sample.
- A horizontal
structural member forming the bottom of a door, opening, or
other entranceway, such as to a conduit or penstock.
- A fine grained
sediment having a particle size intermediate between that of
fine sand and clay.
- sliding circle
- A method of analysis that allows the
determination of the relative stability of a soil mass.
- slope failure
downward and outward movement of a mass of rock or
unconsolidated materials as a unit.
- A passage
for surplus water over, around, or through a dam or similar
- stop log
- A log, plank,
cut timber, or steel or concrete slab or beam fitted into end
guides between walls or piers to close an opening to the
passage of water.
- storage attenuation
decrease in intensity or level of a flood wave as a result of
water being stored in the channel or reservoir.
- The direction or
bearing of a horizontal line in the plane of an inclined
stratum, joint, fault, or other structural plane. It is
perpendicular to the direction of dip.
- Nearly, but
not exactly, parallel.
- tension crack
- A fracture
that is the result of stresses that tend to pull material
- toe of dam
- The base of an
embankment, bank, bench, or slope.
- A map designed to portray an area to a
certain scale, and that primarily depicts the relief of the
hydrograph of streamflow representing the flow resulting from
one inch of rainfall excess occurring uniformly over a drainage
basin in unit time.
- An opening in a rock
or soil not occupied by solid matter.