EM 1110-2-1100 (Change 1)
31 Jul 03
T
T-GROIN
A GROIN built in the shape of a letter "T" with the trunk section connected to land.
TECTONIC FORCES
Forces generated from within the earth that result in uplift, movement, or deformation of part of the earth's crust.
TECTONICS
The study of the major structural features of the Earth's crust or the broad structure of a region.
TERMINAL GROIN
A GROIN, often at the end of a littoral cell or at the UPDRIFT side of an inlet, intended to prevent sediment
passage into the channel beyond.
TERRACE
A horizontal or nearly horizontal natural or artificial topographic feature interrupting a steeper slope, sometimes
occurring in a series.
TERRIGENOUS SEDIMENTS
Literally `land-formed' sediment that has found its way to the sea floor. The term is applied (a) to sediments
formed and deposited on land (e.g., soils, sand DUNES), and (b) to material derived from the land when mixed in with purely
marine material (e.g., sand or clay in a shelly limestone).
TERRITORIAL SEA
The offshore belt in which a coastal state has exclusive jurisdiction. The territorial sea may not extend more than
12 NAUTICAL MILES from the COASTLINE.
TETRAPOD
Concrete armor unit with four stubby legs, used on breakwaters and seawalls to dissipate wave energy.
THALWEG
In hydraulics, the line joining the deepest points of an inlet or stream channel. Often serving as the boundary
between two states.
THRESHOLD OF MOTION
The point at which the forces imposed on a sediment particle overcome its inertia and it starts to move.
THRESHOLD VELOCITY
The maximum orbital velocity at which the sediment on the BED begins to move as waves approach shallow water.
TIDAL CREEK
A creek draining back-barrier areas with a current generated by the rise and fall of the tide.
TIDAL CURRENT
See CURRENT, TIDAL.
TIDAL DATUM
See CHART DATUM and DATUM PLANE.
TIDAL DAY
The time of the rotation of the Earth with respect to the Moon, or the interval between two successive upper transits
of the Moon over the meridian of a place, approximately 24.84 solar hours (24 hours and 50 minutes) or 1.035 times the mean
solar day. (See Figure II-5-16.) Also called lunar day.
A-80
Appendix A Glossary of Coastal Terminology
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