Erosion and Sediment Pollution Control Program Manual.pdf

Terrace -----An earthen embankment or a ridge and channel constructed across a slope to intercept
surface runoff water and outlet it to surface or underground outlets.
Terrace Zone -----Portion of a stream bank inland from the bank zone.
Test Boring -----Soil analysis taken by boring holes into the ground to remove samples.
Texture -----Refers to the relative proportions of clay, silt, and sand in soil.
Thalweg -----The line extending down a channel that follows the lowest elevation of the bed.
Thank-You-Ma’am -----Waterbar.
Thatch -----A layer of organic material between the crown of the plant and the true soil surface.
Thermal Impact -----A measure of the change in temperature in a body of water due to changes in the
tributary watershed.
Thermal Impact Analysis -----An evaluation of the anticipated changes that will occur in a receiving
surface water due to changes in the tributary watershed.
Thermal Pollution -----A temperature rise or decrease in a body of water sufficient to be harmful to
aquatic life in the water.
Threading -----The process of installing a slightly smaller pipe or arch within a failing drainage
structure.
Threatened Species -----Any plant or animal species likely to become an “endangered” species with
the foreseeable future throughout all of a significant area of its range or natural habitat; as
identified by the Secretary of the Interior in accordance with the 1973 Endangered Species Act.
Tidal Wetlands -----Wetlands affected by ocean tides, such as saltwater marshes, brackish water
marshes, mangrove swamps, intertidal flats.
Tie-back -----A variety of techniques used to secure a bulkhead, sea wall, or revetment in place against
a bank or slope.
Tile Drainage -----Land drainage — usually for agricultural purposes — by means of a series of tile
lines laid at specific depth and grade.
Till -----Non-sorted, non-stratified sediment left by glacial action.
Till Plain -----An extensive flat to undulating area underlain by glacial till.
Tillage -----The practice of producing a rough soil surface to maintain surface residue, conserve soil
moisture, and reduce wind erosion.
Tiller -----A plant that produces a new plant at the base of the parent plant.
Tiltmeter -----A device used to detect tilt, or rotation, of a surface point.
Timber Harvesting Activities -----Logging operation. See Chapter 14.
Time of Concentration (TC) -----In the Rational Equation, it is the estimated travel time for a drop of
water landing at the most distant point, usually the top of a hill, to the point of interest, usually an
outfall or a station on a channel. It is the sum of the times for sheet flow, shallow concentrated
flow, and channel flow.
Tipple -----A facility for loading coal in preparation for transporting it.
TMDL -----Total maximum daily load.
TOAD -----Team organizing agency development group, an interagency group conducting workshops
and training on wetland identification and delineation, plant identification, and hydric soils.
Toe -----1. The break in slope at the bottom of a bank or hillside. 2. The portion of a landslide farthest
removed from the head.
Toe Drain -----1. Drainage system installed at the bottom of a fill to collect excess soil moisture and
convey it to a discharge point. 2. Drainage system constructed in the downstream portion of
and earth dam or levee to prevent excessive hydrostatic pressure.
Toe of Dam -----The base or bottom of the sloping faces of a constructed dam at the point of
intersection with the natural ground surface. An inside toe is on the upstream side, while the
outside toe is on the down gradient side.
Toe of Slope -----The base or bottom of a slope at the point where the ground surface abruptly
changes to a significantly flatter grade.
Toe Zone -----Portion of a stream bank between the streambed and the normal flow level.
Top of Streambank -----First substantial break in slope between the edge of the bed of the stream and
the surrounding terrain. The top of streambank can either be a natural or constructed feature,
lying generally parallel to the watercourse, such as a road or railroad grade.
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