FLOOD06421

• County: Statewide
• Basin: Statewide
• Title: Highways in the River Environment
• Date: 2/1/1990
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

Total Sediment Load {or totalloaQl - The sum of suspended load and bedload or
the sum of bed material load and wash load of a stream.

Tractive Force - The drag on a streambank caused by passing water which tends
to pull soil particles along with the streamflow.

Trench-Fill Revetment - Stone, concrete, or masonry material placed in a
trench dug behind and parallel to an eroding streambank. When the erosive action of
the stream reaches the trench, the material placed in the trench armors the bank
and thus retards further erosion.

Tsunami - Long-period ocean wave resulting from earthquake or other seismic
disturbance.

Turbulence - Motion of fluids in which local velocities and pressures fluctuate
irregularly in a random manner as opposed to laminar flow where all particles of the
fluid move in distinct and separate lineS.

Uncontrolled Crossinq - A bridgs crossing that imposes no constraints on the
natural width of the stream or on its ability to shift its channel.

Uniform Flow - Flow of constant cross section and average velocity through a
reach of channel. Both the energy $lope and water surface slope are equal for
uniform flow conditions.

Unit Oischarqe - Discharge per unit width (may be average over a cross section,
or local at a point).

!Jnit Shear Force (shear stress) - The force or drag developed at the channel
bed by flowing water. For uniform flow, this force is equal to a component of the
gravity force acting in a direction par;;lllel to the channel bed on a unit wetted area.
Usually expressed in units of stress, force per unit area.

Unsteady Flow - Flow of variable cross section and average velocity with
respect to time.

Upper Bank - The portion of a streambank having an elevation greater than the
average water level of the stream.

Veqetation - Woody or non woody plants used to stabilize a streambank and
retard erosion.

Velocity - The rate of motion of a stream or of the objects or particles
transported therein, usually expressed in distance per time.

Velocity. Cross-Sectional Averaqe - Discharge divided by cross-sectional area
of flow.

Velocity. Local Averaqe - Local discharge intensity divided by depth of flow.

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