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
The maximum depth of scour attained for a given flow
condition. May require multiple flow events and in cemented or
cohesive soils may be achieved over a long time period.
Flow of constant cross section and velocity through a reach of
channel at a given time. Both the energy slope and the water
slope are equal to the bed slope under conditions of uniform
Discharge per unit width (may be average over a cross section,
or local at a point).
unit shear force
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 parallel to the channel bed
on a unit wetted area. Usually in units of stress, Pa (N/m ) or
Flow of variable discharge and velocity through a cross section
with respect to time.
The portion of a streambank having an elevation greater than
the average water level of the stream.
The time rate of flow usually expressed in m/s (ft/sec). The
average velocity is the velocity at a given cross section
determined by dividing discharge by cross-sectional area.
An abutment, usually with wingwalls, that has no fill slope on its
Turbulent eddy in the flow generally caused by an obstruction
such as a bridge pier or abutment (e.g., horseshoe vortex).
A channel exhibiting a more or less non-systematic process of
channel shifting, erosion and deposition, with no definite
meanders or braided pattern.
A thalweg whose position in the channel shifts during floods
and typically serves as an inset channel that conveys all or
most of the stream flow at normal or lower stages.