Hydraulic Geometry Flashcards
The hydraulic geometry of the channel…
changes further downstream.
Velocity is affected by:
- amount of rainfall
- width and depth of a channel
- gradient
- friction
Thalweg is the point in the river, where…
the water has the highest velocity.
What affects the thalweg:
- depth of water
- addition of tributaries
- introduction of an obstacle
Wetted perimeter is…
the area that is wet.
Hydraulic radius formula:
cross-sectional area/wetted perimeter
Rivers with high hydraulic radius are…
efficient at transporting both water and sediment.
The hydraulic radius gets…
larger/higher further down the river.
Hjustrom curve shows…
the relationship between the size of sediment and velocity at which the sediment is eroded or deposited.
(Hjustrom curve)The smallest and largest particles…
require high velocities to lift them. E.g. 0.1 mm require 100mm/s and 0.01mm require 500mm/s.
The critical erosion velocity is…
the lowest velocity at which grains of a given size can be moved.
Higher velocities are required for…
entrainment than for transport.
When velocities fall below…
a certain level, those particles are deposited.
