Channel Cross Profiles Flashcards
How does a channel cross profile differ from a valley cross profile?
The channel cross profile is a view of the river channel from one side to the other, including the channel bed and banks only.
This does not include the valley shape above the river.
Describe channel cross profile features in different courses of the river.
- Upper Course - narrow uneven channel, broadly rectangular shape.
- Middle Course - asymmetrical shape due to meanders.
- Lower Course - wide deep channel, presence of eyots and levees.
What is the wetted perimeter?
The wetted perimeter is the total length of the river bed and banks that is in contact with the water along a channel cross profile.
How does the length of the wetted perimeter affect the velocity of the river flow?
Large wetted perimeters lead to more friction between the water and river bed and banks.
This leads to a slowing of the river velocity as the river expends energy through inefficient flow.
Water must flow in a non-linear path around obstructions in the channel.
How is hydraulic radius calculated?
Hydraulic radius = cross-sectional area of the channel /wetted perimeter
How is the hydraulic radius related to efficiency of the river?
High hydraulic radius represents an efficient river which loses proportionately less energy to friction than an inefficient river of low hydraulic radius.
