Earth and Environmental Systems
What does the term “stream” mean to a geologist?
Channelized flow at the surface.
Know how the mouth, head, and base level of a stream are spatially related to the stream’s longitudinal profile.
Head: top, steep
Mouth: bottom, more level
Know what will happen if a portion of the land a stream runs through should rise above, or fall below the longitudinal profile.
Land uplift: creates cliffs (waterfalls) and benches (rapids)
Land Sink: stream will deposit up
Besides vertical movement of the land, why else might a stream have to adjust to a new longitudinal profile?
Change in the base level. Ex: dam
Know the difference between a young, middle aged, and old aged stream.
Young: straight, steep slopes
Mid aged: curvy, small flood plains
Old: winding/hairpin turns, large flood plains
Be able to identify the following on a diagram: flood plain, cut bank, point bar, oxbow lake, meander scar, yazoo stream/tributary, terrace, and levee.
Flood plain: flat land on either side of the stream
Cut bank: cut by outside current of stream
Point bar: land, opposite cut bank
Oxbow lake: horseshoe shaped lake
Meander scar: dried up oxbow lake
Yazoo stream: small stream in flood plain, runs alongside main stream
Terrace:a step-like landform that borders a stream flood plain
Levee:sediment built up at end caused by flooding and reflooding
Know the definitions of a watershed (drainage basin) and a drainage divide.
Watershed:area of land that deposits water to a stream segment
Drainage divide:high land that separates two watersheds
Know the difference between stream capacity and stream competence. Know what happens to a stream if its sediment load is greater than its capacity.
Stream capacity: total discharge of sediment the stream is transporting
Stream competence: largest sized particle being moved by the stream (bed load)
If sediment load is greater than capacity: flood
What is the name of the sediment feature created by a mountain stream that discharges onto a relatively flat plain?
Alluvial Fan
What is the name of the sediment feature created by a stream discharging into a larger body of water?
Delta
Know the definition of, and how to calculate, stream discharge.
Q=wdv
discharge=width times average depth times average velocity
Know what a hydrograph is. Know what is plotted on the x-axis and what is plotted on the y-axis.
x axis: time
y axis: discharge
Know the definition of stream stage, and what a graph relating stage to discharge is called.
height of the stream
Rating Curve relates stage to discharge
Know what is meant by flood probability and flood recurrence interval. Understand the statistical nature of these two things.
Flood probability:p=1/R
Flood recurrence interval:R=(n+1)/m
Know how a change in any of the other parameters of the hydrologic cycle can affect flooding (by increasing or decreasing stream runoff).
A decrease in I and ET forces an increase in R
What was the name of the lake that emptied to create the channeled scablands and when did it empty?
Glacial Lake Missoula
Emptied 17,000 years ago
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