Lecture 10: Hydrologic cycle and fluvial systems Flashcards
What is the importance of streams?
- Hydrologic cycle: Streams carry
most water from continents to
the ocean - Landscape evolution: Stream erosion and depositional processes shape the Earth’s surface
- Sediment supply: Billions of tons of suspended and transported sediment to ocean basins
- Solute supply: Dissolved cations
(Na+, Ca2+, Mg2+) and anions (Cl-,NO3-, PO43-, SO42-) – nutrients important for coastal ecosystems - Support complex ecosystems
What is the relationship between CO2 and temperature
- More CO2 = hotter air temperature
- More hot air = more droughts
What is the relationship between temperature and water vapour?
- A warmer atmosphere holds more moisture
- 7% more per 1°C of warming
- Water vapour is also a greenhouse gas
More intense rainfall (more floods) and more runoff (rather than small amounts of rain evenly distributed)
What is sheet flow?
Overland flow when raining
Water concentrated into stream flow within a channel consists of two flows. What are they?
- Consists of storm flow and
base flow
Streams with no base flow are…
ephemeral
Streams with base flow are…
perennial
What three things make up a stream?
– A channel
– A drainage basin
– A divide
What is a streams load?
The stream’ s load is the total sediment and dissolved matter it is transporting
What is a levee?
– A ridge parallel to the course of a stream that regulates water levels
What factors control the shape/size of a stream?
- Erodibility of rock
- Steepness of descent
- Volume of water
Generally speaking, stream width increases downstream
What is a streams gradient?
The vertical distance that a stream channel descends along its course is its gradient, overall this decreases downstream
Generally speaking, stream gradient decreases downstream
What is the equation for discharge?
Discharge (Q) = Cross-sectional Area (A) x average velocity (V) (m3/s)
Following a stream from its source to
its mouth, orderly adjustments occur. What are these?
- Width and depth increase
- Gradient decreases
- Flow velocity slightly increases
- Discharge increases
- Turbulence decreases
What is a hydrograph?
- A graph that shows stream discharge through time
- A hydrograph may be used to show how the water flow in a drainage basin (particularly river runoff) responds to a period of rain.
How do we determine flood recurrance interval?
Determine recurrence interval using
formula:
RI = (n+1)/m
where:
n = number of years of data collection
m = magnitude (rank number where 1
= highest and n = lowest)
Round your RI’ s
How is a streams response related to its basin?
- Stream response to a rain event is based on drainage basin parameters (size, pattern, gradient, geology, and vegetation)
