Flooding Flashcards
What are the steps of the hydrologic cycle?
- evaporation
- condensation
- precipitation
- runoff
- infiltration
- percolation
(repeat)
Is the water flow of the North Saskatchewan River relatively fast?
no
stream vs river
- stream - body of flowing water confined to a channel, regardless of its size
- river - major branch of a stream system
drainage basin
region from which stream draws its water supply
where are the divides of a drainage basin usually found?
usually between countries/provinces
stream discharge? units? calculation?
- volume of water that passes a given point in a given time through a channel of a certain width and depth; m^3/s
- cross sectional area x velocity of flow
laminar flow
- straight or gently curved streamlines run PARALLEL to one another (no mixing)
- characteristic of SLOW rivers or along EDGES of FAST rivers
turbulent flow
- streamlines mix, forming eddies
- characteristic of FAST rivers
How do streams do work?
transport sediments down hill
total sediment load
stream’s capacity
stream’s competence
stream’s ability to carry a material of a given size
How is capacity related to discharge?
faster the stream flows, the more water is present; the more (and larger) material can be moved
How does stream velocity impact sediment sorting?
- slow water = fine-grained sediments
- fast water = wide range of grain sizes
TRUE or FALSE: sediments are commonly WELL SORTED by size and density
TRUE
graded stream? are low spots filled in/eroded? high spots?
- stream in which various factors combine to yield an average of neither erosion nor sedimentation
- AT EQUILIBRIUM
- low spots filled in
- high spots eroded
What is the velocity of a stream largely dependent on?
its gradient - steepness of a stream’s channel
base level? What happens to gradient as the stream approaches base level?
- base level = lowest elevation to which a stream can flow
- gradient DECREASES as it reaches the base level
What is one way that the base level of a stream can be changed?
human intervention –> BUILD A DAM
On what kind of gradients do meandering streams often occur? Are they erosive? if so, what materials do they erode?
- occur on gentle gradients
- erode unconsolidated sediments and weak bedrock –> carry FINE sediments
- path may shift significantly with erosion and deposition
On what kind of gradients do braided streams often occur? Are they typical of low or high sediment loads?
- many diverging and merging channels
- steep gradient
- high sediment load
Describe the formation of a braided stream during low discharge period (summer).
- high velocity, high sediment streams flow over nearly flat, easily eroded terrain
Describe the formation of a braided stream during high discharge period (spring snow melt).
- high velocity, high sediment streams does NOT form OXBOW BENDS
- instead, cuts across soft sediments at edges of existing channels, creating braided channels
When do braided streams usually form? (high or low discharge period)
high discharge period (spring snow melt)
Describe the formation of a meandering stream.
- current faster at outside banks, which are eroded
- sediment deposited at inside banks, where current is slower –> FORM POINT BARS
