Linkages Flashcards
What is stream competence?
What sediment morphological characteristics influence competence?
What are the two categories of streams regarding sediments?
The ability to move grains of sediment.
Shape - smooth or rough
Exposure - surface or buried
Packing - how tightly together they are
Imbrication - overlapping
1) Supply limited - bedrock
2) Capacity limited - transportation of sediments is limited. Alluvial.
What is a graded stream?
Where sediment supply input is in equilibrium with sediment transportation. No net change.
During a flood event, why does sediment transport peak before flow? What type of stream is this characteristic of?
Sediment limited stream. Because sediment is often limited and erodes away before the flow diminishes.
What are the basic channel typologies?
Meandering
Anastomosing - island forming.
Braided - Branching, frequent channel abandonment.
For meandering streams, what is the wave length of a stream?
= 10 x width
Compare the effect of slope and discharge on stream typology. What are the other primary factors that govern stream conditions?
Generally, braided streams have steeper slopes and/or higher discharges than meandering. Straight can be any combination.
Flood regime
Amount, timing and nature of sediment delivered to stream
Underlying material of stream - alluvial or bedrock
Geologic history
If you follow the thalweg, where are you likely to find bars, riffle and pools relative to one another?
Bar - alternating sides of the river
Pools - adjacent to bars
Riffles - at the tail end of bars
In coastal systems, what are the morphological differences between Large, intermediate, and small streams. What is their relation to hillslope processes?
Small: Step-pool. Steep gradient. Colluvial inputs (Coupled). Large sediment size. Woody debris and single particles are major morphological features.
Intermediate - Straight, riffle pool. Semi coupled. Less gradient 1-4%. Med sized sediments. Log jams regulate sediment transportation.
Large: Meandering. Islands and floodplains. Uncoupled. <1% gradient. Small sediment size, character largely determined by sediment supply.
In flatter places, like the Alberta Plateau, how are fluvial characteristic different?
At the headwaters, streams are uncoupled
Lower areas, the streams are coupled
Therefore:
Gradient increases
Sediment source is inverted
Riffle pool to step pool.
What are some secondary factors that govern stream channel conditions?
Local Climate
Type of riparian vegetation
Human modifications of channel (direct)
Land Use (indirect)
What is the measure of peak flow bank to bank width?
Bankfull width
Why is LWD important?
Adds channel complexity, regulates sediment transport, provides habitat, changes channel width and depth.
What are the main sources of LWD?
Landslide, windthrow, bank erosion.
