Ch. 15 - River Systems Flashcards
Where is the head/mouth of the Fraser River?
Head: Mt. Robson (high elevation)
Mouth: Delta/Richmond (sea-level)
What is a Tributary?
A river or stream flowing into a larger river or lake
What is a Distributary?
A branch of a river that does not return to the main stream after leaving it (as in a delta)
What happens at the “Base Level” of a river?
The river joins itself to a much bigger body
What three processes account for the “work” of a river?
Erosion
Transportation
Deposition
What is meant by the term “Ultimate Base Level”?
When a river reaches sea-level, it can’t get any lower.
The final place where water from a river can end up
What is a Drainage Basin?
The basic spatial geomorphic unit of a river system; distinguished from a neighbouring basin by ridges and highlands that form divides, marking the limits of the catchment area of the drainage basin
What are the three main watersheds for greater Vancouver?
Capilano
Coquitlam
Seymour
What is the largest Drainage Basin in Canada?
Hudson Bay
What is the largest Drainage Basin in the US?
Mississippi River
What do Dendritic river patterns look like?
Looks like a tree, with branches growing in all directions off of a larger branch
Most common pattern in the world
What do Trellis River patterns look like?
A drainage pattern characterized by parallel main streams intersected at, or nearly at, right angles by their tributaries
What do Radial river patterns look like?
Common form that is found on a volcano/mountain, with rivers moving in all different directions down the slope. Creates a radial pattern
What do Parallel river patterns look like?
Caused by steep slopes with some relief. Because of the steep slopes, the streams are swift and straight, with very few tributaries, and all flow in the same direction
What do Rectangular river patterns look like?
Rectangular drainage patterns have rivers with right-angle bends. Commonly found on landscapes with fractures. Water flows through the fractures and joints of the land
What does an Annular river pattern look like?
A drainage pattern in which streams follow a roughly circular or concentric path along a belt of weak rock, resembling in plan a ringlike pattern
Generally structured by dome shapes
What is a Deranged river pattern?
There is no obvious pattern of flow. Often found in areas where the old pattern was completely destroyed
How is stream discharge (Q) measured?
Q = Width (m) x Depth (m) x Velocity (m/s)
What are the three types of Fluvial Erosion?
Hydraulic Action
Abrasion
Dissolution
What is Hydraulic Action?
The erosive work accomplished by the turbulence of water; causes a squeezing and releasing action in joints in bedrock; capable of prying and lifting rocks
What is Abrasion?
Mechanical wearing and erosion of bedrock accomplished by the rolling and grinding of particles and rocks carried in a stream, removed by wind in a “sandblasting” action, or imbedded in glacial ice
What is Dissolution?
Dissolving minerals through chemical processes
What are the four types of Fluvial Transportation?
Traction
Saltation
Suspension
Solution
How does Traction work?
A type of sediment transport that drags coarser materials along the bed of a stream
Large, heavy pebbles are rolled along the river bed. This is most common near the source of a river, as here the load is larger
How does Saltation work?
Pebbles are bounced along the river bed, most commonly near the source. Particles jump around
The transport of sand grains (usually larger than 0.2 mm) by stream or wind, bouncing the grains along the ground in asymmetrical paths
How does Suspension work?
Lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river. Very fine, very tiny, allowing them to be suspended within the stream. Dust in the air is another example
Fine particles held in suspension in a stream. The finest particles are not deposited until the stream velocity nears zero
How does Solution work?
The transport of dissolved chemicals. This varies along the river depending on the presence of soluble rocks
What is Stream Competence?
A measure of the ability of the river to transport sediment, erode landscapes, etc. All related to the concept of the work
What is Stream Capacity?
The amount of sediment that a river is capable of moving
What are the characteristics of a Straight Channel?
Things move in a straight line. Most efficient pattern for moving water from one place to another
What is a Meandering Channel?
The sinuous, curving pattern common to graded streams, with the energetic outer portion of each curve subjected to the greatest erosive action and the lower-energy inner portion receiving sediment deposits
More common than a Straight Channel. Formed over long periods of time by “disturbances”
What is an Oxbow Lake?
A lake that was formerly part of the channel of a meandering stream; isolated when a stream eroded its outer bank, forming a cutoff through the neck of the looping meander
What’s a Point Bar?
In a stream, the inner portion of a meander, where sediment fill is redeposited
What’s a Cut Bank?
In streams, a steep bank formed along the outer portion of a meandering stream; produced by lateral erosive action of a stream
What’s a Meander Scar?
A geological feature formed by the remnants of a meandering water channel. They are characterized by a crescentic cut in a bluff or valley wall, produced by a meandering stream
Formed when an Oxbow Lake dries up
What’s an Incised Meander?
A river meander which has been cut abnormally deeply/ is well-developed into the landscape because uplift of the land has led to renewed downward erosion by the river
Water is allowed to “downcut”
What’s a Braided Channel?
A stream that becomes a maze of interconnected channels laced with excess sediment. Braiding often occurs with a reduction of discharge that reduces a stream’s transporting ability or with an increase in sediment load
Braided streams form where the sediment load is so heavy that some of the sediments are deposited as shifting islands or bars between the channels
What is a Nickpoint?
The point at which the longitudinal profile of a stream is abruptly broken by a change in gradient; for example, a waterfall, rapids, or cascade
What are characteristics of a Youth river?
A fast flowing river characterized by a deep, narrow erosion pattern forming a V shaped channel or valley
Carries the most material, runs fastest, has steepest gradient
What are characteristics of a Mature river?
The slope becomes gentler and the river becomes much wider as it is joined by many tributaries. The river is also carrying a load now that has been eroded from further upstream.
Water slows down, sediments begin to deposit
What are characteristics of an Old Age river?
Widest, Deposits the most sediment, has the flattest gradient, lowest elevation, moves the slowest
What is a “Rejuvenation” of a river?
Results from a drop in sea-level or rise in land. Faults occuring on land can form waterfalls/cliffs, rejuvenating the river and making it run faster.
A change in gradient along a river can increase it’s competence
