geog 201 final notes

8/10/2019 GEOG 201 Final Notes

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GEOG 201: Ross s Final Study Notes


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Geography 201: Fluvial Geomorphology Quiz One Study Notes

What are some components of the fluvial system?

Drainage basin divide: The divide between neighboring drainage basins (watersheds).

Watershed (Drainage basin): An area within which water flows. Water from these areascontribute to the discharge at the outlet. (High to low elevation within a drainage divide)

Geomorphic threshold: A point at which a landform becomes unstable and the system shifts toa new equilibrium.

Internal changes are possible independently within the system (meander cuts off andan oxbow forms)

External brought about by change in an external factor to the system (rainfalltriggering landslide)

Feedback (both positive and negative): A change in one variable that leads to a change in oneor more variables.

Positive and Negative: initiated by a change in a system variable which leads toadjustments that counteract effects of the original change.

Steady state vs dynamic equilibrium:

Steady state moves up and down but remains relatively close to the average channelbed elevation, whereas, dynamic elevation moves up and down but is always changing.

Watershed functions

Transportation of sediments, Provide water,


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Stream order: two first order make a second order and two second orders make a third orderand so on and so forth.

Infiltration : movement of water from air into soil columnPercolation : movement of water through the soil columnDrainage Density: Ratio of the total length of streams within a watershed to the total area ofthe watershed (D = L / A)

Quick flow: The discharge under the peak on a hydrograph.

Subsurface water zones

Ground surface zone of aeration (suspended water)

Soil water zone (soil moisture)

Intermediate zone (pore space partially filled with water)

Capillary fringe (capillary rises from water table)

Water table zone of saturation (groundwater)

Infiltration rate vs infiltration capacity:

Rate: is the speed at which water is infiltrating into the system.

Capacity: is the max rate in which water can enter the system.

Hortonian overland flow: Movement of water down slope when the rainfall intensity >infiltration capacity.


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Variable source area concept: concept that runoff-generating areas in the landscape will varyin location and size over time

River discharge: Q = V * A (Q is Discharge, V is average linear velocity, A is cross-sectional area

Annual flow regime: Seasonal variation in flow observed during an average year.

Bankfull discharge: the discharge that produces the average morphological characteristics of ariver channel (When the water is at the ridge of the banks).

Return period: In terms of floods, its the predicted time it takes for a flood to reoccur.

Lag time: The time between the peak of the rainfall discharge to the peak of the river systemsdischarge for a storm.

Base flow: the lowest discharge on an annual basis and usually occurs during the summermonths.

1. What is the difference between ephemeral and perennial rivers? What are the reasonsfor the differences in flow variation within these two river types?

Ephemeral rivers are not always flowing, they are dried up during parts of the year.Perennial rivers however are always flowing. The reason for this has to do with the weather andseasonal patterns. For example, when the weather is really hot ephemeral rivers tend to dry upbut perennial rivers continue to flow.

2. List 4 internal and 4 external variables that influence the processes and forms of afluvial system.

Internal Variables include: Drainage Density, Discharge, depth, Slope

External Variables include: Climate Change, Tectonics, Base level, Human activity

3. What is the difference between internal thresholds and external thresholds? Give oneexample of each.

Internal thresholds are independent and are only a result of the river system itself. Suchas a river meandering to a new location and creating a new channel. External thresholds includethings like rainfall, climate change, etc.

4. List four independent variables that control changes in channel dimension and shape.

Discharge, bank material, sediment load, valley slopes


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5. List and describe the 3 classification systems within a drainage basin.

Drainage basin order (based off the highest stream order within the drainage basin).

Bifurcation ratio (10 1st

order, 4 2nd

order, 2 3rd

order --- 10/4 4/2 2/0 )Drainage Density

6. Draw and label a storm hydrograph.

See Storm Hydrograph definition (Q is in cubic meters per second and T is time)

7. What are the two main effects of increasing drainage density on the hydrograph?

Higher peak discharge and decreased lag time.

8. Describe 3 infiltration scenarios that can occur on landscapes.

Hortonian overland flow: rainfall intensity > infiltration capacity (saturation from above)

Saturation excess overland flow: Saturation from below occurs when the soil becomescompletely saturated and all extra water introduced flows over the land (runoff)

Water table rising and influencing how much water can be absorbed by the soil until itbecomes oversaturated.

1. Draw a conceptual model illustrating hydrological processes on hillslopes that result in

changes to river discharge over time. Give an example of how one type of land disturbancecan affect the rates and magnitudes of three of these processes.

2. You work for consulting firm XYZ that has been retained by a land developer to createa rating curve for a river cross-section for a range of flows. How would you accomplish thistask?

Weathering Process

Uplift > Rock rising above the surface -> Erosion -> Melting near core -> Cooling ->

Weathering : physical/chemical/biological alterations to rock/soil

Physical: mechanical disintegration

Exfoliation separation in concentric layers


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Chemical: decomposition by chemical reactions to water

Carbonation: Calcium carbonate (limestone) dissolving in acidic groundwater

Hydrolysis: mineral cations are replaced by hydrogen ions from acidic water

Factors affecting physical/chemical weathering:Parent material, Topography, Climate, Geology, Time, Biology

Rock Falls : Free-fall from mountain/cliff

Tallus (fallen debris): protects base from eroding.

Landslides: rapid downslope movement of landmass

Mud flows: mainly the smallest mud and split particles caused by heavy rainfall.

Slope failure: no longer can resist the force of gravity

Sudden mass-wasting event triggers: Earthquakes, ice wedging, removal of slope vegetation,over-steeping of a slope.

Geography 201: Fluvial Geomorphology Quiz Two Study Notes

Mass wasting: Downslope movement of earth under the influence of gravity. i.e mud slides.

Slope stability

Soil texture: Used to describe composite sizes of particles in a soil sample. The soil Texturaltriangle uses different percentage amounts of Clay, Sand, and Silt to make up all the soil types.

Capillary water: Holds to soil particles by cohesion and is therefore able to move vertically andhorizontally in a water column.

Infiltration: The process of water seeping from above ground into the ground. (Percolation iswhen the water is already in the ground)

Shear stress: Shear stress is the force applied by flowing water parallel to the stream bed (orbank). T = pgDS (where p = density of water, g is gravity, D is water depth, S is slope)


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Universal soil loss equation: Predicts the long term average annual rate of erosion on a fieldslope based on Rainfall patterns, soil type, Topography, Crop system, and Managementpractices.

A = (R) (K) (LS) (C) (P)

Modes of sediment transport in rivers:

Bed load: particles in regular contact with the channel bed.

Suspended load: particles suspended above channel bed by turbulent eddies.

Wash load: particles (like clay and silt)

Dissolved load: Solutes (anions and cations)

Hjulstroms diagram

Sediment rating curves

They are used to predict the amount of suspended sediment based on different levels ofdischarge.

Sediment yield: The total quantity of sediment moving out of a watershed in a given timeinterval (tonnes / year)

Sediment delivery ratio: The ratio of primary erosion rate on hill slopes to the sediment yield atthe basin outlet.

Isovels: stream velocity contour line so it connects areas of equal velocity.


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Concept of flow Continuity:

Mannings equation A flow Resistance formula


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Froude number

Reynolds number

Re < 500 laminar flow

500 < Re 2000 turbulent flow

Stream power: Determines the capacity of a given flow to transport sediment (Watts/Metre)

Available stream power is related to the water surface slope (s) and discharge (Q), gravitation(g) and mass density of water (1000 kg m2) = pgQs

Flow competence: ability of a given flow to entrain (carry) sediment of a certain size and thisincreases with be shear stress.


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Drag force: acts in the same direction of flow (force of flow felt when wading a stream)

Lift force: acts vertically upward, caused by pressure difference above and below particle(Water flowing over particle moves faster and increase in speed which leads to a decrease inpressure i.e. Bernoulli Principle)

river in regime: A channel is in regime when form fluctuates around an equilibrium conditionover time. (Fluctuates around the average river form)

Lane balance: Important balance between supply of bed load at the upstream end of thechannel reach and the stream power available to transport it.

Supply vs transport limited rivers

Supply limited: The stream has the ability to move all the sediment that is supplied to it.

Transport Limited: Occurs when the sediment supply to the stream is in excess of theability of the stream to transport it.

Hydraulic geometry relationships of river channels

Relationships between the mean stream channel form and discharge both at-a-station anddownstream along a stream network in a hydrologically homogeneous basin.

Independent variable: Discharge (Q)

Dependent variables: width(w), depth(d), velocity(v)

-W,d,v increase downstream so therefore Q increases too.

-Depth influences velocity much more significantly than slope

channel adjustments

Changes that can be made to the channel form by manipulating 4 degrees of freedom (variablesthat can be modified)

Channel cross section, slope, bed roughness

1. What is the difference between erodibility and erosivity?


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2. List four factors that affect the rates of physical and chemical weathering.

3. What is the difference between sediment production and sediment transport?

4. What does the concept of flow continuity refer to?

5. Draw and label Hjulstroms diagram


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6. What is the difference between supply vs transport limited rivers?

7. What is the difference between physical and chemical weathering.

6. Describe how you would calculate the velocity of a river channel if you were given theslope (s), the hydraulic radius (R) and the roughness coefficient (n).

What is the Lane Balance and how is it used to explain river channel adjustments that occurover time (5 marks). Give an example of how a specific land use change would influence thevariables in the Lane Balance and cause either aggradation or degradation in a stream (5marks).

In diagrammatic form, illustrate how variables that describe channel geometry vary with riverdischarge for the upper, middle and lower reaches of a river.

geog 201 final notes

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