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186 Cards in this Set
- Front
- Back
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What do rivers do?
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Excavate/drain water from land surface
distribute water, sediment, and nutrients across the landscape |
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Describe river movement
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From high to low elevation
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How do rivers shape landforms
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Erosion
Sediment transport |
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Why study rivers?
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Natural Hazards
Aquatic Environment Affected by Human Activity |
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Geomorphology
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study of earth's surface processes and land forms.
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Which geomorphic agent is the most effective agent?
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Water
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Water as a geomorphic agent is only affective in the ________ direction.
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Downslope
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What geomorphic agent is only able to move small particles but is able to move upslope?
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Wind
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In humid locations wind assists in the formation of ______.
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Waves
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Beaches are formed by __________ processes.
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aeolian
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Which of the geomorphic agents is the most powerful?
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Ice
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What processes are collectively known as erosion?
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Weathering
Mass Wasting |
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Transportation
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refers to the transfer of sediment
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Deposition
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refers to the accumulation of sediment
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What is the combined outcome of water as a geomorphic agent?
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New lands forms and landscapes
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Erosion
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pickup and removal of sediment produced by weathering and mass wasting
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Combined evaporation and transpiration are known as
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Evapotranspiration
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Overland flow
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water on slopes
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The degree of inclination of earth's slopes is responsible for
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Downslope flow
Erosion and Deposition Rain fall Infiltration |
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Infiltration
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refers to a soils ability to absorb water
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In the equation for water on slopes P represents.
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Rainfall rate (mm/h)
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In the equation for water on slope I represents
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Infiltration capacity (mm/h)
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In the equation for water on slopes if P<=I what is true.
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All water infiltrates -splash
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If P>I what is true?
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Some water does not infiltrate- overland flow and splash
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Overland flow
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Motion of thin surface layer of water over sloping grounf
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Overland flow occurs when
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Precipitation>Infiltration
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Overland flow results in
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soil Erosion
Picking up of weathered material |
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Slope Erosion by water includes
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Erosion of Sediment
Transport of Sediment Deposition of Sediment |
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Accelerated soil erosion occurs when
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Rate of soil erosion >rate of soil formation
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Name the processes of erosion
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Rain splash erosion
Sheet erosion Rill erosion Gully erosion |
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As channels increase in size they become ________.
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gullies
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Rain splash erosion
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Soil erosion caused by direct impact of falling raindrops on slope surface
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Where is rain splash erosion most effective?
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Areas with sparse or no vegetation cover
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The amount of erosion done by rain splash erosion is dependent on
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The kinetic energy (function of drop size and speed) of raindrops
Slope Angle |
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Sheet, rill and gully erosion rely on a ___________.
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Drainage basin
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Drainage basin (watershed)
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Surface area occupied by a drainage system
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In a drainage basin surface runoff drains to ___________.
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one point of stream network
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What do you call a boundary found in a drainage basin?
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Drainage divide
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Sheet erosion
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erosion resulting from sheet flow
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Sheet flow
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Thin layer of water flowing over a smooth surface
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Sheet erosion is effective in ____________.
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transporting the eroded material made available by splash erosion
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Rill erosion
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Erosion process along small channels called rills
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Rills
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closely spaced miniature channels resulting from overland flow
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What do rills result from
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Overland flow
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Where do rills develop
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Along the slope
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Gullies
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Deep, V-shaped channels carved by newly formed streams (rills)
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What do gullies develop into
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Streams, with water flowing under the action of gravity
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Water in streams is _______.
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fluvial
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Fluvial
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running/flowing water
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Fluvial processes include
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Movement of Water
Movement of sediment |
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Fluvial Landforms
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Landforms resulting from the movement of water and sediment
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Stream
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a long, narrow body of flowing water occupying a stream channel, and moving to lower levels under the influence of gravity
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Streams serve as an important link between _________ and ________.
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ground water and overland flow
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Most of what we see in channels is fed by ____________.
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Groundwater
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Only during storms are channels mainly fed by _________.
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Overland flow
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Why are channels fed by mainly groundwater
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Due to the location of the water table
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Stream flow-velocity profiles show how
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erosion depends on velocity of flow
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In a stream flow-velocity profile where is velocity the greatest?
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In the middle and at the top
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In a stream flow-velocity profile where is velocity the lowest
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Near banks and bed/bottom due to friction
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Stream discharge
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refers to the total flow carried by the river as a volume of water passing a point on the stream in a given unit of time
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What is the stream discharge equation
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Q=A*V
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Q is measured in
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units m^3/s
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Stage or heigh of water measurements are _________.
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continuous
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Discharge measurements are __________.
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Periodic
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Hydrograph
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plot of variation in discharge of a stream over time
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What equipment is used to measure stream velocity?
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Current meter
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The stage-discharge relation is show in the ____________.
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Stream flow rating curve
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Name the steps of estimating stream discharge
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Stage or water heigh measurement
Discharge measurements Stage-discgarge relationship Converting stage to discharge |
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What does the lag time on a stream flow hydrographs tell us
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The time required for precipitation water to reach the larger stream channels
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An event hydrograph consists of ___________ precipitation events
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A single precipitation event
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Annual hydrographs show
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multiple precipitation events over the course of a year
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Where does the ragtime on a hydrograph usually occur?
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At middle point of precipitation and midpoint of runoff volume
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When does flooding occur?
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When stream discharge cannot be contained within a channel
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Flood plain
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The low-lying ground next to the river
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During a flood the flood plain becomes
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Inundated
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What natural disaster causes the greatest loss of life and property damage?
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Floods
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Stream load
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Amount of sediment transported at a given discharge
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Stream capacity
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maximum amount of solid sediment that a river can move at a given discharge
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Stream competence
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maximum particle size that a river can move (based on average discharge
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Load ________ with discharge.
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Loads increases with discharge
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The more water that is available to carry sediment the ______ the volume
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The higher the volume
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More erosion of stream bed the _________ velocity
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Higher the velocity
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The more and larger the segment that can be suspended the higher the _____________.
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Higher the turbulence
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Name the types of load
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Dissolved load
Suspended load Bedload |
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What as a result of the bed force keeps particles in motion in a stream?
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The streams turbulence
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Dissolved Load
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Dissolved material carried by the stream, enters the channel network due to solution and other chemical weatering
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Due to what does dissolved load enter the channel network?
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Due to solution and other chemical weathering
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What are the processes involved in dissolved load
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Groundwater flow remains in contact with rock and soil for a long time and therefore carries most of the dissolved matterial
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The composition of dissolved load is important in regulating the _________ and ____________ of the stream.
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Chemistry and biology of the stream
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The suspended load of a stream moves in suspension due to ____________.
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Turbulence
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Turbulence causes
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The mixing and movement actions in a stream
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What makes up suspended load
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Fine material (clay, silt, and sand)
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Suspended load accounts for ________ of sediment load
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90% or more
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Suspended load depends on
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Discharge
Sediment availability |
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Bedload
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Sediment travels by bouncing (saltation), rolling or sliding over the stream bed
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Particles in the bed load move ____________.
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Short distances
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Bedload is composed of
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Larger particles (sand, gravel, and boulders)
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Bed load accounts for _______ of the sediment load
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10%
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Stream profile
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a graph of elevation of a stream plotted against its distance downstream
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Upstream segments of a longitudinal stream profile have a _________ gradient
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steeper
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Downstream segments of a longitudinal stream profile have a _________ gradient
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gentler
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Balance in a stream is reached when
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Average export of sediment=average import
Inflow=outflow |
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A stream adjusts its gradient ____________.
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gradually
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In streams what are referred to as discontinuities
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lakes, falls, and rapids
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When a stream achieves a balanced stated it is said to be _________.
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a graded stream
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Stream gradient is highest at the ______.
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Head of a stream
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The Mouth of a stream can be a
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Lake
Ocean Land area |
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A stream mouth is characteristic in that it has _________.
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no gradient
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Base level
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Lowest level a river can reach where a river's mouth is located
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All rivers have an objective to _________.
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Achieve a base level
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Rivers achieve base level through the process of
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Erosion
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Channel Pattern
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Arrangement of the stream channels in a drainage basin
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Name the types of single channels
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Meandering
Straight |
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Name the characteristics of upland streams
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Rapid Flow
Steep Slopes Erosional or degradation state =sediment sources |
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Name the characteristics of lowland rivers.
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Slow flow
Low gradients High sediment load Depositional or aggradational state=sediment accumulation |
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Drainage Pattern
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arrangement of the stream network in a drainage basin
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Name the thing drainage patterns reflect
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Geology of an area
Climate Time |
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Name the types of drainage patterns
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Dendritic
Dome Trellis Radial |
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Dendritic drainage patterns are
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Treelike/ branched pattern
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Braided channel patterns are the only example of a type of __________.
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Multiple channel
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What type of channel pattern is rare?
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Straight
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Name the characteristics of a straight channel pattern
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Rare
Very Low gradient Only over short distance |
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What type of channel pattern has a low gradient?
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Straight
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Name the characteristics of a meandering channel pattern
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Very common
Slightly higher gradient than straight channel pattern Cohesive banks Relatively Low sediment supply Fine parcel size distribution |
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In meandering channels cohesive banks refer to
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Deep and narrow cross-section
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In meandering channels what sediment transport dominates
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Suspended sediment transport
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What are the features of Meandering rivers
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Cut bank
Point Bar Floodplains wider than channel gradual channel course changes Oxbow lake |
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Cut bank
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constantly erode material outside the bend
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Point bar
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Constantly deposited material inside the bend
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Oxbow Lake
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Bow or crescent shaped lake that forms when meanders within floodplain erode and cut off the bends
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The maximum velocity of meander bend is found on the
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Erosional slope
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The erosional slope of a meander bend occurs in the direction of __________.
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direction of meander migration
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Braided Channel
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a network of multiple interconnected channels separated by bars
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Name some characteristics of braided channels.
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Very common
Higher gradient than meanders non-cohesive back aggradation (higher sediment supply) coarse particle size distribution |
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What type of sediment load dominates braided channel patterns.
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Bed load
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Non-cohesive basnks
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shallow and wide cross section
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Name the three river features/landforms
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Alluvial terraces
Deltas Alluvial fans |
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Alluvial terraces
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Bench-like landforms carved in alluvium by a stream during degradation
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How are alluvial terraces formed
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Stream erodes into floodplain
Forms new floodplain at lower elevation |
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In alluvial terraces the number of paired terraces correspond to
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The number of erosional periods
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Where do depositional landforms accumulate
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where a river reaches base level
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Why do depositional landforms require
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Flat land surface or standing water
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Due to reduced velocity at base level what depositional land forms may form
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Alluvial fans
Deltas |
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From where do branch channels emerge?
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From single channel (distributaries)
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Delta
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Large body of sediment built by stream flowing into a body of standing water (oceans, lakes)
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What controls the shape of a Delta
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Fluvial System (sediment load)
Waves (sediment redistribution) Tides (changes in water level) |
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Name the types of Deltas
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Bird's foot
Triangular Volcanic Coast |
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Alluvial Fans
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Cone-shaped, relatively steep alluvial deposits
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Where do alluvial fans occur
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Where a stream channel emerges from a steep, confined valley onto a broader, flatter land surface
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What are alluvial fans composed of
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composed of coarse sediments (usually gravel to boulders with sand mixed in)
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Alluvial fans are _____ steep
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Modertately steep ( 1-4 degrees)
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What is always true of delta formation?
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They are formed in water (built by stream flowing out into base level of water)
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Name characteristics of a Delta
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Fertile areas
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Why are deltas fertile areas.
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Due to being supplied by new nutrients and sediment every year
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What restricted the fertility of the Nile Delta
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The dams built (Aswan)
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How did dams restrict the fertility of the Nile Delta?
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Restricted delta flooding
no nutrients can be deposited now have to use excessive fertilizer Erosion of delta (balance is lost as sediment supply is low) |
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Alluvial fans differ from deltas in that they are _______.
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Formed on land
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Percolation
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filtering of fluids as done by gravity
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Drainage divide
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a line that surrounds all drainage lines and passes through the highest point between adjacent basins
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Internal drainage
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When water leaves the drainage basins by means of evaporation and groundwater flow
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Soil moisture zone
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Area immediately below the ground surface water that does not fully saturate pores in which thin fils of water molecules adhere to the surface of soil particles
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Acquifers
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an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted
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zone of saturation
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is the area in an aquifer, below the water table, in which relatively all pores and fractures are saturated with water.
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What marks the top of the zone of saturation?
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The water table
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Water table
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level at which groundwater can be found
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abrasion
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mechanical scraping of a rock surface caused by the friction between two rocks
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corrosion
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deterioration of rock caused by chemical weathering
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Incise
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Downcut action of their channels into the landscape done by streams
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Name the Erosional Landforms of streams
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Channels
Gullys Graded Stream Alluvial Terraces Cut banks Oxbow Lake |
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Name the Depositonal landforms
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Levees
Point bars Deltas Alluvial Fans |
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What is a loess
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Sediment deposited by the wind
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What river is the most sediment laden in the world
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Yellow River, Lanzhou, China
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Where does the yellow river get its sediment
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The loess plateau
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The yellow river in china is an example of a
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Suspended load
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saltation
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The bouncing movement of bedload
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levees
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ebankment, floodbank or stopbank to prevent flooding
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nick point
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an abrupt change in the gradient of the profile of a river due to a change in the erosional rate
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colluvium
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soil and debris that accumulate at the bottom of a slope due to mass wasting or sheet erosion
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entrainment
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the process by which surface sediment is accumulated into a fluid flow as a part of the process of erosion
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entrenched meander
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a deepened meander of a river which is carried downward further below the valley surface in which it originated
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scour and fill
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the process of first digging out and then refilling a channel instigated by the action of a stream or a tide, typically occurs during a flood
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sinuosity
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the ability of a river to curve or bend
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sheetwash
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the detritus deposited by a sheet flood
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thalweg
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the line of lowest elevation in a valley or watercourse
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traction
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process by which sediments in a river are transported by rolling along the bottom
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backswamp
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swampy depressed area of a floodplain
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