GEOL 100 - Streams and Floods
Formation of a v-shaped valley
-River is cut down my vertical erosion (hydraulic action and abrasion) -Mass movement of material slides down the valley
Pothole
A depression formed in a stream channel by the abrasive action of the water's sediment load.
radial drainage
A flow pattern where streams flow outward and downward from a central elevated point.
badlands topography
A landscape with steeper slopes, sparse vegetation, thin soils, and extensive stream network.
Permanent stream
A stream that flows year-round because its bed lies below the water table, or because more water is supplied from upstream than can infiltrate the ground
Formation of a U-shaped valley
A v-shaped valley fills with glacial ice. The glacier widens, deepens and straightens the valley through abrasion and plucking. Interlocking spurs are cut off to create truncated spurs.
ephemeral streams flow _____ the water table and exist in ____ climates
Above, arid
Meanders form only in ____ plains
Alluvial/flat
Watershed
An ecosystem where all water runoff drains into a single body of water
dendritic drainage
An irregular stream drainage network that resembles the limbs of a branching tree.
Radial drainage form around _____
Cone-like mountains
_____ separates drainage into one once an from drainage into another ocean
Continental divide
Amazon watershed has a _____ drainage network
Dendritic
Formation of stair-step canyon
Downcutting through alternating hard and soft strata
rectangular drainage
Drainage along joints and develops a grid or vertical joints
Erosion by running water
During flood stage, rivers can move massive amounts of sediment.
Canyon
Formed by linkage of potholes
Swampy inland delta
Forms where river reaches a closed drainage basin where all water evaporate and never reaches any lake or ocean
Dendritic drainage networks have _____ and _____
Gentle slopes, substrate uniform
Water with ____ results in a strong erosional force
High sediment load
Stream down cuts and produces new alluvial plain due to _____ or _____
Increase in discharge, lowering of base level
Amazon watershed
Largest drainage basin in the world and discharges 200,000 m^3 / second
headward erosion
Lengthening of the stream
The river flows the fastest in ____ because there is ______ between substrate and banks
Middle of river, friction
Velocity highest at outer edge leads to
Outer bank erodes faster
If streambed is curved, water flows fastest on _____ of curve
Outside
Badlands topography is caused by
Parallel drainage
Valley shapes
River (v) and glacier (u)
Meanders form when ______
Running water travels over a plain that has a very gentle slope
Majority of water on earth is _____
Salt water
Sediment is transported through _____ and _____
Saltation, rolling
Velocity lowest at inner edge leads to
Sediment depositing there, forming point bars
Turbulence flow develops because of ____ of one water volume against its neighbor
Shearing
The greater that the wetted perimeter is, the ____ the flow
Slower
Flow in hyporheic zone is ____ than in stream bed due to ______ in the hyporheic zone
Slower, friction
In a curved stream, water flow in middle of river is _____
Slowest
Meandering Streams
Streams that have channels with many curves
Permanent streams rely on ___, ____, and _____
Temperature, tropical climates, elevation with respect to water table
Flow velocity
The distance the fluid travels through a system in a given period of time.
suspended load
The load contains small rocks and soil in suspension, which can make the river look muddy.
Saltation
The movement of sand or other sediments by short jumps and bounces that is caused by wind or water
hyporheic zone
The portion of the substrate below and adjacent to a stream bed where water movement still occurs, either from the stream or from groundwater moving into the stream.
When ocean currents are strong, deltas have a ___ shape
Triangular
Shape of stream evolves due to ____ and ____
Variation in water depth, associated friction
Erosion efficiency depends on ____, ___, and ____
Velocity of water, volume of water, sediment load, gradient of water
Dissolution
Water dissolved soluble minerals and carries the resulting ions away
Bird's foot delta
When ocean currents are weak compared to river current and mini deltas are formed out of bigger deltas
Abrasion
When water is loaded with sediment, it acts like sandpaper, grinding of channel bed and walls
deposition of point bar
__ _ ___ ___ occurs on the *inside of a bend* to produce a point bar; low velocity
Point bars
a crescent-shaped accumulation of sand and gravel deposited on the inside of a meander
sheetwash
a film of water less than a few mm thick that covers the ground surface during heavy rains
Bedload
a load of coarse sediment, mostly coarse silt and sand, that moves along a riverbed (bottom) due to the flowing of water, in contrast to being carried in suspension
terrace
a raised, flat mound of earth (dirt) that looks like a platform with sloping sides
parallel drainage
associated with steep slopes
trellis drainage
drainage pattern in which most of the streams occupy parallel ridges and valleys, pattern usually develops on folded strata of rocks with differing resistance to erosion
Formation of deltas
found at the mouth of large rivers. They are formed by deposition. > When a river reaches another body of water, such as an ocean, it loses velocity and deposits sediment. > If the river deposits sediment faster than coastal processes erode it, sediment builds up in layers in a fan-shape. > As the river is now flowing slowly over an almost flat gradient, the channel fills up and the river splits into many smaller channels called distributaries and creates large areas of wetlands.
Ephemeral streams
have flowing water either episodically or during a portion of the year
Drainage divides
highland or ridge that separates one drainage basin from another
Whirlpools can be created in some restricted shallow passages due to ________.
reversing tidal currents/eddies
eddy
swirling current of water caused by friction along banks
drainage basin
the area from which a single stream or river and its tributaries drains all of the water
cut bank
the area of active erosion on the outside of a meander/stream
hydrologic cycle
the movement of water through the biosphere
Trunk stream
the primary stream of a drainage basin
downcutting
the process in which water flowing through a channel cuts into the substrate and eroded the substrate relative to its surroundings
Alluvium
the sorted fluvial material deposited by a stream