FLUVIAL LECTURE NOTES


VOCABULARY: fluvial; hydrologic cycle; sheet flow; sheet runoff; gully; permanent; perennial; intermittent; source; head; mouth; tributary; headwaters; stream system; drainage basin; watershed; divide; valley; bed; channel; banks; load; discharge; velocity; stream orders; gradient; run; laminar; turbulent; hydraulic plucking; abrasion; solution; suspension; traction; capacity; competence; waterfall; plunge pool; meander; whirlpool; pothole; alluvium; delta; distributary; alluvial fan; braided stream; life cycle; youth; V-shaped valley; maturity; U-shaped valley; graded stream; old age; floodplain; base level; cutoff; oxbow lake; oxbow swamp; meander scar; natural levee; backswamp; yazoo stream; headward erosion; rejuvenation; entrenched meanders; terraces; stream piracy; stream capture; beheaded; peneplain; monadnock; drainage pattern; dendritic; trellis; rectangular; radial; centripetal; annular; parallel; deranged; water gap; wind gap

agent--running water
process--fluvial


FLUVIAL PROCESSES
next to gravity, running water is most important force in reducing the land surface
MOST EFFECTIVE AGENT--powered by gravity

hydrologic cycle

water stays on surface, begins trip to sea as sheet flow, sheet runoff--across land, does little eroding
as slope steepens, concentrates, carves small gullies which later become small streams
steeper slope yields greater erosional capacity

GENERAL VOCABULARY (you should know)
stream--any flow of water
permanent--perennial--all year
intermittent--part of year is dry
source, head--highest part of stream
mouth--lowest part
tributary--stream which flows into another
headwaters--tributaries near head
stream system--main stream and its tributaries
drainage basin, watershed--land drained by a stream
divide--highland which separates one drainage basin from another
valley--lowland between the hills of drainage basin
bed, channel--part covered by water
banks--land running along side of the stream and just above it
load--material carried by stream
discharge--total stream flow

stream water from--1) rainfall, 2) sheet runoff, 3) tributary streams, 4) ground water, 5) melting glaciers

erosional effectiveness of stream is determined by: • VOLUME OF WATER

controlled by the watershed (area and climate)
hierarchy of sizes
stream orders

• VELOCITY

gradient or slope--feet per mile of channel

gradient '/ mile = difference in elevation (in ft.)/ distance along stream (in mi.) OR rise/run

if gradient large (steep)--high velocity
small (gentle)--low velocity

• TYPE OF FLOW

depends on gradient--low produces laminar flow--sheet like, little erosion
high produces rough and irregular-turbulent, more erosion

• TYPES OF EROSION

streams erode by
stream transports material by:
DISCUSS EFFECT OF SIZE AND CHANGES IN VELOCITY

capacity--how much weight it can carry
competence--size of largest piece it can carry

• LOCATION
erosional action is most pronounced in turbulent areas velocity fastest in center

total load--amount of material the river transports by all erosional methods
load depends on: velocity; volume; and amount and kind of material available for transport

•alluvium--deposits made by running water
•delta--load carrying capacity reduced when velocity drops, stream enters standing water--
•DISTRIBUTARIES--the branches off
•alluvial fan--if gradient drops suddenly, deposition on flat land surface
•braided stream--sudden decrease in volume OR increased load, drop material

STREAM LIFE CYCLE
gradient influences channel shape and characteristics as stream erodes its channel, removes materials, reduces gradient

Youth--characteristically STEEP gradient
steep walled, V-shaped valley
few tributaries
large number of water falls and rapids
(deepens valley by eroding bed, widens valley by eroding banks, steepness depends on speed of deepening by stream, widened by other forces)
LESS THAN 1/10 life

Mature--started by eliminating irregularities in bed
well established tributaries
effective drainage of watershed
gradient less
few waterfalls or rapids (worn away)
channel wanders--meanders
U-shaped valley
graded bed--just steep enough to allow stream to transport its load

Old Age
very low gradients
slow flow
valley quite wide--floodplain wider than meander belt
great meanders--large loops
well developed floodplain
broad U-shaped valley
close to base level
down cutting and lateral erosion practically stopped

meander to cutoff to oxbow lake to oxbow swamp to meander scar

Meander Stages

Meander Cross Section

back swamp
floodplain
natural levee--deposits alongside the stream channel during floodstage
yazoo stream--tributary stream which flows along the floodplain before joining the main stream

Mature Flood Plain

headward erosion--stream can be youthful, headwaters, mature and old age

rejuvenation--uplift surface or lower base level



landforms resulting from rejuvenation