Fluvial Geomorphology 1 Flashcards
fluvial geomorphology=
the long-form study of running water
What are the 3 zones of running water?
zone 1: headwaters
zone 2: mainstream
zone 3: delta/ estuary
How might rivers (any channel of running water) develop?
- precipitation or snow melt
- sheets of water across a plane
- rills form (start of channels!)
eventually= gullies/ rivers
Fluvial geomorphology focuses on the ___, ___, and ___ of sediment
erosion, transport, and deposition
The amount of runoff (overland surface flow) and thus surface erosion depends on 3 things:
- precipitation intensity (rate and duration)
- infiltration rate (subsurface)
- connectivity
Surface water hydrology=
the study of the hydrological cycle involving water at the earth’s surface
Vadose vs phreatic zone?
vadose= zone above the water table
phreatic zone= the part of an aquifer, below the water table, in which relatively all pores and fractures are saturated with water (saturated)
give 7 factors affecting run-off vs infiltration?
- sediment/ lithology: grain size, porosity
- vegetation/ water bodies: evapotranspiration, root depth, leaf density
- precipitation intensity/ durations (saturating the subsurface)
- Climate: arid, temp, prev ground saturation
- slope/ topography
- land use (pavement, deforestation, mining, storm surges)
- structures like joints, roots, permeability (eg karsts)
T/F
average annual runoff is higher in areas where average annual precipitation is high
true
because ground becomes saturated, so more runoff
Once channelized flow exists, why might you want to measure it? Give 2-4 reasons
- policy (water use, agriculture, etc)
- erosion rates
- water quality
- chemodynamics
In a hydrograph:
- through flow= _____
- base flow= ____ ___
interflow
groundwater flow
storm flow=
overland flow + through flow
what are some key considerations for long-term use in regards to discharge rating curves?
shifts in bed morphology!
Recurrence Interval (RI)=
the recurrence of a particular discharge over time
- measured as a mean frequency over a Q record duration
What are the 2 types of flood frequency analysis?
- annual duration
- partial duration
annual duration flood frequency analysis=
each record-year’s peak discharged is considered in the analysis as the “annual maximum flood” (AMF)
partial duration flood frequency analysis=
max discharge of “n” events (peaks) over some threshold
- this timeseries analysis method may include more than one peak Q in a single year
- “Peaks-Over-Threshold” (POT)
How do you calculate the Recurrence Interval?
RI= (n+1)/r
- n= # of events (length of record
- r= rank of event from largest to smallest with highest magnitude flood having r=1
How do you calculate flood probability?
P= 1/RI
so you need to calculate RI first
What are some ways you might be able to estimate RI beyond the record duration?
tree ring records or flood plain deposits
Give some potential issues with a long record of floods
- It’s a static record, but there are land use changes/ water management changes, etc
- data quality issues can happen over long records
Give the 6 important fluvial processes
- weathering
- erosion
- entrainment
- transport
- deposition
- re-suspension and deposition
weathering=
physical, chemical, or biological breakdown of material (bedrock or sediment)
erosion=
removal of material (sediment) from the landscape
entrainment=
incorporation of sediment into the fluid column
transport=
movement of particle/ sediment by the fluid (ice/ water/ wind)
deposition=
loss of particle from the fluid column; its motion has stopped
stream ____ is principally related to erosion, transport, and deposition
velocity
What (4) landscape and channel characteristics might impact stream velocity?
- slope
- channel shape (wide or deep)
- channel roughness- cobbles veg etc
- amount of discharge
How does Q (discharge) change downstream?
tributaries combine, so Q increases downstream
remember, Q= volume/ time
as discharge increases downstream, stage ____ downstream, and the ratio of water in contact with the bed generally ____
increases
decreases
As Q increases, the water in contact with the bed decreases, therefore ___ can increase
velocity can increase because there is less friction (with the bed)
as gradient increases, velocity of water typically
increases
what is the relationship between velocity and distance from headwaters?
as velocity increases, so does distance (linear/ exponential?)
