Studied by 10 people
fluvial geomorphology
a sub-discipline of geomorphology that investigates how flowing water shapes and modifies earth’s surface through erosion and deposition
what are the two processes linked with fluvial geomorphology
hillslope process and channel process
what are the key geomorphic processes?
erosion
transportation
deposition
what is erosion
it is the removal of weathered rock and soil particles
what is transportation
it is the movement of eroded materials from place to place
what is deposition
it is the laying down of eroded materials
hydrolic cycle
the movement of water in its various forms from place to place
key processes in the hydrolic cycle are
condensation and precipitation
condensation and precipitation are what kind of processes
processes that remove water vapor from the atmosphere
condensation
conversion of water vapor to liquid water as it cools
precipitation
the movement of condensed liquid or solid water from the atmosphere to solid surfaces
evaporation and transpiration are what kind of processes
processes that move liquid into the atmosphere
evaporation
conversion of liquid water to water vapor as it absorbs energy
transpiration
release of water vapor from the leaves and stems of plants
what is the evaporation + transpiration called
evapotranspiration or ET
surface water hydrology
the sub-field of hydrology concerned rainfall and runoff, the routes that surface water takes (across the surface or through rovers or lakes), and the occurrence of floods and droughts
drainage basin
an area of land where precipitation collects and drains to a common outlet
what is another word for a drainage basin
watershed
what happens when precipitation hits the ground
it either infiltrates or runs off
infiltration
soaks into the soil
runoff
flows over the surface into streams and rivers
what is infiltration rate
a measure of how fast water enters the soil, typically expressed in inches per hour
what are some factors that control infiltration
surface permeability, rainfall characteristics and antecedent moisture
surface permeability
soil texture and structure, presence of impervious surfaces
impervious surface
a surface which cannot be penetrated by water
permeable surfaces have what
high infiltration capacities and low runoff
impermeable surfaces have what
low infiltration capacities and high runoff
rainfall characteristics and antecedent moisture
rate of rainfall and amount of water already in storage
sheet flow
water flowing over the hillslope first moves a thin, non concentrated sheet
what is another word for sheet flow
overland flow
rills
sheet flow can then be funneled into tiny erosional depressions
gully
rills can converge to form gullies which are wider, deeper, erosional channels
is a rill or gully wider
gullies are wider and deeper
what are gullies usually
they are dry
what are the two phase processes in hillslope erosion
detachment and transport
what is the first phase process in hillslope erosion
detachment of individual particles
what is the second phase process in hillslope erosion
transport of particles by erosive agents
what eventually happens to particles in the hillslope erosion process
they are deposited, either downslope or into water
erosive energy comes from what
kinetic energy of moving water
raindrop impact
the kinetic energy of a falling raindrop as it impacts the soil surface facilitates detachment
kinetic energy of moving water as it does what
flows over the soil surface
sheet erosion
erosion associated with overland flow that removes loose soil and weathered material
rill and gully erosion
erosion of surface materials as sheet flow is concentrated in hillslope rills and gullies
precipitation and intensity and amount
greater intensity and amount lead to more detachment and transportation
topography
longer and steeper slopes lead to more kinetic energy and erosion
soil characteristics
structure and texture influence the ability of the soil to absorb water and its physical resistance to erosion
vegetation and land use practices
effects of plant cover in rainfall and runoff
river channel
depressions with defined boundaries within which water flows
what is another word for a boundary
bank
river discharge
the volume of water flowing past a given point in a given period of time
what is the river discharge calculation
q = a times v
a in the river discharge calculation is what
channel area
v in the river discharge calculation is what
velocity
discharge is a function of what
velocity and channel area
in a rectangular channel, the calculation would be
q = (w times d) times v
what is w in the river discharge calculation
width
channel depth and width, as well as current velocity, can be measured using a range of what
manual techniques
what is becoming more common
automated systems
are automated systems cheap or expensive
expensive
what does ADCP stand for
acoustic doppler current profiler
stage
the height of a river above a locally defined elevation
staff gages
simple ruled markers on which stage is read manually
automated gages
water level is tracked using an electric sensing system
factors affecting discharge are
weather and climate, rock and soil type, and vegetation cover/land use, topography, drainage basin characterstics
heavy continual rain or melting snow affects what
time for infiltration
what is antecedent rainfall
rain that has already happened, potentially saturating the soil
do permeable rocks and soil absorb what easily or not
they absorb them easily
permeable rocks and soil absorbing water easily causes what
slowing of runoff and discharge
impermeable rocks and soil do what
limit infiltration
what does impermeable rocks and soils limiting infiltration do
causes the water to reach the rivers more quickly
plant cover reduces what
amount and speed of runoff
plant cover reduces amount and speed of runoff by
intercepting incoming rainfall and slowing runoff, which enhances infiltration
steep slopes gives runoff what
less time to infiltrate
characteristics of more gentle slopes
overland flow is slower and infiltration is more likely
erosion by streams
hydraulic action, abrasion/corrasion, solution/corrosion
hydraulic action
erosion of river banks and bed by flowing water
abrasion/corrasion
wearing away of river banks and bed by materials carried in the river flow
solution/corrosion
chemical weathering and erosion by water in the stream
dissolved load
carried in solution
suspended load
solid materials carried within the water flow
bedload
coarser material carried along or near the river bed by saltation and traction
streams deposit material where
they are forced to slow down
what is groundwater
water present beneath the earth’s surface in rock and soil pore spaces and in the fractures of rock formations
what does groundwater do
fills the spaces between soil particles and fractured rock beneath the earth’s surface
zone of aeration
water does not occupy all spaces in the soil and rock
zone of saturation
water occupies all spaces in the soil and rock
what is water budget
the relationship between water input and output at a location over the course of a year
depth to the water table is influences by the rate of
water withdrawal and water recharge
what is water withdrawal
losses
what is water recharge
additions
when withdrawal is greater than recharge what happens
water table drops
when recharge is greater than withdrawal what happens
water table rises
True or False: Just because the soil is saturated in a place, it doesn’t mean the water table is changing
True
capillary soil water is
held in the soil by surface tension
capillary soil water is held in the soil by surface tension and will do what
may return to atmosphere through ET
where does groundwater reemerge at the surface?
places where the land surface drops below the water table, which can help to support rivers, lakes, and springs
what is another place that groundwater reemerges at the surface
wells
what is a well
places where people dig or drill below the water table to remove water
aquifer
a layer of porous rock or material that both stores and transmits water
