hydrology and fluvial Flashcards
flows
movement of water from 1 store to another
store
where water is kept
drainage basin
total area of land drained by a river and its tributaries
open system
water moves across the boundary into and from other drainage basins
inputs
precipitation
outputs
evapotranspiration and runoff
stores
river channels, kales, vegetation and soil moisture
total amount of precipitation in drainage basin
more rainfall = more infiltration, percolation is increased so water table may rise
intensity of precipitation in drainage basin
heavy rain = ground saturated quickly = more surface runoff and increased channel flow
type of precipitation in drainage basin
infiltration = quickest with rain
snow takes a while to melt = longer to infiltrate
distribution of precipitation in drainage basin
if falls directly on river channel = affects river quicker
interception
water that’s caught and stored by vegetation
interception loss
water that’s retained by plant surfaces and water is later evaporated away/absorbed by plant
through flow
water that falls through the gaps in vegetation or drops from leaves
stem flow
water that trickles along twigs and branches
factors affecting rates of evaporation
temp - warmer = more humidity - higher = slower wind speed = faster = more albedo = lighter = less water available = less = less
potential evaporation
water loss that would occur if there was an unlimited supply of water
infiltration
process in which water soaks into/absorbed by soil
infiltration capacity
max. rate at which rain can be absorbed by soil in a given condition
duration of rainfall affects rates of infiltration/surface run off
SR increases, longer the duration
infiltration decreases, longer the duration
vegetation cover affects rates of infiltration/surface run off
SR increases
I stays low in bare earth, in forest decreases slowly over time
antecedent soil moisture affects rates of infiltration/surface run off
saturated, SR increases
I lower in wet soil
raindrop size affects rates of infiltration/surface run off
SR increases as bigger
I decreases as bigger
soil porosity affects rates of infiltration/surface run off
SR decreases with porosity
I increases with porosity
slope angel affects rates of infiltration/surface run off
SR increases with steeper
I decreases with steeper
Hortonian flow
soil not saturated but water can not infiltrate. water flows over the surface as overland flow
Saturated overland flow
soil full up of water so can not take any more so water flows over surface as overland flow
ground water
subsurface water comes from precipitation onto the land
recharge
filing of water in pores where water has been dried up or extracted by human activities
discharge of groundwater
water from underground coming up to surface
how does recharge occur?
Infiltration of precipitation
seepage through the banks and beds of river
Leakage from adjacent aquifers and rocks
where does discharge of groundwater occur?
aquifer fills up with water reaches land surface, where flows from ground as springs
aquifer
rock underground storing groundwater in it
river regime
annual variation in the flow of a river, shown on annual hydrograph
discharge
volume of water passing along rivers channel over given period of time
flood hydrographs
used to plot rivers discharge during 1 single event
storm hydrographs
shows amount of rainfall during storm event
type/amount precipitation affects shape of hydrograph
high intense = quick overland flow
low intensity = infiltrates slowly
soil moisture affects shape of hydrograph
if rain previously, ground = saturated = quick overland flow
drainage basin shape affects shape of hydrograph
rounder = respond quicker
drainage basin size affects shape of hydrograph
smaller = quicker , shorter lag time
drainage density affects shape of hydrograph
high DD = quicker , shorter lag time
geology affects shape of hydrograph
impermeable - more overland flow, increase peak flow
gradient affects shape of hydrograph
steeper = more overland flow, shorter lag time, higher peak flows
vegetation type affects shape of hydrograph
broader leaf, intercepts more rainfall, reduces overland flow , longer lag time
land use affects shape of hydrograph
impermeable surface = reduced vegetation = increased overland flow/shorter lag time
gradient
angle the slope which river runs
velocity
distance divided by time
cross-sectional area
width x mean depth
discharge
vol. water passing through a river at a given point
discharge
vol. water passing through a river at a given point
hydraulic radius
cross-sectional area divided by wetted perimeter
hydraulic action
force of water on banks of river
abrasion
wearing away of beds/banks by load carried
attrition
wearing away of load carried by a river
corrosion
removal of chemical ions
suspension
fine clay particles carried along within water
saltation
small stones bounced along river bed at times of high discharge
traction
boulders/pebbles rolled along river
solution
minerals dissolved
thalweg
line of fastest movement in meander
Point bar
occurs on inside of bend of meander when deposition accumulates
floodplain
formed when rivers burst banks and flood on regular basis
levees
coarse material deposited near channel during repeated floods
alluvial fans
alluvium is dropped by river when looses momentum
deltas
when river flows into standing body of water
ARCUATE
deposition into fan shape, LSD occurs
BIRD FOOT
when river brings down fine salt, carried for long distances
CUSPATE
deposition occurs into a points like a tooth
Human Impact on interception/infiltration
urbanisation = impermeable surfaces with compact soil deforestation = decreases infiltration
Human Impact on interception/infiltration
urbanisation = impermeable surfaces with compact soil deforestation = decreases infiltration
causes of floods : types of precipitation
by heavy rainfall - if falls as snow, water stored in surface until melts
causes of floods : vegetation
limited on surface then no interception = increase surface run off
causes of floods : climate
dry = water can't penetrate soil wet = saturated = excess water
causes of floods : rock type
permeable/porous water infiltrates = slow lag time
impermeable water can’t infiltrate = increase overland flow
flooding solutions : prediction
weather satellites to predict high rainfall
river gauges to study river levels
flooding solutions : preparing people
loss sharing adjustments
flooding solutions : prevention
hard engineering = defence schemes, halting natural processes
soft engineering = use of natural environment
hard engineering
embankments
construction of water holding areas
dams/réservoirs
soft engineering
reseeding vegetation
afforestation
drought
extended period of dry weather
