The human impact on hydrology Flashcards
urbanising influence: removal of trees and vegetation impact on hydrology
decrease evapotranspiration
incterception
increased stream sedimentation
urbanising influence: construction of houses streets and culverts
decreased infiltration
lowerted groundwater table
increased storm flows
decreased base flows
urbanising influence: redevelopment of residential and commercial areas
decreased porosity reduced time of runoff concentration increasing peak discharge increased volume of runoff and flood damage potential
urbanising influence: construction of storm drains and channel improvements
local relief from flooding
concentration of floodwaters may aggravate flood problems down stream
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how have human increased evaporation and transpiration through urbanisation
reduction in evapotrandpirwtion due to lack of vegetation
slight increase in evaporation due to high temperatures and increased surface storage
fact about infiltration forests and grassland
up to five times greater in forests
what does deforestation lead to
reduced evapotranspiration
increase in surface runoff
decline or surface storage
decline in lag time
effects of drought
malnutrition and hunger declining crop yields reduced water supply for farming stress on natural ecosystem increased risk
explain how humans impact hydrology in abstraction and water storage
centre pivot irrigation
high plains of texas
30-50m decrease in water level
problems of groundwater levels rising
surface water flooding flooding of basements increased leakage into tunnels flooding of basements increased leakage intontunnels
what is drought
extended period of dry weather leading to conditions of extreme dryness
causes of dry conditions?
continentality (distance from sea) - limits amount of water carried across by winds
desertification (rise of the spread of desert conditions) previously fit for agriculture
cold offshore currents limit the amount of condensation in the overlying air
human related factors that alter the drainage basin response to a storm:
more rapid discharge in urban areas due to impermeable surface and increased number of drainage channels (worsened by urban growth and urbanisation)
floodplain developments increasing risk of damage
human induced climate change
river engineering works eg levees
change in vegetation cover eg agriculture
what is recurrence interval
regularity of a flood of a given size
small floods are regular
larger floods less frequent
how does urbanisation lead to flooding
water can’t infiltrate through tarmac and concrete
combined with gutters and drains and direct runoff
water can be carried at great speed to the nearest waterways
