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Human causes that cause slope instability - Coggle Diagram
Human causes that cause slope instability
Urbanisation
often in MICs on marginal land (land which would be unsafe to develop infrastructure on in ACs such as sloped environments
heavy buildings and undercutting for roads increase sheer stress on slope and also the deforestation that occurs in order to be able to build urban environments
Rio de Janeiro has favelas (shanty towns) built on slopes
2010, 257 people killed and over 1,000 left homeless after mudslides in Rio
Po Shan Road landslide, Hong Kong, 1972, 156 deaths
Acid rain
increased emissions of sulphur dioxide = moresluphuric caicd
this can weather rocks more quickly, eroding the slopes
in evaluation, this is a long term, but large scale cause of slope instability
Farming (ploughing)
leads to deforestation
terracing can be used to stabilise slopes if done effectively. improvement on un-terraced agricultural slopes but not as useful as forested slopes
however, farming involving ploughing and terracing weakens the slope by creating steeper sections and removing larger plants, reducing sheer strength
Overloading the slope (waste dumping)
Transport construction
Mining + extraction (undercutting)
by removing material from underground, you are hollowing material out of the ground and reducing sheer strength
the waste rock produced from mining is stacked on waste tips, which are unstable, loose mounds of rock on slopes next to mines
prime example = Aberfan, Wales. Worst mass movement in UK, engulfed a school at 9am, 147 people killed, 116 children
the spoil tips were placed on top of water springs, which also decreased the cohesion of the tips
intense Welsh rainfall along with unstable tips of waste rock meant the pile toppled over
open pit mines can increase gradient of slope
however, USA has restrictions to terrace the mine to reduce stress, however LICs do not have such enforced regulations
Recreation
Scarborough, 1993
1993 was particularly wet, following a period of dry summers. Hence, the top layer of cliff became quickly saturated and moved slowly downhill, taking Hollbeck Hall Hotel down with it
Deforestation
soil is less tightly bound as tree roots are non-existent --> decreases cohesion and thus increases sheer stress
decreases interception rate as tree leaves intercept precipitation
no transpiration which removes moisture from the slopes