HK Mass Movement ‘72 Flashcards
1
Q
Causes
A
- 60% of land in HK is mountainous
- most landslides occur during or after rainstorms
- tropical climate increases rate of chemical weathering which decreases shear strength of slopes
- granite and volcanic rocks on higher ground are prone to failure and are seriously weathered
- prev v.dense population w/ lack of management = shanty towns build on slopes, increased chance of mass movements
2
Q
impacts of landslides and deaths
A
more than 156 deaths
3
Q
management response (tlews)
A
- 1977 introduced territorial landslide early warning system
- needs to be constantly improved as prospect of increasingly intense rainfall grows due to climate change
4
Q
geotech engineering office (6)
A
- updating + maintaining slopes
- landslide potential index indicates areas that are most at risk (only 10 ppl had heard of it)
- if the slope doesnt comply with rules, 50k fine and 1yr imprisonment
- gps sensors on slopes to detect movement
- monitored 60000 slopes
- new warning system which gives foreast 6 hrs ahead compared to 3 hrs
5
Q
maintenance of slopes
A
- mulching system: high water retaining capacity, resistance to rain erosion, ability to hold position in steep slopes.
- long rooted grass, natural, cheap, fast and easy, can be applied on steep slopes
- fibre reinforced soil system: low maintenance fibre strengthens soil, visual improvement, restoration of habitats
6
Q
challenges
A
- Hk is compact
- money available to invest in the tech needed
- however, sierra Leone don’t, in 2017 landslide killed 1000+ & authorities have little data to provide to citizens about the likelihood of another disaster.
7
Q
soft engineering
A
- afforestation plan
- used natural vegetation near roads and motorways near slopes
- 50% risk reduction of landslides since 1977
BUT takes time, and some plants struggle to grow on steep slopes
8
Q
hard engineering
A
Drainage pipes:
- drainage systems in over 87 locations in Hong Kong
- prevented 2200mm of precip that HK receives from oversaturating slopes
BUT very expensive, so only richest can afford