Week 8: Hong Kong's Mass Wasting

 Mass Wasting 

Mass wasting is a term that is given to any downslope movement of the earth's materials (which include debris, rock, avalanches, etc). The general term is "landslides" but this concept also refers to mudslides, rockfall, debris flows, and earth flows. Although it is sometimes triggered by a "transporting medium" such as water, wind, or glacial ice... these forces are not necessarily required. All that is needed is GRAVITY!😱

Variables in safety factors of slopes:

• Type of earth materials
• The role of slope and topography 
• Role of vegetation
• The role of water
• The role of time

Often times landslides are followed by a series of sliding and flows. The mass movement can start as one type and finish as another. When it is more than one it is called a "complex".

Landslides are one of the most common natural hazards in Hong Kong. Due to seasonal rainstorms that it experiences, it triggers the chances for mass wasting to occur. Not only that, but Hong Kong is a very mountainous, yet populated area. Many houses are located on the foot of steep man-made slopes. 

A slope around a 25 to 40-degree angle is actually stable -the resisting and the driving force are within the range for center mass to be still- anything steeper though will fall.This poses a potential threat to the population of the area. 

It is also important to know that once one landslide has occurred, the chances of another one happening are only greater and greater. 

In order to mitigate this hazard:

• People looking to build, sell, or buy a home in a higher-risk area can educate themselves on the location of the house they are trying to buy/sell.
• Identify your position in a slope stability map or a landslide hazard map
• When cultivating, be aware of slopes because the weight of the crop can also trigger an unbalance in the slope safety factor. 
• Consider road and drainage placement. 

“Hong Kong Slop Safety.” Landslide Risk in Hong Kong, 10 Feb. 2023, https://hkss.cedd.gov.hk/hkss/en/slope-safety-in-hong-kong/landslide-risk/index.html.

Keller, Edward A., and Robert H. Blodgett. “Ch. 7 Mass Wasting .” Natural Hazards: Earth's Processes as Hazards, Disasters, and Catastrophes, Routledge, Taylor & Francis Group, Abingdon, Oxon, 2016.