Final Blog: Main Hazards

 The two main natural hazards of Hong Kong are mass wasting and flooding. I believe these hazards should be the priorities of Hong Kong due to their sub-tropical climate. In Hong Kong, the weather is warm and cool most of the year, depending on the season. However, in the summertime, the climate becomes hot and rainy; this is the wet season for Hong Kong. About 80% of rainfall occurs between May and September, and the average precipitation per year is 2400 mm(94.4 inches). The rain can be very violent, especially during June and August or tropical storms. With an excess amount of rainfall and Hong Kong's rapid urban development on hilly terrains, the environment has all sorts of reactions.

When there is too much water, the soil will become oversaturated, which significantly decreases the integrity of the ground and increases the chance of a mass movement happening. And the landslides of Hong Kong are usually fast and instantaneous rather than slow; this makes landslides in Hong Kong a hazardous event. In addition, surface runoff can occur when soil is oversaturated because precipitation exceeds the rate that the soil can absorb. As a result, there is a higher risk of flooding in low-lying areas. 

Since flooding and mass wasting have a chance of happening simultaneously, I think they should be the country's main hazards to focus on mitigating. In fact, the government has already invested a lot of resources into mitigating such threats. Since 1995, the city has heavily invested $3.8 billion into projects that include nearly 1500 miles of drains, 225 miles of river channels, and four underground tunnels that span 13 miles. Additionally, there are four massive stormwater storage tanks implemented and 11 more developed for the future. The rainwater drainage system minimizes the erosion impact of heavy rainfall on hillside soil by redirecting and storing stormwater in containment tanks.

If I were to pick an area to help first, I'd pick locations closest to hazard zones. In Hong Kong's case, low-lying areas, places surrounded by hills, and coastal areas. These zones are at higher risk of flooding and landslides when there is heavy rainfall.

If I were to build a house in Hong Kong, I would do it at a high elevation. This way, I'd avoid the risk of flood damage and landslides. So the house would be either at a high cliff or closer inland and further from the coast, located away from hills, although there's is rarely any flat ground in Southeastern Asia. 

References:

https://earth.org/hong-kong-hillside-communities-affected-by-climate-change/ (Links to an external site.)

https://storymaps.arcgis.com/stories/c3d76d90cd474bf58b4a4c1464aa1dbe

Week 13: Coastal Problems

This week I'm talking about Hong Kong's coastal problems, and the main issue they're facing is rising sea levels. Since the mid 19th century, the rate of sea-level rise has significantly increased, and this is because of many factors. However, the leading cause is global warming, which increases temperature and melting of ice and snow, resulting in a rise in mean sea level.

So what if the sea levels are rising? Well, elevated sea levels create risk for other hazards such as typhoon-generated storm surges. Storm surges rapidly increase the sea level due to low pressure and high winds from a tropical cyclone. Note that storm surges are more extreme if they occur during high tides, resulting in flooding of low-lying areas.

There is no plausible solution to stopping or slowing down the rising sea level as far as mitigation efforts go. The best course of action for Hong Kong is to be prepared for extreme storm surges. I've mentioned in other blog posts the different mitigations HK has in place to prevent flooding. This included many miles of storm drains and tunnels, they also have large storm water tanks. Hong Kong has invested heavily into preventing/ reducing floods as this country is very prone to it.

Sources:

https://www.hko.gov.hk/en/education/aviation-and-marine/aviation/00505-on-sea-level-rise-and-abnormal-sea-level-in-hong-kong.html

Week 10: Extreme Weather

 Hong Kong has a long summer that lasts from June to September. During this time, it is hot, humid, and rainy, with heavy showers and thunderstorms. The summer is significantly hotter than the rest of the year, with temperatures reaching 90 degrees Fahrenheit. Hong Kong is affected by the urban heat island making the summers more hot and humid. 

The actual extreme weather in Hong Kong is its thunderstorms that bring heavy rain. On average, there are 5 thunderstorms per month during the summer. The thunderstorms are severe but are more often than not short-lived.

 

To alert people, the Hong Kong observatory issues thunderstorm warnings. These are short-term warnings to notify people of the likelihood of thunderstorms that affect any part of Hong Kong. When issued, the warning is broadcasted over television and radio, including the observatory's website. These warnings stay active until the thunderstorm is over.

Sources:

https://www.climatestotravel.com/climate/hong-kong

https://www.hko.gov.hk/en/wservice/warning/thunder.htm

Week 8: Mass Wasting Hazards in Hong Kong

 Hong Kong is a very wet country due to tropical storms that bring heavy rainfall. This, coupled with Hong Kong's rapid urban development on hilly terrains, has led to widespread occurrences of devastating landslides. 

The rainfall is very high but seasonal, averaging 2000 mm (78.7 in) in the wet season from May to October. The precipitation occurs in heavy downpours that last several days. As a result, the rainfall fully saturates the soil several times throughout the season, and when the soil is fully saturated, the strength is significantly lower. This increases the chance for a mass movement. 

Focusing on 1972 in Hong Kong, they faced a series of landslides, the worst in Hong Kong's history. This year, Hong Kong faced two deadly landslides that occurred on the same day, claiming 138 lives. The landslides in Hong Kong are rarely slow; they occur almost instantaneously, making them very dangerous. This tragedy, however, led Hong Kong to be more proactive at mitigating landslides, their most dangerous threat.

After the 1970s, Hong Kong's government set up the Landslip Preventative Measures (LPM) program to deal with slopes that could result in landslides. The program essentially observes slopes that could be potential threats, and they gain more info on an identified slope by continually following it. If needed, LPM designs and constructs an upgraded incline that lessens the chance of a landslide. This system works very effectively for Hong Kong as future landslides were less common and had fewer deaths. 

 

An image of one of the twin landslides from 1972

Sources:

http://www.geog.com.cn/EN/10.11821/xb1997S1013

https://qjegh.lyellcollection.org/content/8/1/31

https://storymaps.arcgis.com/stories/c3d76d90cd474bf58b4a4c1464aa1dbe

Week 5: Volcanic Activity

 Hong Kong itself does not have much volcanic activity at the current time. However, throughout the land of Hong Kong, volcanic rocks and plutonic rocks are dominant.  Geologists have confirmed that the very existence of Hong Kong is because of a huge volcanic eruption that occurred 140 million years ago. The eruption came from a very rare supervolcano, one of only about 50 supervolcanoes that have erupted since man walked the earth. So although it may be dormant, the main city of Hong Kong sits atop a very old ancient volcano.

Here are some images of a volcanic rock formation in Hong Kong resulting from the supervolcano. The rocks formed hexagonal shapes.

Sources:

https://www.scmp.com/yp/discover/lifestyle/features/article/3067002/how-was-hong-kong-made-really-big-volcanic-eruption

https://hkss.cedd.gov.hk/hkss/eng/education/gs/eng/hkg/chapter6.htm

Week 3: Earthquakes

 Hong Kong is considered to be in a region of low to moderate seismic activity. There have not been any major earthquakes during this period. The largest recorded earthquake close to Hong Kong was a magnitude 6.0 event in Honghai Bay, 52 miles east of Hong Kong, in 1911. Since 1979, there have only been 82 locally felt tremors, on average 2 per year. The chances of a strong earthquake in Hong Kong are low but to mitigate damages, there is a "code of practice for structural use of concrete" in place. This code essentially ensures that structures will have the ductility to withstand deformation and have the durability to maintain structural integrity over time.

There have been no known active faults in Hong Kong. Although it doesn't sit right on a tectonic boundary, Hong Kong is no stranger to transforming faults. The seismic activity in the area is mainly a result of the interaction between the Eurasian and Philippine plates and the faults in the region are considered to have been most active from the Jurassic to Cretaceous periods, at this time strike-slip faults were most common. Above is a mapping of Hong Hong's major faults. Most of the fault lines run from northwest to southeast and from northeast to southwest. These major faults are what shapes the landscape of the region. 

Sources:

https://hkss.cedd.gov.hk/hkss/eng/education/gs/eng/hkg/chapter7.htm

https://www.hko.gov.hk/en/gts/equake/felt_intro1.htm

https://www.researchgate.net/profile/Mandar_Ganbavale/post/Does-anyone-know-where-I-can-find-Singapore-standard-for-concrete-penetration-testing/attachment/59d63618c49f478072ea400c/AS%3A273873646358528%401442307973305/download/Sigapore+2.pdf

Week 2: Tectonics

 Hong Kong is located within the Eurasian plate. Looking at the map it is located West of the Philippine plate (encircled in red). It is rather far away from the closest tectonic boundary which is a convergent boundary that runs through Japan, Taiwan, and the Philippines. 

Expect to learn more about Hong Kong's seismic activity next week, when I'll talk about earthquakes.

Link:

https://hkss.cedd.gov.hk/hkss/eng/education/gs/eng/hkg/chapter7.htm