Saturday 17 August 2013

Three people killed in Guangxi landslides.

At least three people have been killed by landslides in Cangwu County in the Guangxi Zhuang Autonomous Region in South China. The first incident happened in Hongshan Village at about 1.50 am local time on Saturday 17 August 2013 (5.50 pm on Friday 16 August, GMT), when a landslide destroyed a number of homes. At least one person, described as a senior citizen, is known to have died. The second incident happened approximately two hours later in Sifeng Village, when at least two people were buried and killed by a landslip. Search teams are still looking for further victims at both locations.

The location of Cangwu County. Google Maps.

These landslides have been linked to the arrival of Typhoon Utor, which hit south China on Wednesday 14 August, brining with it torrential rains and flooding. The low pressure above tropical storms causes water to rise there by ~1 cm for every millibar drop in pressure, leading to a storm surge that can overwhelm low-lying coastal areas, while at the same time the heat leads to high levels of evaporation from the sea - and subsequently high levels of rainfall. This can cause additional flooding on land, as well as landslides, which are are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

Tropical storms are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere.These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.

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