Four people have been injured following a landslide at the Ayeyarwady Bridge in the Magwe Region of Myanmar on Thursday 15 October. The incident happened at about 10.00 am local time on the Minbu side of the bridge, when a section of hillside collapsed onto a motorcycle lane close to a toll booth, overturning and partially burying two motorbikes and striking the booth. Four people were treated for minor injuries at local hospitals, the toll collector in the booth was reportedly unharmed.
The scene of the 15 October 2015 Ayeyarwady Bridge landslide. Nay Aung/The Myanmar Times.
Myanmar has suffered an exceptionally wet monsoon season this year, with widespread flooding and a number of deadly landslides. Landslides 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.
The approximate location of the Ayeyarwady Bridge landslide. Google Maps.
Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea.
Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.
The severity of the 2015 monsoon appears to be related to a strong El Niño affect recorded over the southern Pacific Ocean this year. The El Niño is the warm phase of a long-term climatic oscillation affecting the southern Pacific, which can influence the climate around the world. The onset of El Niño conditions is marked by a sharp rise in temperature and pressure over the southern Indian Ocean, which then moves eastward over the southern Pacific. This pulls rainfall with it, leading to lower rainfall over India and higher rainfall over Myanmar. This increased rainfall during the already wet monsoon season leads to widespread flooding. Worryingly climatic predictions for the next century suggest that global warming could lead to more frequent and severe El Niño conditions, making such South Asian heat waves a common occurrence.
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