Sunday 19 July 2015

Landslide kills three on Pune-Mumbai Expressway in Maharashtra State, India.

Three people have been confirmed dead and another two are being treated for injuries following a landslide that struck the Pune-Mumbai Expressway close to the Adoshi Tunnel in Maharashtra State, India, at about 12.15 pm local time on Sunday 19 July 2015. Debris fell on both lanes of the expressway, with three vehicles being struck and partially buried on the Mumbai-bound side of the road. Traffic towards Pune was able to move again from about 1.30 pm local time, but the Mumbai-bound lane remains closed, with traffic being diverted to the old Mumbai-Pune Highway, and extra trains being run between the cities in an attempt to slow the buildup of congestion.

A damaged car and boulders on the Pune-Mumbai Expressway following the 19 July 2015 landslide. Times of India.

The area where the incident occurred is known to suffer a high risk of landslides, particularly during the  monsoon season when high rainfall frequently triggers such events. Landslides 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. To this end the slopes above the expressway had been re-enforced against such events. However local press sources are reporting that these defenses are largely iron in construction, and in places are showing signs of severe corrosion.

The approximate location of the 19 July 2015 Pune-Mumbai Expressway landslide. Google Maps.

Maharashtra State has a monsoon climate, with the rains typically arriving around the start of June and peaking in July. The area where the 19 July 2015 landslip occurred typically receives over 500 mm of rain in June and over 1300 mm in July, and the area suffers frequent landslip and flooding events. This situation is made worse by widespread deforestation and quarrying for construction materials (much of it illegal) which tends to destabilize hill slopes.

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.

See also...

Five people have reportedly died following a landslide which destroyed the home in which they were staying in the village of Mohechiwadi in the Raigad District...

At least 41 people have died and between 120 and 350 are missing after a landslide destroyed the village of Malin, about 80 km north of Pune in Maharashtra State, on the morning of Wednesday 30 July 2014...

Parts of the Indian city of Mumbai are suffering from flooding after being hit by a series of freak waves on Thursday 12 June 2014. The waves occurred around high tide, and rose over four meters above expected levels, inundating low lying coastal parts of the city...

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