A home and two shops have been destroyed in a landslide at Mussoorie in Dehradun District, Uttarakhand, on Thursday 30 July 2020. No casualties were reported in the incident, which happened following days of rain in the area, associated with the annual Monsoon. 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.
The aftermath of a landslide at Mussoorie in Dehradun District, Uttarakhand, on Thursday 30 July 2020. Hindustan Times.
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.
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