CLOUDBURSTS
– GEOGRAPHY
News:
Heavy rains in Himachal
Pradesh: When is high rainfall termed as a ‘cloudburst’?
What's
in the news?
●
Following heavy rains in Himachal Pradesh,
landslides have occurred in the state. Uttarakhand has also witnessed high
rainfall.
Cloudbursts:
●
The change in monsoon extremes and
cloudbursts we see now are in response to the 1°C rise in global surface temperature.
●
As emissions continue to increase and
global commitment to reduce emissions proves insufficient, these temperatures
are set to hit 1.5°C during 2020-2040 and 2°C during 2040-2060. We will need
urgent action and policies to protect lives and property from extreme events
that will amplify as the global temperature change doubles.
Reasons
behind Cloudburst:
●
It is difficult to predict when exactly a
cloudburst will occur. However, they are more likely to occur in mountainous zones mainly because of terrain
and elevation.
●
Cloudburst is mostly caused by an
excessive amount of condensation in the clouds during a thunderstorm. During a
thunderstorm, the warm air currents pull the falling drops of water upwards
creating an excess accumulation of water in the clouds. If it reaches a point
where the upward air current is weakened, it results in sudden precipitation
and downpour of all the accumulated water, in a short time causing floods in
the surrounding areas.
Difficulties
in forecasting:
●
Possibility of specific cloudburst events
cannot be forecasted. But heavy to very heavy rainfall events are routinely
forecasted four to five days in advance. Even, possibility of extremely heavy
rainfall, that may result in cloudburst kind of situations, are forecast six to
12 hours in advance.
●
No meteorological agency or weather
scientists including Indian Meteorological Department (IMD) predict the quantum
of rainfall ie. how much rain is likely to fall at any given place but they can
forecast rainfall events in advance.
●
Most of the forecasts are for a relatively
large geographical area (region, a state, a meteorological sub-division, or
district), and it is uncertain to
forecast for a smaller area.
●
Current
technologies are unfeasible to forecast rainfall over a very
small area as it requires a very dense network of weather instruments, and
computing capabilities.
How
common are cloudbursts?
●
Cloudbursts are not uncommon events,
particularly during the monsoon months.
●
Most of these happen in the Himalayan
states where the local topology, wind systems, and temperature gradients
between the lower and upper atmosphere facilitate the occurrence of such
events.
●
However, not every event that is described
as a cloudburst is actually, by definition, a cloudburst.
●
That is because these events are highly
localized.
●
They take place in very small areas which
are often devoid of rainfall measuring instruments.
Are
cloudburst incidents increasing?
●
There is no direct long-term trend suggesting that cloudbursts are rising.
●
However, there are well established facts
that incidents of extreme rainfall or
weather events are increasing across the world.
●
In case of India, there is no substantial
change in overall amount of rainfall but an increasing proportion of rainfall
is happening in a short span of time meaning that the wet spells are very wet,
and are interspersed with prolonged dry spells even in the rainy season, due to
climate change suggesting that cloudburst events might also be on the rise.
Impacts
of Cloud bursts:
1.
Human loss:
●
The very nature of flash floods makes them
fast and very difficult to predict. Since they can occur without warning, it is
no surprise that people can be seriously injured or killed by these natural
disasters.
2.
Structural damage:
●
In addition to the force of the water,
cloud bursts can carry large debris such as boulders.
●
This combination can cause heavy
structural damage to homes making them uninhabitable and can carry away large
pieces of property such as vehicles.
3.
Loss of Critical Infrastructure:
●
Large debris and flood waters can cause
structural damage to bridges and roadways, making travel impossible.
●
Power, telephone, and cable lines can be
taken out by flash floods as well.
●
Flood waters can disrupt or contaminate
groundwater, making tap water unfit for consumption.
4.
Deposited Sediment & Silt:
●
Floods can leave behind large amounts of
silt and other debris that can make travel difficult and can be costly to
remove.
5.
Economic Losses:
●
Depending on the damage caused, it may
prevent local businesses from opening or keep customers from getting to those
businesses.
6.
Flash floods:
●
A cloudburst can have a devastating impact
triggering flash floods. These floods can cause uprooting of trees and movement
of boulders and other debris.
7.
Landslides:
●
Because of the nature of terrain, the
heavy rainfall events often trigger landslides.
Measures
to prevent and reduce the devastating impacts of cloudbursts:
●
Regulation
of construction activities along river banks with special
consideration to water level during heavy rainfall.
●
Strengthening of embankments, barrages and dams to constrain & regulate water
flow.
●
Localized
planning taking into consideration the ecologically fragile
nature of the region and involving the local communities’
●
Regulate
infrastructure projects and preserve the sanctity of
eco-sensitive zones.
●
Better
forecasting by IMD and incorporation of advanced technology
to monitor and predict extreme weather events can enable early warning,
evacuation and preparedness
●
Adoption of ecofriendly policies and eco-sensitive tourism for development of
the region.
●
Incorporation of disaster management and prevention into the developmental planning
process.
WAY
FORWARD:
●
Multiple
doppler weather radars can be used to monitor moving cloud
droplets and help to provide nowcasts (forecasts for the next three hours).
●
A long-term
measure would be mapping the cloudburst-prone regions using automatic rain
gauges.
●
If cloudburst-prone regions are co-located
with landslide-prone regions, these locations can be designated as hazardous.