Risk of Flash Floods and Landslides in Himalayan Region
I hope you are familiar with NDRF i.e. National Disaster Response Force involved in search
and rescue operations in Himachal Pradesh following flash floods and landslides which has
been triggered by excessive rainfall in Himachal Pradesh in the recent times.
You might remember one of the biggest incidents causing massive devastation in the recent
times i.e. Chamoli disaster (Uttrakhand) in 2021 triggered by rupture and collapse of
glacial rock creating tsunami like flash flood.
Kedarnath Tragedy in 2013 is another such incident triggered by heavy rains
accompanied by faster melting of glaciers causing massive flash floods. It is one of the
biggest disaster that India had suffered.
Kerala witnessed massive floods in the monsoon in 2018-19.
What do you mean by disaster ?
A disaster is any calamity or catastrophic event involving large scale loss of human life, large scale injuries to human beings as well as serious damage to infrastructure and public property. It can even damage the environment as well have an impact on environmental biodiversity.
Is Disaster different from Hazard?
When hazard meets with exposure and vulnerability and habitated population in a given area are vulnerable and exposed to the impact of hazard then it turns into disaster.
What is a Hazard?
Hazard is a potential event which could trigger a disaster. For example, a region prone to landslides or flood are facing the hazard because of natural factors. If the population in that area are exposed to the impact of hazard it turns into a disaster.
Disaster Management in India-
Analyzing the impact of disasters and large scale loss of life, loss of biodiversity,
economical impact, how it can cause serious damage to infrastructure and property, it is
very important to work on disaster management.
Disaster management can not be seen as a temporary or ad hoc measure but a part of
mainstream governance.
Stages of disaster management cycle -
- Pre disaster preparedness and planning,
- During disaster response and
- Post disaster reconstruction.
Flood Hazard Zones in India -
National disaster management authority (NDMA) has provided a map showing flood prone zones in India. These are:
- Indus basin
- Gangetic basin
- Brahmaputra basin
- Krishna, Godavari, Kaveri basin
- Mahanadi basin .
Factors responsible for these incidents :
- Large scale development,
- Rampant construction activities,
- Deforestation,
- Long term climate change.
Vicious cycle of Flash Floods and Landslides-
Heavy rains which is Meteorological hazard could led to secondary and tertiary disasters
such as flash floods and landslides.
Current incident in Himachal Pradesh is triggered by heavy rainfall in the ecological
sensitive Himalayan belt.
As Himalayas are young fold mountains and unstable in their structure having steep valleys
where water flows down at a very high velocity, in such a vulnerable region if excessive
sudden outburst of rain happens, the surface runoff will increase in the slope areas. The
water flowing down will pick up velocity as it is flowing down and other factors play role
in arresting flow of water.
Now if slope is the denuded because of deforestation and urbanization and the forest areas
have been cleared, there is nothing to hold the water back and if water is flowing down at a
very fast rate it is going to weaken the structure and integrity of the soil. Because of
saturation of soil structure would become weak and this entire soil-rocky material would
slide down under the influence of gravity. This sudden shifting of debris and rock material
under the influence of gravity is known as landslide also known as Mud-slide, Land-slip,
Rock Avalanche etc.
Landslides pushes all the soil and material down into the valley creating a Natural-Dam like
structure and stops the natural flow of water in the valley areas creating a blockage. Here
the water starts accumulating. It could put enough stress on natural temporary dam and this
natural Dam breaching within few hours or days led to flash floods in downstream areas.
Flash Floods and Landslides -
Floods occur when the flow rate exceeds the carrying capacity of the river channel. a landslide is defined as the sudden movement of a mass of Rock debris or Earth down a slow it is triggered by a specific event such as heavy rainfall and earthquake a slope cut to build a road etc.
Disaster Risk Management Cycle:
Sendai Framework adopted by the UN focuses on reduction on disaster risk. It includes:
- Prevention and Mitigation
- Preparedness
- Disaster
- Response
- Rehabilitation and Recovery.
Disaster Risk Management steps includes:
