FLASH
FLOODS – GEOGRAPHY
News:
Spike in flash floods
raises concern of ‘micro’ climate changes in Himachal
What's
in the news?
●
The number of flash flood events in
Himachal Pradesh has surged dangerously over the past few years, killing
hundreds of people, damaging critical infrastructure, and raising concern about
the ecologically fragile Himalayan region.
What
are flash floods?
●
Excessive or continuous rainfall over a
period of days or during particular seasons, can lead to stagnation of water
and cause flooding.
●
Flash floods occur in a much shorter span
of time (say, when rainfall creates flooding in less than 6 hours) and are
highly localised.
●
Flash floods can also be caused by factors
apart from rainfall, like when a dam over flows
Vulnerability
status of India:
●
According to government data, India is the
worst flood-affected country in the world, after Bangladesh.
●
40 million hectares of land in the country
are liable to floods annually. (National Flood Commission)
●
India accounts for one-fifth of the global
death count due to floods.
●
Flash floods have been commonly witnessed
in cities like Chennai and Mumbai.
Causes:
1. Heavy rain:
●
Apart from heavy rain, flash floods can
also be caused by dam or levee failures, ice or debris jams, or sudden release
of water from natural reservoirs such as glacial lakes.
2. Cloudburst:
●
In India, flash floods are often
associated with cloudbursts – sudden, intense rainfall in a short period of
time.
3. Saturated Soil:
●
If the soil is already saturated due to
previous rainfall or a prolonged wet period, it cannot absorb additional water,
leading to an increased risk of flash flooding.
4. Drought Conditions:
●
Surprisingly, flash floods can occur after
a period of drought. Dry and hardened soil cannot readily absorb sudden heavy
rainfall, resulting in rapid runoff and flash floods.
5. Melting Snow or Glaciers:
●
Rapid melting of snow or glaciers,
especially in mountainous regions, can contribute to flash floods downstream.
6. Breaches or Dam Failures:
●
Sudden release of water from upstream
reservoirs, breaches in landslide dams, or embankment failures ca…
Impacts
of flash floods:
1.
Loss of Life and Injury:
●
They can lead to drowning, injuries, and
even loss of life, especially in areas where warning systems and preparedness
measures are inadequate.
2. Property Damage:
●
Floodwaters can damage or destroy homes, buildings,
and infrastructure such as roads, bridges, and utilities.
3. Displacement and Homelessness:
●
Flash floods can force people to evacuate
their homes, leaving them temporarily or even permanently displaced.
4. Crop and Livestock Losses:
●
Floodwaters can destroy crops and wash
away livestock, leading to significant losses for farmers and agricultural
communities.
5. Spread of Waterborne Diseases:
●
Stagnant water after flash floods can
become breeding grounds for disease-carrying mosquitoes and other vectors,
leading to an increased risk of waterborne illnesses.
6. Erosion and Sedimentation:
●
Flash floods can cause erosion of soil and
sediment deposition in water bodies, affecting aquatic ecosystems and
contributing to siltation in rivers and reservoirs.
Government
measures:
1.
Flash flood guidance program:
●
India has launched first-of-its-kind Flash Flood
Guidance services for India and other South Asian countries –
Bangladesh, Bhutan, Nepal, and Sri Lanka.
2. Doppler radars:
●
IMD has been using Doppler radars, flash
flood forecasting and warning systems to predict the occurrence of flash
floods.
3. National Disaster Management Authority:
●
The NDMA also advises the inhabitation of
low-lying areas along the rivers, nullah and drains to be regulated by the
state governments/State Disaster Management Authorities (SDMAs)/ District
Disaster Management Authorities (DDMAs) as a preventive measure.
4. Central water commission:
●
Central Water Commission (CWC)/ National
Remote Sensing Agency (NRSA)/ state governments/ SDMAs also check for
landslides and blockages in rivers with the help of satellite images.
WAY
FORWARD:
1. Early warning systems:
●
Implementing early warning systems like iFLOWS
can help provide timely information about potential flash floods, allowing
people to take necessary precautions.
2. Flood-resistant infrastructure:
●
Building elevated and reinforced
structures in flood-prone areas can help minimize damage.
3. Check valves in sewer traps:
●
Installing check valves can prevent flood
water from backing up into drains.
4. Community
awareness:
●
Educating communities about flash floods
and their risks can help people prepare and respond effectively.
5. Integrated approach:
●
Managing floods requires a holistic
approach, considering water management, physical planning, land use,
agriculture, transport, urban development, and nature conservation.