Hundreds stranded as a flash flood, landslips disrupt Himachal highways

Subject : Geography

Section: Indian Physical geography

Context:

Chandigarh-Manali National Highway was blocked following flash floods and landslips.

Details:

The alternative Mandi-Kullu route, via Katola, blocked after landslips, was opened again.

About Flash Floods

Flash Floods are highly localized events of short duration with a very high peak and usually have less than six hours between the occurrence of the rainfall and peak flood.
The flood situation worsens in the presence of choked drainage lines or encroachments obstructing the natural flow of water.
Flash floods have a different character than river floods, notably short time scales and occurring in small spatial scales, which make forecasting flash floods quite a different challenge than traditional flood forecasting approaches.
Urban areas are more likely to experience this type of “surface water” flooding because they have a lot of hard surfaces.
- When rain hits them it can’t soak into the ground as it would do in the countryside.

Consequences of flash flood:

Frequently, flash floods are accompanied by landslides, which are sudden movements of rock, boulders, earth or debris down a slope.
It is common in mountainous terrains, where there are conditions created for it in terms of the soil, rock, geology and slope.
Natural causes that trigger landslides include heavy rainfall, earthquakes, snow-melting and undercutting of slopes due to flooding.
Landslides can also be caused by human activities, such as excavation, cutting of hills and trees, excessive infrastructure development, and overgrazing by cattle.
India is one of the countries most likely to face landslides. For a statewide analysis of this phenomenon, do read our previous explainer.

Flash flood-prone area:

Flash flooding commonly happens more where rivers are narrow and steep, so they flow more quickly.
They can occur in hilly regions and in urban areas located near small rivers since hard surfaces such as roads and concrete do not allow the water to absorb into the ground.
India is the worst flood-affected country in the world, after Bangladesh, and accounts for one-fifth of the global death count due to floods.
Flash floods have been commonly witnessed in cities like Chennai and Mumbai.
Depression and cyclonic storms in the coastal areas of Orissa, West Bengal, Andhra Pradesh, and others also cause flash floods.
As per the NDMA, nearly 75 per cent of the total Indian rainfall is concentrated over a short monsoon season of four months (June to September).

NDMA Guidelines for Flash Floods: Do’s & Don’ts

Before floods
- Do not litter waste, plastic bags, plastic bottles in drains
- Try to be at home if high tide and heavy rains occur simultaneously
- Listen to the weather forecast at All India Radio, Doordarshan. Also, messages by Municipal bodies from time to time and act accordingly.
- Evacuate low-lying areas and shift to safer places.
- Make sure that each person has a lantern, torch, some edibles, drinking water, dry clothes and necessary documents while evacuating or shifting.
- Make sure that each family member has identity card.
- Put all valuables at a higher place in the house.

In the Flood Situation
- Obey orders by government and shift to a safer place.
- Be at safe place and they try to collect correct information.
- Switch of electrical supply and don’t touch open wires.
- Don’t get carried away by rumors and don not spread rumors.

After Floods
- Drink chlorinated or boiled water.
- Take clean and safe food
- Sprinkle insecticides in the water ponds/ stagnant water.
- Please cooperate with disaster survey team by giving correct information.

DO’s
- Switch off electrical and gas appliances, and turn off services off at the mains.
- Carry your emergency kit and let your friends and family know where you are going.
- Avoid contact with flood water it may be contaminated with sewage,oil, chemicals or other substances.
- If you have to walk in standing water, use a pole or stick to ensure that you do not step into deep water, open manholes or ditches.
- Stay away from power lines electrical current can travel through water, Report power lines that are down to the power company.
- Look before you step-after a flood, the ground and floors are covered with debris, which may include broken bottles, sharp objects, nails etc. Floors and stairs covered with mud and debris can be slippery.
- Listen to the radio or television for updates and information.
- If the ceiling is wet shut off electricity. Place a bucket underneath the spot and poke a small hole into the ceiling to relieve the pressure.
- Use buckets, clean towels and mops to remove as much of the water from the afflicted rooms as possible.
- Place sheets of aluminium foil between furniture and wet carpet.

Don’t’s
- Don’t walk through flowing water – currents can be deceptive, and shallow, fast-moving water can knock you off your feet.
- Don’t swim through fast-flowing water – you may get swept away or struck by an object in the water.
- Don’t drive through a flooded area – You may not be able to see abrupt drop-offs and only half a meter of flood water can carry a car away. Driving through flood water can also cause additional damage to nearby property.
- Don’t eat any food that has come into contact with flood water.
- Don’t reconnect your power supply until a qualified engineer has checked it. Be alert for gas leaks – do not smoke or use candles, lanterns, or open flames.
- Don’t scrub or brush mud and other deposits from materials, This may cause further damage.
- Never turn on ceiling fixtures if the ceiling is wet. Stay away from ceilings that are sagging.
- Never use TVs, VCRS, CRT terminals or other electrical equipment while standing on wet floors, especially concrete.
- Don’t attempt to remove standing water using your vacuum cleaner.
- Don’t remove standing water in a basement too fast. If the pressure is relieved too quickly it may put undue stress on the walls.