Over 20 people have been killed in destruction caused by cloudbursts and flash floods in different parts of Himachal Pradesh and Uttarakhand over the last three days. Several of the regions in these two districts witnessed heavy rains, which created havoc.
The Indian Meteorological Department warned of more flash floods in the northern parts of the Country as well as in some other regions.
Well, let us take a look at Flash Floods and its frequency in the country
FLASH FLOOD; EXPLAINED
Flash flooding is a specific type of flooding that occurs in a short time frame after excessive or continuous rainfall over a period of days. According to the UK MET office, flash flooding happens when rain falls so fast that the underlying ground cannot cope, or drain it away fast enough. If the rain is falling too fast for the ground or drains to cope, there is a risk of flash flooding, it said. The National Weather Service says that Flooding that begins within 6 hours, and often within 3 hours, of the heavy rainfall (or other causes) is called as Flash flooding. It explained that Urban Areas are also prone to flooding in short time-spans and, sometimes, rainfall (from the same storm) over an urban area will cause flooding faster and more severe than in the suburbs or countryside. The impervious surfaces in the urban areas do not allow water to infiltrate the ground, and the water runs off to the low spots very quickly.
Flash Flooding occurs so quickly that people are caught off-guard. Their situation may become dangerous if they encounter high, fast-moving water while travelling. If people are at their homes or businesses, the water may rise quickly and trap them, or cause damage to the property without them having a chance to protect the property.
FLASH FLOOD; INDIA
In India, flash floods are often related to cloudbursts. Himalayan states further face the challenge of overflowing glacial lakes, formed due to the melting of glaciers, and their numbers have been increasing in the last few years.
The National Disaster Management Authorityof India says that the country is highly vulnerable to floods. Out of the total geographical area of 329 million hectares (mha), more than 40 mha is flood prone. They said that one of the reasons for flood situations occurring so frequently in India is that nearly 75 per cent of the total rainfall in the country is concentrated over a short monsoon season of four months (June to September). This causes the rivers to a heavy discharge during these months. About 40 million hectares of land in the country are liable to floods according to the National Flood Commission, and an average of 18.6 million hectares of land are affected annually.
FLASH FLOOD; CAUSES
The UK MET Department says that Flash flooding commonly happens more where rivers are narrow and steep, so they flow more quickly. It can also occur from small rivers in built-up urban areas, where hard surfaces such as roads and concrete do not let the water drain away into the ground. This leads to surface overflow and can often overwhelm local drainage systems, leading to flash flooding.
FLASH FLOOD; ALERTS
- Be aware of any signs of heavy rain
- Move to higher ground if rapidly rising water is seen or heard
- Not attempt to cross the flowing water