India: Early warning system for flash floods can save thousands of lives at risk

By Karthikeyan Hemalatha and Mayank Aggarwal

Every time there is persistent and intense rainfall in Ladakh, the cold desert region of India’s northern state Jammu and Kashmir, the locals begin to worry. It brings back images of the 2010 flash floods that affected thousands of people in the region. This year, several low lying areas in the region were inundated following the rains, triggering rescue operations by the local administration.

With an aim to prevent loss of life and extensive damage due to flash floods, the India Meteorological Department (IMD) is working on a Flash Flood Guidance System (FFGS) that will predict the possibility of flash floods up to six hours in advance and alert disaster relief forces as well as local residents.

Floods, specifically flash floods, are among the leading causes of deaths due to natural disasters. While general floods take days or even weeks to develop, flash floods can inundate vast areas within a few hours. Given this, the FFGS could be a significant tool in disaster risk reduction as it will provide alerts in advance that will help residents of the affected areas and relief teams prepare for the oncoming flash floods.

India among top disaster-prone countries in the world

According to the World Meteorological Organisation, some 5,000 people lose their lives each year, across the world, to flash floods, accounting for 85 percent of all kinds of floods (like riverine and coastal). India is also among the 10 most disaster-prone countries in the world, according to a report by the government of India and United Nations Development Programme (UNDP).

IMD’s upcoming system is of significance, especially for India, where nearly 12 percent of the landmass is prone to floods and river erosion.

In 2018 itself, several lives have already been lost across India since the arrival of the south-west monsoon which accounts for the majority of India’s annual rainfall.

So far, floods in Assam, Tripura and Manipur have claimed 23 lives and displaced nearly a million (eight lakh) people from their homes in these states as the water level in the Brahmaputra rose beyond its embankment, according to this report. The southern state of Kerala has already lost 54 lives since the onset of monsoon on May 29 − three days ahead of its normal date of onset.

According to Indian government’s Ministry of Water Resources, River Development and Ganga Rejuvenation, 107,487 human lives and 6.02 million cattle have been lost to floods and heavy rains across India during a period of almost 65 years, from 1953 to 2017.

In 2017-18, cyclonic storms, heavy rains, floods and landslides claimed 2,231 human lives and 50,638 cattle deaths. They also resulted in damage to over 1.19 million houses and 38,500 square kilometres of crop area.

Technology that will save lives at risk

Under the FFGS, using existing satellites and on-ground equipment, the IMD hopes to gather not just more accurate data but also predict the onset of flash floods in remote areas of the country.

The system will be able to track real-time rainfall in any part of the country. Along with other data points like soil moisture, soil temperature, level of soil saturation and the topography of the land, the system will help the meteorological department officials predict flash floods up to six hours in advance.

It is the soil’s ability to absorb rainwater that greatly determines the probability of flash floods.

Explaining the system, IMD’s Director General K. J. Ramesh said, “There is something called local soil hydrology. Some moisture is retained by the soil (when it rains).”

“Once the soil gets saturated, the runoff − outflow from the soil − starts. Until then, whatever rain has come will be absorbed by the soil. Local hydrology will be computed on daily basis (under the new system). We are trying to sub-divide the whole of India into about 27,000-28,000 micro watersheds, each about 50-70 sq km in size. At that scale, the soil hydrology model will be run on a daily basis by which you can clearly assess the run-off potential of the soil of an area,” Ramesh told Mongabay-India.

Ramesh stressed that with FFGS they will be able to ascertain how temperature, soil and rainfall are interacting and “when incremental run-off starts” from the soil.

According to the system, whether the run-off from the soil will lead to flash floods is something that the intensity of rainfall will decide.

“But it will give some guidance that there is an evolving scenario towards possible flooding … and then authorities have to take action,” added Ramesh.

In areas like Rajasthan and Madhya Pradesh, where the soil is more absorbent, even 10 to 20 centimetres of rainfall may not cause floods, but it can be different for other terrains. In regions like Ladakh in Jammu and Kashmir, where the terrain consists of mostly loose soil, flash floods can happen with lesser rainfall.

“Combined sloped terrain, raging waters from the river and torrential rain can easily run-off and cause flash floods,” Sonam Lotus, director of the meteorological department in Jammu and Kashmir, told Mongabay-India.

IMD’s director general Ramesh, also informed that the system is being tested and will be operational across the country once completed.

“The system will allow the state and central administration to prepare and reach the affected area for evacuation and rescue. Our staff is undergoing training to understand the system better. We plan to use it in full scale by next year,” said B.P Yadav, a senior scientist at IMD and the deputy director general of meteorology (Hydro-Meteorology).

Relief for flood prone states in sight

In August 2010, Ladakh experienced one of its worst natural disasters in its history. The cold desert district received 350 mm of rain in just two days − three and half times its annual average. As per reports, 234 people died and more than 800 went missing due to the floods.

In September 2014, Kashmir too saw one of its worst natural disasters in 50 years. Torrential rains from the South-West monsoon had gathered pace causing Chenab and Jhelum rivers to breach their embankments. Over the following days, nearly 2,600 villages in the state were affected, 390 of which were completely submerged. Some 280 people had died and half a million people were trapped in their homes for nearly three weeks, with the city of Srinagar drowning under nearly 18 feet of water.

“Our relationship with nature changed after that. We do not look at rains the same way after these floods,” said additional deputy commissioner for the Ladakh Autonomous Hill Development Council (LAHDC) Moses Kunzang.

For Sonam Lotus, FFGS is a significant step ahead in technology and the forecasting prowess of IMD.

“The FFGS is really required for a district like Ladakh. IMD, at the moment, forecasts on rainfall. Based on local knowledge of geographical parameters, we can somewhat predict floods. But the new system makes it all the more accurate. The 2010 floods were beyond anyone’s imagination. No one thought Ladakh would experience something like this. But the next time it happens, we will be better prepared,” said Lotus who heads the local meteorological department.

While flash floods are fairly recent in Ladakh, in places like Bihar, India’s most flood-prone state, about 76 percent of the population in the north of the state lives under the threat of flood devastation, according to the state’s Water Resources Department.

A little more than 73 percent or about 68,800 sq km out of the state’s total geographical area of 94163 sq km is flood affected. The state faced major floods in 2007, 2008, 2011, 2013, 2016 and 2017. Last year, the floods took away the lives of 514 people and affected 3 million families.

Using conventional methods to predict flash floods is extremely difficult, not just in Bihar but across the country, according to scientists. However, a system like FFGS can herald a new era.

“We do not have rain-gauges or flood forecasting stations in remote areas as they are not logistically possible to maintain. Besides, rains are not the only factor that can cause flash floods,” said IMD scientist Yadav.

Cyclones can also cause flash floods during the north-east monsoon in south-east coastal regions of the country, while the south-west monsoon can wreak havoc in other parts.

“The pilot phase is showing good results. We were able to accurately predict the floods in Mangalore this year. If things go well, we can roll out the system for the next year’s monsoon,” Yadav added.