2023 North India floods: Types of floods, loss and damage, and health effects post-flooding

“Rivers are essential to human life, and provide us with food, water and fertile land to grow crops. But they can be a destructive force too, with catastrophic effects on human life and the environment, especially during floods,” says Himanshu Garg, who has been studying freshwater bodies in the Himalayas for the past decade.

Loss and damage

As per the National Disaster Management Authority (NDMA), India is highly vulnerable to floods. Out of the total geographical area of 329 million hectares (mha), more than 40 mha is flood-prone. The average annual flood damage in the 10-year period from 1996 to 2005 was Rs 4,745 crore as compared to Rs 1,805 crore, the corresponding average for the previous 53 years. It is also a continuously rising trend. In 2021, economic losses from flooding in the country were a staggering $3.2 billion, as per The State of the Climate in Asia 2021 report.

These losses can be attributed to a steep increase in population, rapid urbanization, deforestation, poor drainage systems, damming of rivers, and growing developmental and economic activities in the flood plains. Global warming, too, is a major contributor. Climate change is exacerbating extreme weather events in the country, making floods more frequent and intense. For instance, in 2022, the country witnessed 314 days of extreme weather, as per the Delhi-based non-profit Centre for Science and Environment (CSE). It included 214 days of heavy rains, floods and landslides, the most recurring extreme weather event type in the year. Floods have claimed 1,600 lives on average every year, according to the NDMA.

“What is also concerning is that floods now occur in areas that were earlier not considered flood prone,” says Garg.

What you need to know about floods

Unfortunately, a one-size-fits-all solution cannot be applied since floods are of many types. In India, more than 70 percent of the precipitation takes place from June to September. Heavy rainfall over low-lying landscape leads to areal flooding. When river systems overflow due to heavy monsoon rain, cloudbursts, or glaciers melting, you get riverine flooding.

Storm surges from cyclones can lead to coastal flooding, while urban flooding occurs when densely populated areas receive heavy rainfall but have improper and inadequate drainage systems. Of these, urban floods are most destructive since they occur in highly populated areas and cause more deaths.

Floods have a wide range of negative and positive effects on their surroundings, depending on their location, magnitude, depth, and intensity. “Seasonal floods are known to renew ecosystems in floodplains. They bring in nutrients that help improve soil quality and boost plant productivity. They can recharge groundwater, and also trigger breeding and migration events for wildlife. In fact, they are essential for the survival of wetlands,” says Veena Kamath, who studies wetlands in Asia.

Deep impact of floods

But flooding also makes agricultural land less fertile due to soil erosion and the deposition of sediments. Stagnant water weakens plants. As per Ministry of Agriculture data, over 339 lakh hectares were lost due to hydro-meteorological calamities between 2015-16 and 2021-22. Madhya Pradesh, Karnataka, Rajasthan, Bihar, and West Bengal reported the highest damage due to flooding and rains. About 65 percent of the total crop damage due to floods in India in the last seven years were reported from these top states.

Floods also contaminate groundwater and its consumption is the leading cause of water-borne diseases like cholera, typhoid, and diarrhoea. Health experts in Delhi have already warned that ingesting the floodwaters of the Yamuna, which is mixed with various pollutants such as sewage, industrial waste, and harmful chemicals, could result in a rise in water-borne diseases. The stagnant waters could also become a breeding ground for mosquitoes and cause a spike in vector-borne diseases such as malaria and dengue.

Floodings can have a negative effect on wildlife. Contaminated waters, when they enter the ocean, affect water quality and disrupt delicate ecosystems such as coral reefs. “They can also lead to a severe deoxygenation of rivers, which can result in the death of fish. Wildlife can drown, and die due to disease proliferation, and habitat destruction. In 2012, for instance, hundreds of animals, including many one-horned rhinos, were killed in floods that swamped Kaziranga National Park in Assam,” says Kamath.

While floods cannot be stopped, their effects can be mitigated to a large extent. Natural flood control measures focus on deciding where the most successful interventions can be introduced, with an emphasis on increasing water retention capacity.

“You can realign coastal areas or reconnect rivers with their floodplains to restore natural flows. The preservation of wetlands can help slow the flow of floodwaters, while green spaces and sustainable drainage can reduce their impact in urban areas. Small measures, but they can save many lives,” says Garg.