[Explainer] What are floodplains and how have they been managed in India?

India is one of the most flood-prone countries in the world.
Concretisation and development in the country’s floodplains reduce the carrying capacity of rivers and streams, which exacerbates urban flooding.
Only a few states such as Manipur, Rajasthan, Uttarakhand, and the erstwhile union territory of Jammu and Kashmir, have policies for floodplain zoning.
Experts have reiterated the need to effectively implement these laws in the states, and to pass floodplain zoning laws in other states, especially those prone to flood.

Cities and towns are often built close to riverbanks and floodplains for easy access to water and transport. Historically, in India, the fertile land of the riverbed and floodplains, that was available for agriculture when seasonal rivers wane, was allotted to farmers by the state on temporary lease. For example, in the Maharashtra Land Revenue Code, this provision was known as a “temporary right to alluvial lands of small extent”. Known as the ‘gaal per land’ (alluvial land) in Maharashtra, this land belonged to the river.

However, in recent times, encroachment on the riverbed and floodplains, both legal and illegal, are a regular occurrence in India. This has worsened the effects of floods in several states such as Maharashtra in 2005, Chennai in 2015, and Kerala in 2018.

What are floodplains?

Floodplains are the lands, adjacent to both sides of a river, that are submerged under water when a river swells. The shape and size of a floodplain depend on the side slopes of the river. If they are steep, the floodplain area is less, but if they are flat, the floodplain can span across kilometres.

India’s Model Bill for Flood Plain Zoning, 1975, defines “floodplain” to include the “water channel, flood channel, and that area of nearby lowland susceptible to flood inundation.”

This definition was subsequently incorporated in the Rajasthan, Manipur, Uttarakhand, and Jammu and Kashmir floodplain zoning acts.

Geomorphologically, the floodplains in India are of two types: a) peninsular (found in the Deccan plateau) where there are rock terraces (step-like structures created by lava flows), and b) those found in the Himalayan region, which are old, wide and depositional (created by the deposition of sediment). “The depth of the sediment in the Himalayan floodplains is considerable; at some places it can be as deep as 300-400 metres,” explains Shrikant Karlekar, a geomorphology and geoscience expert who has authored a few books on the subject.

Aerial view of Brahmaputra river. While a river expands and contracts naturally over seasons, concretisation and development in the floodplains reduce the carrying capacity of rivers and streams, which exacerbates flooding. Photo by Akarsh Simha/Wikimedia Commons.

Urban planner and a professor of sustainable development, Aneeta Gokhale-Benninger offers another classification of floodplains based on the definitions of “floods” and “river”. She says, if a river means a waterbody that flows within its naturally defined banks, then instances of water entering structures built within these naturally defined banks cannot be called “floods”.

With this definition of floods in mind, inner floodplains are the land within the river channel, which is exposed when the river wanes during the summer. The outer floodplains are the land that is susceptible to flooding when the river overflows its banks. “In the peninsular rivers, the land in the river’s channel should be protected,” shares Gokhale-Benninger. She says that protecting the entire floodplain area is not feasible. “If you factor in the floodplains outside the river banks, then it is unending. Cities and towns have always been built on floodplains,” she adds.

In north India, the course of the rivers shifts because the floodplains are created by alluvial soil. The floodplain zoning policy for the Himalayan rivers must be developed after studying the patterns in the changing course of the rivers, she says. The peninsular rivers, on the other hand, flow through Deccan trap rock, and so there is less alluvial soil in this region, says Gokhale-Benninger. “The river’s space between its naturally defined banks has to be protected. The river is a natural entity that needs space to flow, to wax, and to wane. The integrity of all the waterbodies must be considered sacrosanct. As of now, this space is encroached upon too, not only by illegal construction but also by legally permitted construction of residential buildings,” she shares.

Satellite imagery of Mahad city and tehsil in Raigad district, Maharashtra, before and after heavy rains in July 2021. The tehsil and city have been built on the floodplain of the Savitri river. This region floods year after year. Map by Technology for Wildlife Foundation.

Satellite imagery from 2022 of the Commonwealth Games Village built on the floodplains of Yamuna river. The venue flooded before the games in 2010. Map by Technology for Wildlife Foundation.

Which laws and regulations have covered this issue?

Floodplain zoning laws aim to prevent or restrict development on floodplains in order to prevent loss of life and property and to reduce the impact of floods.

The Central Water Commission prepared floodplain zoning guidelines and the Model Bill for Floodplain Zoning was circulated by the Government of India in 1975. Four states followed this up by passing floodplain zoning acts: Manipur in 1978, Rajasthan in 1990, Jammu and Kashmir in 2005 and Uttarakhand in 2012. These acts provide for the establishment of a “Flood Zoning Authority” who is authorised to conduct surveys to determine the nature of extent of floodplains, prohibit or restrict the use of land in the floodplains, and impose penalties for non-compliance.

Floodplain zoning has been recognised as a “non-structural measure” to mitigate flood disasters as development in the floodplains reduces the carrying capacity of rivers and exacerbates the effects of floods.

Experts have thus reiterated the need to pass floodplain zoning laws in the other states, especially those prone to floods, and to implement the laws in the states where they have been passed.

Another state where floodplain zoning has been enforced to a certain extent through regulations is Maharashtra, says Himanshu Thakkar, Coordinator at the South Asia Network on Dams, Rivers, and People (SANDRP). The irrigation department issued guidelines in 1989 requiring floodlines to be marked for all the rivers.

“We cannot floodproof any land. There is a misconception that flood control and floodproofing is possible. Floods will happen. The only question is when, how frequently, and what kind of flood. Secondly, floods are not equal to disaster if you follow proper policies as to what kind of activities and structures are allowed in these areas,” shares Thakkar.

View from Pune's Bundgarden bridge showing commercial and residential buildings in the floodplains of the Mula Mutha river. Photo by Vivek Shenoy. — View from Pune’s Bundgarden bridge showing commercial and residential buildings in the floodplains of the Mula Mutha river. Photo by Vivek Shenoy.

Floodlines were marked for the Mula, Mutha, and Pavana rivers in 2011, but the demarcation of floodlines for several other rivers in Maharashtra has still not been done. Stalin Dayanand, Mumbai-based environmentalist and director of Vanashakti, an NGO, filed a public interest litigation in 2014 for the final demarcation of floodlines and removal of encroachment from all rivers. “Rivers need breathing space to swell and ebb. All construction on floodplains needs to be removed and future construction must be banned. We filed a PIL for floodplain protection in 2014 and have been repeatedly pushing for a hearing,” he shares.

The Noida Development Authority demolished illegal farmhouses and buildings worth Rs. 40 crores last year, responding to complaints by farmers about encroachment on the Yamuna floodplains. Though there is no floodplain zoning law in Uttar Pradesh, the move was carried out by the Noida Development Authority as per its mandate to regulate building construction, allot plots as per regulations, and demarcate sites for land use under the Uttar Pradesh Industrial Area Development Act, 1976.

“Protection of floodplains falls within the jurisdiction of the irrigation department, but this demolition was carried out by the Noida Development Authority drawing on its power to approve the development projects in their jurisdiction and also to enforce the National Green Tribunal order. The irrigation department can take lawful action to protect floodplains but I have not heard of any such case where the irrigation department has taken action,” shares Vikrant Tongad, a Noida-based environmentalist and founder of the non-governmental organisation, Social Action for Forest and Environment.

Read more: Risk-informed planning essential to prevent floods in Kochi

How are the states that have passed floodplain zoning laws faring?

Manipur was one of the early movers of floodplain zoning, having passed the law in 1978 after the Model Bill for Floodplain Zoning was circulated in 1975. Delimitation of flood zones, prohibiting construction activities, was performed by the state government through a notification in 1988. However, this notification was not widely publicised to the citizens.

In 2018, the Manipur government enforced the act by demolishing structures built metres away from the Imphal river.

“The public had little or no knowledge of the existing prohibited and delimited zones, and so the enforcement of the act took a piecemeal approach. If the floodplains are to be protected, demarcation of floodlines and regulation of structures according to the zones is a must,” says Abujam Manglem Singh, Assistant Professor, Department of Geography at Manipur University. Singh studied the perceptions of the people affected by Manipur’s floodplain zoning policy and found that around 50% of the respondents supported the implementation of the Manipur Flood Plain Zoning Act.

Uttarakhand passed its floodplain zoning act in 2012. The Uttarakhand government started demarcating floodlines in 2020. A study that surveyed the survivors of the 2013 flash floods in Uttarakhand to understand the preferred mitigation strategies found that the survivors are aware of the fragile environment they live in but do not prefer to relocate. Instead, they prefer improved emergency planning systems, strict enforcement of the floodplain zoning act, and better communication with the state disaster management agency.

Demarcation of floodlines and enforcement of floodplain zoning has not been done in the other two states where floodplain zoning laws have been passed, i.e., Rajasthan and Jammu and Kashmir (now a union territory). In most places, there is no legal definition of the space of the river either. As Himanshu Thakkar of SANDRP asks, if construction were to be prohibited for 500 metres on both sides of a river, where would these 500 metres start and end?

Streams that act like rivers during the monsoons also deserve to be protected like rivers, says Sarang Yadwadkar, Pune-based environmentalist and activist. “More than 20 people lost their lives and several vehicles were washed away in 2019, by Pune’s Ambil Odha (Ambil stream). We need laws to ensure that such streams are protected and we do not build structures in their channels,” says Yadwadkar.

Flood-affected area in India (1998-2022), one of the most flood-prone countries in the world. Map from Flood Affected Area Atlas of India.

Who is responsible for floodplain zoning?

Retired professor at the Water and Land Management Institute in Aurangabad, Pradeep Purandare believes that the irrigation departments of respective states are responsible for the enforcement of floodplain zoning laws. “In Maharashtra, where this is no floodplain zoning act, the topic is covered by the Maharashtra Irrigation Act, 1976, which is the parent act; all irrigation management is based on it. The irrigation department notifies rivers and has the power to remove encroachment. However, this power is not used by the authorities because there is no accountability in the law for failing to protect the floodplains,” shares Purandare.

Sarang Yadwadkar, however, says that the responsibility for floodplain protection falls on the urban local bodies. In Pune, the irrigation department marked floodlines in 2011 but the Pune Municipal Corporation, the urban local body responsible for enforcing the guidelines, has granted permissions to construct buildings inside the blue line (i.e., in the prohibited zone). “The irrigation department and urban local bodies are jointly and severally responsible for floodplain protection in Maharashtra. The irrigation department is responsible for identification of floodlines, and enforcing the floodplain zoning is the responsibility of the urban local bodies,” says Yadwadkar.

With climate change influencing rainfall patterns, the definitions of the once-in-25-year-flood and once-in-100-year-flood need to be revised, say experts. This makes it increasingly important to implement changes in our floodplain zoning policies.

According to the experts, the same authorities entrusted with protecting the floodplains are legalising the encroachment on them in the name of “riverfront development”. They warn that concretising the floodplains to eke out land for commercial interests is an environmental catastrophe in the making. “Riverfront development projects are essentially looking at legalising encroachment not only on the floodplains but also the riverbed and riverbanks by constructing parks, hotels, tourist spots, and so on. Concretising the riverbanks does nothing for flood control. In fact, this will worsen floods,” warns Yadwadkar.

Note: For the maps of Savitri and Yamuna rivers, pixel values in the satellite images were analysed using thresholding methods to detect inundated areas. The blue in the maps represents the presence of water (water bodies or inundated areas).