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

Subject :Geography

Section: Physical Geography

Context:

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.

Types:

Peninsular (found in the Deccan plateau) where there are rock terraces (step-like structures created by lava flows), and
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
Another classification of floodplains is based on the definitions of “floods” and “rivers”.
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.

Floodplain protection:

If we factor in the floodplains outside the river banks, then it is unending. Cities and towns have always been built on floodplains.
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.
The peninsular rivers, on the other hand, flow through Deccan trap rock, and so there is less alluvial soil in this region.
The river’s space between its naturally defined banks has to be protected.

Laws and regulations to cover these issues:

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.

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

Manipur:

Delimitation of flood zones, prohibiting construction activities, was performed by the state government through a notification in 1988.
In 2018, the Manipur government enforced the act by demolishing structures built metres away from the Imphal river.

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 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.

Other states:

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.

Who is responsible for floodplain zoning?

The irrigation departments of respective states are responsible for the enforcement of floodplain zoning laws.
The irrigation department notifies rivers and has the power to remove the encroachment.
The responsibility for floodplain protection falls on the urban local bodies as well.