Context: The National Green Tribunal has formed a panel of experts to ensure that the construction of the medical college and river front development takes place without damage to the flood plains of the Mahanadi river.

• The NGT order came in response to a petition filed to the state government’s plan of transforming the state-run SCB Medical College and Hospital into an AIIMS Plus. 

NGT Order

• There is a need to prevent irreversible damage to the riverine ecology by enforcing the applicable rules.
• Flood plain zones need to be identified and demarcated.

What are the Issues?

• The Mahanadi riverbed is likely to be affected by setting up of the medical college or other permanent constructions in the floodplain of the river.
• Encroachment of Kathajodi and Mahanadi rivers and construction in floodplain area may adversely affect the riverine ecology.

Illegal construction activities such as

• Panchamukhi Hanuman Temple
• Paddy threshing ground 
• Proposed structures such as toilet, graveyard, market complex, Kalyan mandaps and other activities.
• Adversely affect the river ecology and disturbed the flow of Mahanadi river.

Legal provisions to regulate floodplains

• The 2016 notification issued by the Ministry of Water Resources, River Development, and Ganga Rejuvenation, with respect to Ganga river, prohibits any construction in the active floodplain area of river Ganga or its tributaries.

There are some State Acts like

• Manipur Flood Zoning Act, 1978
• Uttarakhand Flood Plain Zoning Act, 2012.
• The Wetlands (Conservation and Management) Rules, 2017 prohibit any permanent constructions within 50 meters of the Wetlands.
• In Maharashtra, there are norms for demarcating regulatory and prohibitory zones in the floodplains of the rivers.
• There are also similar restrictions in certain Master Plans like the Revised Master Plan of Bangalore (Karnataka) restricting constructions in catchment area of the lakes.
• Odisha does not have any legislative and administrative measures regulating and prohibiting activities in the floodplain zones of the rivers in the state.

About Mahanadi River

• The Mahanadi is a major river in East Central India.
• It drains an area of around 141,600 square kilometres and has a total course of 858 kilometres.
• The river flows through the states of Madhya Pradesh, Chhattisgarh and Odisha.
• It is one of the most-active silt-depositing streams in the Indian subcontinent.
• Its upper course runs north as an insignificant stream, draining the eastern Chhattisgarh Plain.
• Its flow is augmented by the drainage of hills to the north and south.
• At Sambalpur the Hirakud Dam on the river has formed a man-made lake 35 55 km long.
• Below the dam the Mahanadi turns south, piercing the Eastern Ghats through a forest-clad gorge.
• Bending east, it enters the Odisha plains near Cuttack and enters the Bay of Bengal at False Point by several channels.
• The river supplies several irrigation canals, mainly near Cuttack.
• Puri, at one of its mouths, is a famous pilgrimage site.

Tributaries

• Left- Seonath, Mand, Ib, Hasdeo
• Right- Ong, parry, Jonk, Telen

Major projects

• Hirakud Dam Project is a multipurpose scheme intended for flood control, irrigation and power generation.
• The dam is built across river Mahanadi at about 15 km upstream of Sambalpur town in the state of Odisha.
• This is one of the oldest hydel projects of India, being the first post-independence major multi-purpose river valley project in the country.
• Ravishankar Sagar, Dudhawa Reservoir, Sondur Reservoir, Hasdeo Bango and Tandula are other major projects.

About Floodplain 

• It is an area of low-lying ground adjacent to a river, formed mainly by flooding of rivers and deposition of sand sediments on the riverbanks.
• These sandy floodplains are exceptional aquifers where any withdrawal is compensated by gravity flow from a large surrounding area.
• Some floodplains such as those of Himalayan Rivers contain up to 20 times more water than the virgin flow in rivers in a year.
• Since recharge is by rainfall and during late floods, the water quality is good.