Punjab is witnessing flood for over a month now. The villages along the rivers Sutlej, Beas, Ravi and Ghaggar are the worst affected.
What is a flood plain?
A floodplain is a flat area of land next to a river or stream.
It stretches from the banks of the river to the outer edges of the valley.
The river expands and contracts naturally over seasons and in different years.
A flood plain is an area adjacent to the river which normally gets flooded when the river swells.
Floodway- It is the main channel of the river. It can sometimes be seasonal, meaning the channel is dry for part of the year.
Flood fringe- It is present beyond the floodway. It extends from the outer banks of the floodway to the bluff lines of a river valley.
Bluff lines, also called valley walls, mark the area where the valley floor begins to rise into bluffs.
Formation-
Erosion- It describes the process in which earth is worn away by the movement of a floodway.
Aggradation - It describes the process in which earthen material increases as the floodway deposits sediment.
Why flood plain is important?
Clear water- A healthy floodplain gives rivers the space to spread out and slow down, which allows such sediment to settle.
It keeps water cleaner, protecting local drinking water and aquatic species like fish.
Shading of streams by floodplain vegetation also helps regulate water temperature.
Habitat- They are rich and biologically diverse environments that can support an abundance of plants, birds, fish, and other species on land and in the water.
For example, Chinook salmon rely on floodplains for survival during the freshwater phase of their life cycle.
Flood storage-Floodplains take on and store excess water in times of flood, releasing it slowly over land and into groundwater.
Groundwater recharge-Rainwater travels deep into the ground of a floodplain to replenish groundwater supply.
Groundwater travels slowly into rivers, lakes, and wetlands, regulating the availability of water during drier periods when people, plants, and animals need it most.
Food- They have rich, fertile soils that have made them attractive to farmers for generations.
Sustainable agricultural practices can help support key floodplain functions.
Culture- Floodplains provide numerous recreational opportunities via lakes, rivers, etc.,
The long history of settlement in floodplains as people have been drawn to the fertile land and abundant resources create a shared culture and sense of place in these locations.
Example- Indus valley civilization situated near the river Indus.
How flood plain zoning is done?
Identification- Experts find flood plain based on topographical features around rivers.
For instance, flood plains often contain oxbow lakes basically abandoned meandering channels of the river, where it once flowed prior to changing its course.
Demarcation of areas - It is done around rivers likely to be affected by floods of different magnitudes and frequencies, in order to specify the types of permissible developments there.
This is done so that whenever floods do actually occur, the damage is minimal.
Guidelines- As per guidelines on floodplain zoning by the National Disaster Management Authority,
Defence installations, industries, and
Public utilities like hospitals, electricity installations, water supply, telephone exchanges, aerodromes etc., should be located such that they are above the levels corresponding to a 100-year frequency or the maximum observed flood level.
What are the issues in Punjab?
NGT - According to the National Green Tribunal (NGT), there should be no construction within 500 m area from the central lining of a river.
However, despite NGT’s directions to the Government of Punjab, the state is yet to carry out flood plain zoning.
The NGT even sent directions to the state’s chief secretary to personally monitor progress of zoning and ensure compliance of its directions.
Encroachment-The flood plain areas of Sutlej, Beas, Ravi and Ghaggar have been encroached, making villages along these rivers perennially at risk of floods whenever they swell.
Mismanagement- Encroachment and mismanagement of flood plains leading to non-suitable construction activity and concretization of flood plains.
Non-suitable constructions- It pushes the flood further inland, increasing the area harmed and damage caused during floods.
Concretisation- It takes far longer for floods to subside as the water simply does not drain.
Affects soil- Floods is not good for floodplain and it affects the fertility and quality of the soil as well.
Time constraints- The work on zoning of flood plains has started, but it will take time to be completed.
Urban population-60% of the state is flood prone as four rivers Sutlej, Beas, Ravi and Ghaggar, flow through Punjab.
The protection bundhs are made to protect the urban population from floods.
Inadequate- Areas along the rivers in the districts of Ropar, Moga, Ferozepur etc., come under flood plains.
It further highlights the risks that Punjab faces if it does not prepare adequately for floods.
What lies ahead?
Flood plain zone regulation is adopted only by three states so far, States should stick to the regulation and formulate proper demarcation of floodplains.
This would reduce the hazard and challenges posed by the flood in the long run.
