Zoning of flood plains

Why in news: Punjab has been reeling under floods for well over a month now and the proposed solution to this is zoning of flood plains.

Significance of flood plains:

  • A 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.
  • Well maintained flood plains, free from wanton construction and concrete, are natural defences against flooding farther inland.
  • They are also useful for recharging groundwater levels and maintaining the water table.

How flood plains are identified?

  • It is done 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.

Zoning of flood plains

  • Zoning of flood plains is done to regulate land use.
  • Zoning involves demarcating areas 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.

As per guidelines on floodplain zoning by the National Disaster Management Authority, the following should be located such that they are above the levels corresponding to a 100-year frequency or the maximum observed flood levels:

  1. defence installations,
  2. industries,
  3. public utilities like hospitals, electricity installations, water supply, telephone exchanges, aerodromes, railway stations, commercial centres, etc.

Implications of lack of zoning:

  • Encroachment and mismanagement of flood plains leading to non-suitable construction activity and concretization of flood plains.
  • Non-suitable constructions play a part in pushing floods further inland, increasing the area harmed and damage caused during floods.
  • Concretisation leads to it taking far longer for floods to subside as the water simply does not drain.
  • This kind of flooding is not good for flood plains themselves, affecting the fertility and quality of the soil as well.

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