Thread by @rajbhagatt

Short #Story of a river, a sea, a fishing village, and a groyne

Satellite image from 2005 shows the delta of Porunai river (Thamirabarani) in Thoothukudi district of Tamil Nadu.

1/n

The river settled some amount of sand in the sea and close to the mouths the sea was shallower and with lots of sand.

2/n

A village (Punnaikayal) was dependent on this onfluence of the river and the sea but the fishing boats had difficulty in moving particularly during low tides

3/n

So they constructed groynes in the mouth of the river so that the mouth doesnt get affected by sand deposits which could then be traversed by the fishing boats

4/n

But we always tend to think that the sea is "static". Every time waves crash on the seashore and go back, they bring sand and take away. Depending on wind directions etc, the direction of transportation changes

If the budget is affected, then coastlines change significantly

5/n

And in this shore where the predominant drift is towards north (for most of the year and it is reverse for the rest), the groyne became a block and affected the transportation of sand

6/n

So to the south of the groyne sand began accumulating and to the north of the groyne, the coastline was starving in need of sand which had been reduced significantly.

Animation of satellite images show the change in the last decade

7/n

And as an unintended result of the construction of groyne, sand accreted on the south side creating a large beach and eroded for more than 100m to the north side of the groyne so much so that the groyne is now disconnected from land

Image below shows the change in coastline
8/n

There are many such cases. Construction projects of this size typically have large unintended effects & these unintended effects are largely forgotten or ignored when projects are designed or promoted. Just a reminder to look carefully into large development projects

The End

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