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  • Writer's pictureHamsen B Paramahamsa MSc geology

Unawathuna coastal Erosion. As if after a Naval Battle

Unawathuna coastal erosion

Unawathuna is near the City of Galle on the southern coast of SL. The Unawathuna Coast is a tourist attraction, and many come to rest.

The coast is facing a loss of coast-scape due to erosion. And certain parts look as if there has been a devastating Naval Battle. The erosion appears to be very rapid during recent decades, for, some rock outcrops aren’t bold.

This outcrop at Unawathuna ( on the left) shows it has been under full soil just a few decades ago. Maybe even a few years ago.

On the right the pic shows the outcrop is not old and the soil covering had been full. The covering had been millions of years.

The height of the outcrop is more than two meters. The undersoil chemical erosion has taken its toll. The surface is very rough and has many dents and corroded depressions with sharp edges. The rock has many shades. Red-brown color reflecting oxide of iron; and whitish reflecting calcium minerals. The original rock is of gneiss, some call it granite, too. The rock has minerals composing Na, K, Fe Ca, and SI.

In the process of chemical erosion Na, and K eroded first and move dissolved in water, and settle in the seas. Calcium follows them leaving whitish flakes on a brownish-reddish colour of iron minerals. Deeper inside the mother rock is present.

The calcium that leaves the rock is not fast moving like Na, and K. It moves slowly and is also dissolved in water. This slow movement facilitates calcareous species to thrive. A kind of barnacle has found a place to thrive and is spreading around the rock like a rash on the beach. In the pic 1-4 the white rash-like spots and surface are well seen.

The tragic story narrated by the eroded rock is that the beach Coast at Unawathuna has been full of Flora, and soil just a few decades ago. The coastal scape must have been hundreds of meters in the sea, and height a few tens of meters. It is further understood by the presence of rock outcrops in the water itself.

In this erosion, one can understand that when the flora on the coast is removed the coastal erosion commences gallopingly. First, the immediate sand (soil) at the water’s edge is washed away. As it proceeds the rock surfaces under the soil (sand) surface gets eroded. With the surfacing of the rock surface, erosion is catalyzed because of the bouncing of the waves followed by the energisation of the waters.

The force of the K.E. waves is severely energised when the K.E. waves thrash the rocks. It is different from the K.E. waves flowing down after washing ashore on the sandy coast.

The rocks cropping out, when not engineered properly, whence they become useful, they energise the water to thrash the coast. and invades deeper into become a bay. With change of generation the future will be brighter.


The coast of Unawathuna is severely eroded due to the ignorant activities of humans. It began with the removal of the first coastal flora. It is nothing but the first exposure of the coast to become a beach. Under natural conditions there are no beaches. A beach develops only after exposure of the coast at the line where water meets the flora.

After initial ignorant errors, the attempts to repair the coast gave the “coup de grace” to the coast. The repair had been roughly wrong.

It could be mended. But needs an administrative change which is not possible at present.

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