Climate vagaries to blame for coastal erosion: studies

Most studies held prior to the port works and after point to climate change induced cyclonic systems and unscientific structures built to check sea erosion as the major reasons for the aggravated sea erosion. But fishermen, citing the works for the worsening situation, has called for a scientific study after stopping construction to assess the damage

Updated - August 26, 2022 12:52 pm IST

Published - August 25, 2022 09:09 pm IST - THIRUVANANTHAPURAM 

Fishers and citizens lay siege to Adani port during their protest against Adani Group’s port development project at Vizhinjam, in Thiruvananthapuram

Fishers and citizens lay siege to Adani port during their protest against Adani Group’s port development project at Vizhinjam, in Thiruvananthapuram | Photo Credit: PTI

The protest against the Vizhinjam international seaport in Thiruvananthapuram by fishermen and their families has reached a feverish pitch with the agitating fishers trying to lay siege to the under-construction port at sea and on land. 

The round-the-clock protest led by the Latin Catholic Archdiocese, Thiruvananthapuram, does not seem to be ending soon what with the protesters insisting that any compromise other than halting the multi-crore port work, the first phase of which is about to be commissioned next year, cannot be agreed upon.

Their main demand is that the port construction should be stopped straightaway to take stock of the damage caused by the construction along the coast of Thiruvananthapuram.

Coastal erosion in Kerala

The coastline of Kerala has been witnessing constant erosion in varying degrees due to seasonal changes in waves triggered by monsoons. This gets aggravated if there are cyclonic weather systems over the Arabian Sea and the Indian Ocean. The cyclonic systems will normally leave a long-term impact on the overall beach morphology. If there are any hard structures such as groynes, seawalls, or breakwaters constructed unscientifically, the morphological impact on its adjacent coastal region will be more severe. 

Also read: Coastal erosion likely to turn severe along Thiruvananthapuram, says study

Shaji E., Associate Professor and Head of the Department of Geology, University of Kerala, who headed a study on coastal erosion, coastal accretion, and shoreline changes (from 2006 to 2020) along the 58-km coastal stretch between Pozhiyoor and Anchuthengu in Thiruvananthapuram, says an increase in the number of cyclones over the Arabian Sea is one of the main reasons for the rise in shoreline changes along the southern coast.

“Normally, port activities are prohibited on eroding coast as any structure will only aggravate sea erosion. Disregarding these facts, the authorities went head with the work. ”Joseph Vijayan | Spokesperson of Coastal Watch, an outfit which works for the causes of fishermen

However, the striking fishermen are not ready to buy the argument. “It is a known fact that the coast of Thiruvananthapuram is highly eroding even before the port construction. Normally, port activities are prohibited on eroding coast as any structure will only aggravate sea erosion. Disregarding these facts, the authorities went head with the work. Further, many scientific studies have earlier proved that coastal erosion is man-made. Even as everyone accepts the fact that coastal erosion has intensified along the coast of capital in recent years, the authorities are not ready to hold a scientific study stopping the port construction. It is against this backdrop the fishermen decided to stall the port construction until their legitimate demands are met,” says Joseph Vijayan, spokesperson of Coastal Watch, an outfit which works for the causes of fishermen, Thiruvananthapuram.

The social worker and local activist has fought a case in the National Green Tribunal (NGT) against the port project

NGT’s expert committee

When environmental clearance (EC) for the project was challenged in the NGT, it appointed an expert committee and a cell to monitor the shoreline changes in the project area — within 10 km on either side.

These committees have been monitoring shoreline changes along a 20-km stretch (Instead of the mandatory 10 km) on either side of the port every six months and filing reports. Contrary to the argument of the fishermen and the Latin Archdiocese, none of these reports endorses any form of coastal erosion due to port construction. 

Coastal erosion in Kerala is not limited to Thiruvananthapuram alone. Valiyathura and Shangumugham beaches are the most erosion-hit areas about 13-15 km north of the port site. However, there is no major accretion or erosion in Adimalathura, Pulluvila, and Poovar regions on the south side. Port development is likely to cause minor accretion for about 2.6 km to the south of the port, the maximum rate being 21.6 m per year which will reduce to 0.6 m per year by the tenth year and will stabilise thereafter, according to studies carried out by L&T-Ramboll Consulting Engineers Limited in connection with the Environmental Impact Assessment. 

Climate research and data

Maximum wave height (Hmax) recorded along Vizhinjam coast post-Ockhi  
Average wave height during: rough weather period – 2.5 m; in normal fair-weather condition - 1 m
Cyclone Ockhi - 7.29 m
Depression over Arabian Sea - 6.2 m
Cyclone Luban - 3.62 m
Cyclone Vayu - 6.13 m
Cyclone Maha - 6.13 m
Cyclone Amphan - 4.99 m
Cyclone Nisarga - 4.5 m
Low pressure under the influence of cyclonic circulation - 8.84 m
Deep depression over East Central Bay of Bengal- 4.5 m
Cyclone Gati - 2.92 m
Cyclone Tauktae - 9.44 m
Source: National Centre for Sustainable Coastal Management, Ministry of Environment and Forests, Government of India

A reference manual on Climate Change Adaptation Guidelines for Coastal Protection and Management in India prepared by the Asian Development Bank for the Ministry of Water Resources, and published in 2019, notes that the Valiathura is typical of a tropical coast which has waves as the predominant hydrodynamic force controlling the coastal processes.

The data available with the National Institute of Ocean Technology say that during the Ockhi cyclone, the maximum wave height along the coast had touched 7.29 metre. The highest maximum wave height was recorded during the time of cyclone Tauktae in 2020 at 9.44 metre.

There is a constant longshore sediment transport along the coast of Kerala that indicates the transport, or drift, of beach material caused principally by the action of waves and tidal currents. When there is high wave activity induced by cyclones, depression or low pressure during monsoon, a large portion of the beach will be gnawed away by the waves. This has become a regular feature on the Kerala coast. 

Existing studies’ findings

The proposed Vizhinjam port is being constructed inside a ‘sediment cell,’ which is a pocket-like area in which interruptions to the movement of sand along the coast do not significantly affect the adjacent length of coastline. Further, it has been found that shoreline changes are negligible to the north of the proposed port even after the complete phase of development, according to the L&T study.

In addition, around five-km north of the port site are rocky headlands and pocket beaches where the rate of sediment movement along the coast is significantly low , says the study. 

Several other studies had reported the high erosion zones along the coast of Thiruvananthapuram. The Department of Ocean Engineering, IIT, Madras, in a report to the government in 2007, stated that Beemapally and Shangumugam stretches were under constant threat during high wave seasons.

Unscientific construction of seawalls

A view of the Muthalapozhi near perumathura in Thiruvananthapuram district

A view of the Muthalapozhi near perumathura in Thiruvananthapuram district | Photo Credit: MAHINSHA S

Studies by the National Centre for Sustainable Coastal Management in 2010, Indian National Centre for Ocean Information Services in 2012, and the Space Applications Centre in 2014 have also found Valiyathura and Poonthura coastal areas vulnerable to high-intensity erosion. This is mainly due to the unscientific construction of seawalls and groynes in the south of Valiyathura to check erosion, says the ADB report.

There has been no proper impact assessment preceding the construction of coastal structures at many places, says a senior officer at Vizhinjam International Seaport Limited (VISL). The unscientific construction of a breakwater at Muthalapozhi is an example where scores of fishermen have lost their lives, where sand bypassing is urgently required to mitigate the problem, he says.

“Coastal erosion is a reality and the rate of erosion has increased recently, especially after Ockhi. It is not right to club erosion with port construction as there are permanent mechanisms to monitor the shoreline changes due to construction. Perhaps this is the only port project in India that began after completing all comprehensive studies to address all impact with a high level of stakeholder participation,” says VISL CEO Jayakumar.

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