Coastal Erosion Explained: Can Seawalls Save Us from Warming Arabian Sea?
Thank you guys for showering your love on my first post!
I didn’t expect that. It garnered more than 95 views, three subscribers and truly meaningful comments. I was on the moon for the past couple of days.
In those happy moments, I read about some elderly women who blocked a state highway as a form of protest.
The headline read: Sea incursion: Coastal residents lay siege to Fort Kochi-Alappuzha State highway in Kerala
I found the kicker of this headline pretty interesting. The kicker is the part of the headline that introduces it.
In this case, it is - ‘Sea Incursion’.
I just thought - why would someone use a word like incursion that means ‘an invasion or attack’ next to a word like Sea? It was an interesting choice of words.
So I read the story but there was a lot to unpack. It included words sea incursion, coastal erosion, sea wall, tetrapods, and groynes.
I was also curious to know if the sea wall would fix the woes of these women.
In this post, I am trying to explain this issue as comprehensively and easily as my skills allow
What’s the story?
Let me first tell you this story briefly and then I will begin to explain it.
As per the reports published in The Hindu and several other newspapers, these women live in and around Ernakulam district’s coastal erosion-affected Chellanam fishing village.
They were protesting for the completion of a 10 km long sea wall. It should have been completed by May 2023. But so far only 7.36 km of it has been completed.
Locals claim that the delay in the completion of this project is intensifying the coastal erosion in Chellanam.
So this is the story in a nutshell. You may have a lot of questions about the sea wall, its purpose as a sea defence, its impact etc.
But let’s take a step back from the ongoing protest of these women and focus on the plight of these women.
During the annual monsoon season & stormy weather, these women face the fury of the Arabian sea.
As per the report of Kerala University of Fisheries and Ocean Studies, about 1000 houses have suffered partial damage due to the annually occurring natural calamities.
So, now we know that the residents of this fishing village are suffering from coastal erosion.
But to truly understand the predicament of these villagers, we need to unpack a few basic concepts like coastal erosion and sea walls first.
What’s Sea Incursion & Coastal Erosion?
The term sea incursion isn’t just a unique set of words. It means the arrival of huge amounts of seawater on coastal lands, especially during monsoon season and stormy weather.
It causes frequent flooding in low-lying areas of the coastline. The continued breaking of waves against coastal structures causes ‘coastal erosion’ which means the erosion of a coastline.
If you have ever visited a sea shore then you may have witnessed a sandy beach. You may find it astonishing but the sand you see on the beach is the output of coastal erosion.
I will tell you how does this happen.
So when a wave hits a coastline, it hits the things that form the coastline. These things can be natural rocks, sandy beaches, or man-made structures like houses. The waves keep on hitting such structures as long as they remain. Over time, these structures wear away and disappear from the coastline.
Their departure changes the coastline. It’s called the change in coastline. The gradual erosion of these structures is called coastal erosion as they form the coast. There is another term called coastal accretion which is the exact opposite of coastal erosion. This process creates long sandy beaches that we all love.
Beaches appear and disappear over time, influenced by seasonal factors. In certain months, the sea erodes parts of the coastline while depositing sediment elsewhere. Eventually, the sea may return what was previously eroded. These are natural processes that have been occurring for ages.
But as you factor in the human habitation along the coastline, you have a huge problem at hand.
What’s happening in Kerala?
India has a coastline of more than 7500 kilometres. On the west coast, it faces the Arabian Sea and on the east coast, it faces the Bay of Bengal.
Every 3 out of 12 Indians live within 50 kilometres of its coastline.
As per the data provided by the Ministry of Environment, Forest and Climate Change in 2023, five out of ten Indian beaches are facing the brunt of coastal erosion.
If you zoom in a little bit on this dataset, you will find that 6 out of 10 beaches in Kerala are facing the brunt of erosion.
The village of these women Chellanam is one such place which is facing intense coastal erosion.
But why it is so?
If these processes are natural then why Chellanam’s situation is worse than others?
I found the answer to this question in a report from the Kerala University of Fisheries and Ocean Studies.
This report tells us -
The construction of the Harbour at south Chellanam obstructed the northward sediment transport at the south of the coastal belt and making the Chellanam coast a sediment-deprived area. It has been observed that a lot of sediments are deposited near Andhakaranazhi south of Chellanam. The northward transport of sediments is blocked by the fishing harbour disturbing the natural sediment balance. Furthermore, sediment transported to the Cochin Sea mouth (port inlet channel) is continuously dredged away affecting the natural course of beach development along this coastal stretch.
In simple words, the creation of artificial structures has blocked the natural flow of sediments that are affecting the natural course of beach development.
It happens because such structures obstruct the natural flow of sea waves and sediments.
It stops the natural process of erosion and accretion. Now, if the sea can’t take the coastline, it can’t return.
The National Centre for Coastal Research also tells about it in its 2018 report.
It says -
Construction of structures such as fishing harbours, ports, groins, seawalls and beach sand mining for monazite ores has highly altered the nature of the coastline and induced changes….Shoreline change analysis carried out for a span of 26 years (1990-2016) indicates that 45% of the coast (Kerala) is eroding, 34% is stable and 21% is accreting. The coasts of Kasaragod, Kannur, Malappuram, Ernakulam and Kollam are dominated by both erosion and stable conditions with a few pockets of accretion.
But isn’t the demand for a sea wall completion weird when it is being held responsible for coastal erosion?
Well, don’t reach a conclusion yet. There is more to know.
What’s a Sea Wall?
So, the question is this - Why demand a sea wall if it can’t help?
To understand the logic behind this demand, you need to first understand what a sea wall is.
As the name suggests, it is a wall erected to save coastal communities from seawater flooding. There are mainly three kinds of walls - vertical walls, curved walls, and mound walls.
The purpose of these walls is to stop the waves from entering the coastal land as they naturally do.
So sea waves hit the walls. They are made using hard physical structures like tetrapods, concrete blocks or uneven stones.
Structures like Tetrapods & uneven stones help in reducing the energy of waves. As the wave energy dissipates upon hitting tetrapods.
Structures like groynes also dissipate the energy of waves. You may find many such structures on the coasts the world over.
There are a few other things like break water which is an off-shore solution to the same problem - high energy sea waves.
It is a concrete strip-like structure. It is placed a little bit ahead parallel to the shore to protect the coast from the arrival of ferocious waves.
These structures are not new inventions. Researchers believe that the first sea wall was made about 7000 years ago. It was about 100 metres long.
So, they have been used by coastal communities as defences against powerful waves.
Can Sea Walls Save Us?
You must be thinking - if they have been helpful in the past then why they are being seen negatively now?
There are three reasons for this.
The first reason is that a sea wall is not a cure but a desperate measure, similar to placing someone on life support to sustain heart function despite knowing there is no chance of recovery.
Because you can’t keep on higher walls. It is like locking yourself in an endless struggle. It is just that only you have an expiry date, your enemy doesn’t.
American Journalist Danial A. Gross has written a really wonderful piece on this issue in The New Yorker.
Quoting Johan Van Veen, a Dutch engineer, from his book ‘Dredge Drain Reclaim: The Art of a Nation‘ he writes “Seawalls lock the land into place, trade in a dynamic shoreline for one that could not adapt as easily, and that would need to be defended forever.”
Gross further writes -
‘Hard seawalls may be the bluntest instrument in coastal engineering. Typically, they are made from concrete, stone, wood, or metal, and rise vertically from the shore. But a wave that strikes a seawall never breaks and dissipates, as it would on a beach; instead, it bounces off like an echo, its destructive force intact. In the end, the flow of water and sediment is a zero-sum game. For a wave to spare one place, it has to strike another; for sand to accumulate somewhere, it has to wash away from somewhere else.’
This is what Chellanam residents have been claiming all along.
Speaking to The Hindu, Joyce Babu, a resident of Kannamaly says -
"The half-baked work has only worsened the problem further with even those houses which were not previously affected getting inundated even in relatively small waves. With drains led to the brim and canals encroached, there is no outlet for the invading water from the populated areas. A walk through the coast in Kannamaly will reveal how houses are damaged, deposited with mud and are being increasingly abandoned by the owners.”
Kannamaly is only less than 4 kilometres away.
This area is part of the patch which is facing major erosion, as per the report of Kerala University of Fisheries and Ocean Studies.
The second reason is the warming oceans. The higher sea surface temperature results in increased air activity over the ocean which produces stronger waves.
The stronger waves hit the sea walls or any other kind of hard structure more powerfully.
When storms and swell surges come, the waves strike with more power than before and they attack the unprotected areas more aggressively than the protected ones.
So, this is why it is also being seen as an inequitable sea defence.
You can watch this video to understand it in a more comprehensive manner
If not artificial structures then what?
Now, the question is this - if sea walls can’t save us then what will?
The answer to this is natural coastal defences like mangrove forests. They are found to be capable of dissipating the power of waves in a much more efficient manner. On the other hand, Mangroves are a much cheaper solution.
As per the UNDP, when it comes to storm protection and sea level rise, mangroves are 1000 times cheaper per kilometre than building sea walls.
Supplementary readings
Can Sea Walls Save Us - New Yorker
Scientists warn seawalls can make rising waters worse in the long run
In the Shadow of the Seawall: Coastal Injustice and the Dilemma of Placekeeping
What’s happening in Chellanam: Broken Sea Walls and Promises Make Life Difficult in Chellanam... - TA Ameerudheen
This was a man-made disaster: Residents of Kerala’s flood-ravaged Chellanam village
CLIMATE CHANGE : COASTAL RISK AND ADAPTATIONOPTIONS
Hi Anant. Somewhere in my thousands of bookmarks, I have an article about a $56 billion plan to protect NYC from the rising Atlantic. I also watched an interesting documentary about a high-tech dyke system that has been created to stave off the destruction of Venus. These types of "solutions" fail to deal with reality and the root of our problem, continued burning of fossil fuels.
Very helpful and important report Anand. Keep writing more such reports. More power to u 🌸