Prof. Sikke Hempenius is counted as a great benefactor to Thailand because he initiated the systematic study of coastal erosion in Thailand by bringing students from Delft University of Technology over 10 years ago to conduct research on major causes of erosion. He has tried to interest Thai researchers in this problem but has not received as much interest as there should be. Erosion has become more severe.  Assoc Prof Somboon Pornpinatepong of PSU’s Faculty of Engineering recognized the damage and has devoted himself to studying the coast and disseminating his findings.

Prof. Hempenius is a professor of Engineering Physics and Remote Sensing from Delft University of Technology in the Netherlands and is the teacher of Prof Dr Phasook Kullavanij, former Rector of Prince of Songkhla University (PSU), and Assoc Prof Dr Weerapant Musikasarn, former President of the PSU Teachers’ Council.

On his retirement from Delft University of Technology, he was invited to join PSU’s Faculty of Engineering as a special adviser until the age of 70. 

Even though he is now reaching 77, Prof. Hempenius still holds the position of advisor to the International College programme of PSU. 

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What is your interest in Thailand’s coasts? 

I am from the Netherlands, next to the sea, and I studied physics and learned about coasts, the sea and sand sedimentation.  The Netherlands is strongly affected by the sea.  We have to understand it.  My work has given me an opportunity to see coastal changes in around 50 countries.  I got interested in the behaviour of coasts.

When I retired I came to live in Thailand.  The first thing I saw about 20 years ago was the coast of Pak Phanang District in Nakhon Si Thammarat.  Houses had fallen into the sea, which meant that the coast was sick.  From there I went to Narathiwat, Pattani and Songkhla because there had to be something unusual about the Thai coast.   What I saw was that earlier there were coconut palms along the shoreline.  They’ve all gone and where they used to be is now sea.  That’s what I saw. 

I began to wonder and asked Delft University of Technology, where I used to teach, to cooperate by sending 5 research students.  I learned alongside them and discovered the problems of the Thai coast from this group.  

The Dutch students’ studies can be summarized clearly.  The changes in the Thai coastline come from a lack of sand in the sea.

How can this be?  It’s a strange problem to say that the Thai coast lacks sand.

What we found was that Thai coastal sand was gradually moving northwards from Narathiwat to Pattani, Songkhla and Pak Phanang, always moving north without pause.  Sandy beaches were formed from sand slowly moving northwards.  This has never been known before.

I went to the shore at PSU’s Pattani campus.  A beach there had grown to 100 metres.  The university had used this area to put up many buildings.  

The point is that while this beach was growing, another was disappearing.  The growth and disappearance happen at the same time.  That’s what makes me wonder.  

When I investigated, I found that the problem started when the Bang Lang dam was built, blocking the Pattani River in Yala Province.

The Bang Lang dam completely blocked the flow of sediment.  This meant that the sediment was not carried by the Pattani River to the sea.  So this led to the phenomenon of the coast of Pattani disappearing, because there was no sediment to top it up.

It’s clear that coastal erosion is caused by human activity and not a result of climate change as is claimed.

Songkhla is interesting.  When the waste water treatment pond was built at Kao Seng (Kao Seng community in Songkhla Municipality), a pipe was laid at Ko Taeo (in Songkhla District) direct to the waste water treatment pond.  The waste water would overflow in the rainy season.  I observed that all the way from Kao Seng to Ko Taeo, there were no trees to be seen, just sand.

There was just a narrow beach, but when you got to the waste water treatment pond at Ko Taeo, there was mud, and this mud came from the waste water treatment pond in the rainy season and formed on the beach, allowing trees to sprout up.  This shows that apart from the lack of sand, the Thai coast also has the problem of a lack of soil accumulation.  

So if we want to have trees growing along the shore, we need soil to accumulate on the beach.

I saw that the feeder canal at the Kao Seng waste water treatment pond served as a connection between Songkhla Lake and the Gulf of Thailand.  This canal flows past rice fields and hills, and reach the sea at Kao Seng.  It deposits soil and sand sediments.  When these soil sediments are pushed onto the shore, they help trees grow.  This means the coast is fertile.  

By patrolling along the shore, I found that in Sathing Phra District there are no shrimp ponds but when you get to Ranot District, it’s full of shrimp ponds.  This shows a difference between the two sites.  

While sand gradually moves, the clay or mud that settles in various spots stays there and doesn’t go anywhere.  There are trees sprouting up.  So the coast doesn’t depend only on sand but also on mud.  When the sand or soil that flows along the coast gets dry, the wind blows it into banks.  Sathing Phra and Ranot alternate between sand and mud.  Where there is mud, it will be fertile.  

Roads and reservoirs built in the past stop the accumulation of sand and soil.  The sediment in the rivers is blocked and cannot reach the sea.  This is the basic problem that deprives the shore of sand.  Building blockages changes things.

A shore that has both sand and mud will be dense and can resist the force of the waves.  This is the characteristic of the shore.  If you walk along a beach you will find both pure sand and sand mixed with mud which has trees growing on it. 

If we look at today’s behaviour, it shows that the Thai people don’t know about coasts.  In the Netherlands, undergraduate students can learn quickly.  I’m surprised that Thais know so little about coasts.  

A friend of mine came from the Netherlands and, walking along the shore, he saw the Kao Seng waste water treatment pond.  He realized immediately that it had been set up wrong.  He asked why it hadn’t been sited right at the wall of the 2nd Fleet.  He asked if Thais know anything about coast or what.

First, a waste water pond is expensive and you shouldn’t put expensive things next to the sea.  Why put it where there is the risk that it will be damaged by salt spray?  This shortens its useful life and increases maintenance costs.  

He predicted that when the monsoon came, the sand at Kao Seng waste water pond would be eroded away.  And what he predicted in fact happened.

That was the beginning of the problems of Chalathat beach.  The waste water pond was built in 2002 and in 2004 I flew up for an aerial view.  The waves in fact had eroded the sand.  The reason was the same as at Pak Phanang.  The area was gradually eroded.  But the news said it was caused by climate change.  Blaming this or that will not solve the problem.  

The problem is that the coast lacks sand and mud from the blocking of the flow of water and preventing the accumulation of sand and mud.  If it can flow, the coast will be dense and can resist the waves and stay put.  Not allowing the sediment to flow into the sea and build up sand and mud on the shore will destroy the condition of the shore so that it cannot take care of itself.

So in summary, the problem is that the flow of sand and mud sediments from the watershed is blocked and cannot reach the sea to add to the sand and mud on the shore.

That’s correct.  Things that block waterways, like embankments, reservoirs or roads, create the problem that the coast lack sand to replace the sand eroded by the waves and gradually build up the shore.

The upshot is that building things that block waterways creates the long-term problem of the lack of sand for the shore.  When you build embankments against the sand, embankments against the waves in the sea or right on the coast, or you build something rigid in the sea, this creates local erosion problems and severe local damage.

PSU’s Physics Department experimented with scattering irradiated sand at Songkhla deepwater port to see where it went and how far in a day.  This confirmed that the sand didn’t stay put but gradually moved.  But the mud sticks and will go nowhere.

How appropriate is it for the Harbour Department to be given responsibility for solving the problem of coastal erosion?

If there is a problem with the coast, don’t give it to the Harbour Department to manage because the Harbour Department knows nothing about coasts.  The Harbour Department has the job of dredging.  Coastal work is natural resource conservation work.  The Harbour Department has the job of dredging channels for shipping, building ports.  These are different jobs.

We see that the Harbour Department emphasizes building things, like ports, breakwaters and embankments against sand.  These are rigid vertical structures.  These structures are no friend to the coast because nature has nothing vertical.

The Harbour Department knows nothing at all about coasts.  It can only conceive of rigid structures for shipping.  So this means that the Harbour Department should not get mixed up in coastal conservation.  The artificial structures that it thinks up, whether they are embankments or walls, are rigid vertical structures.  They are used in building ports.  They can’t be used in coastal conservation.  This is not the job of the Harbour Department.

If we build any kind of rigid vertical wall, the waves will strike it with force.  The beating of the waves will suck away the sand underneath.  These structures will not protect the coast because that needs natural regeneration.

The Netherlands has an easy-to-remember rule:

Rule 1: Don’t mess with the coast, whether it is sand or mud.

The shore slopes a little and rises to reach the shoreline.  A wave reaches a certain point before losing force and falling gently back where it meets the next incoming waves.  Striking the next waves causes it to lose force.

Let the waves fight each other.  Don’t build rigid structures across the line of the waves because if you do, the waves will strike forcefully against the rigid structure you have built.  When the waves recede, they will suck sand from under the structure, which will completely disappear, because nothing can withstand the force of the waves.

The way to live with the sea is to let everything rise and fall according to its nature.  Don’t block it.  Let the waves neutralize each other’s force.  That’s the right way.

The gabion embankment that Songkhla Municipality is going to build will run into the problem.  Building rigid structures to solve coastal problems will only worsen the damage.  They’ve done it already at Pak Phanag and it doesn’t work..  It was finished one year and the next year, kaput.

The more concrete walls are built, the more forcefully the waves strike.  The waves hit the wall, the wind blows the salt spray into homes where cars and electrical appliances are rusted.  Even the villagers’ houses are destroyed.

The experience of the Netherlands tells us that we shouldn’t build anything that stands up straight.  It should be at a very low angle.

If we solve the problem here and there by dismantling embankments and any obstacle on the coast, will this solve the problem?  Will the sand beaches be restored?

Removing the waste water pond at Kao Seng hasn’t solved the problem or stopped the erosion of sand on Chalathat beach.  As long as the flow of rivers is blocked by dams, reservoirs and things built across the water flow, so that the sand and mud cannot reach the sea, or it is allowed to extract sand from the sea for other purposes, so that the balance is upset, then without sand and mud to maintain the coast, the coast will be damaged.

The problem of the Thai coast now is that the coast lacks sand and soil to maintain it.

So how can this be put right?

If we are going to solve this problem 100%, we have to revive the natural ecological system.  Whatever blocks the flow of water must be opened up so that the water freely carries soil and sand sediments down to the sea.  At Chalathat and Samila beaches, if the problem cannot be solved in the rivers, then let soil and sand sediments flow from Songkhla Lake to the sea by using feeder canals as connections.  Let the canals carry sediments from Songkhla Lake to maintain the coast.

At present, all the waterways are blocked.  No sediment moves.  When the system fails, the natural ecological system must be restored so that nature can heal itself.

And about the timing of solutions for this kind of problem, we have to know which season to do things and which season not to do things, because if we remove something in the storm season, it will be a mess.  If we decide to do something, we watch the timing. 

What should be done first?

To look after Chalathat and Samila beaches, what needs to be done is to get the flow of sand from the waterways down to the sea as normal.  Wherever the flow is blocked, unblock it.  Right now there is no alternative.  Whether or not you remove embankments, or remove waste water ponds, there must be sand to maintain the coast.  This is the ultimate answer.

Why are the Dutch interested in coasts?

The Dutch have to understand waves and coasts and the sea because the Netherlands is lower than sea level.  Every monsoon season, seawater could flood in up to neck height.  This is life-threatening because we are a cold climate country. 

So the Dutch must learn quickly to save their own lives.  Rotterdam port was built by hand.  The Dutch people helped each other to dig out the soil.  We have to learn everything at the same time.  After 20 years you stop everything to evaluate and summarize the results before moving on.  In the Netherlands, whatever you do, once it’s done, you have to stop and evaluate and learn what’s good and what’s bad before starting again.  That’s the Dutch way of working.  We don’t let anyone go on without an evaluation.

For example, when the Harbour Department built an embankment against the waves at the mouth of the Saiburi River in Pattani, the damage was visible because the coast was ruined.  But they still built another embankment at Pak Bang and Sakom in Chana District in Songkhla.

Pak Phanang already has the design for an embankment and although the impact of the embankment at the mouth of the Saiburi River is not yet known, they are going ahead with construction.  It’s being built without stopping to think.  There’s no review.  There’s no evaluation.

In summary, the Harbour Department is inappropriate for this work.  There should be a new agency, a new approach which correctly solves the problems of the coasts.  Some things you know, the people know, but the Harbour Department does not accept that.  This is the problem.  The problem isn’t entirely from the sea.  The problem starts on the shore.  On the shore, they build the problem for the sea.  The blame to sea but in fact that’s wrong.  The problem starts here; the problem is on the land.  We are the ones who make problems fop the sea, not the sea making problems for us.

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Assoc Prof Dr Somboon Pornpinatepong 

Faculty of Engineering, Prince of Songkhla University

What we are doing now will affect Samila Beach like the Huai Sai coast in Nakhon Si Thammarat.  From now on the monsoon season won’t look good.  The waves will strike the wall, whether it is gabions or sandbags or artificial coral.  The waves beating against it will jump over.

Whether or not the waste water pond at Kao Seng is moved, it will make no difference.  As long as sand can flow into the sea and there is sand to maintain it, the beach will stay.  The waste water pond cannot damage it, even if it is removed.  If there is no sand to top up the beach, there will be damage.  If there is sand, the beach will stay as before.

Whether you move it or let it stay there, when there is no beach, there will be erosion.  If it’s moved, the erosion will be even more severe, because the beach will have no waste water pond.  The waves will reach up to the road.  If it’s moved, a beach must be created first.  It must be filled up or sediment must be found to add to the beach before it is dismantled.

Where they built an embankment at Kao Seng is full of sand because the embankment trapped the sand.  They built an embankment at Chalathat beach in the hope that it would build up sand, but it didn’t happen because there was no sand to fill it up.

Do you remember the Panamanian ship?  When it got beached, the beach on the south side grew because the sand in the sea came in to fill it up.  North of the ship, the beach curved inward because the sand could not move.  It was blocked by the Panamanian ship.  When the ship was removed, the sand started moving north.  The beach that was hollowed out was filled in again.

That is what is important about the Panamanian ship.  In 1994 we still hadn’t built anything too far.  Then there wasn’t even one embankment.  Now they are everywhere.  At Na Thab, at Ko Taeo.  If the waves bring in another Panamanian ship, there’s no beach to ground it on, because now there’s not even a grain of sand.  

The building of gabion embankments by Songkhla municipality creates a chain of problems.  If we build one here, next we have to do Samila beach.  If we don’t, the beach is ruined.  If we decide to do Samila beach, it will become a pebble beach.

Foreigners notice this.  They see things systematically.  From the sea they look at the forests in the watershed.  In comparison, when Thais speak, they speak only about the coast.  Prof. Hempenius talked about the hills.  When we heard this, it seemed irrelevant, but it’s part of the same thing.  

We have to look at the whole system before we can see the origin of the problem.