Tuesday, June 25, 2024

Safeguarding Vietnam’s coastline with wave measurement technology

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The Mekong Delta in Vietnam is home to over 20 million people and is recognized as a globally important agricultural region. However, the health and longevity of this crucial ecosystem are being threatened by rising sea levels and coastal erosion. Researchers depend on advanced wave measurement devices from Nortek to validate ocean models and provide accurate data for the development of coastal erosion defences.

The Mekong Delta encompasses the southern tip of Vietnam and is home to some of the world’s most fertile land. Over past decades, this area has faced increasing environmental pressure.

Upstream dams and sand mining reduce the flow of sediments that feed the delta, causing it to recede. Farmers pumping water from the ground create additional stress on the delta. Together with these activities, the creation of infrastructure such as buildings and roads is compacting the once loose (unconsolidated) sediments, causing the delta to sink.

The impact of climate change

Climate change and rising sea levels pose significant challenges to the Mekong Delta. With an average elevation of just 0.8 meters above sea level, the delta is extremely vulnerable, facing the threat of submersion from rising seas, aggravated by the effects of dams and groundwater extraction.

If greenhouse gas emissions continue unchecked, sea levels could rise by an estimated 75 cm to 1 meter by 2100, potentially resulting in the loss of almost half of the delta and endangering the livelihoods of millions of residents in one of the most densely populated rural areas across the globe.

Effective coastal protection is vital to combat rising sea levels, prevent erosion from powerful monsoon waves, and reduce seawater intrusion. However, traditional barriers like wooden fences and concrete breakwaters have proven ineffective.

To find a more effective solution, Jonas Bauer, a PhD student at the Karlsruhe Institute of Technology (KIT), and colleagues from KIT have joined forces with Vietnamese institutions to better understand the sea and coast at the very southern end of the Mekong Delta.

Understanding wave progression

“It’s important to lower the wave energy at the coast, but the challenge is to ensure that sediments brought in from the ocean currents can still deposit along the coast,” said Jonas Bauer.  “If you build something that stops the wave energy going through but blocks the sediments, it will just add to the erosion problem.”

Bauer emphasizes that to develop suitable countermeasures, they need to understand wave progression as it moves toward the coast.

Evaluating ocean models

Ocean models play a key role in predicting how different coastal defense measures will fare against storms, helping researchers understand how waves move towards the coast. To ensure the accuracy of these predictions, the models must be validated and calibrated using real-world measurements.

Using a combination of Signature and AWAC ADCPs to measure the movement and dynamics of waves as they travel towards the coast during the monsoon season, the researchers verified the accuracy of two different ocean models and assessed their limitations. “We used a Signature ADCP and an AWAC to look at the wave conditions during the peak of the monsoon season,” Bauer added.

The team deployed the instruments along two transects stretching from the coast into deeper waters. They placed the AWAC offshore, approximately 25 km from the coast, and the Signature ADCP 2km from the coast.

With a 20-year history, the AWAC ADCP has proven its reliability. (Image courtesy: Nortek)

Predicting the behavior of waves

With verifications from the in-situ measurements in place and model limitations known, the researchers can be more confident in using the models to predict the behavior of waves as they move toward the coast under different scenarios. This will allow them to explore various coastal protection options that can help slow down the erosion of the Mekong Delta’s coastline.

“With this information and the other research gathered over the years, we can really start to develop countermeasures to protect the Mekong Delta from drowning and keep people safe,” said Bauer.

Advancing ocean research capabilities

Recent technological improvements enable the latest version of the AWAC wave measurement instrument to meet the next generation of user needs. Nortek has employed modern electronics and processing techniques to extend the deployment lifespan of this instrument, enhance its durability, maximize data collection, and simplify maintenance.

The Signature1000 ADCP is often referred to as Nortek’s ‘academic powerhouse’ because of its numerous capabilities packed into a small, easy-to-deploy instrument. With the Signature1000, scientific researchers can measure currents, waves, turbulence, and even biomass. This ADCP is capable of measuring several of these parameters simultaneously, eliminating the need for users to sacrifice one type of measurement for another.

ADCPs like the Signature1000 are vital tools for researchers working to protect valuable coastal areas such as the Mekong Delta.

The Mekong River Delta, Vietnam, in this false-colour (NIR-G-B) Landsat 8 satellite image. (Image courtesy: USGS, NASA)

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