The Mekong Delta in Vietnam is home to over 20 million people and acts as a globally important agricultural area. The health and longevity of this important ecosystem is being threatened by rising sea levels and coastal erosion.
Researchers rely on advanced wave measurement devices from Nortek to validate ocean models and provide accurate data for the development of coastal erosion defenses.
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.
Climate change and rising sea levels also affect the delta.
The Mekong Delta is just 0.8 m above sea level on average, placing it in a particularly precarious position, at risk of being overtaken by rising sea levels, even without the pressure created by dams and groundwater pumping.
Should our greenhouse gas emissions continue unabated, estimated sea level rises of 75 cm to 1 m could see almost half the delta lost to the sea by 2100, threatening the livelihoods of the approximately 20 million people who live there.
Coastal protection is essential for staving off rising sea levels, protecting the coast from erosion caused by powerful waves during the monsoon season, and minimizing seawater intrusion.
However, barriers such as wooden fences and concrete breakwaters haven’t proven adequate.
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 to develop effective coastal protection systems
“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,” says 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 says that to develop suitable countermeasures, they need to understand wave progression as it moves toward the coast.
Evaluating ocean models against real-world wave measurement data
Models of the ocean are useful for predicting how different coastal defense measures may perform when faced with storms, in part by contributing to the researchers’ understanding of how the waves will move toward the coast. To ensure the models’ predictions are accurate, they must be validated and calibrated against 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 adds.
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 2 km from the coast.
Predicting the behavior of waves with more confidence
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,” says 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 utilized modern electronics and processing techniques to prolong deployments with this instrument, increase robustness, maximize data collection and simplify instrument maintenance.
The Signature1000 ADCP is Nortek’s “academic powerhouse” because of the many capabilities it packs into a small and easy-to-deploy instrument. The Signature1000 allows scientific researchers to measure currents, waves, turbulence and even biomass. This ADCP can measure several of these parameters at the same time, so users don’t have to sacrifice one type of measurement to make another.
ADCPs like these are a key tool for researchers aiming to protect valuable coastal areas such as the Mekong Delta.
Home to some 20 million people and acting as a globally important agricultural area, the Vietnamese Mekong Delta faces various threats, including rising sea levels and increasing coastal erosion. (Photo: NASA/Wikimedia Commons)
Parts of the coast of the Mekong Delta are already experiencing significant flooding and erosion, putting people’s homes and livelihoods at risk. (Photo: Karlsruhe Institute of Technology)
Comparison of the significant wave height and peak period at Transect 1 measured by the AWAC (offshore, red), the Signature1000 (nearshore, blue) and the model predictions for the nearshore (green). (Image: Karlsruhe Institute of Technology)
With a long history spanning more than 20 years, the AWAC ADCP has a proven track record of reliability and longevity. (Photo: Nortek)
The Signature1000 ADCP is an “academic powerhouse” for scientific ocean researchers. (Photo: Nortek)
Nortek’s advanced Acoustic Doppler Current Profilers (ADCPs) and Doppler Velocity Logs (DVLs) use the Doppler effect to measure motion in the marine environment. ADCPs are used to measure oceanographic processes as seen in currents and waves, while DVLs help subsea vehicles to navigate underwater.
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