An AZTI study unveils the keys to improving coastal management to protect against storms

24/10/2024

The technology centre has been monitoring the impact of storms on 13 Basque beaches for three years.

This monitoring is carried out with data from the Basque coast’s videometry network, based on KOSTASystem technology.

The results, published in the Ocean and Coastal Management journal, show that dry beaches and natural and man-made barriers are key to protecting the coast from storms and prove the importance of such monitoring stations for effective coastal management.

The AZTI technology centre has analysed the impact of storms on 13 Basque beaches that are representative of the coastal geography of northern Spain. The findings, recently published in the “Ocean and Coastal Management” journal, highlight the importance of geomorphological features, such as the width and height of the dry beach, which is the portion of the beach lying landward from the mean high water mark, and the height of natural (dunes) and man-made (walls) defence barriers, for effective coastal management. The 13 beaches in the study were the following: La Arena, Arrigunaga and Arriatera, in Bizkaia; and Saturraran, Ondarbeltz, Deba, Itzurun, Santiago, Gaztetape, Malkorbe, Zarautz, Antilla and Hondarribia, in Gipuzkoa

To carry out the study, AZTI used the Basque coast’s videometry network, based on KOSTASystem technology, which covers 150 km of coastline. This network allows simultaneous monitoring of the main sandy areas of the Basque coastline, providing essential data for the development of coastal management tools. These tools are useful for long-term analysis of the morphological evolution of the beaches, as well as for short-term applications, including density of occupation, detection and prediction of rip currents, and monitoring of the impact of storms, among other things.

This technology allowed AZTI’s research team to classify the sand areas into three categories based on their response to storms:

Firstly, beaches dominated by the impact of waves on the defence barriers and the presence of overflows. A clear example is Zarautz beach, where the beach is less than 3.5 metres high and the dry sand area is just under 30 metres wide. Sandy areas like this one are the most vulnerable to damage during storms. In fact, Zarautz beach is recognised as one of the most vulnerable spots on the Basque coast. Together with the city of Donostia-San Sebastián, it is the Basque coastal municipality with the highest number of insurance claims for storm damage.

Secondly, beaches with occasional wave impact on the defence barriers. One example is La Arena, which is between 4 and 6.5 metres high and between 40 and 75 metres wide, this type of sandy area is less vulnerable to damage during storms compared to the previous group.

Lastly, beaches without occasional wave impact on the defence barriers. They are less prone to damage, up to 7.5 metres high and with a wide strip of sand over 50 metres wide, such as Hondarribia or Arrigunaga.

“The result of our research highlights that the greater the width and height of the dry beach and the height of the defence barrier, the greater the natural protection against storms,” explained Aritz Abalia, Expert in Coastal Engineering and Operational Oceanography at AZTI. “This stresses the importance of these parameters in assessing the potential impact of storms on a regional scale and highlights the need to maintain these values, limiting erosion, in order to protect coastal areas,” said Abalia.

The research team also stresses the importance of continuous maintenance of the videometry stations to collect long-term data, which is crucial for evidence-based coastal management. “Our work highlights the importance of using advanced technology to better understand storm impacts and support regional management strategies. This research is also an important step towards improving the resilience of the Basque coast, laying the foundations for the development of a robust regional early warning system,” concluded the AZTI expert.

The Basque videometry network has been funded by the Bizkaia Provincial Council, the Port Authority of Bilbao, Zarautz Town Council and Gipuzkoa Provincial Council. This study is also part of a wider collaboration in the context of the cross-border applied research laboratory Kostarisk, and has received European funding through the Urban Klima 2050 and Regions4Climate projects.

About KOSTASystem

AZTI’s KOSTASystem videometry network is used in Spain, France and Morocco to monitor the morphological evolution of beaches, to assess, anticipate and mitigate the impacts of climate change such as sea level rise and extreme waves, to control the influx to sandy areas and improve beach safety