The hidden layers of nearshore sandbars revealed with high-resolution underwater imaging

What is it about?

Nearshore sandbars are underwater ridges of sand that help protect beaches from storms, yet their internal structure is rarely seen. We used a high-resolution acoustic tool to scan a sandbar along Poland’s Vistula Spit on the Baltic coast before and after a major winter storm. The images revealed layers of sand up to several meters deep and showed how the storm eroded some parts of the bar and quickly rebuilt others. From the surface the sandbar looked stable, but inside it had been almost completely rearranged. This means what seems like the same bar over many years may in fact be a series of new bars formed in the same place after each big storm. Our study demonstrates that sub-bottom acoustic profiling can capture these hidden changes, offering a powerful way to understand how coasts react to extreme weather and how natural underwater features help protect shorelines.

Featured Image

Photo by Jo Van de kerkhove on Unsplash

Photo by Jo Van de kerkhove on Unsplash

Why is it important?

This study provides the first high-resolution view of a Baltic nearshore sandbar, revealing how storms reshape it from the inside while its surface appears unchanged. Traditional surveys record only the seabed outline, leaving the deeper layers invisible and giving a misleading sense of stability. By comparing acoustic images taken before and after a powerful winter storm, we show that the bar was almost completely rebuilt within days. Understanding this hidden cycle of destruction and rapid rebuilding matters for coastal protection and climate adaptation.

Perspectives