Sands Through the Hourglass

Sand dunes play a critical role in the natural world as they protect areas along coastlines from storms and waves. But climate change and rising sea levels affect the stability of these dunes, making their relationship to wave activity an important focus of study.

In contrast to swells and wind waves known to break in the surf zone, infragravity waves typically associated with storm surges have lower frequencies and longer wavelengths; and with less energy loss, they cause more impact to shorelines and the dunes that front them. Previous research has yielded insights into the complex interactions between these waves and beach morphology.

Qu et al. confirmed the efficacy of existing models in predicting wave “uprush” that occurs as undissipated energy arrives at the shoreline, and introduced new metrics for assessing dune stability that may help inform early detection of coastal erosion.

“Our study evaluates dune stability by collecting key parameters such as wave run-up, dune crest elevation changes, and dune erosion rates,” said author Ye Meng. “Specifically, analyzing the impact of waves on dunes and changes in dune height helps determine the extent of erosion.”

Based on experimental data from a wave flume, the study reveals a linear relationship between the amount of sediment erosion and the retreat distance of the shoreline.

“Variations in dune erosion rates are closely linked to shoreline retreat,” said Meng. “Our findings offer insights for developing effective dune protection measures as they integrate advanced modeling with experimental data, and provide a framework for mitigating the impacts of sea level rise on coastal dunes.”

Source: “Coastal processes and dune stability: Insights from wave transmission and runup modeling,” by Zhipeng Qu, Ye Meng, and Bingchen Liang, Physics of Fluids (2024). The article can be accessed at https://doi.org/10.1063/5.0218370 .