Earth Surface Dynamics 

River meandering is a long standing source of interest for scientists interested in how the Earths surface is shaped. Here, Noh et al., use a novel probablistic approach to create geomorphic risk maps where areas that have the potential for meandering can be assessed in an arguably more rigorous way than before.

The transition between ripples and dunes dependent upon sediment and flow conditions has been classically represented with a phase space diagram differentiating between the different bedforms based on these drivers. This work, importantly, introduces the role of clay content within the sediment and shows how this shifts these fundamental long standing relationships.

Do earthquakes result in higher levels of sediment in rivers in the years following the event? There are several reasons to believe this could be the case. Previous studies have even provided evidence of increased sediment loads in mountainous areas after major earthquakes. However, a study by Graf et al. challenges this perspective. They demonstrate that despite the thousands of landslides triggered by the 2015 Gorkha Earthquake in Nepal, there were only minimal increases in coarse sediment in river channels during the subsequent years. Instead, the study reveals a different story. In June 2021, a single, exceptionally heavy rainfall event mobilized large volumes of sediment, leading to riverbed elevation by as much as 12 meters. This effect greatly overshadowed any sedimentary impact left by the earthquake along the river corridor. The study underscores that earthquake evidence may not always be found in the sedimentary records of alluvial areas. In high-mountainous regions, records of riverbed elevation may be strongly influenced by unique and localized events.

Multiple techniques are used to monitor the collapse of an Alpine landslide in the United States. It is shown that the landslide was moving rapidly pre-failure. Given that the frequency of extreme events is likely to increase with future climate change, additional monitoring of Alpine regions is essential to limit hazards from future Alpine mass movements.

This paper may be of wider interest as it provides an important quantification of the rates of cliff retreat for the chalk cliff coasts of Southern England and Northern France. This is the first time we have been able to look back at this level of detail and reconstruct how this coastline has changed and retreated.