Extreme Mediterranean rainfall impact on sedimentary routing systems: what can we learn from Storm Alex using in situ detrital 10Be?
Mariotti, A.; BLARD, P.; Charreau, J.; Toucanne, S.; Jorry, S.; Joseph, O. (2026). Extreme Mediterranean rainfall impact on sedimentary routing systems: what can we learn from Storm Alex using in situ detrital 10Be? Geomorphology (Amst.) 492: 110061. https://dx.doi.org/10.1016/j.geomorph.2025.110061
In: Geomorphology. Elsevier: Amsterdam; New York; Oxford; Tokyo. ISSN 0169-555X; e-ISSN 1872-695X, more
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| Author keywords |
Heavy precipitation events;Sediment transport;Storm Alex;Cosmogenic(10)Be;long-term erosion;denudation rates;cosmogenic nuclides;temporal variability;flood dynamics;river-basin;catchment;scale;connectivity;landslides |
| Authors | | Top |
- Mariotti, A.
- BLARD, P., more
- Charreau, J.
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- Toucanne, S.
- Jorry, S.
- Joseph, O.
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| Abstract |
Understanding how extreme meteorological events influence sediment transport is critical for predicting landscape evolution under a changing climate. Detrital cosmogenic Be-10 can provide insights into sediment dynamics following extreme rainfall, but high-resolution datasets tracking Be-10 variations before and after a storm, alongside long-term records, remain rare. The Var catchment (French Southern Alps) presents a unique case study, as its Be-10 signal was well-documented before the October 2020 Storm Alex (>500 mm of rainfall/24 h), which triggered flash floods, mobilized large sediment volumes, and formed a 10 km-long sediment plume in the Mediterranean Sea. We compare Be-10 concentrations in river sediments collected pre-storm (2016-2018), and at +7 days, +21 days, +4 months, and +7 months post-storm. We also use a historical offshore sample and contextualize these results with a 75 ka-long Be-10 record from deep-sea sediment cores. At the Var outlet, Be-10 concentrations initially increased by similar to 25 % at +7 and +21 days, attributed to the mobilization of Be-10-rich sediments from the upstream Var and Tin & eacute;e sub-catchments. Concentrations returned to pre-storm levels within four months, primarily due to dilution with Be-10-poor sediments from the V & eacute;subie sub-catchment fluvioglacial terraces. While short-term Be-10 fluctuations at the Var outlet reflect complex sediment sourcing, our comparison with the 0-75 ka record confirms that major glaciation events and potential anthropic influences remain distinguishable, demonstrating that Be-10 is a robust proxy of denudation changes, even when extreme events are involved. |
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