Discharge and rainfall control the size and shape of alluvial fans

Discharge and rainfall control the size and shape of alluvial fans | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Discharge and rainfall control the size and shape of alluvial fans Jean Braun, Amanda Wild, Safa Khan, Luca Malatesta This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8638473/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Alluvial fans are sedimentary deposits that form at the foot of mountain belts. Their surficial and internal structures are used to infer past tectonic or climatic events. They all share a characteristic conical shape with their apex forming at the mouth of a large river flowing from the mountain side. Their size varies widely and appears to be related to the size of their upstream catchment. Here we show that, contrary to the common assumption that fan size is controlled by basement subsidence, this relationship is a direct consequence of the control of discharge (and therefore rainfall) on the efficiency of sediment transport on the fan. We demonstrate this point by comparing morphometric data that we compiled on 69 fans of varied sizes and environments to an analytical solution derived from the most widely used model for sediment transport. We also show, using a two-dimensional numerical model, that fans are dynamical features that reach a quasi steady-state form where frequent avulsions control the distribution of deposition events along the main channel, whilst rainfall-driven erosion takes place elsewhere. Our findings provide a novel framework to interpret the record stored in fans stratigraphy in terms of climatic or tectonic signals. Earth and environmental sciences/Solid Earth sciences/Geomorphology Earth and environmental sciences/Solid Earth sciences/Sedimentology Full Text Additional Declarations There is NO Competing Interest. Supplementary Files BraunetalNGSM.pdf Additional figures and detailled methodological explanations BraunetalNGAnimation.mov 2D numerical model of an evolving sedimentary fan Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8638473","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":577329992,"identity":"f3e056ef-9d37-4a5b-af7b-3fc067385cbc","order_by":0,"name":"Jean 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