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Article Dans Une Revue Journal of Geophysical Research: Earth Surface Année : 2023

Debris‐Flow Process Controls on Steepland Morphology in the San Gabriel Mountains, California

William Struble
Luke Mcguire
  • Fonction : Auteur
Scott Mccoy
Katherine Barnhart
Odin Marc
  • Fonction : Auteur
  • PersonId : 1294062
  • IdHAL : odin-marc

Résumé

Abstract Steep landscapes evolve largely by debris flows, in addition to fluvial and hillslope processes. Abundant field observations document that debris flows incise valley bottoms and transport substantial sediment volumes, yet their contributions to steepland morphology remain uncertain. This has, in turn, limited the development of debris‐flow incision rate formulations that produce morphology consistent with natural landscapes. In many landscapes, including the San Gabriel Mountains (SGM), California, steady‐state fluvial channel longitudinal profiles are concave‐up and exhibit a power‐law relationship between channel slope and drainage area. At low drainage areas, however, valley slopes become nearly constant. These topographic forms result in a characteristically curved slope‐area signature in log‐log space. Here, we use a one‐dimensional landform evolution model that incorporates debris‐flow erosion to reproduce the relationship between this curved slope‐area signature and erosion rate in the SGM. Topographic analysis indicates that the drainage area at which steepland valleys transition to fluvial channels correlates with measured erosion rates in the SGM, and our model results reproduce these relationships. Further, the model only produces realistic valley profiles when parameters that dictate the relationship between debris‐flow erosion, valley‐bottom slope, and debris‐flow depth are within a narrow range. This result helps place constraints on the mathematical form of a debris‐flow incision law. Finally, modeled fluvial incision outpaces debris‐flow erosion at drainage areas less than those at which valleys morphologically transition from near‐invariant slopes to concave profiles. This result emphasizes the critical role of debris‐flow incision for setting steepland form, even as fluvial incision becomes the dominant incisional process.

Domaines

Géomorphologie
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Dates et versions

hal-04187895 , version 1 (07-12-2023)

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Copyright (Tous droits réservés)

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William Struble, Luke Mcguire, Scott Mccoy, Katherine Barnhart, Odin Marc. Debris‐Flow Process Controls on Steepland Morphology in the San Gabriel Mountains, California. Journal of Geophysical Research: Earth Surface, 2023, 128 (7), ⟨10.1029/2022JF007017⟩. ⟨hal-04187895⟩
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