Preprints
https://doi.org/10.5194/esurf-2021-61
https://doi.org/10.5194/esurf-2021-61

  25 Aug 2021

25 Aug 2021

Review status: this preprint is currently under review for the journal ESurf.

Development of a surface roughness curve to estimate timing of earthflows and habitat development in the Teanaway River, central Washington State, USA

Sarah Anne Schanz and Armistead Peyton Colee Sarah Anne Schanz and Armistead Peyton Colee
  • Geology Department, Colorado College, Colorado Springs, 80903, USA

Abstract. Salmon habitat is enhanced by the wide valleys and channel heterogeneity created by landslides. Earthflows, which are slow moving and fine-grained mass movements, can further potentially alter habitat by constricting valleys and sustaining delivery of debris and fine sediment. Here, we examine the influence of earthflows on salmon habitat in the Teanaway River basin, central Cascade Range, Washington. We mapped earthflows based on morphologic characteristics and relatively dated earthflow activity using a flow directional surface roughness metric called MADstd. The relative MADstd ages are supported by six radiocarbon ages, three lake sedimentation ages, and 20 cross-cutting relationships, indicating that MADstd is a useful tool to identify and relatively date earthflows, especially in heavily vegetated regions. Our age and MADstd distributions reflect a period of earthflow activity in the mid-Holocene and some sustained movement through the late Holocene that is primed by regolith production in the Pleistocene and early Holocene and triggered by a warm and wet climate during the mid-Holocene. The timing of earthflows is coincident with stabilization of salmon habitat and abundant salmon populations, indicating the fine sediment from earthflows did not negatively impact habitat. Wide valleys formed upstream of valley-constricting earthflows have added habitat zones, which may be of increased importance as climate change causes lower flows and higher temperatures in the Teanaway basin over the next century.

Sarah Anne Schanz and Armistead Peyton Colee

Status: open (until 12 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Sarah Anne Schanz and Armistead Peyton Colee

Data sets

Landslide location, surface roughness, and age for the Teanaway basin, USA Sarah Schanz, A. Peyton Colee https://doi.org/10.5281/zenodo.5153965

Model code and software

Jungle Creek diffusion Sarah Schanz https://github.com/schanzs/JungleCk_diffusion

Sarah Anne Schanz and Armistead Peyton Colee

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Short summary
We dated 187 earthflows to determine how they impacted salmon habitat in the Teanaway basin, central Washington State, USA. We developed a new method to date earthflows that uses the texture and directionality of the landscape. Earthflows were active 3-5000 years ago, with some active in the last 1000 years. The period of earthflow activity coincides with climate change as well as large salmon populations, suggesting the wide floodplains formed by earthflows overall increased habitat.