I. Title: An ecogeomorphic evaluation of the post-flood restoration of the Little Thompson River: A Colorado Front Range (USA) stream constrained by infrastructure II. Running title: Restoration of the Little Thompson River, Colorado USA

River restoration is a multibillion-dollar industry, but oversight, assessment requirements, and frameworks remain disparate. This study examines the case of the Little Thompson River (Colorado, USA), a mountain stream disturbed by a 2013 flood (500-year recurrence interval) and subsequently reconstructed for flood mitigation. We compare the Restored Site to a Reference tributary impacted by the flood event, allowing for an assessment of stream recovery under different scenarios. Results suggest the Reference Site has an equilibrium among ecogeomorphic variables, while the Restored Site does not. The Restored Site had a step-pool/pool-riffle design but a plane-bed slope (0.023 m/m). Grain-size analysis showed a distribution (D 50 = 55 mm and D 90 = 126 mm) not mobilized by typical flows (e.g., 2-year), and typical flows (>2-year) do not inundate the floodplain region. The Reference Site had expected pool-riffle morphology and grain size (slope = 0.013 m/m; D 50 = 38 mm and D 90 = 108 mm), is mobilized by typical flows, and the floodplain region inundates at flows >2-year. Vegetation surveys show that only Salix and naturally recruited Populus are thriving at the Restored Site, while the Reference Site has a denser and more diverse plant community. Our study suggests allowing for natural recruitment of Populus, focusing on cheap/simple Salix plantings, and preserving seed banks where possible could aid future restoration projects. Our results raise questions about the efficacy of channel construction and revegetation efforts in post-flood restoration of a mountain stream and highlight simple recommendations for future restoration projects. Information & Authors Information Version history Copyright This work is licensed under a Non Exclusive No Reuse License.

Authors Metrics & Citations Metrics Article Usage 170views 96downloads Citations Download citation Haylie Brown, Sharon Bywater-Reyes, Sara Rathburn, et al. I. Title: An ecogeomorphic evaluation of the post-flood restoration of the Little Thompson River: A Colorado Front Range (USA) stream constrained by infrastructure II. Running title: Restoration of the Little Thompson River, Colorado USA. Authorea. 13 February 2025. DOI: https://doi.org/10.22541/au.173943615.58312122/v1 DOI: https://doi.org/10.22541/au.173943615.58312122/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.