Morphology of boulder-bed semi-alluvial channel beds: a flume study modelling streams in northern Fennoscandia

Creator/Principal investigator(s)

Lina Polvi - Umeå University, Department of Ecology and Environmental Science orcid

Description

In northern Fennoscandia, semi-alluvial boulder-bed channels with coarse glacial legacy sediment are abundant and due to widespread anthropogenic manipulation during timber-floating, unimpacted reference reaches are rare. The landscape context of these semi-alluvial rapids— with numerous mainstem lakes that buffer high flows and sediment connectivity in addition to low sediment yield— contribute to low amounts of fine sediment and incompetent flows to transport boulders. To determine the morphodynamics of semi-alluvial rapids and potential self-organization of sediment with multiple high flows, a flume experiment was designed and carried out to mimic conditions in semi-alluvial rapids in northern Fennoscandia. Two slope setups (2% and 5%) were used to model a range of flows (Q1, Q2, Q10 & Q50) in a 8 x 1.1 m flume with a sediment distribution analogous to field conditions; bed topography was measured using structure-from-motion photogrammetry (SfM) after each flow to obtain digital elevation models (DEMs). Ground-based LiDAR was used to obtain control points needed to create the SfM-based DEMs

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Responsible department/unit

Umeå University, Department of Ecology and Environmental Science

Creator/Principal investigator(s)

Lina Polvi - Umeå University, Department of Ecology and Environmental Science orcid

Identifiers

SND-ID: 2020-96

Description

In northern Fennoscandia, semi-alluvial boulder-bed channels with coarse glacial legacy sediment are abundant and due to widespread anthropogenic manipulation during timber-floating, unimpacted reference reaches are rare. The landscape context of these semi-alluvial rapids— with numerous mainstem lakes that buffer high flows and sediment connectivity in addition to low sediment yield— contribute to low amounts of fine sediment and incompetent flows to transport boulders. To determine the morphodynamics of semi-alluvial rapids and potential self-organization of sediment with multiple high flows, a flume experiment was designed and carried out to mimic conditions in semi-alluvial rapids in northern Fennoscandia. Two slope setups (2% and 5%) were used to model a range of flows (Q1, Q2, Q10 & Q50) in a 8 x 1.1 m flume with a sediment distribution analogous to field conditions; bed topography was measured using structure-from-motion photogrammetry (SfM) after each flow to obtain digital elevation models (DEMs). Ground-based LiDAR was used to obtain control points needed to create the SfM-based DEMs

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Language

English

Time period(s) investigated

2015-08-01 — 2015-09-01

Geographic spread

Geographic location: Sweden, Västernorrland County, Jämtland Province, Norrbotten Province, Västerbotten Province, Finland

Geographic description: The study models a type of stream that is common in northern Fennoscandia (Scandinavia & Finland) and is not based on a specific stream in a particular geographic area.

Funding

Swedish Research Council Formas — Ref. 2014-00484

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Morphology of boulder-bed semi-alluvial channel beds: a flume study modelling streams in northern Fennoscandia

Suggested citation

Lina Polvi. Umeå University, Department of Ecology and Environmental Science (2020). <em>Morphology of boulder-bed semi-alluvial channel beds: a flume study modelling streams in northern Fennoscandia </em>. Swedish National Data Service. Version 1. <a href="https://doi.org/10.5878/kz4r-6y69">https://doi.org/10.5878/kz4r-6y69</a>

Creator/Principal investigator(s)

Lina Polvi - Umeå University, Department of Ecology and Environmental Science orcid

Description

A mobile-bed physical model of the semi-alluvial prototype streams in northern Sweden was setup in an 8-m long, 1.1-m wide fixed-bed flume at the Colorado State University Engineering Research Center in Fort Collins, Colorado, USA. Using a geometric (yr and zr) scaling factor of 8, the initial sediment distribution was scaled-down to be analogous to that in the semi-alluvial prototype streams; because the D10 was 4 mm and Dmin was 0.14 mm, all sizes were sand-sized or above so there were no issu

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Data format / data structure

Geospatial

Published: 2020-10-21