Assessing the effects of check dams on sediment dynamics in a debris-flow catchment through SfM technique

(1)

Vienna, 23 - 28 April 2017 EGU2017 - 815

Assessing the effects of check dams on sediment dynamics

in a debris-flow catchment through Structure-from-Motion photogrammetry

S. Cucchiaro

1,2

, M. Cavalli

3 , D. Vericat

4 , A. Beinat

1 , A. Calsamiglia

5 , S. Crema

3 , L. Marchi

3 , F. Cazorzi

1

University of Udine, Udine, Italy (*sara.cucchiaro@uniud.it) - 2University of Trieste, Trieste, Italy - 3CNR-IRPI, National Research Council of Italy - Research Institute for Geo-Hydrological Protection, Padova, Italy -

4

Damià Vericat, Fluvial Dynamics Research Group, University of Lleida, Spain- 5University of Balearic Islands, Palma de Mallorca, Spain.

WHY:

high resolution repeat Digital Elevation Models allow understanding the effects of torrent control works on sediment dynamics and, consequently, provide relevant information to improve management strategies and torrent control planning in highly dynamic catchments.

WHAT:

A standardized workflow for data-acquisition, post-processing and uncertainty analysis is proposed to obtain usable and accurate Digital Elevation Models (DEMs), Aerial Photographs and DEMs of Difference (DoDs) using Structure from Motion (SfM) and Multi-View Stereo (MVS) photogrammetry.

WHERE:

The Moscardo debris flow catchment (eastern Italian Alps), in which several torrent control works have been built in the last years.

Illustration of workflow

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RESULTS

DoD

Thresholded DoD Estimate

December 2015 - June 2016 June 2016 - July 2016 July 2016 - August 2016 August 2016 - October 2016 December 2015 - October 2016

Volumetric (m3)

Erosion 238 ± 45 119 ± 25 177 ± 29 76 ± 19 358 ± 43

Deposition 331 ± 70 451 ± 83 174 ± 31 196 ± 30 975 ± 125

Net Volume Difference 93 ± 84 332 ± 87 -3 ± 43 119 ± 36 617 ± 132

WORKFLOW

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Illustration of workflow

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WORKFLOW

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Wheaton JM, Brasington J, Darby SE, Sear DA. (2010). Accounting for uncertainty in DEMs from repeat topographic surveys: improved sediment budgets. Earth Surface Processes and Landforms 35(2): 136–156.

Westoby MJ, Brasington J, Glasser NF et al. (2012). 'Structure-from-Motion' photogrammetry: A low-cost, effective tool for geoscience applications. Geomorphology vol. 179, 300-314. Brasington J, Vericat D, Rychkov (2012). Modelling river bed morphology, roughness and surface sedimentology using high resolution terrestrial laser scanning. Water Resources

Research vol. 48, (11) 1-18.

Marteau B., Vericat D., Gibbins C., Batalla R.J., Green D.R. (2016). Application of Structure-from-Motion photogrammetry to river restoration. Earth Surface Processes and Landforms. 10.1002/esp.4086.

REFERENCES

FINAL REMARKS:

DoD shows evident deposits upstream of the check dams in the period from December 2015 to October 2016, proving that the check dams effectively stored sediment transported by the debris-flows. Downstream of the check dams important erosion can be observed. Such excavations, ascribed to the impact of streamflow depleted from sediment deposited upstream, could undermine the stability of the check dams. Moreover, it can be argued that, once the check dams will be completely filled, they will lose their functionality and the material deposited upstream of the check dams could act as sediment sources increasing downstream debris-flow magnitude.

Assessing the effects of check dams on sediment dynamics in a debris-flow catchment through SfM technique