Laboratory tests for the optimization of mesh size for flexible debris-flow barriers

Abstract. Laboratory tests were performed to study the loading aspects of flexible debris-flow barriers. Debris material from the Milibach river (Canton Berne, Switzerland) has been used to quantify the influence of different mesh sizes and the gap between the lower barrier edge and the river bed compared to the maximum grain size. It was possible to study the filling process and the retaining behaviour of the barriers as a function of the mesh size. A reasonable retention was reached with the net having a mesh size and a basal gap smaller than d90 where d90 is the maximum diameter of 90% of the grains. By scaling the laboratory tests to the natural size using Froude similarity a recommendation is given for the best net mesh size and the gap in natural conditions. The conclusions are supported by the results of numerous laboratory tests using different debris material, e.g. from the Illgraben river (Canton Valais).

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Laboratory tests for the optimization of mesh size for flexible debris-flow barriers

Natural Hazards and Earth System Science ◽

10.5194/nhess-15-2597-2015 ◽

2015 ◽

Vol 15 (12) ◽

pp. 2597-2604 ◽

Cited By ~ 16

Author(s):

C. Wendeler ◽

A. Volkwein

Keyword(s):

Grain Size ◽

Debris Flow ◽

Laboratory Tests ◽

Mesh Size ◽

Field Measurements ◽

Maximum Diameter ◽

Small Scale ◽

Dimensionless Numbers ◽

Flexible Barrier ◽

Flexible Barriers

Abstract. Flexible barriers can be used within channelized riverbeds as an effective and efficient alternative to protect from debris flows. Their retention capability strongly depends on the size of the mesh openings and the gap between the lower barrier edge and the channel's floor. The question is now whether there is a relation between the grain size distribution of the debris material and the openings of a flexible barrier. Small-scale laboratory tests were performed to study these loading aspects of flexible debris-flow barriers for the Milibach river (Canton Berne, Switzerland). In situ debris material has been used to quantify the influence of different mesh sizes and the gap between the lower barrier edge and the riverbed compared to the d90 grain size and the flow height, where d90 is the maximum diameter of 90 % of the grains. It was possible to study the filling process and the retaining behaviour of the barriers as a function of the mesh size. A reasonable retention was reached with the net having a mesh size and a basal gap smaller than or equal to d90. These relations could be transferred to the field. A dimensional analysis reveals possible dimensionless numbers that can be used to scale the laboratory results. The findings are supported by the results of similar laboratory tests using debris material from different locations and by the available field measurements.

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STUDY ON RIVER-BED VARIATION AND ITS GRAIN SIZE DISTRIBUTION IN COMPOUND STONY-BED RIVER WITH MEANDERING AND STRAIGHT CHANNEL

Journal of Japan Society of Civil Engineers Ser B1 (Hydraulic Engineering) ◽

10.2208/jscejhe.67.i_769 ◽

2011 ◽

Vol 67 (4) ◽

pp. I_769-I_774

Author(s):

Tatuya MAESHIMA ◽

Masayuki IWASA ◽

Kengo OSADA ◽

Shoji FUKUOKA

Keyword(s):

Grain Size ◽

Size Distribution ◽

Grain Size Distribution ◽

Straight Channel ◽

River Bed

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Extreme mass wasting during 2021 Dhauli Ganga event in the Higher Himalaya: insight from the landscape

10.5194/egusphere-egu21-16587 ◽

2021 ◽

Author(s):

Anand Kumar Pandey ◽

Kotluri Sravan Kumar ◽

Virendra Mani Tiwari ◽

Puranchand Rao ◽

Kirsten Cook ◽

...

Keyword(s):

Debris Flow ◽

Extreme Event ◽

Rock Avalanche ◽

Slope Instability ◽

Mass Wasting ◽

Outburst Flood ◽

Flood Warning ◽

River Bed ◽

High Flood ◽

Glacial Lake Outburst Flood

<p>The slope instability and associated mass wasting are among the most efficient surface gradation processes in the bedrock terrain that produce dramatic landscape change and associated hazards. The wedge failure in periglacial Higher Himalaya terrain on 7th&#160;February in Chamoli, Uttarakhand (India) produced >1.5 km high rock avalanche, which amalgamated with the glacial debris on the frozen river bed produced massive debris flow along the high gradient Rishi Ganga catchment. The high-velocity debris flow and a surge of high flood led to extensive loss of life and infrastructures and issuing the extreme event flood warning along the Alakananda-Ganga river, despite there was no immediate extreme climatic event. The affected region is the locus of extreme mass wasting events associated with Glacial Lake Outburst Flood (GLOF) and Landslide Lake Outburst Flood (LLOF) in the recent past. We analyzed the landscape to understand its control on the 7th&#160;February 2021 Rishi Ganga event and briefly discuss other significant events in the adjoining region e.g. 1893/1970 Gohna Tal/Lake LLOF and 2013-Uttarakhand events in Chamoli, which have significance in understanding the surface processes in Higher Himalayan terrain.</p>

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Study on the interference of pier on the channel bed

WEENTECH Proceedings in Energy ◽

10.32438/wpe.252021 ◽

2021 ◽

pp. 278-284

Author(s):

Atul Kumar Rahul ◽

Akash Priyadarshee ◽

Prabhat Kumar Singh ◽

Shyam Bihari Dwivedi

Keyword(s):

Laboratory Tests ◽

The Other ◽

Straight Channel ◽

Sand Mining ◽

Continuous Processes ◽

River Bed ◽

Natural Flow ◽

Scouring Process ◽

Study Laboratory ◽

The Impact

Scoring and sedimentation are two continuous processes which take place in river bed. These two phenomena have significant impact over the overall behavior of river. Scoring and sedimentation process get affected due the construction of structures like Bridges. Piers of bridge alter the natural flow of rivers. Due to this scouring process increases near to the pier. The scouring process gets affected due to the other activities like sand mining or filling. Also any obstruction like some construction can also affect the scouring. In this study laboratory tests were conducted to understand the nature of scouring near to the pier. For this purpose, model test were conducted in a straight channel with a model concrete pier. The impact of the obstruction in flow, mining of sand and filling of the sand is investigated through this investigation. The finding of this study can be utilized in understanding and development of techniques of controlling scouring near the pier

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Calculating debris flow density based on grain-size distribution

Landslides ◽

10.1007/s10346-018-01130-2 ◽

2019 ◽

Vol 16 (3) ◽

pp. 515-522

Author(s):

Taiqiang Yang ◽

Yong Li ◽

Qishu Zhang ◽

Yu Jiang

Keyword(s):

Grain Size ◽

Debris Flow ◽

Size Distribution ◽

Grain Size Distribution ◽

Flow Density

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Study on Ground Motion Characteristics of River-bed Caused by Debris Flow after an Earthquake Using Distinct Element Method

Journal of Japan Association for Earthquake Engineering ◽

10.5610/jaee.19.6_272 ◽

2019 ◽

Vol 19 (6) ◽

pp. 6_272-6_282

Author(s):

Masayuki YAMADA ◽

Satoru YAGI ◽

Koji HADA ◽

Yoshinori FUJINO ◽

Sosuke FUKATSU ◽

...

Keyword(s):

Debris Flow ◽

Ground Motion ◽

Distinct Element ◽

Distinct Element Method ◽

River Bed ◽

Motion Characteristics ◽

Element Method

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Study on the downcutting rate of a debris flow dam based on grain-size distribution

Geomorphology ◽

10.1016/j.geomorph.2021.107891 ◽

2021 ◽

pp. 107891

Author(s):

Hechun Ruan ◽

Huayong Chen ◽

Yong Li ◽

Jiangang Chen ◽

Huibin Li

Keyword(s):

Grain Size ◽

Debris Flow ◽

Size Distribution ◽

Grain Size Distribution

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Sedimentation in the Reservoir of the Altenwoerth Hydropower Plant

Water Science & Technology ◽

10.2166/wst.1990.0026 ◽

1990 ◽

Vol 22 (5) ◽

pp. 173-180

Author(s):

H. P. Nachtnebel ◽

W. Summer ◽

H. Mueller ◽

B. Schwaighofer

Keyword(s):

Heavy Metal ◽

Grain Size ◽

Longitudinal Section ◽

Hydropower Plant ◽

Sediment Layer ◽

Stream Power ◽

Metal Concentrations ◽

Heavy Metal Concentrations ◽

Sludge Disposal ◽

River Bed

This paper addresses two objectives. The first objective is to describe the sedimentation process in the reservoir of the hydropower scheme Altenwoerth. It is located on the Austrian part of the Danube about 60 km upstream from Vienna. Starting in 1976 the aggradation of the river bed has been monitored annually to estimate the sedimentation rate along a longitudinal section in the reservoir. Further, cores were taken over the whole sediment layer to analyse the grain size distribution, the bulk density, the mineralogic structure of the sediment and the heavy metal concentrations in the layer. It was found that the annual average sedimentation of suspended material amounts to 390 000 m3/a. The grain size of the samples vary from well sorted sands to poorly sorted, clay rich sediments. The heavy metal concentrations refer to the fraction less than 20 µ m. In comparison to the guidelines for sewage sludge disposal the observed heavy metal content of zn and Pb is slightly above the respective limits. The second objective is to demonstrate the application of a one dimensional sedimentation model which describes the accumulation over the operation period from 1976 to 1985. The model is related to the unit stream power concept and is based on the transport capacity equation of Engelund and Hansen. The model yields satisfying results for both the quantity of the sediment and also its gradation.

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Subsurface Stone Lines, Stone Zones, Artifact-Manuport Layers, and Biomantles Produced by Bioturbation via Pocket Gophers (Thomomys Bottae)

American Antiquity ◽

10.2307/281712 ◽

1989 ◽

Vol 54 (2) ◽

pp. 370-389 ◽

Cited By ~ 82

Author(s):

Donald L. Johnson

Keyword(s):

Laboratory Tests ◽

Fine Fraction ◽

Archaeological Site ◽

Site Formation ◽

Maximum Diameter ◽

Field Observations ◽

Pocket Gophers ◽

Subsurface Zone ◽

Thomomys Bottae ◽

Gravelly Soil

A prominent subsurface zone (layer) of large stones with diameters greater than 6-7 cm occurs in gravelly soil on colluvial aprons in the Lompoc area of California. The soil is mounded and churned by botta pocket gophers (Thomomys bottae). Sedimentological analyses show that the soil within and above the stone zone—and within the gopher mounds—is relatively homogeneous in fine fraction and forms a biomantle. None of the mounds contained stones with long-axis diameters greater than the maximum diameter of gopher burrows, about 6-7 cm. Larger stones gradually subside and form a stone zone. Both field observations and laboratory tests confirm that gopher bioturbation produces stone zones in coarse gravelly soil. This finding, and similar findings in two other recent studies, have important implications for interpreting archaeological site formation, and for interpreting geologic-pedologic processes inasmuch as artifact layers (and nonartifact layers) in some sites entirely may be due to nonanthropic, nongeologic, postdepositional biological agents.

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