A laboratory experiment on the incipient motion of boulders by high‐energy coastal flows

Bressan, Lidia; Guerrero, Massimo; Antonini, Alessandro; Petruzzelli, V.; Archetti, Renata; Lamberti, Alberto; Tinti, Stefano

doi:10.1002/esp.4461

Cited by 23 publications

(38 citation statements)

References 41 publications

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“…In this paper we refer to the experiments carried out at the Hydraulic Engineering Laboratory of the University of Bologna, Italy [22], whose data are freely available from the site (ftp://137.204.48.34).…”

Section: Laboratory Experimental Setupmentioning

confidence: 99%

“…In contrast to Nandasena and Tanaka [21], who set the initial water heights in the tank at a high value to reduce the effects of turbulence in the flow along the slope, Bressan et al [22] increased the initial water height gradually in the basin starting from a small value with the aim to better identify the instability condition of the block. Notice that the flume remained wet when the experiments were conducted.…”

Section: Laboratory Experimental Setupmentioning

confidence: 99%

“…In all the experiments, Bressan et al [22] placed a set of instruments consisting of three water level sensors (WL), three Doppler velocimeters (DVn), and one 100 fps camera to record the information. DV1 was set up with the acoustic beam aligned with the flume basis and was suitable to record the along-flume component of the flow velocity.…”

Section: Laboratory Experimental Setupmentioning

confidence: 99%

“…The time when the block started moving and the corresponding flow height were determined by analyzing the images recorded by the camera. All relevant details can be found in Bressan et al [22].…”

Section: Laboratory Experimental Setupmentioning

confidence: 99%

“…Although gradually more sophisticated studies have been carried out to figure out the dynamic process of boulder transport, investigations are still needed to verify the accuracy and capability of the existing numerical models and to better understand the basic physical process. On the basis of the experiments on the incipient motion of boulders impacted by water flows conducted by Bressan et al [22], the aim of this paper is to explore the performance of the shallow water equations in predicting the flow properties (depth and velocity) and to improve our understanding of boulders mobilization. The investigation focuses on the properties of the impacting flow with regard to the instability condition of the boulders, and the numerical results are compared with the laboratory experiments.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigations on the Instability of Boulders Impacted by Experimental Coastal Flows

Wang

Bressan

Tinti

2019

Water

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Coastal boulders transported inland by marine hazards, such as tsunamis and storms, are commonly found worldwide. Studies on the transport process of coastal boulders contribute to the understanding of a wide range of phenomena such as high-energy flow events, fluid-structure interaction, and coastal sediments. Consequently, it is crucial to understand how boulders move, but even more important to determine the instability condition for boulder transport. The hydrodynamic formulas including drag and lift coefficients are widely used to predict the incipient motion of boulders while few studies are conducted to evaluate the capability of these formulas. Recently, a series of laboratory experiments carried out at the Hydraulic Engineering Laboratory (Italian acronym LIDR) of the University of Bologna, Italy, revealed that boulders can start moving when the flow height and flow velocity are lower than the theoretical threshold computed by hydraulic formulas. In this paper, we use a numerical shallow water model to reproduce these freely available laboratory data with the aim of testing the capability of the model in capturing the main evolution of the process, and of casting new light on the instability condition of coastal boulders.

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Section: Laboratory Experimental Setupmentioning

confidence: 99%

Section: Laboratory Experimental Setupmentioning

confidence: 99%

Section: Laboratory Experimental Setupmentioning

confidence: 99%

Section: Laboratory Experimental Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Numerical Investigations on the Instability of Boulders Impacted by Experimental Coastal Flows

Wang

Bressan

Tinti

2019

Water

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Boundary condition control of fluvial obstacle mark formation – framework from a geoscientific perspective

Schlömer

Herget

Euler

2020

Earth Surf Processes Landf

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Obstacle marks are sedimentary bedforms, typically composed of an upstream local scour hole and a downstream sediment accumulation in the vicinity of an obstruction that is exposed to a current. However, specific morphologies are variable in fluvial, coastal and submarine environments. Although obstacle marks and the phenomenon of local scouring are subject to different scientific disciplines, the objectives of investigations are rather incoherent and no systematic framework for analysing and evaluating boundary condition control exists yet, especially concerning limited knowledge of the cause and effect relationship of obstacle mark formation at instream boulders or vegetation elements in variable environmental conditions. Thus, a parameter framework is developed which identifies a spectrum of extrinsic and intrinsic boundary conditions that control the major process dynamics of obstacle mark formation. The framework is composed of dimensionless control parameters that are separated by a hierarchical order regarding their significance for obstacle mark formation. Primary control parameters determine the geometrical scale of flow field at the obstacle, and therefore control the potential maximum size of the obstacle. Secondary control parameters affect the dynamics of the flow field in geometrical scale and limit the potential maximum size of the emerging sedimentary structure if thresholds are crossed. The framework is supposed to be a foundation for subsequent quantification and determination of thresholds by systematic laboratory studies. To elucidate this, flume-based research is presented, evaluating the influence of different flow levels at boulder-like obstacles of different shapes. The results show that obstacle mark dimensions were maximized at shallow flow depths compared to obstacle dimensions, while deep flows at submerged boulder-like obstructions caused considerably smaller obstacle marks. In interdependency with a rounded and more streamlined obstacle shape, deep flows even cause a deviation of morphology if the flow depth above an obstacle exceeds 1.6 times the obstacle's dimensions.

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Controls on large boulder mobility in an ‘auto‐naturalized’ constructed step‐pool river: San Clemente Reroute and Dam Removal Project, Carmel River, California, USA

Smith

Kortman

Caudillo

et al. 2020

Earth Surf Processes Landf

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A 1200 m‐long river segment of Carmel River (California) was constructed to bypass trapped reservoir sediment when San Clemente Dam was removed from the Carmel River in 2015. Hundreds of large boulders were used to construct 53 steps in an 800 m‐long reach of the project. Nearly all the boulders were scattered to new locations in high flows of 2017, and have been relatively stable since that time. We analysed the causes of incipient motion and distance travelled for 226 randomly selected large boulders (0.5–1.8 m) impacted by a flood event in winter of 2019. Channel width, water depth, and isolation from neighbouring boulders were the main variables controlling individual large boulder incipient motion during a 10‐year peak flow event in the ‘auto‐naturalized’ constructed step‐pool river in 2019. There is weak statistical evidence that a combination of shear stress and the presence of boulders located laterally downstream of the subject boulder controlled the distance the boulder moved. Frequentist statistics and Akaike information criterion model comparison determined that boulder size, boulder shape, boulder roundness, and local thalweg slope were not good predictors of large boulder incipient motion or distance transported. Average dimensionless critical shear value for the four largest mobilized boulders (1.5–1.6 m) was 0.014. We describe the geomorphic history of the site and use our results to discuss potential causes of unanticipated large boulder transport at the site that occurred in a <2‐year peak flow of winter 2016 soon after step construction. © 2020 John Wiley & Sons, Ltd.

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A laboratory experiment on the incipient motion of boulders by high‐energy coastal flows

Cited by 23 publications

References 41 publications

Numerical Investigations on the Instability of Boulders Impacted by Experimental Coastal Flows

Numerical Investigations on the Instability of Boulders Impacted by Experimental Coastal Flows

Boundary condition control of fluvial obstacle mark formation – framework from a geoscientific perspective

Controls on large boulder mobility in an ‘auto‐naturalized’ constructed step‐pool river: San Clemente Reroute and Dam Removal Project, Carmel River, California, USA

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