Tsunami deposits in a super-large wave flume

Yoshii, Takumi; Tanaka, Shiro; Matsuyama, Masafumi

doi:10.1016/j.margeo.2017.07.020

Cited by 29 publications

(21 citation statements)

References 32 publications

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“…Modelling and calculations demonstrate that the backwash develops into a supercritical flow, also on low‐gradient coasts (Simpson & Castelltort, ; Weiss, ; Apotsos et al ., ; Bahlburg & Spiske, ; Jiang et al ., ; Yoshii et al ., ). Rapid deceleration upon entering the sea invokes high settling rates of suspended sediment that may lead to the formation of hyperpycnal flows (Coleman, ; Le Roux & Vargas, ; Weiss, ), particularly where coastal funnelling of receding tsunami water occurs.…”

Section: General Tsunami Characteristicsmentioning

confidence: 97%

“…Because backwash flows are characterized by an initial waxing and final waning stage (Apotsos et al ., ; Yoshii et al ., ), their deposits commonly encompass graded beds overlying an erosional base (Dawson, ; Nanayama et al ., ; Fujino et al ., ; Nanayama & Shigeno, ; Fujiwara & Kamataki, ; Bahlburg & Spiske, ). Thus, sediment deposited onshore during the run‐up and stagnation phases and the evidence of landward‐directed currents are potentially removed or reworked during backwash.…”

Section: General Tsunami Characteristicsmentioning

confidence: 99%

“…Numerical simulations offer a powerful tool that complements the understanding of tsunamigenic sediment transport dynamics (Xiao et al ., ; Apotsos et al ., ; Gusman et al ., ; Kihara et al ., ; Ranasinghe et al ., ; Sugawara et al ., ), demonstrating that the backwash current normally operates in a Froude‐supercritical flow regime (Simpson & Castelltort, ; Weiss, ; Apotsos et al ., ; Yamazaki et al ., ; Jiang et al ., ), which is consistent with observations from laboratory flume experiments (Yoshii et al ., ) and calculations of flow parameters of real‐world tsunamis (Bahlburg & Spiske, ). Rapid deceleration of the supercritical flow, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Geological record of marine tsunami backwash: The role of the hydraulic jump

Slootman

Simpson

Castelltort

et al. 2018

The Depositional Record

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Tsunamis are marked by distinct phases of uprush during coastal inundation and backwash when tsunami water recedes. Especially in the case of a steep coastal profile, the return flow may operate in a Froude-supercritical regime, eroding the flooded area and transporting large volumes of sediment seawards. Important sediment accumulation occurs when the supercritical flow goes through a hydraulic jump where it becomes subcritical upon deceleration. An inferred example in coarse-grained, mixed carbonates from the Lower Pleistocene on Rhodes (Greece) is described, with offshore bars up to 10 m long with scour-and-fill structures and steep antidune stratification. In finer-grained sandy depositional systems such structures may be much longer, up to hundreds of metres. It is suggested here that, analogous to some turbidite beds, the apparent lack of structures or the presence of faint stratification that is common for graded sand layers within marine tsunamiites may in fact consist of extremely low-angle, landward-dipping backset-strata that formed under a landward-migrating hydraulic jump during the basinward retreat of tsunami water. Numerical simulations that focus on the internal stratification of backwash-generated offshore bars support this hypothesis. The recognition of such deposits in the sedimentary record enlarges the toolbox for assessing the past frequency of tsunamis in coastal areas.

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Section: General Tsunami Characteristicsmentioning

confidence: 97%

Section: General Tsunami Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Geological record of marine tsunami backwash: The role of the hydraulic jump

Slootman

Simpson

Castelltort

et al. 2018

The Depositional Record

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“…However, another imprint that tsunamis leave behind on the coast is geomorphological change (Nishimura and Miyaji, ; Dawson and Shi, ; Scheffers and Kelletat, ; Moore et al ., ; Paris et al ., ; Wilson et al ., ; Engel et al ., ). Accordingly, attention is drawn to the tsunami‐induced sediment transport, and this forms another focus of tsunami research (Apotsos et al ., ; Goto et al ., ; Sugawara et al ., ; Yamashita et al ., ; Yoshii et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Modelling scour and deposition in harbours due to complex tsunami‐induced currents

Son

Lynett

Ayça

2020

Earth Surf Processes Landf

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In this paper, a set of models responsible for hydrodynamics, sediment transport, and morphological evolution are introduced with their theoretical backgrounds, and it is explained how they are fully connected through a two‐way coupling to yield an integrated sediment transport model applicable to tsunami cases. In particular, a fully nonlinear Boussinesq model with bottom shear‐induced rotational terms is chosen for the hydrodynamic model in order to provide a better physical approximation of tsunami‐related, near‐bed hydrodynamics in the nearshore. A finite‐volume scheme, stable and suitable for phase‐resolving model runs longer than 10 simulated hours, is adopted in the numerical discretization. The accuracy and applicability of the developed model are investigated through numerical tests on various sediment problems in the shallow region. Calculated results agree well with existing experimental records. Finally, an ocean‐wide, field‐scale simulation of the 2011 Tohoku‐oki tsunami is attempted, with a focus on the localized effects of tsunami‐induced morphological changes at Crescent City Harbor and Santa Cruz Harbor (USA). Consistent with the reported observations, strong and vortical velocity fields are generated through the model and result in significant changes in morphological configurations. Depth variations and areas of scouring and deposition are compared between modelled and observed records, and the results are discussed. © 2019 John Wiley & Sons, Ltd.

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“…Experimentally, Yoshii et al (2017) and Yoshii et al (2018) investigated tsunami inundation and sediment transport and deposition in the coastal hinterland using two large wave ume studies. However, laboratory investigations of onshore tsunami scour at structures are very limited.…”

Section: Introductionmentioning

confidence: 99%

Experimental observations of tsunami induced scour at onshore structures

McGovern

Todd

Rossetto

et al. 2019

Coastal Engineering

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Tsunami inundation of the coastal environment can induce scour at structure foundations leading to failure. A series of experiments are made using a unique Pneumatic Long Wave Generator to generate tsunami wave periods of 25-147 s equating to 3-17.3 mins at 1:50 Froude scale. The waves propagate over a sloping bathymetry and impinge upon a square structure founded onshore in a at sediment bed. Flow velocity, height and scour are recorded as a function of time during tsunami inundation. The rate of scour is observed to be time dependent. Equilibrium, which is not attained, is argued to be an inappropriate measure for time-dependent transient ows such as tsunami in which the ow velocity, depth and direction are variable. The maximum scour depth is recorded and critically is observed not to be equal to the nal depth due to signicant sediment slumping when ow velocities reduce in the latter stages of inundation. Current and wave scour predictor equations over predict the scour, while the ASCE 7-16 method under predicts. Comparisons with available data in the literature show longer inundation durations increase the amount of scour.

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Tsunami deposits in a super-large wave flume

Cited by 29 publications

References 32 publications

Geological record of marine tsunami backwash: The role of the hydraulic jump

Geological record of marine tsunami backwash: The role of the hydraulic jump

Modelling scour and deposition in harbours due to complex tsunami‐induced currents

Experimental observations of tsunami induced scour at onshore structures

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