TY - JOUR
T1 - Modeling boulder transport by coastal waves on cliff topography
T2 - Case study at Hachijo Island, Japan
AU - Watanabe, Masashi
AU - Goto, Kazuhisa
AU - Imamura, Fumihiko
AU - Kennedy, Andrew
AU - Sugawara, Daisuke
AU - Nakamura, Norihiro
AU - Tonosaki, Takayuki
N1 - Funding Information:
This research was financially supported by a Grant-in-Aid for JSPS fellows (project number 16 J01953). This research was also supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (experimental study for K. Goto: no. 26302007). AK was supported by NSF grants 1727662, 1661015, and by a grant from the National Institute of Standards and Technology (NIST). Finally,we would like to thank the two anonymous reviewers for their constructive comments which helped improve the manuscript.
Funding Information:
This research was financially supported by a Grant‐in‐Aid for JSPS fellows (project number 16 J01953). This research was also supported by a Grant‐in‐Aid for Scientific Research from the Japan Society for the Promotion of Science (experimental study for K. Goto: no. 26302007). AK was supported by NSF grants 1727662, 1661015, and by a grant from the National Institute of Standards and Technology (NIST). Finally,we would like to thank the two anonymous reviewers for their constructive comments which helped improve the manuscript. 1
Publisher Copyright:
© 2019 John Wiley & Sons, Ltd.
PY - 2019/12/1
Y1 - 2019/12/1
N2 - Clifftop coastal boulders transported by storm waves or tsunamis have been reported around the world. Although numerical calculation of boulder transport is a strong tool for the identification of tsunami or storm boulders, and for estimation of the wave size emplacing boulders, models which can reasonably solve boulder transport from below a cliff or from a cliff-edge onto a cliff-top do not yet exist. In this study, we developed a new numerical formulation for cliff-top deposition of boulders from the cliff edge or below the cliff, with validation from laboratory tests. We then applied the model using storm and tsunami wave forcing to simulate the observed boulder deposits at the northwest coast of Hachijo Island, Japan. Using the model, the actual distribution of boulders was explained well using a reasonable storm wave height without assumption of anomalously high-water level by storm surge. Results show that boulder transport from the cliff edge or under the cliff onto the cliff-top was possible from a tsunami with periods of 5~10 min or storm waves with no storm surge. However, the actual distribution of boulders on the cliff was explained only by storm waves, but not by tsunami. Therefore, the boulders distributed at this site are likely of storm wave origin. Our developed model for the boulder transport calculation can be useful for identifying a boulder's origin and can reasonably calculate cliff-top deposition of boulders by tsunami and storm waves.
AB - Clifftop coastal boulders transported by storm waves or tsunamis have been reported around the world. Although numerical calculation of boulder transport is a strong tool for the identification of tsunami or storm boulders, and for estimation of the wave size emplacing boulders, models which can reasonably solve boulder transport from below a cliff or from a cliff-edge onto a cliff-top do not yet exist. In this study, we developed a new numerical formulation for cliff-top deposition of boulders from the cliff edge or below the cliff, with validation from laboratory tests. We then applied the model using storm and tsunami wave forcing to simulate the observed boulder deposits at the northwest coast of Hachijo Island, Japan. Using the model, the actual distribution of boulders was explained well using a reasonable storm wave height without assumption of anomalously high-water level by storm surge. Results show that boulder transport from the cliff edge or under the cliff onto the cliff-top was possible from a tsunami with periods of 5~10 min or storm waves with no storm surge. However, the actual distribution of boulders on the cliff was explained only by storm waves, but not by tsunami. Therefore, the boulders distributed at this site are likely of storm wave origin. Our developed model for the boulder transport calculation can be useful for identifying a boulder's origin and can reasonably calculate cliff-top deposition of boulders by tsunami and storm waves.
KW - boulder transport model
KW - cliff-top deposition
KW - identification of tsunami or storm boulder
KW - numerical simulation
KW - wave-tank experiment
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U2 - 10.1002/esp.4684
DO - 10.1002/esp.4684
M3 - Article
AN - SCOPUS:85074293337
SN - 0197-9337
VL - 44
SP - 2939
EP - 2956
JO - Earth Surface Processes and Landforms
JF - Earth Surface Processes and Landforms
IS - 15
ER -