Takenori Shimozono 교수

Abstract Super typhoon Haiyan struck the Philippines on 8 November 2013, marking one of the strongest typhoons at landfall in recorded history. Extreme storm waves attacked the Pacific coast of Eastern Samar where the violent typhoon first made landfall. Our field survey confirmed that storm overwash heights of 6–14 m above mean sea level were distributed along the southeastern coast and extensive inundation occurred in some coastal villages in spite of natural protection by wide fringing reefs.

Propagation and inundation characteristics of the 2011 Tohoku tsunami on the central Sanriku coast are investigated through field surveys and numerical simulations using offshore wave recordings as incident wave conditions. The numerical model successfully reproduces the extent of flood areas as well as the distribution of tsunami heights along the intricate coastline except for run-up of extreme heights over steep slopes. The survey and computed results suggest significant variations of tsunami

A post-event survey of the coastal impacts of Typhoon Hagibis was conducted in the Greater Tokyo and Shizuoka areas. The typhoon’s intensive landfall generated the highest-level storm surges recorded in the study area with a maximum sea-level anomaly of nearly 2 m at the head of Tokyo Bay. Highly populated coastal areas in the inner sheltered part of Tokyo Bay were subject to only minor damage partially because the peak storm surge occurred during a low spring tide. High water levels along the c

An estuary is a dynamic environment where marine and fluvial processes meet to form complex and transient morphology. The estuary morphology is largely determined by net sediment transport by two-way tidal flows, but the hydrodynamics also depends on the morphology of the tidal channels. The estuary inherently accommodates cyclic processes that are internally generated through hydro-morphodynamic interactions. In addition, the estuary evolves in response to changes in external forces by natural

Analytical solutions are derived to describe two-dimensional wave evolution in converging bays. Three bay types of different cross-sections are studied: U-shaped, V-shaped and cusped bays. For these bays, the two-dimensional linear shallow water equations can be reduced to one-dimensional linear dispersive wave equations if the transverse flow acceleration inside them is assumed to be small. The derived solutions are characterized as the leading-order plane-wave solutions with higher-order corre

Monitoring the morphological evolution of a river-mouth bar is of both practical and scientific importance. A large amount of sediment is transported from a river to surrounding littoral cells via a deltaic bar after an extreme weather event. However, it is often not feasible to capture drastic morphological changes in the short term with conventional bathymetric surveys. This paper presents a depth-inversion method based on unmanned aerial vehicle technology to estimate two-dimensional bathymet

Long-wave propagation on a uniformly sloping beach is formulated as a transient-response problem, with initially stationary water subjected to an incident wave. Both the water surface elevation and the horizontal flow velocity on the slope can be represented as convolutions of the rate of displacement of the water surface at the toe of the slope with a singular kernel function of time and space. The kernel, which is typically expressed in the form of an infinite series, accommodates the dynamic

A detailed laboratory study of swash zone sediment transport under dam-break waves on a fine sandy slope was carried out. A newly developed sediment transport measurement system was applied for simultaneous measurement of sediment concentration and transport velocity with a vertical resolution of 0.53 mm based on particle image velocimetry (PIV) and a light extinction method, respectively. Concentration data were combined with velocity data to produce sediment flux and were used to investigate t

Abstract Many atolls in tropical oceans are under the threat of sea‐level rise. Mitigation planning requires reliable estimates of increasing wave runup in response to sea‐level rise and changes in wave climate. However, shoreline dynamics on reef‐lined coasts, particularly the effect of low‐frequency waves, are not yet fully understood. Herein, we present a field study on the southernmost atoll of the Maldives to clarify the variability of shoreline water levels driven by waves and tides. The a

Laboratory experiments were performed to investigate characteristics of boundary layer flows under different types of bores. Temporal variations of nearbed velocity profile were measured by a PIV technique and compared with solutions of the boundary layer equation under upper boundary conditions given by the measured free-stream velocities. The results suggested that the boundary layer remained laminar at the bore front even for the case of a fully-developed turbulent bore. The bore-induced turb

A new system of sediment concentration measurement was developed with the light-extinction method for wide range of concentration. A thin electroluminescence sheet which caused minimal disturbance to the flow was used as a light source, and the transmission was detected by a digital video camera which had a 2-dimensional capability. The relationship between the light attenuation and sediment concentration was formulated with preliminary test results on the basis of the modified Lambert-Beer law