In 2011, Japan was hit by a tsunami that was generated by the greatest earthquake in its history. The first tsunami warning was announced 3 min after the earthquake, as is normal, but failed to ...estimate the actual tsunami height. Most of the structural countermeasures were not designed for the huge tsunami that was generated by the magnitude
M
= 9.0 earthquake; as a result, many were destroyed and did not stop the tsunami. These structures included breakwaters, seawalls, water gates, and control forests. In this paper we discuss the performance of these countermeasures, and the mechanisms by which they were damaged; we also discuss damage to residential houses, commercial and public buildings, and evacuation buildings. Some topics regarding tsunami awareness and mitigation are discussed. The failures of structural defenses are a reminder that structural (hard) measures alone were not sufficient to protect people and buildings from a major disaster such as this. These defenses might be able to reduce the impact but should be designed so that they can survive even if the tsunami flows over them. Coastal residents should also understand the function and limit of the hard measures. For this purpose, non-structural (soft) measures, for example experience and awareness, are very important for promoting rapid evacuation in the event of a tsunami. An adequate communication system for tsunami warning messages and more evacuation shelters with evacuation routes in good condition might support a safe evacuation process. The combination of both hard and soft measures is very important for reducing the loss caused by a major tsunami. This tsunami has taught us that natural disasters can occur repeatedly and that their scale is sometimes larger than expected.
•Effects of solitary waves and tsunami overflow are numerically investigated in comparison with a potential tsunami.•Practical engineering applications of numerical simulations given in the present ...study are discussed.•Two parameters on the stability of the single stone supporting the crown-wall of the rubble mound breakwater are derived.•Approximate threshold values are given for these parameters to determine stability of the cross-section.
A numerical assessment study of tsunami attack on the rubble mound breakwater of Haydarpasa Port, located at the southern entrance of the Istanbul Bosphorus Strait in the Sea of Marmara, Turkey, is carried out in this study using a Volume-Averaged Reynolds-Averaged Navier-Stokes solver, IHFOAM, developed in OpenFOAM® environment. The numerical model is calibrated with and validated against the data from solitary wave and tsunami overflow experiments representing tsunami attack. Furthermore, attack of a potential tsunami near Haydarpasa Port is simulated to investigate effects of a more realistic tsunami that cannot be generated in a wave flume with the present state of the art technology. Discussions on practical engineering applications of this type of numerical modeling studies are given focusing on pressure distributions around the crown-wall of the rubble mound breakwater, and the forces acting on the single stone located behind the crown-wall at the rear side of the breakwater. Numerical modeling of stability/failure mechanism of the overall cross-section is studied throughout the paper.
The present study shows that hydrodynamics along the wave flume and over the breakwater can be simulated properly for both solitary wave and tsunami overflow experiments. Stability of the overall cross-section can only be simulated qualitatively for solitary wave cases; on the other hand, the effect of the time elapsed during tsunami overflow cannot be reflected in the simulations using the present numerical tool. However, the stability of the overall cross-section under tsunami overflow is assessed by evaluating forces acting on the rear side armor unit supporting the crown-wall of the rubble mound breakwater as a practical engineering application in the present paper. Furthermore, two non-dimensional parameters are derived to discuss the stability of this armor unit; and thus, the stability condition of the overall cross-section. Approximate threshold values for these non-dimensional parameters are presented comparing experimental and numerical results as a starting point for engineers in practice. Finally, investigations on the solitary wave and tsunami overflow experiments/simulations are extended to the potential tsunami simulation in the scope of both representation of a realistic tsunami in a wave flume and stability of the rubble mound breakwater.
Ports are one of the most vulnerable coastal utilities in case of marine natural hazards such as tsunamis and need to be protected against their devastating effects. Thus, studying the effects of ...tsunamis on protective structures such as breakwaters is critical. The Sea of Marmara is a part of an active earthquake zone that has generated tsunamis in the history. In terms of population density, coastal utilization, and economic potential, Marmara coastline seems most vulnerable to marine hazards. The availability of natural stones allows for wide use of rubble mound breakwaters as coastal protective structures in Turkey. The stability of these types of structures under the attack of storm waves has already been studied. However, their stability and performance under the effect of long waves and tsunami attacks have not yet been studied experimentally. The present study is a case study focusing on Haydarpasa Port, located at the southern entrance of Istanbul Bosphorus Strait (North coast of the Sea of Marmara). It aims to investigate the performance level of the port in case of tsunami attack.
Physical model experiments were conducted in the 105-m long wave flume in the Port and Airport Research Institute (PARI), Japan, with a Froude-type length scale of 1/30. The experiments conducted to test the stability of rubble mound breakwater were twofold: (i) solitary wave experiments and (ii) tsunami overflow experiments. The heights of incoming tsunami waves were selected from results of simulations were conducted in the same region (Oyo Int. Co., 2007; Ayca, 2012; Yalciner et al., 2014; Guler et al., 2014; Aytore, 2015). First, the incoming solitary wave heights were selected as 5, 7.5, and 10cm. Using the overflow heights obtained from solitary wave experiments, i.e., wave height at the top of crown wall when the solitary waves are overtopping the crown wall, tsunami overflow experiments were conducted ranging from an overflow height of 1.1cm to 4.6cm. Results of these experiments showed that Haydarpasa Breakwater, especially the crown wall of the breakwater, is not stable under a moderate tsunami attack. Therefore, an improved cross section was also tested under the same conditions, and the improvement proved successful.
Estimation of the potential consequences from events occurring downstream of a dam is part of the risk assessment needed during the installation phase of a new dam. In the case of specific natural or ...man-made ongoing or prospected events, it may also be important to carry out fast computations that can provide information on the areas at risk either because the original design analyses are not available or because the parameters needed are different. This study aimed to develop a procedure that strongly facilitates the preparation of the input deck and the derivation of the output quantities to allow a fast analysis of a dam break event using a shallow water model, NAMI DANCE, as the analysis tool. The analysis shows that in a few minutes, it is possible to obtain the input deck for a new case. This makes it possible to include the prospected methods into automatic routines in analytical tools such as the Global Disasters Alerts and Coordination System (GDACS) to have a quick overview of the expected flood due to a dam break event.
The 20th July 2017 Bodrum–Kos Tsunami Field Survey Dogan, Gozde Guney; Annunziato, Alessandro; Papadopoulos, Gerassimos A. ...
Pure and applied geophysics,
07/2019, Letnik:
176, Številka:
7
Journal Article
Recenzirano
The July 20, 2017 Bodrum–Kos Earthquake caused tsunami wave motions and damage in the south of Bodrum Peninsula, Turkey, and on Kos Island, Greece. Immediately after the earthquake, we conducted ...several post-tsunami field surveys including interviews in coastal zones impacted by the tsunami, i.e., the coastlines of Bodrum Peninsula, Karaada Islet and Akyaka Town in Gökova Bay, Turkey, and eastern Kos Island, Greece. We present observations and measurements to document the variation of the tsunami effects along the coast. The largest tsunami runup was about 1.9 m and observed at the mouth of a small dry streambed at Gumbet Bay, Bodrum. No significant water motions were reported at the northern and western coasts of Bodrum Peninsula. The tsunami runup distribution along the coast of eastern Kos was overall regular, with runup not exceeding 1 m except in the Port of Kos where a 1.5 m tsunami runup was measured.
The March 2011 Great East Japan Tsunami was one of the most disastrous tsunami events on record, affecting the east coast of Japan to an extreme degree. Extensive currents combined with flow depths ...in inundation zones account for this devastating impact. Video footage taken by the eyewitnesses reveals the destructive effect and dragging capability of strong tsunami currents along the coast. This study provides a numerical modeling study in Kamaishi Bay, calculating the damage inflicted by tsunami waves on structures and coastlines in terms of the square of the Froude number
Fr
2
; and also other calculated hydrodynamic parameters, such as the distribution of instantaneous flow depths, maximum currents and water surface elevations that occurred during this catastrophic tsunami. Analyses were performed by using the tsunami numerical modeling code NAMI DANCE with nested domains at a higher resolution. The effect of the Kamaishi breakwater on the tsunami inundation distance and coastal damage was tested by using the conditions of "with breakwater," "without breakwater," and "damaged breakwater." Results show that the difference between the hydrostatic pressure on the seaward side of the breakwater and the leeward side of the breakwater is quite high, clarifying conditions contributing to failure of the breakwater. Lower water surface elevations were calculated in the case of a breakwater existing at the entrance, a partly valid condition for the damaged breakwater case. The results are different for current velocities and
F
r
max
2
in the "with breakwater" condition due to the concentration of energy through the breakwater gaps.
This paper describes the analysis of a parameter, “hydrodynamic demand,” which can be used to represent the potential for tsunami drag force related damage to structures along coastlines. It is ...derived from the ratio of drag force to hydrostatic force caused by a tsunami on the structure. It varies according to the instantaneous values of the current velocities and flow depths during a tsunami inundation. To examine the effects of a tsunami in the present study, the analyses were performed using the tsunami numerical model in two altered regular-shaped basins having different bottom slopes. The simulations were implemented using a single sinusoidal wave with particular initial conditions, such as leading elevation wave and leading depression wave profiles with different wave periods. Two different initial wave amplitudes were employed to assess the diversity in the distribution of the square of the Froude number
Fr
2
along the coastline. The numerical results were compared quantitatively.
Numerical modeling of tsunami evolution, propagation, and inundation is complicated due to numerous parameters involved in the phenomenon. It is important to assess the performance of numerical codes ...that solve tsunami motion, as well as flow and velocity patterns. NAMI DANCE is a computational tool developed for the modeling of long waves. It provides numerical modeling and efficient visualization of tsunami generation, propagation, and inundation mechanisms and computes the tsunami parameters. In the theory of long waves, the vertical motion of water particles has no effect on the pressure distribution. Based upon this approximation and neglecting vertical acceleration, the equations of mass conservation and momentum are reduced to two-dimensional depth-averaged equations. NAMI DANCE uses finite difference computational method to solve linear and nonlinear forms of depth-averaged shallow water equations in long wave problems. In this study, NAMI DANCE is applied to a benchmark problem which was discussed in the 2015 National Tsunami Hazard Mitigation Program (NTHMP) annual meeting in Portland, USA. The benchmark problem features a series of experiments in which a single solitary wave propagates up a triangular shaped shelf which has an offshore island feature. The problem provides detailed free surface elevation and velocity time series in the vicinity of the island. The comparison of the results showed that NAMI DANCE is able to satisfactorily predict long wave evolution, propagation, amplification, and tsunami currents.
Predicting the arrival time of natural hazards such as tsunamis is of very high importance to the coastal community. One of the most effective techniques to predict tsunami propagation and arrival ...time is the utilization of numerical solutions. Numerical approaches of Nonlinear Shallow Water Equations (NLSWEs) and nonlinear Boussinesq-Type Equations (BTEs) are two of the most common numerical techniques for tsunami modeling and evaluation. BTEs use implicit schemes to achieve more accurate results compromising computational time, while NLSWEs are sometimes preferred due to their computational efficiency. Nonetheless, the term accounting for physical dispersion is not inherited in NLSWEs, calling for their consideration and evaluation. In the present study, the tsunami numerical model NAMI DANCE, which utilizes NLSWEs, is applied to previously reported problems in the literature using different grid sizes to investigate dispersion effects. Following certain conditions for grid size, time step and water depth, the simulation results show a fairly good agreement with the available models showing the capability of NAMI DANCE to capture small physical dispersion. It is confirmed that the current model is an acceptable alternative for BTEs when small dispersion effects are considered.
Tsunamis in shallow water zones lead to sea water level rise and fall, strong currents, forces (drag, impact, uplift, etc.), morphological changes (erosion, deposition), dynamic water pressure, as ...well as resonant oscillations. As a result, ground materials under the tsunami motion move, and scour/erosion/deposition patterns can be observed in the region. Ports and harbors as enclosed basins are the main examples of coastal structures that usually encounter natural hazards with small or huge damaging scales. Morphological changes are one of the important phenomena in the basins under short and long wave attack. Tsunamis as long waves lead to sedimentation in the basins, and therefore, in this study, the relation to the current pattern is noticed to determine sedimentation modes. Accordingly, we present a methodology based on the computation of the instantaneous Rouse number to investigate the tsunami motion and to calculate the respective sedimentation. This study aims to investigate the effects of the incident wave period on an L-type harbor sedimentation with a flat bathymetry using a numerical tool, NAMI DANCE, which solves non-linear shallow water equations. The results showed that the corner points on the bending part of the basin are always the critical points where water surface elevation and current velocity amplify in the exterior and interior corners, respectively.
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