Run-up Height Research Articles

Influence of Excavation Pits on the Wave Hydrodynamics of Fringing Reefs under Regular Waves

Dredging materials from reef flats have become an important source of sand and aggregates for meeting the infrastructure needs of coral-lined shores in subtropical and tropical regions, especially for low-lying atoll islands. Dredging at the reef flats can generate artificial excavation pits, which not only have profound influences on coral ecological stability but also deeply affect the hydrodynamic characteristics of coral reefs. To deepen the understanding of the influence of excavation on the wave hydrodynamics of fringing reefs, the wave propagation, wave transformation, wave setup, and wave runup processes of regular waves on fringing reefs with artificial pits have been systematically analyzed using a non-hydrostatic numerical wave solver (NHWAVE). The effects of some significant factors have been carefully investigated. According to the study findings, the existence of artificial pits can result in a slight decrease in the wave height around the artificial pit. The time-mean maximum of wave runup height at the backreef slope can be reduced to some extent when the artificial pit is present. When placed close to the reef edge, the artificial pit can have noticeable effects on the hydrodynamic characteristics of fringing reefs, particularly the wave setup along the reef flat. It is hoped that the study findings can provide further reference for evaluation of the influences of artificial pits on the wave hydrodynamics of fringing reefs.

Class A Prediction Symposium on Debris Flow Impact Forces on Single and Dual Barriers

Over recent years, significant advances have been made in the modelling of the impact dynamics between debris flows and single and dual rigid and flexible barriers. Numerical tools and analytical formulations have been proposed to predict the impact force, runup height, barrier deformation, and overflow and landing dynamics. However, there remains a dearth of well-recognised tools that can be used in routine engineering design practice because their reliability is unclear. On 8 and 9 May 2022, a virtual Class A Prediction Symposium on Debris Flow Impact Forces on Single and Dual Barriers was held to evaluate the reliability of existing design tools and identify areas for improvement to advance the current state of barrier design. The symposium was organised by The Hong Kong University of Science and Technology, Norwegian University of Science and Technology, Institute of Mountain Hazards and Environment of the Chinese Academy of Sciences, and the Geotechnical Engineering Office of the Civil Engineering and Development Department of the HKSAR Government. This paper summarises the existing research on flow-barrier interaction, and details of the symposium, including the prediction cases and results, roundtable discussion, and future research directions.

Analysing Civilian Video Footage for Enhanced Scientific Understanding of the 2011 Tohoku Earthquake and Tsunami, Japan, with Implications for PNG and Pacific Islands

Approximately 70% of global tsunamis are generated within the pan Pacific Ocean region. This paper reports on detailed analysis of civilian video footage from the 2011 Tohoku earthquake, Japan. Comprehensive scientific analysis of tsunami video footage can yield valuable insights into geophysical processes and impacts. Civili22an video footage captured during the 2011 Tohoku, East Honshu, Japan tsunami was critically examined to identify key tsunami processes and estimate local inundation heights and flow velocity in Kesennuma City. Significant tsunami processes within the video were captured and orientated in ArcGIS Pro to create an OIC (Oriented Imagery Catalogue). The OIC was published to ArcGIS Online, and the oriented imagery was configured into an interactive website. Flow velocity was estimated by quantifying the distance and time taken for an object to travel between two known points in the video. Estimating inundation height was achieved by taking objects with known or calculable dimensions and measuring them against maximum local inundation height observations. The oriented imagery process produced an interactive Experience Builder app in ArcGIS Online, highlighting key tsunami processes captured within the video. The estimations of flow velocity and local inundation height quantified during video analysis indicate flow speeds ranging from 2.5–4.29 m/s and an estimated maximum local run-up height of 7.85 m in Kesennuma City. The analysis of civilian video footage provides a remarkable opportunity to investigate tsunami impact in localised areas of Japan and around the world. These data and analyses inform tsunami hazard maps, particularly in reasonably well-mapped terrains with remote access to landscape data. The results can aid in the understanding of tsunami behaviours and help inform effective mitigation strategies in tsunami-vulnerable areas. The affordable, widely accessible analysis and methodology presented here has numerous applications, and does not require highly sophisticated equipment. Tsunamis are a significant to major geohazard globally including many Pacific Island states, e.g., Papua New Guinea, Solomon Islands, and Tonga. Video footage geoscientific analysis, as here reported, can benefit tsunami and cyclone storm surge hazards in the Pacific Islands region and elsewhere.

Energy Transfer and Reverse Flow Characteristics in the Interaction Process between Non-Breaking Solitary Wave and a Steep Seawall: A Case Study

This study utilized a two-dimensional numerical viscous wave tank to simulate the run-up and run-down processes of non-breaking solitary waves on a steep seawall. The research aimed to investigate the transformation between wave potential energy and kinetic energy, the evolution mechanisms of the wave and flow fields, and the correlation between the dynamic pressure gradient and the reverse flow near the sloping bed. The numerical model results were consistent with laboratory measurements of free surface elevations and flow velocity profiles, demonstrating the accuracy of the numerical model. This study focused on a solitary wave with a wave-height-to-water-depth ratio of 0.15, propagating on a representative seawall with a steep slope of 1:3 along the western coast of Taiwan. The simulation results indicate that the maximum run-up height occurs when the potential energy is at its highest. Undertow is caused by the adverse pressure gradient within the flow field, and the dynamic pressure on the sloping bed is directly proportional to the free surface elevation. Therefore, by observing the spatial changes in the free surface elevation, we can indirectly determine the occurrence time of undertow.

Numerical modelling of wave run-up heights and loads on multi-degree-of-freedom buoy wave energy converters

With the development of wave energy converters (WECs), multi-degree-of-freedom (multi-DOF) buoy has become popular. The effect of nonlinear phenomena, such as wave run-up and wave impact, on an oscillating buoy WEC, may decrease its efficiency and even lead to overturning, plastic deformation, and fatigue failure. This study used a Fortran code for the custom development of Flow-3D software to apply independent power take-off (PTO) damping to each DOF. A hydrodynamic simulation model of the interaction between a wave and cylindrical buoy under six types of motions was developed and verified through model tests of the motion response of the buoy and wave run-up on it. Wave run-up heights and maximum wave loads on buoys with different motions and PTO combinations were investigated and compared. The numerical results show that coupled motion can lead to a less intense wave field distribution than a single motion and reduce the risk of overtopping. In addition, the bottom pressure of the buoy for the pitch–surge motion increased by a maximum of 101.6 % compared to the initial pressure. For independent linear PTO damping, heave damping has the most significant influence on the maximum wave load on the coupled motion buoys, followed by surge damping, while pitch damping has no significant effect. The results of this study can guide the designing of safe and reliable multi-DOF buoy WECs.

Using 17 years of beach/dune profile monitoring to characterize morphological dynamics related to significant extreme water level events in North Brittany (France)

Long-term in situ monitoring of beach morphology is crucial for understanding the physical processes of coastal changes and defining the strategies of sustainable coastal management. Monthly surveys based on the beach/dune profile measurements started in July 2004 along six transects distributed along the Vougot beach (North Brittany). The analysis of these data from 2004 to 2021 shows that the eastern part of the beach has experienced chronic erosion during the 17-year period. This erosion has led to a lowering of the beach profile by about −1 to −1.5 m, and has resulted in the removal of beach sand such that waves now impact the underlying Holocene peat and Pleistocene silts or pebbles during most of the year. Conversely, the western part of the beach has accreted. Vougot beach is thus experiencing a rotation phenomenon characterized by a longshore sediment flux from the east to the west. The multidecadal evolution of the beach/dune system is punctuated by events causing significant retreat of the dune, especially when storm waves are combined with high spring tide levels. The event causing the most significant morphological changes was associated with extreme water levels (EWL) up to 9.6 m (i.e., Anne storm in February 2014), causing 14.5 m3 l.m−1 of dune sediment loss. The analysis of 17 years of hydrodynamic conditions (waves and water levels) indicates an increase in the wave runup height (+65 %) and EWL (+17 %). Calculation of the water level that exceeds the dune toe position (Δzexceedance) helps to further quantify the impacts of storm events on dune volume changes. The Anne storm had an EWL with a return period of approximately 13 years, but when combined with the dune toe position, showed the largest dune toe exceedance value (3.0 m), corresponding to a return period of approximately 21 years. Lastly, the events causing the most significant dune erosion during this 17-year study period have also caused shoreline erosion and/or landward barrier migration at many other sites in North Brittany, showing the broader scale impacts of observations at individual study sites.

DETERMINATION OF WAVE RUN-UP THROUGH THE TIMESTACK METHODOLOGY AND THROUGH A RESISTIVE WAVE GAUGE. A COMPARATIVE ANALYSIS

The objective of this work is the comparison of two methodologies used for run-up measurements in a two-dimensional physical model, which represented the protection breakwaters of the Peniche and Ericeira’s ports. Tests were carried out in the scope of the BSafe4sea project. The methodologies used were: a) the traditional measurement of the run-up height with a resistive wave gauge; b) the use of video cameras and image processing techniques images to infer the run-up heights, having its performance evaluated for some of the test conditions. Regarding the results obtained, in terms of Ru2% and Rumax, it was found that the magnitude of the values obtained with the two techniques were quite similar, although the video analysis returned slightly higher values than the wave gauge. Thus, it was found that the video image technique is a viable alternative to measure the run-up. It is recommended the use of diffused light during the tests, along with stabilizing the video camera, to improve the accuracy of the results obtained by the video-based technique. Besides, the quality of the video image and the use different colors of the armour units of the phicial model, could contribute to achieve better results with the TimeStack methodology.

Inundation, runup and flow velocity of wavemaker generated bores on a planar beach

Undulating and breaking bores are generated in the laboratory using a programmable long-stroke wavemaker. By changing the stroke length and the speed of the wavemaker, both non-decaying and decaying bores are generated and studied. Bore strength, height and duration are measured and compared with the solutions derived by using the method of characteristics, with excellent agreement. The measurements for inundation depth, runup height and flood duration are checked with the formulas presented in Barranco & Liu (J. Fluid Mech., vol. 915, 2021). The comparisons show that the formulas are also accurate for the non-decaying bores generated by the wavemaker. The maximum inundation depth predicted by the formula for zero bore length at the beach toe agrees with the laboratory observations for decaying bores. Using a high-speed particle image velocimetry system, the ensemble-averaged velocities and fluctuating velocities under undulating bores and breaking bores are measured in constant water depth and in the vicinity of the still water shoreline. Detailed analyses of the velocity fields are presented and discussed. For the undulating bore a long quiescent flood duration is observed, while for the breaking bore the up-rush flow changes into down-rush flow almost linearly.

Superelevation and runup height of debris flows in bends based on typical rectangular cross-sections and gravity center offset

Superelevation and runup height of debris flows in bends based on typical rectangular cross-sections and gravity center offset

Foredune defending role: Vulnerability and potential risk through combined satellite and hydrodynamics approach

The paper presents an approach to assessing potential risks for coastal areas, where the foredune acts as the first and main line of defense against storm surges. The local correction technique for satellite data via morphodynamics and hydrodynamics features, applicable for the southern part of the Baltic Sea was developed. The proposed combination of regionally adapted height of the wave run-up and the surge height made it possible to clarify the width of the beach through analyzing ESA Sentinel-2a satellite images. Using digitized shorelines from ESA Sentinel-2a imagery as a reference, together with the results of modeling the near-hydrodynamic conditions, a study of the beach width dynamics between measurements was performed. This is due to the regularity of satellite data being affected by cloud cover and the period of circulation. Identifying hot spots on the shore made it possible to establish areas with a significant excess in the repeatability of small dry beach width and, correspondingly, the erosion rate. The hot spots were detected within the Curonian Spit protective dune ridge, identifying the vulnerable areas, which are able to serve as breach points to flooding. The hydrological analysis of the flood zones under storms of varying frequency was performed, and predictions were made regarding the regional sea level rise by BACC and Team (2015) regional climate analysis. The work shows the possibilities of combining hydrodynamic and hydrological modeling, satellite observations into a single forecasting and assessment system, which allows to analyze and model risks of various origins. The results obtained can significantly improve the existing models or become the background for the integrated coastal zone management system, especially in protected natural areas.

Development of a typhoon wave overtopping prediction model based on an artificial neural network

In this study, an artificial neural network (ANN) model for the typhoon wave overtopping was developed using the database by a numerical wave flume simulation. The developed ANN model is effective for saving calculation time largely. The accuracy of the model is also approached to over 95% of the numerical simulation. This accuracy was evaluated by the correlation coefficient and the root mean square error with the target data of the numerical simulation and output of the ANN model. This model quickly produces the mean wave overtopping rate, maximum wave run-up height, maximum wave overtopping depth and velocity at the middle point in the coastal road without high-fidelity numerical model and high-computing resources. It means that the typhoon warning system including the ANN models is powerful and useful rather than only the monitoring warning system currently in use.

Coral reef structural complexity loss exposes coastlines to waves

Coral reefs offer natural coastal protection by attenuating incoming waves. Here we combine unique coral disturbance-recovery observations with hydrodynamic models to quantify how structural complexity dissipates incoming wave energy. We find that if the structural complexity of healthy coral reefs conditions is halved, extreme wave run-up heights that occur once in a 100-years will become 50 times more frequent, threatening reef-backed coastal communities with increased waves, erosion, and flooding.

Numerical investigation of effects of artificial excavation pit on transformation and runup processes of tsunami-like wave over fringing reef

In recent years, excavating materials from the reef flat gradually becomes the main source of sand and aggregate for the coral-lined coasts in tropical and subtropical regions, especially the low-laying atoll islands. These artificial excavation pits are bound to have significant impacts on the wave hydrodynamics over the fringing reefs. However, effects of the excavation pit on the hydrodynamic characteristics of tsunami-like wave over the fringing reef are few studied. To fill the knowledge gap of previous research, effects of artificial excavation pit on the transformation and runup processes of tsunami-like wave over the fringing reef have been systematically investigated in this study based on a high-resolution two-phase flow model. Effects of several main factors are carefully discussed. Research results indicate that the presence of excavation pit can have noticeable influences on the wave transformation and runup processes of tsunami-like wave over the fringing reef. Complex interactions between the breaking surge bore and the water body in the excavation pit can be observed. The complicated flow field in the pit can dissipate more wave energy and result in a lower maximum wave runup height. However, the local wave height near the pit in most situations can be amplified. It is hoped that the research findings can broaden the understandings on the wave hydrodynamics over the fringing reef with the artificial excavation pit.

Assessment of Run-Up Height and Arrival Time of 365 AD Tsunami at Lampedusa Island, Italy

The eastern Mediterranean Sea is a subduction zone between the African plate and the Eurasian plate that has high seismicity. The tsunami of July 21, 365 AD was one of the most severe in the region, and its impact was estimated to have extended to the islands around the Aegean Sea, Cyprus, southern Calabria, Sicily, Malta, and Lampedusa. However, an analysis of tsunami waves reaching Lampedusa Island has not been conducted. Therefore, this study will present the run-up height and arrival time of tsunami waves near the Lampedusa coast. The methods applied are linear and non-linear shallow water equations by inputting the rupture parameters of the 365 AD earthquake. We used Delft Dashboard and Delft3D software to simulate tsunami wave propagation offshore. The simulation results indicate that an earthquake with a magnitude of approximately Mw 8.5 triggered tsunami waves with a maximum run-up height of 2.02 m in nearshore Lampedusa. The travel time for the maximum run-up height was 3.5 hours after the generation of the first tsunami wave in the western Hellenic Arc, Greece. We infer that seawater most likely inundated the coast of Lampedusa during the tsunami earthquake in 365 AD.

Keynote lecture. Impact dynamics of debris flow against slit dam: Experimental and numerical investigation

Debris flows are gravity-driven phenomena common in mountainous regions that are hazardous to downstream facilities. To mitigate the impacts of these disastrous processes, structural countermeasures such as slit dams are constructed in gullies and along mountain slopes. Existing studies on the impact dynamics of debris flows against slit dams typically focus only on the flow characteristics but fail to take the geometry of the structure into account. Here we develop an analytical model, derived from the momentum approach, that allows for the estimation of the runup height and impact load of debris flows on slit dams. The model is validated against discrete element simulations and small-scale flume experiments. It is found that the runup height is controlled by both the Froude number and slit size. The proposed analytical model can predict the runup height well within a certain range of Froude numbers. Results from experiments further reveal that the fontal dynamic pressure is sensitive to the flow properties whereas the peak dynamic pressure is strongly affected by the slit size.

Tsunami Hazard Mapping and Evacuation Path Determination using field Survey and Geographical Information Systems at Widarapayung Wetan, Cilacap

In 2006, a tsunami hit Pangandaran, and its effects were felt in Cilacap. There were 664 fatalities, 498 injuries, and 55 million dollars in damages, and 1623 homes were destroyed or severely damaged due to the tsunami. Furthermore, the village of Widarapayung was among those devastated by the tsunami, which reached a height of up to 5 meters and claimed the lives of 12 people. In addition, Widarapayung is a popular tourist destination and one of the venues for 2019’s professional surfing events. Therefore, disaster prevention measures are essential to lessen the impact of disasters and save lives. The objective of this study is to assess the vulnerability of the Widarapayung Wetan area to a tsunami and make recommendations for evacuation routes and regional infrastructure development to reduce casualties and damage. This research utilized COMCOT to model the megathrust segment with a possible magnitude of 8.7, with worst-case values acquired from the catalog PuSGeN 2017. Additionally, the data on topography and bathymetry collected by DEMNAS and BATNAS are utilized in this investigation. The modeling results indicated a 50-minute arrival time for the tsunami waves, a maximum run-up height of 14-18 meters, and a submerged area of roughly 4.57 km2. In addition, the most effective evacuation routes were determined by combining the outcomes of field surveys and Geographic Information System simulations. This research will provide local governments with helpful information for making informed decisions about infrastructure and spatial development in the future.

Flow-type landslides Impacting V-shaped Diversions: Physical Modelling

In rural and sparsely populated areas, government issued pamphlets often recommend the construction of V-shaped diversions to protect personal property from flow-type landslides hazards, including debris flows. V-shaped diversions are advantageous because they attract low impact forces and runup heights due to their oblique impact angle. However, current design approaches are empirical, so it is unclear what resisting forces and wall heights are required. In this extended abstract, details of a new experimental setup and some preliminary results are presented. It is envisioned that findings from this study will help to shed light on scientific-based recommendations to design V-shaped diversions to enhance the resiliency of mountain communities globally.

Using GIS to Determine Tsunami Shelter Location in South Coast Pangandaran District, Pangandaran Regency, Indonesia

The geographical condition of the Pangandaran Regency affects the coastal area, periodically suffering hydrological hazards. Based on the Regional Disaster Management Agency of Pangandaran, Pangandaran Regency experienced Tsunami with a run-up height of 8 to 15.7 meters in 2006. The Tsunami caused 664 people to die, many to be injured, and caused social environment disruption. Therefore, this research aims to support disaster mitigation by identifying additional shelter locations and generating evacuation routes sequentially. This research uses the network analyst method of Geographic Information System (GIS). The identification of evacuation shelters utilizes several parameters, e.g., tsunami hazard catchment area, land slope levels, land cover, and street network. In addition, the spatial analysis considers average travel time as the impedance to resemble the actual evacuation process. The result indicates that 11 evacuation shelters scattered over the study area were dominantly located in Pangandaran Village. Moreover, this research generates 24 evacuation routes from the incident location to each shelter. The closest shelters accessed 8 minutes from incidents 4 and 18 are shelters 3 and 9, respectively. On the contrary, the farthest shelter is shelter 9, with a maximum impedance of 22 minutes from incidents 14 and 15. Furthermore, the most appropriate shelters are shelters 2 and 8, considering the elevation height of 10 and 7 in the open space.

Utilization of Seismic Data as a Tsunami Vulnerability Review

This study aimed to analyze seismic data, which is then made into an infographic to map the level of tsunami hazard in the Sikka District. The research was carried out in Sikka District, East Nusa Tenggara, located between 121°55'40''-122°41'30'' east longitude and 08°22'-08°50' south latitude. The data source comes from the IRIS Earthquake Browser, and the analysis stage was carried out in two phases. The first analysis used seismic data analysis, and EQ Energy used IRIS (Incorporated Research Institutions for Seismology) data. Meanwhile, the second analysis maps the tsunami risk by determining the tsunami hazard in areas with the potential for a tsunami. Based on the analysis of seismicity data showed that Sikka District has the potential for an earthquake accompanied by a tsunami. In contrast, the results of the EQ Energy analysis caused by the December 14, 2021 earthquake were known as the value of Ehf = 6.46 × 1014 J and EBB = 5.48 × 1015 J. The analysis of the level of tsunami susceptibility based on the tsunami run-up height in Sikka District showed that the northern coastal area of ​​Flores had various potentials, where the highest vulnerability level was in the Alok subdistrict and parts of Talibura. Meanwhile, the area with the lowest potential was the Kewapante subdistrict.

Numerical Simulation on Reduced Runup Height of Solitary Wave by Fixed Submerged and Floating Rectangular Obstacles

The wave runup height is one of the most important parameters for affecting the design of coastal structures such as dikes, revetments, and breakwaters. In this study, SWASH (Zijlema et al., 2011), a non-hydrostatic pressure numerical model, was used to analyze the effect of reducing The wave runup height of solitary waves by submerged and floating rectangular obstacles. It was confirmed that the SWASH model reproduces the propagation, breaking, and runup of solitary waves quite well. In addition, it was confirmed that the wave deformation of the solitary wave by submerged and floating rectangular obstacles was well reproduced. Finally, we conducted an examination of the effect of reducing the runup height of submerged and floating rectangular obstacles. Reduced runup heights are calculated and the characteristics of runup height reduction according to the dimensions of the obstacle were analyzed. The energy attenuation effect of the floating obstacle is greater than the submerged obstacle, and it is shown to be more effective in reducing the runup height.