Study and modelling of rapid shoreline displacement due to coseismic subsidence along the Kamchatka subduction zone

The first studies of geological evidences of coastal coseismic subsidence (associated with subduction-zone earthquakes) were carried out in Russia at the Institute of Volcanology and Seismology, in Kamchatka. We developed a special method based on tephrostratigraphy and tephrochronology, descriptions and dating of the soil-pyroclastic sequence (SPS) overlying the coastal wave-build beach ridges. Three seismic events accompanied by coastal coseismic subsidence were detected in the northern part of Avachinsky Bay during the past ~5 thousand years. We found subsidence from one of the greatest historical tsunamigenic earthquake (1952 AD) south of Petropavlovsk-Kamchatsky. We identified, that 5 events of coastal coseismic subsidence had occurred during the past ~6 thousand years at the coast of Kronotsky Bay and Shipunsky Peninsula. Amplitudes of subsidence were estimated by geological data using three different methods. Erosion of the active beach and marine accumulative terrace becomes active after coastal subsidence. We calculated the shoreline retreat process and the amount of horizontal erosion by numerical simulation using Bruun rule. In some areas, shoreline retreat was about 300 m according to the model results.

The Shoreline Deformation in Convex Beach due to Sea Level Rise

Sea level rise (SLR) is become more serious on a global scale and has become one of the main reasons causes shoreline changes, and erosion, even on an extreme scale can cause the sinking of coastal areas and islands. It was recorded that many big cities were damaged by SLR. The Bruun rule is the most widely used method for predicting the horizontal translation of the shoreline associated with a given rise in sea level. In this study, however, the change in the average shoreline at the convex beach, which is more vulnerable to erosion due to sea level rise, is investigated. The increase in water depth by sea level rise causes a change in the wave crestline, ultimately leading to a linearization of the shoreline. In general, it is assumed that the annual average shoreline is parallel to the annual mean wave crestline. Moreover, assuming that the equilibrium depth contour is formed according to the crestline, the retreat of the shoreline is predicted. The shoreline change is indirectly predicted through the wave crestline deformation obtained from a wave model and this method is applied to the convex beach. Our result showed that for a convex beach with a length of 1 km has open ends with free littoral drift at both ends, the sea level rise of 1 m cause the erosion of 10 m in the protruding area, and the sea level rise of 2 m causes erosion of 23 m. However, if the convex beach is blocked at both ends, sea level rise of 1 m causes the erosion of 6.3 m in the convex area, but the shoreline advance of 3.8 m at both ends, and if the sea level rise of 2 m occurs, the erosion of 14.3 m can occur in the convex area and shoreline advance of 8.6 m can occur at both ends.

Reinterpreting the Bruun Rule in the Context of Equilibrium Shoreline Models

Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models.

Development of Tools for Coastal Management in Google Earth Engine: Uncertainty Bathtub Model and Bruun Rule

Sea-level rise is a problem increasingly affecting coastal areas worldwide. The existence of free and open-source models to estimate the sea-level impact can contribute to improve coastal management. This study aims to develop and validate two different models to predict the sea-level rise impact supported by Google Earth Engine (GEE)—a cloud-based platform for planetary-scale environmental data analysis. The first model is a Bathtub Model based on the uncertainty of projections of the sea-level rise impact module of TerrSet—Geospatial Monitoring and Modeling System software. The validation process performed in the Rio Grande do Sul coastal plain (S Brazil) resulted in correlations from 0.75 to 1.00. The second model uses the Bruun rule formula implemented in GEE and can determine the coastline retreat of a profile by creatting a simple vector line from topo-bathymetric data. The model shows a very high correlation (0.97) with a classical Bruun rule study performed in the Aveiro coast (NW Portugal). Therefore, the achieved results disclose that the GEE platform is suitable to perform these analysis. The models developed have been openly shared, enabling the continuous improvement of the code by the scientific community.

Development of Tools for Coastal Management in Google Earth Engine: Uncertainty Bathtub Model and Bruun Rule

Sea-level rise is a problem increasingly affecting coastal areas worldwide. The existence of Free and Open-Source Models to estimate the sea-level impact can contribute to better coastal man-agement. This study aims to develop and to validate two different models to predict the sea-level rise impact supported by Google Earth Engine (GEE) – a cloud-based platform for planetary-scale environmental data analysis. The first model is a Bathtub Model based on the uncertainty of projections of the Sea-level Rise Impact Module of TerrSet - Geospatial Monitoring and Modeling System software. The validation process performed in the Rio Grande do Sul coastal plain (S Brazil) resulted in correlations from 0.75 to 1.00. The second model uses Bruun Rule formula implemented in GEE and is capable to determine the coastline retreat of a profile through the creation of a simple vector line from topo-bathymetric data. The model shows a very high cor-relation (0.97) with a classical Bruun Rule study performed in Aveiro coast (NW Portugal). The GEE platform seems to be an important tool for coastal management. The models developed have been openly shared, enabling the continuous improvement of the code by the scientific commu-nity.

Development of Tools for Coastal Management in Google Earth 2 Engine: Uncertainty Bathtub Model and Bruun Rule

Sea-level rise is a problem increasingly affecting coastal areas worldwide. The existence 15 of Free and Open-Source Models to estimate the sea-level impact can contribute to better coastal 16 management. This study aims to develop and to validate two different models to predict the 17 sea-level rise impact supported by Google Earth Engine (GEE) – a cloud-based platform for plan-18 etary-scale environmental data analysis. The first model is a Bathtub Model based on the uncer-19 tainty of projections of the Sea-level Rise Impact Module of TerrSet - Geospatial Monitoring and 20 Modeling System software. The validation process performed in the Rio Grande do Sul coastal 21 plain (S Brazil) resulted in correlations from 0.75 to 1.00. The second model uses Bruun Rule for-22 mula implemented in GEE and is capable to determine the coastline retreat of a profile through the 23 creation of a simple vector line from topo-bathymetric data. The model shows a very high correla-24 tion (0.97) with a classical Bruun Rule study performed in Aveiro coast (NW Portugal). The GEE 25 platform seems to be an important tool for coastal management. The models developed have been 26 openly shared, enabling the continuous improvement of the code by the scientific community.

Equilibrium beach profile on sandy beach of the Mehdya coast of Morocco

The world’s coastlines are shaped by mean sea level, wave conditions and storm surge. Climate change driven variations in these environmental forcing’s will inevitably have a profound effect on the coastal zone. They will result in unprecedented coastal recession, threatening billions of dollars worth of coastal developments and infrastructure. Coastal erosion is observed in some locations along Atlantic alluvial plain (Kenitra coastal (Morocco)) and is an important factor to consider for the coastal zone management. Therefore, for coastal recession estimates are obtained via the simple, deterministic method (Bruun rule) especially, that has been widely used over the last 50 years. It is in widespread contemporary use at a global scale both as a management tool and as a scientific concept. We investigated the potential erosion at the site and the result was very important. The result shows a severe erosion of the 21st century.

CROSS-SHORE MODEL APPLICATION TO HASAKI BEACH, JAPAN: EVALUATION OF PARAMETER SETTING

Japan's coasts is being suffered by significant erosion. There is already a high demand to protect coasts from the erosion but climate change threatens further erosion. Udo and Takeda (2017) projected future beach loss in Japan due to sea-level rise using Bruun rule. However, its restrictive assumption that they probably do not exist in nature makes difficult to assess uncertainties of the projection results. In this paper, Cross-shore (CS) model developed by Larson et al. (2016), which is more realistic model considering the cross-shore sediment exchange, is applied to calibrate the parameter settings at Hasaki beach in Japan, and model applicability was evaluated.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/sOFr9Jb5a_s

Beach Nourishment as an Adaptation to Future Sandy Beach Loss Owing to Sea-Level Rise in Thailand

A recent study suggested that significant beach loss may take place on the coasts of Thailand by the end of the 21st century as per projections of sea-level rise by the Intergovernmental Panel on Climate Change (IPCC). The present study adapts a framework and provides broad estimations for sand volumes and costs required to apply beach nourishment to each coastal zone in Thailand using a technique based on the Bruun rule assumption. Results indicate that a minimum of USD 2981 million (the best scenario) to a maximum of USD 11,409 million (the worst scenario) would be required to maintain all sandy beaches at their present width. Further, the effect of filling particle size on beach nourishment was analyzed in this study. The cost of beach nourishment ranges between USD 1983 and 14,208 million when considering filling particle size diameters of 0.5 and 0.2 mm. A zonal sand volume map for all 51 sandy beach zones in Thailand was created for use as an overview to help decision makers develop a more feasible adaptation plan to deal with the future sea-level rise for Thailand.

Likely and High-End Impacts of Regional Sea-Level Rise on the Shoreline Change of European Sandy Coasts Under a High Greenhouse Gas Emissions Scenario

<p>Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario “likely-range” and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.</p>