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Coastal Erosion and Shoreline Change
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
Sea walls are shore-parallel walls designed to stop further landward erosion. Waves still impact beaches in front of the seawall, which almost inevitably results in the narrowing or complete disappearance of the usable beach (Figure 6.4). Sea walls can be constructed from a wide variety of materials, including boulder revetments, concrete, steel, and wooden bulkheads, gabions, and sandbags as a few examples. For centuries, sea walls were the most preferred strategy to slow coastal erosion. Their negative effects on the beach environment—especially the loss of the dry “visible” beach—has led to a shift in strategy toward beach nourishment.[10] Sea walls are no longer permitted in many locations due to these concerns.
Barriers, limits and limitations to resilience
Published in C. Patrick Heidkamp, John Morrissey, Towards Coastal Resilience and Sustainability, 2018
Robin Leichenko, Melanie McDermott, Ekaterina Bezborodko
Coastal engineering and infrastructure-related measures were the most prominent type of resiliency strategy, suggested by approximately half of the stakeholders. These measures also provoked much discussion of both limits and limitations to resilience-based approaches. Beach replenishment or nourishment was mentioned by the majority of stakeholders as an important option to protect coastal assets. While many conceded the short-term effectiveness of this practice in buffering storm impacts and maintaining a recreational space valued by tourists and residents, stakeholders raised concerns about limited effectiveness and mounting costs of these efforts over the longer term. …If the feeling among policy makers in the state is, we want to stay involved in beach nourishment, there’s got to be some recognition that it really isn’t the long-term answer. It’s going to get more expensive over time because the material is going to erode more quickly.(Real-estate stakeholder)…To the extent that beach nourishment is probably a preferable approach to storm mitigation than building sea walls, right. It’s one of those strategies that is available, that you know is obviously designed to help address the impacts of climate change … Its future is probably fairly limited.(Conservation stakeholder)
Geomorphic Features Associated with Erosion
Published in Ramesh P. Singh, Darius Bartlett, Natural Hazards, 2018
Niki Evelpidou, Isidoros Kampolis, Anna Karkani
The population on Earth has increased rapidly in the last decades. A large part, about 50% of Earth’s total population, is located on the coastal zone. This fact imposes stress on the natural processes occurring in coastal areas. The increased inhabitancy on coastal plains triggered the industrial and construction development and significant utilization of the coastal resources. Consequently, man altered the land uses of the coastal zone, and his constructions disturbed the related natural processes, resulting in enormous erosion and landward retreat of the coastline. For instance, the construction of sea walls for the protection of ports alters the longshore current regime, resulting in erosion by removal of the beach sediments on the outer sea wall side and in the accumulation of sediments on the inner sea wall side.
Simulations of future typhoons and storm surges around Tokyo Bay using IPCC AR5 RCP 8.5 scenario in multi global climate models
Published in Coastal Engineering Journal, 2020
Ryota Nakamura, Tomoya Shibayama, Miguel Esteban, Takumu Iwamoto, Shinsaku Nishizaki
Tsuboki et al. (2015) calculated future possible typhoons in the northwestern Pacific Ocean by using a combination of GCM and CReSS model. They found that the average wind velocities of typical typhoons are currently 61 m/s from 53 m/s, though the maximum wind velocity of super-typhoons will range from 88 m/s to 74 m/s by the late 21st century (2074 year – 2087 year), an increase of 15.1–18.9%. It should be noted that Tsuboki et al. (2015) did not project the change in future landfalls of typhoon around Tokyo Bay, and only estimated the averaged features of the future 30 most intense typhoons over the Northwestern Pacific Ocean. Nevertheless, their studies do consider many possible future extreme typhoons near the Japanese Archipelago. Thus, of the authors decided to use their results despite the limitations described above. In addition, for the case of the Tokyo Bay, sea walls are built to a height of 3.0 m at Tokyo tide station, and can currently be expected to resist storm surges generated by winds under 50.7 m/s in velocity (as shown in Figure 24). However, by 2074 −2087 the likely wind speeds of typhoons at this location could increase to 58.4 ~ 60.3 m/s (15.1 ~ 18.9% increase). Thus, in order to maintain the same level of protection between the present (1979–1993 period) and future (2074–2087 period), the design sea wall should be between 3.67 and 3.85 m high by the end of the 21 century (an increase in the expected surge height of 3.67 ~ 3.85 m).