Projections of Future Beach Loss in Japan Due to Sea-Level Rise and Uncertainties in Projected Beach Loss

Abstract

In this study, we projected the future beach loss in Japan's 77 coastal zones due to sea-level rise (SLR) based on representative concentration pathway (RCP) scenarios and 21 models of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The beach-loss curve for SLR in Japan was constructed, and uncertainties associated with SLR projections and sediment sizes were evaluated. Beach-loss rates in the future (2081-2100) were projected to be 62% for the ensemble mean RCP2.6 scenario, 71% for RCP4.5, 73% for RCP6.0, and 83% for RCP8.5, and the rates projected by the CMIP5 models for RCP4.5 ranged widely from 61% to 87%. The effect of the spatial distribution of SLR in each CMIP5 model on beachloss rate in Japan is insignificant, while the effects of differences in the SLR values among RCP scenario and CMIP5 models are significant. The maximum uncertainties associated with sediment sizes (0.2--Q.6 mm) against the same SLR were assessed to be 38%. Despite significant uncertainties in the projected beach loss, results in the near future (2046--2065) reveal that the beach-loss rates between 18% and 79% differed by 60% in the near future and between 28% and 96% differed by 70% in the future. For the worst case scenario in the near future, the projected beach width is less than 10m in more than half of the 77 coastal zones, which would cause serious damage to coastal structures such as seawalls and revetments in beach areas. Thus, the development of effective measures to combat beach loss is critical for Japan's coastal management.

Estimates of mortality in sandy beach populations of <i>Haustorioides japonicus</i> (Amphipoda: Crustacea) and <i>Excirolana chiltoni</i> (Isopoda: Crustacea) during winter storm seasons

“…According to the prediction of global climate change, the sea-level rise and wave intensification will decrease the width of sandy beaches and eventually induce disappearance of sandy beach habitats (Yoshida et al 2013, Udo & Takeda 2017. The results of the present study indicate that, even before the loss of habitats, sandy beach peracarids may become extinct because of the increase in winter mortality caused by wave intensification.…”

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

“…However, the models require a load of observed coastal data such as wave height, sediment budgets, historical shoreline changes that are not available for most of the coasts of Thailand. This research conducted on a national scale, and based on the availability of the data set, the Bruun Rule is still a viable method to be used for the projection of future beach loss due to SLR [20]. It should be noted that, due to the mentioned limitations of the Bruun Rule, this study can only provide a broad estimation for sand volume and costs of beach nourishment.…”

“…Yoshida et al [2] proposed a framework for beach nourishment as an adaptation to beach erosion induced by SLR for all Japanese coastlines. Their framework was based on future beach width resulting from SLR based on Udo and Takeda's study [20], and it aimed to specify vulnerable beach areas and estimate the sand volume and costs required to maintain beach width to satisfy different beach functions. However, currently, adaptation plans to deal with future SLR in Thailand are lacking.…”

Adaptation Assessment to Future Beach Loss Due to Sea Level Rise in Thailand

“…Coastal erosion induced by seal level rise could become more serious problems worldwide (Hinkel et al, 2013;Udo and Takeda, 2017). There has been recent study regarding the projection of future (2100) erosion due to SLR in Thailand according to Intergovernmental Panel on Climate Change's (IPCC) projection of SLR based on representative concentration pathway (RCP) scenarios.…”