Effect of Spatial Resolution on Nationwide Projection of Future Beach Loss Rate in Japan

Abstract

Takeda, Y. and Udo, K., 2020. Effect of spatial resolution on nationwide projection of future beach loss rate in Japan. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1310–1314. Coconut Creek (Florida), ISSN 0749-0208The amount of sea-level rise (SLR) changing along with climate change greatly affects beaches. Projecting nationwide future beach loss requires datasets having sufficient spatial resolutions; however, there has been no case study for an appropriate level of spatial resolution. The present study aims to clarify the effect of spatial resolution on the nationwide projection of future beach-loss rates. We divided the 77 coastal zones specified with reference to Japan's Coast Act, into 586 coastal zones set by the fundamental plan of coastal preservation formulated by prefectures, whose beach length was further separated by nearly every 10 km, resulting in 886 coastal zones. Regarding these 77, 586, and 886 zones, we projected future beach-loss rates in Japan in response to SLR based on the RCP2.6, RCP4.5, RCP6.0, and RCP8.5 scenarios using the Bruun rule. Our projection results showed that the beach-loss rates of the 886 zones decreased by about 6% at maximum compared to those of the 77 zones. The projection results derived from the 586 and 886 zones were nearly the same. This study indicates that higher spatial resolutions less than 20 km in beach length are desirable to project future beach loss in Japan on a nationwide scale.