Seawall Tetrapod Counting

Summary

This report presents a Sentinel-2 based framework for mapping armored coastal segments along Japan’s shoreline, including seawalls, revetments, and tetrapod-protected stretches. Rather than counting individual concrete units, the study identifies defended shoreline segments using spectral contrasts and a U-Net segmentation model trained across climatically and geomorphologically different coastal regions. Applied nationally, the workflow produces a spatially consistent inventory of coastal defense infrastructure and highlights stronger concentrations along parts of the Sea of Japan coast and typhoon-exposed Pacific prefectures. The output is positioned as a baseline for coastal vulnerability assessment, climate-adaptation planning, and longer-term monitoring of engineered shorelines.