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合成開口レーダ（Synthetic Aperture Radar）衛星はマイクロ波レーダを搭載した衛星であり，雲天時，夜間にも観測可能である．そのため光学（可視）衛星に比べ同一地点のシーンを高頻度に取得できる．年に複数回取得されたシーンより汀線位置を読み取り，漂砂系内の季節的な汀線変動を追跡した．高頻度に観測されたデータの解析結果を示し，その優位性を検討する．具体的には地球観測衛星ALOS (PALSAR)（運用期間：2006～2011年）とALOS-2 (PALSAR-2)（2014年～現在）が取得した鹿島灘南部（鹿島港～利根川河口）の32シーンを分析した．2006年から2016年にかけての約10年間の汀線変動の特徴を議論し，年に1回取得される観測結からは抽出できない汀線変動特性を説明する．

application/pdf, Intertidal morphology was monitored continuously with an X-band radar at the research pier HORS in Hasaki, Japan. Hourly-averaged radar images were processed to observe longshore distributions of shoreline positions. Variations of longshore mean shoreline positions and their fluctuation intensities observed in the years 2005 and 2006 showed a seasonal change which followed the so-called beach-cycle. Longshore pixel intensities close to the waterline were extracted from time-averaged images for every hour of the two years to process longshore time-stack image. Longshore migration speeds of shoreline mega-cusps were estimated by cross correlation analysis of the time-stack image, and the reliability of the method was checked. Migration speeds were compared to measured longshore current speeds at the pier and the longshore component of the wave power, showing that they are highly synchronized for most conditions. Finally, the migration statistics were related to the wave data, and the results showed that the northwards migration rates were typically larger than southwards rates, which was consistent with the statistical results for wave forcing variables. Also, the relationship between the migration speeds and the forcing variables indicates that the migration was more active when the wave incidence angle was close to 45◦.

application/pdf, An X-band nautical radar system was employed to observe the wave field during a storm around the research pier HORS in Hasaki, Japan. The radar system provides instantaneous distributions of wave crests in the near-shore region, with image sequences comprising a clear spatial and temporal variation of the wave pattern. The spectra of radar echo signals and water surface elevations from wave gauge records were compared, and a relatively high coherence for a particular bandwidth was observed. A sequence of radar images was filtered at the dominant frequency, which was used to estimate the wavenumber distribution of the refraction field. The Fast Fourier Transform (FFT) andMaximum EntropyMethod (MEM) were used to estimate the wavenumbers. The estimated wave angles were then compared with linear refraction analyses. The water depths along the pier were also estimated using the linear dispersion relationship and compared with the surveyed depths. The linear estimates of hydrodynamic parameters during the passage of the storm are presented in this paper to demonstrate the potential of radar measurements in capturing essential characteristics of coastal dynamics.

ベトナム北部ナムディン県にあるハイハウ海岸とその背後地は地域の漁業，農業等を支える重要な沿岸域である．海岸の主要部（延長約30 km）では100年来に及ぶ数百メートル規模の広域的，長期的な侵食が進行している．一方，この海岸の北部と南部の河口域では堆積が今も進んでおり，紅河とその支流からは一定の土砂供給があると推定される．本研究では，現在見られている侵食のメカニズムを説明することを目的として，過去数百年の海岸の発達過程の分析とこれが長期間に亘る侵食に転じた原因を，文献調査，採取資料の年代測定，One-line modelによる数値的検討を通じて調べた．その結果，かつては同海岸の中央部に紅河の流路がありここを中心にデルタが発達してきたが，これが1787年の洪水による紅河の流路変更によりハイハウ海岸のある区間が長期的な侵食へと転じたことを明らかにした．