鹿島灘南端部の汀線変動の特徴  [in Japanese] STUDY ON SHORELINE VARIABILITIES OBSERVED AT THE SOUTHERN END OF KASHIMANADA COAST  [in Japanese]

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Abstract

鹿島灘南部(鹿島港-波崎漁港,延長約17 km)の南端部の約4 kmの範囲の汀線変動をXバンドレーダにより6年間(2009年12月-2015年11月)にわたり観測した.Xバンドレーダの観測結果より平均画像を作成し,汀線位置をおおよそ2日間隔で読み取った.対象域の南端には波崎漁港があり防波堤が沖合約1kmまで延びている.また,侵食対策として複数のヘッドランド,突堤が設置されている.ヘッドランドと突堤を境界とする4区間毎に観測結果を分析した.各区間の平均的な汀線位置は観測期間中,継続的に前進していた.各区間の汀線が延びる方向(汀線勾配)を求めた.漁港から離れた区画では,入射波浪の季節的な変動に応じたサイクリックな汀線位置の前進・後退と汀線勾配の変動が見られた.一方,漁港直近の区画の汀線変動は異なる様相を示し,いわゆる港湾の防波堤が砂を呼び込むという表現で説明される堆積過程が見られた.

 Variation of shoreline position at the southern end of 17 km-long Kashima Coast, with Kashima Port at the north end and Hasaki Fishery Port at the southern end, has been observed with a X-band radar for 6 years. The radar captures hourly distribution of shoreline position approximately over 4 km. At the southern end, there is a 1 km long breakwater of the fishery port, which shelters southern incident waves. Further, the sandy beach is protected by headlands and a jetty from erosion. Shoreline positions of approximately every 2 days have been digitized from the radar images. Mean shoreline positions and shoreline inclinations of 4 sections bordered with headlands and jetty have been analyzed. Mean shoreline positions of all sections migrated seawards continuously during the observation period. At the farthest section from the fishery port, shoreline inclination showed a seasonal variation accordant with the wave incidence direction: sand between headlands is transported to the downwave resulting periodic changes in shoreline inclination. On the other hand, shoreline inclination close to the fishery port varied in a different manner due to sheltering effect of breakwater.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 73(2), I_679-I_684, 2017

    Japan Society of Civil Engineers

Codes

  • NII Article ID (NAID)
    130006171958
  • NII NACSIS-CAT ID (NCID)
    AA12508551
  • Text Lang
    JPN
  • Article Type
    journal article
  • ISSN
    1884-2399
  • NDL Article ID
    028751634
  • NDL Call No.
    YH267-236
  • Data Source
    NDL  IR  J-STAGE 
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