天竜川河口砂州の浸食パターンと規模に関する研究  [in Japanese] FLUSHING PROCESSES OF RIVER SAND BAR OBSERVED WITH X-BAND RADAR AT RIVER TENRYU  [in Japanese]

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Abstract

天竜川の河口砂州は,出水・高波浪時に浸食され,その後回復するサイクルを繰り返している.河口砂州は,出水時には流水の疎通を妨げ河川水位を上昇させる一因となるが,一方では高波浪・塩水の侵入を防ぐ機能があり,河川管理者はその挙動を理解・予測できれば河川流水のより高度な管理が可能になる.ここでは,Xバンドレーダにより河口周辺の地形を複数年間にわたり継続的に観測した結果を分析し,出水と波浪の作用に伴う河口砂州の浸食パターンと規模と頻度,河口砂州の存在位置の変遷を説明し,短期的,中長期的な河川管理に資する情報を示す.

 River sand bar may become a barrier of smooth release of flood flow from the river channel into the sea until it is flushed. On the other hand, it prevents intrusion of sea water and transmission of high waves in to the channel. If flushing and recovery processes of the river sand bar are understood well, a sophisticated river management can be achieved. In this context, this study examines river sand bar flushing processes from eight years observation with X-band radar at the River Tenryu. 23 flushings of the river sand bar was analyzed and categorized into three patterns: (1) washed by the flood flow, (2) eroded by high waves, and (3) by the combination of flow and waves. The width of the river mouth before the flood is and important factor that determines the magnitude and pattern of the river sand bar flushing. Flushing and widening of the river mouth of 100 m or larger can be expected by flood of approximately 3 years return period. Further, the location of the river sand bar during the observation period was tracked: the mean location of the river sand bar migrated gradually and intermittently to the river side. During the migrations, erosion at the sea side of the river sand bar was observed frequently, while the area of itself increased slightly.

Journal

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

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 72(2), I_721-I_726, 2016

    Japan Society of Civil Engineers

Codes

  • NII Article ID (NAID)
    130005282479
  • Text Lang
    JPN
  • ISSN
    1884-2399
  • NDL Article ID
    027809881
  • NDL Call No.
    YH267-236
  • Data Source
    NDL  J-STAGE 
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