バーの段数と後浜上限高度との関係

スポンサーリンク

概要

• 論文の詳細を見る

• The backshore is the zone acted on only by the swash during storms. The position of the landward limit of the backshore is given by the base of the sea cliff, the seaward end of coastal dunes, or the seaward limit of vegetation colonization which coincides with the uprush limit of storm waves. Since the swash runup height is directly proportional to the shore break height, the height of the landward limit of the backshore, B_H, should be related to the shore break height in storms. Using data obtained from the Ishikawa coast of Japan, the present study investigated B_H in connection with the number of nearshore bars, N. The analysis indicates that B_H decreases abruptly with increasing N, starting from B_H = 9.4 m at N= 0, and tends to approach 2 m at N= 4. The shore break height is not only controlled by the offshore wave height, but is also affected by nearshore bottom morphologies. When a nearshore bar exists in the surfzone, storm waves break on its seaward slope and broken waves advance shoreward as bores, dissipating their energy by viscous damping and bottom friction, and the height of waves landward of the bar is reduced. The bar produces a wave-filtering effect by acting as a submerged breakwater. Since all series of nearshore bars work as submerged breakwaters during storms, the sum of the wave-filtering efficiency increases with increasing the number of nearshore bars. Consequently, B_H should decrease as N increases. Wave height in very shallow water regions is a depth-controlled quantity The shore break height, which depends on the height of waves reaching the shore, is also influenced by the water depth at the shore. Wave set-up, a water level rise in the surf zone, comes to be a major controlling factor in the shore break height for multiple bar beaches. Since the rate of set-up is proportional to offshore wave height, the maximum shore break height is restricted to a certain quantity independent of the number of nearshore bars on multiple-bar beaches. For this reason, B_H gradually approaches to a certain height as the number of nearshore bars increases.

• 2003-10-25

著者

• 武田 一郎

  京都教育大学地理学教室

• 武田 一郎

  京都教育大学

関連論文

• わが国における沿岸砂州段数の地域的差異 : 砂州の砕波起源仮説に基づく解析
• 日本沿岸における礫質砂州の離水量
• 「伏見」を歩く・調べる・紹介する : 第10回ふれあい伏見フェスタ・「歩いて再発見!伏見の魅力」の記録
• 地域研究に長けた人材を育てるための授業の試み : 地理学・社会学・地域環境学のインテグレイト
• 地理学教室あんない--国公立大学編-26-京都教育大学(教育学部)
• バーの段数と後浜上限高度との関係
• 海岸で野外活動を指導する際の安全面に関する留意点 : 地形学の観点から
• 非外洋性海浜における後浜上限高度
• 北海道オホーツク海沿岸および鹿児島県吹上浜における後浜上限高度
• 日本海沿岸における後浜上限高度(堆積過程に対応した地層解読をめざして)
• 茨城県那珂海岸における後浜上限の位置と高度
• 3.水とかかわる地域を学ぶ(2) : 宇治川・水害学習の実践記録
• 2.水とかかわる地域を学ぶ(1) : 宇治川・水害学習の実践記録
• 砂州地形に関する用語と湾口砂州の形成プロセス
• ビーチ・ステップの基部水深
• 一段バー海岸と二段バー海岸の侵食条件の比較
• バー海浜およびバーなし海浜のバーム高度

もっと見る 閉じる

スポンサーリンク