広域海浜流の観測と定式化

Abstract

冬季日本海沿岸における現地観測より, 沿岸域の広範囲にわたり海上風と波浪の影響を受けた広域海浜流動場の形成が確認されており, 沿岸域の流動場および広域漂砂系を考える上において, 広域海浜流場の特性を把握することは重要である.本報では, 上越・大潟海岸の広範囲において実施された現地観測結果から荒天時に発達する流動場の状況を明らかにするとともに, 広域海浜流の沿岸方向流速の岸沖分布についての定式化を行ったものである.

In the Central Japan Sea, winter monsoon winds develop high waves together with strong wind-induced currents in the wide area of nearshore zone. The currents are the dominant external force of beach changes and coastal environment.Field observation has carried out in the wide area of Joetsu-Ogata coast from December 1998 to March 1999, and the structure of coastal current fields are investigated.It is obvious from the results that strong offshore-going currents are in the surf zone, such as undertow, as well as longshore currents in the wide area of nearshore region by wind.Additionally, a empirical equation of cross-shore velocity distribution oflongshore currents is shown, and it gives velocities of longshore currents at early stages of storm conditions.Stormy condition.