ADCP observation of nearshore current and suspended load profile

在面向日本海的日本沿海地区，由于海上沉积物运输造成的海滩侵蚀是一个严重的问题。目前尚不清楚近海泥沙输运的机理。本研究的主要目的是利用t型观测墩（TOP）的ADCP观测，揭示新泻绪泻海岸冲浪区的近岸水流结构。县。从观测结果中，我们估计出的流速特征为：(1)速度剖面：在斜风斜浪的作用下，近岸流变强，近岸流强度变弱，形成类似海底流的速度剖面。在波谷水平以下，近岸流和近海流的速度分布几乎是均匀的。(2)岸流：斜向风和波浪在冲浪区产生强烈而均匀的岸流。它的方向很好地响应风向的变化，例如西风激发东岸流，反之亦然。(3)近海海流：几乎所有海浪以下的海流都直接在近海的冲浪区。当风向和浪向为W（西）-> NW（岸-正）->N（东）时，该海岸典型的风演化模式，在岸-正风阶段观察到强烈的近海气流。(4)冲浪区附近风阻系数：采用紊流耗散法（紊流耗散法，TDM）推导出包括破波在内的极浅高波条件下的风阻系数，如图3所示。当U(10m)> 10m/s时，拟合曲线isCd=0.0223 exp(10/3)**(-U/15)。(5)浊度浓度与ADCP回波强度：分析中。

Beach erosion due to offshore-going sediment transport is a serious problem in Japan's coasts facing the Japan Sea. It has hot yet been made clear the mechanism of sediment transport offshore. The main aim of this study is to unveil the nearshore current structure in the surf zone by ADCP observation with the T-shaped Observation Pier(TOP), on the Ogata Coast, Niigata. Prefecture.From the observation, we estimated current characteristics as :(1) Velicity Profile : When the longshore currents become strong due to oblique winds and waves, intensity of the offshore currents becomes weak with undertow-like velocity profile are formed. Velocity profiles of both longshore and offshore currents are almost uniform below the wave trough level.(2) Longshore Currents : Strong and uniform longshore currents are generated in the surf zone by oblique winds and waves. Its direction well responds to changes in wind direction, ex. westerly wind excites east word longshore currents and vice versa.(3) Off-Shore Currents : Almost all current below the wave trough direct offshore in the surf zone. When wind and wave direction changed, W(westward) -> NW(shore-normal) ->N (eastward), the typical wind evolution pattern in this coast, strong offshore currents are observed in the shore-normal wind phase.(4) Wind Drag Coefficient near the surf zone : Wind drag coefficient near extremely shallow and high wave condition including wave breaking is derived by using Turbulent Dissipation Method (TDM), as shown in Fig.3. The fitting curve isCd=0.0223 exp(10/3)**(-U/15) when U(10m)> 10m/s.(5) Turbidity concentration vs Echo intensity of ADCP : under analyzing.