Nearshore current

Japanese: 海浜流 - かいひんりゅう（英語表記）nearshore current

A current that occurs near the coastline as a direct result of waves near the coast. It has been attracting attention since ancient times because it is closely linked to the movement of drift sand that causes coastal erosion and deposition. When waves approach the coast, mass transport occurs as the waves advance, along the coast as they approach the coast and break (→ longshore current), and rip currents flow offshore in a narrow, concentrated manner are all called longshore currents or longshore current systems. Rip currents occur on the coast at approximately regular intervals (several tens to 300 meters). The flow speed of longshore currents can change depending on the state of the waves, but in large places they can reach 1 m/s, making them dangerous places for swimming. Longshore currents are thought to be related to the formation of cusps (triangular piles of sand at the edge of a sandy beach) that are often seen on the coast. If the characteristics of waves change due to the construction of breakwaters or port facilities, sand can move locally, causing erosion and deposition.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

海岸付近での波浪が直接の原因となって海岸線の近くに起こる流れ。海岸の浸食や堆積をもたらす漂砂の動きと密接に結びついていたので，古くから注目されてきた。波が海岸に近づくとき，波の進行によって生じる質量輸送，さらに近づいて砕波して生じる岸沿いの並岸流（→沿岸流），幅狭く集中的に沖向きに流れる離岸流（リップカレント）を含めて海浜流もしくは海浜流系という。海岸には離岸流がほぼ一定の間隔（数十～300m程度）で並んで生じている。海浜流の流速は波の状態によって変わりうるが，大きいところでは 1m/sにも達し，海水浴には危険な場所とされる。海岸によく見られるカスプ（砂浜の波打ちぎわに見られる三角形の砂礫の高まり）の形成に海浜流が関係していると考えられる。防波堤や港湾施設の構築により波浪の特性が変わったりすると局所的に砂の移動が起こり，浸食や堆積をもたらすことがある。

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