The slope of the beach can also affect this current. Once established, the current moves at a speed of about one knot in the same direction as the advancing wave train. Longshore currents are more prevalent along lengthy straight coastlines. Sandbars often form in areas where longshore currents frequently occur. Rip currents are formed when longshore currents, moving parallel to the coastline, are deflected seaward by bottom irregularities, or meet another current deflecting the flow seaward.
Development depends upon wave conditions.
Tides Tides are the slow, periodic rise and fall of the sea surface. They are usually described as being either diurnal or semi-diurnal. Tidal ranges along the shoreline vary by location. For example, the tides in Canada's Bay of Fundy, an Atlantic Ocean inlet west of Nova Scotia, rise and fall as much as 50 feet, while the tidal ranges in Lake Superior, Mich., is measured in inches. The rise and fall of the tide is accompanied by the horizontal flow of water called a tidal current.