Shore Buddies Wisdom Wednesday 12/16/2020
A sandbar, or shoal is a long and narrow (linear) landform which is in or partly in a body of water. Usually it is made of sand, silt, and/or small pebbles. The swirling turbulence of waves breaking off a beach excavates a trough in the sandy bottom. Some of this sand is carried forward onto the beach and the rest is deposited on the offshore flank of the trough. Sand suspended in the backwash and in rip currents adds to the bar, as does some sand moving shoreward from deeper water. The bar’s top is kept below still-water (half-wave height) level by the plunge of the waves breaking over it. Barrier bars or beaches are exposed sandbars that may have formed during the period of high-water level of a storm or during the high-tide season. During a period of lower mean sea level they become emergent and are built up by swash and wind-carried sand; this causes them to remain exposed. Barrier bars are separated from beaches by shallow lagoons and cut the beach off from the open sea. Since prehistoric times humans have chosen some sand bars as a site of habitation. In some early cases the locations provided easy access to exploit marine resources. In modern times these sites are sometimes chosen for the water amenity or view, but many such locations are prone to storm damage.