On Wednesday 04 April 2018, Warin wrote: > > So a 'beach' may include a 'tidal flat' ... confused.
I tried to explain the difference - a beach is primarily shaped by waves while a tidal flat is shaped by tidal currents. The domination of waves can usually be seen in the form of a smooth surface where structures (like waves in the slope) typically form parallel to the shore. Like here: https://commons.wikimedia.org/wiki/File:The_beach_11111.JPG On tidal flats OTOH the water flow often form small or large channels like here: https://commons.wikimedia.org/wiki/File:Waikaraka_Cycleway_from_Mangere_Bridge_IV.jpg Beaches can only form from relatively coarse material (sand or coarser) - fine silt cannot form beaches because it does not settle fast enough in the fast moving water so the beach would quickly erode away. Tidal flats can form both from fine silt and coarse sand. At coasts with a significant tidal range (like in the UK) there is often a beach in the upper part of the tidal range with a steeper slope and coarse sand and a tidal flat with less slope with either sand as well or finer material. Example: https://mc.bbbike.org/mc/?lon=-4.390229&lat=51.716636&zoom=14&num=3&mt0=bing-satellite&mt1=mapnik&mt2=google-satellite In the upper part this is clearly a beach (as visible in the Bing image with high water level). In the lower part with the tidal channels visible in the Google image it is clearly a tidal flat. -- Christoph Hormann http://www.imagico.de/ _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
