When you open the map, a winding blue line between the land and the ocean comes into view. That is the coastline that marks the location of the coast. In fact, from the perspective of marine geography, the coast is not a line, but a transition zone between land and ocean. It is also a zone where land and ocean interact. People call this zone a coastal zone.
coastal zone landform
The range of the coastal zone generally takes the place where the storm surge or extremely high tide can affect as its landward boundary. It takes the depth at which waves begin to act on the seabed under normal weather conditions (wave base), which is equivalent to 1/2 wavelength of water depth., as its seaward boundary, its depth is usually 10 to 20 meters. According to the characteristics of land-sea interactions and differences in ecological environments, the coastal zone can be divided into three different zones, namely, suprantidal zone, intertidal zone and subtidal zone.
The suprantidal zone is between the upper limit of storm surges or super high tides and the average spring high tides line. It is exposed to the surface most of the time and is only affected by seawater during storm surges or super high tides. Vast coastal swamps are often distributed on muddy coasts; landforms such as sea cliffs, coastal sand dunes and coastal sand bars are generally seen on sandy coasts.
The intertidal zone is between the average spring tide line and the average spring tide line, and is a zone where seawater is periodically submerged and withdrawn. The intertidal zone of a muddy coast is generally called a tidal flat, or tidal flat. The beach is wide and the slope is gentle. The width of the tidal flat can reach several kilometers, or even exceed 10 kilometers. Tidal gullies are common on tidal flats, where many organisms are inhabited; sandy coasts have large beach slopes, and the beach width is between tens of meters and hundreds of meters. Low and gentle beach ridge terrain is common on the beach surface.
The subtidal zone lies between the mean spring tide line and the depth of water at which waves begin to act on the seabed. Because it is basically under the sea water, it is also called an underwater bank slope. In the depths of the water where waves touch the seabed, or in the seabed where wave breaking zones, underwater sand bars and trough valleys are often formed parallel to the coast.
Since the coastal zone is a zone where the lithosphere, hydrosphere, atmosphere and biosphere meet, its ecological environment is very complex, involving deltas, estuaries, bays, lagoons, beaches, coastal dunes, coastal wetlands, coral reefs, mangroves and Inshore waters have various types of natural geographical environments and unique ecosystems. The coastal zone is also the area with the most frequent human activities. Unreasonable development activities, coupled with global climate change and sea level rise, will lead to increased coastal erosion and the loss of coastal wetlands, making the ecological environment of the coastal zone very fragile. Therefore, it is particularly important to strengthen comprehensive coastal zone management and protect the ecological environment of coastal zones.