The event in the picture above is a process that occurred at the Sub Aerial Deposition Coast, which is the process of forming a delta. Delta is a fluviomarin geomorphological phenomenon in the form of deposition of terrestrial sediment material that is transported by streams and deposited along river mouths that enter lakes or the sea. Delta occurs when the flow velocity in the estuary is minimal, the amount of material transported is large but not disturbed by wave activity, the water in the estuary is calm and the river bed is sloping, and there is also no tectonic and volcanic disturbance.
Delta forming factors include the characteristics of the stern land and the characteristics of the receiving basin. The characteristics of stern land include watershed characteristics and climate regimes, while recipient basin characteristics such as coastal and bathymetry processes. Generally deltas form in wet tropical climates with thick vegetation. In the territory of Indonesia, an example of delta formation is at the mouth of the Mahakam river as shown above. In the Mahakam delta, the deltanya type is Elongated or bird’s foot. The shape of the delta with this type is characterized by elongated shapes such as bird legs, formed in areas with abundant alluvium, and the influence of rivers is greater than the effects of waves and tides.
The process of delta formation which results in material deposition in the mouth can bring benefits to the coastal area. Material that is deposited if it is a potential material such as the Mahakam delta which has the potential of coal will bring good and bad impacts. The good impact is certainly on the economic improvement of the area. Adverse effects if overexploited. In addition, the delta is a place to grow and develop mangrove vegetation. Mangroves themselves are very useful vegetation for coastal areas, such as to maintain a stable coastline, protect beaches and cliffs from erosion or abrasion, and hold strong wind from sea to land, retain sediment until new land forms and also as a buffer zone intrusion process or seawater seepage to land.