Small waterways, large waterways

Small waterways are called as stream (Chon) and large waterway as river (Gang) in Korean. Jungrang-Chon in the upper Seoul area flows to the larger waterway, Han River. Onchon-Chon in Busan also flows to the larger waterway, Suyoung River. The biggest river is called as Ha, which is only used in China, Hwang-Ha (the Yellow River). However, such all the waterways are generally called as rivers (Hachon).

What is river?

River is a natural waterway where water flows to the lower place gathering rains in a catchment basin. Rivers not only make water flow but also bring soil and contaminants downward.
If it rains in mountainous areas, river water flows quickly along valleys. In this case, high velocity results in the V-shaped valley under strong force, which is called as erosion. Erosion tends to occur when the flow rate of water gets bigger in amount due to heavy rain and the flow velocity is higher under a steep gradient condition of the river bottom. Soil particles eroded are passed to the downstream mixed with the water, is called transportation. Light soil particles are flowed downward floating on the surface of water, but heavy soil particles are transported by rolling on the riverbed. These eroded soil particles change the color of river water to red during the heavy rain period.
Heavy sediments are accumulated on river floor due to losing the energy of flowing downward when they meet flat river bed. This phenomenon is called sedimentation. The fertile land made due to deposit of the sediment flowing from mountain areas is called alluvial fan. Sediment soils are accumulated also on estuary between river mouth and sea, which is called delta.

Delta