What is River?
Rivers are defined as a wide, natural stream of freshwater that flows into an ocean or other large body of water and is usually fed by smaller streams, called tributaries that enter it along its course. Rivers, the flowing bodies of water are dynamic and constantly change according to the water flow. Some of the changes are to do with space or location along a river - these changes are spatial. Some of the changes are to do with time, especially the season of the year – these changes are temporal. Some changes happen suddenly, others happen much more gradually. Some changes are caused by human.
Rivers generally start at a source, a point which will flow through downhill slope into a larger body of water, like an ocean, sea, or large lake. Gravity plays an important role in directing rivers pathway of flow. Thus, the point of origin for rivers placed at the highest point in the watercourse. It’s also known as the watershed, area of land from which runoff drains.
Rainfall or precipitation usually brings water in large amount which forms rivers on the highlands. When a heavy rain falls on the ground with steeply sloped or is already saturated with water, water runoff piled up down Earth’s surface rather than being absorbed by the soil. At the beginning, the water runs in narrow path called surface runoff.
After traveling for a while, the running water continued to flow into rills, the small parallel rivulets. As the rills pass over fine soil or silt, they begin to create shallow channels which soon will merge to form a stream. The stream is permanent whereby there is continuously flowing body of water, the brook. Finally the rivers formed when the brooks flow along with groundwater supplies add to the amount of water in carries.
Most rivers end at large body of water called the mouth. At the mouth, there is usually a river delta, a large, silty area where the river splits into many different slow-flowing channels that have muddy banks. River and its tributaries form a drainage basin, or watershed, that collects the runoff throughout the region and channels it along with eroded sediments toward the river. The sediments are typically deposited most heavily along the river's lower course, forming floodplains along its banks and a delta at its mouth.
Rivers change the landscape through which they flow. They alter it by erosion, transportation and deposition. Erosion happens when the moving water in a river erodes or removes material such as rocks, soil, vegetation from the bed and banks of the river. The eroded materials where then transported downstream. This process is called transportation. When the flow of the water is too slow as the water moves towards the downstream, the materials transported will be deposited or dropped. This is known as deposition process and the deposited material is called sediment.