Flowing over ground as runoff or underground as groundwater, water finds its way to a stream and then eventually to the sea. Why do rivers continue to flow, even when little or no rain has fallen? Much of the water feeding a stream runs slowly underground through shallow aquifers.

In a natural, wild river, the water runs freely. But in more developed or degraded rivers, dams and other structures can slow or stop a river’s flow. When a river’s flow is blocked, migratory fish like salmon can suffer, unable to move up or downstream.

Low flow in our streams and rivers occurs during summer months when there is less rain and warmer temperatures and the snow-pack has been depleted through spring melt. On this page: About Stream Flow.

The velocity of a river is determined by many factors, including the shape of its channel, the gradient of the slope that the river moves along, the volume of water that the river carries and the amount of friction caused by rough edges within the riverbed.

Here is a list of five longest rivers of the world

• Nile River: The longest river in the world.
• Amazon River: Second longest and the largest by water flow.
• Yangtze River: The longest river in Asia.
• Mississippi-Missouri.
• Yenisei.

What three factors affect how fast a river flows and how much sediment it can erode? A river’s slope, volume of flow, and the shape of its streambed.

At 6,275 kilometers (3,902 miles) the Mississippi-Missouri-Jefferson River system is the fourth longest in the world and the longest river in the United States.

Flood Erosion and Deposition: As flood waters rise, the slope of the stream as it flows to its base level (e.g., the ocean or a lake) increases. Also, as stream depth increases, the hydraulic radius increases thereby making the stream more free flowing. Both of these factors lead to an increase in stream velocity.

The two main sources of the sediment carried by the streams and rivers are from the mass movement and runoff.

Deltas, river banks, and the bottom of waterfalls are common areas where sediment accumulates. Glaciers can freeze sediment and then deposit it elsewhere as the ice carves its way through the landscape or melts.

The two main flow factors in sediment transport are the settling rate and the boundary layer shear stress 27.

The general term used to refer to the force that moves sediment is erosion. This erosion is described as the removal and transportation of sediment. Sediment varies drastically in size, and can be as small as a grain of sand or as large as a boulder.

Sediments are also classified by origin. There are four types: lithogenous, hydrogenous, biogenous and cosmogenous. Lithogenous sediments come from land via rivers, ice, wind and other processes. Biogenous sediments come from organisms like plankton when their exoskeletons break down.

There are three types of sediment, and therefore, sedimentary rocks: clastic, biogenic, and chemical, and we differentiate the three based on the fragments that come together to form them.

Weathering is often divided into the processes of mechanical weathering and chemical weathering. Biological weathering, in which living or once-living organisms contribute to weathering, can be a part of both processes. Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble.

Weathering erodes and breaks apart minerals and rocks.

• Cracking and Breaking. ••• Mechanical weathering physically breaks down rocks because of environmental factors that include heat, cold, water and wind.
• Altering Mineral Structure. •••
• Changing Chemical Composition. •••
• Resistance to Weathering. •••

Chemical weathering is when the rock is chemically broken down. Some common examples of this are rust forming on granite or acid rain breaking down limestone. This type of weathering is not considered a type of stress because there is no pressure on the rock (remember that stress is pressure applied to an area).