Why is it important for a stream to access its floodplain?

Floodplains are hydrologically important, environmentally sensitive and ecologically productive areas that perform many natural functions. Streams that can meander and access floodplains are part of a riparian system that can store water, sediment, nutrients, and woody debris and convey water during flood events.

How do streams that flow on floodplains move?

Most rocks and minerals are much denser than water. Several factors cause a stream to slow down, including the stream channel widening, the stream overflowing its banks and spreading into a floodplain, the stream gradient (downhill slope) diminishing, and the stream emptying into a larger, slower moving body of water.

Why are higher order streams more flood prone?

As more and more tributaries join together a larger stream network is formed and the master stream, the highest order stream in the system has a discharge that is the sum of all the tributary discharges. When flooding occurs, higher order streams take longer to build up to flood stage than lower order streams and longer for the flood to subside.

What kind of sediments are found in floodplains?

Floodplains are filled with sediments spread by the stream. These sediments are known as alluvium. Because alluvium is loose material that is easy for the stream to erode and redeposit, the location of a stream channel in a floodplain changes frequently.

What happens to the growth rate of a floodplain?

The floodplain surface, therefore, is inundated less frequently, and the growth rate necessarily decreases. Indeed, studies have shown that the initial phase of floodplain elevation by vertical accretion is quite rapid because flooding occurs frequently.

How long does it take for a river to move across a floodplain?

For example, if a floodplain is one kilometre wide and the river shifts laterally at a rate of two metres a year, it will take approximately 500 years for the river to migrate completely across the valley bottom.