Another example of how human and physical processes can interact...... RIVER FLOODING...

As you looked at the geography of festivals, you would have noticed how both human and physical processes can interact to cause problems!

When both these processes interact in relation to rivers, there can be devestating effects.

Human processes, such as deforestation can cause a physical process such as flooding. Leaves on trees reduce raindrop impact, and the gentler rain causes less erosion meaning less sedimentation in rivers. Tree roots absorb water from the soil, making the soil drier and able to store more rainwater, decreasing surface runoff, and tree roots hold the soil in place, reducing the movement of sediment that can shrink river channels downstream. When trees are chopped down, and logging takes place, precipitation is no longer intercepted by trees, and therefore has a much faster run off into rivers. The lack of trees can also cause a higher amount of sedimentation in rivers as the run off into the rivers erodes sediment once compacted by vegetation.

This picture shows the devastating effects flooding can have on a community:

Another example of when human processes can seriously affect physical processes is the use of flood plains for building houses.

The construction of homes on the flood plain increases the risk of flooding as the concrete and tarmac used for homes is impermeable for precipitation, and man made drainage systems often fail to cope with high amounts of rain in small amounts of time. Insurance policies for homes built on the flood plain are much more expensive than national averages for other homes; which emphasises the risk of building and buying homes on flood plains.

The pictures below show a site built on a flood plain, and what could happen....

In this picture a new housing construction site has been located very near the river bank. On the opposite side is a railway track; but what has been done to prevent flooding of this transport link?

This plan shows the events that could occur if flooding was to take place. If you were to plan a building site, where would you definitely not build your housing estate, why? Where would you plan to build, and why?

Have a think about any instances where you have seen human processes interacting with physical processes, in a negative, but also in a positive way.