Explain how flooding affects rivers and how flooding can be influenced by human activity.

A lot of things can affect rivers, like garbage, harmful chemicals, etc. When flooding happens in a poor country, the flood can pick up many things and it will go in any water resources. Many people rely on getting water in rivers and if their water get contaminated, people will not be able to use the river for water.   

Multiply the 3 dimensions, assuming it is a rectangular cuboid, to get the volume in cm³ divide mass by volume to get density in g/cm³