Answer:

When rain falls, the surface runoff can move very quickly from mountainous or hilly areas to low lying areas making these low lying areas more prone to flooding.

How can low lying areas prevent floods?

For a quick method of flood protection, consider an inflatable cofferdam like the Aqua-Barrier. This balloon-like dam fills with water and creates an airtight seal along the ground to keep up to 5 feet of water at bay. Once the floodwaters drain, simply deflate the cofferdam and store it out of the way.