Terrain Toolkit

I have created the snowy environment for my level by adding an asset to the project called the 'Terrain Toolkit.' This was used to randomly generate the environment, such as hills, the link for this download is below:

https://code.google.com/p/unityterraintoolkit/downloads/detail?name=Terrain%20Toolkit%201.0.2.zip&can=2&q=

Once downloaded you simply drag the folder into the assets folder of your unity project.
You then add the terrain toolkit component to your terrain.

Here you can see the terrain toolkit component to the right of the screen.