Create a different Portfolio
You can create as many portfolio as you like. To achieve that go to Appearance > Theme Options > Portfolio Generator, there you can create the new portfolio.
But then you have to duplicate this file from the original portfolio in the theme's folder:
That's to duplicate all the functionality from the original portfolio to the new one.
For example if your new portfolio is called "landscapes", then you have to rename the duplicated file to this:
And that's it.