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Going south, you will usually fine more plains and praries that are flatter than the forested mountains you mostly encounter at spawn.
Check the config files and tweak some of the noise values. They are commented and should explain themselves.
It should be possible to add a meta-noise function - similar to the temperature control - that amplified or muted the noise factor over a large area... You could then travel east /west to travel into areas of more, or less, extreme terrain. I don't know if the author reads these forms (or even would entertain adding yet another noise function )