Does a cheat/mod exist where you can edit the neighborhood terrain levels without expansions?

In Strangetown, one of my non Maxis homes was made against a massive hill and now even when I move the lot to flat land it creates a huge cliff on the back side as if the hill were there too. I feel like an idiot.

You can flatten the lot edges using the LotAdjuster. You can use flat lots to "fix" the neighborhood terrain. Niol has a tutorial:
http://www.modthesims.info/showthread.php?t=103896

There is a cheat to adjust Neighborhood terrain, to see if you have it open the cheat window and type Help. You will be looking for ModifyNeighborhoodTerrain.

I should mention that the cheat can not be used to modify terrain with a lot on it.

RebaLynnTS, that cheat was included in Free Time and anything with a subsequent game engine. The OP is looking for such a cheat without expansion packs.