See Team-RTG/Realistic-Terrain-Generation#352 for details.

Basically, streams are generating way outside the expected generation area, to the left of the map, when negative seeds are used.

i ve found a similar issue with RTG and Streams.

http://i.imgur.com/EWNZeKD.png
http://i.imgur.com/FagFsNX.png

we think it might be a pregen issue, but other areas of the map are like this which were generated correctly.

Reported fixed on the RTG side.