It would be nice to be able to specify the biomes to use when the terrain generator adds rivers. For example, having a biome called "PlainsRiver" that would be used when a river passes through a section of Plains. A setting could be added to the WorldConfig called "RiverBiomes" where the map maker could add a list of all their custom river biomes, and then a setting could be added to BiomeConfigs called "BiomeIsRiver" which would specify which biomes the current biome would be a river in.

The practical uses of this new functionality include - the abiltiy to adjust river height to match biome height, the ability to fine-tune resource and BO2 spawning in a section of river, and the ability to easily change the "content" of a river from water to lava or some other material.

Also related, it would be nice if there was a way to stop rivers from flowing along biome borders and instead flow directly through biomes instead. I've seen a number of instances where rivers would flow between a biome (such as plains) and a nearby border biome (such as beach serving as the border for an ocean biome) and it ends up looking strange.

Good things. And i think we may do it.

@Wickth implemented it - see 0c4e5c3. 😃