Coal Deposits should be found more often below River biomes.

Coal is a sedimentary rock. In real life, most areas which have water (rivers, lakes) have sedimentary deposits.

I propose that in river biomes, coal should generate more commonly. This ties into the strategy which the developers are aiming for with this update. Need coal? - Find a river biome and dig down and there you go! more coal than you would usually get from normal biomes.

I know coal isn't THAT desirable of a resource to get, but this would add onto the strategy pillar that the devs are working with the caves & cliffs update.