Perhaps you could try a multi-resolution chunk system - LoD for chunks. For large scale features like rivers, generate those at coarse resolution on very large

Perhaps you could try a multi-resolution chunk system - LoD for chunks. For large scale features like rivers, generate those at coarse resolution on very large chunks. When generating the detailed chunks, take input from the coarser resolution levels which overlap the same spatial region, and add fine scale detail. A couple of levels of detail might suffice in practice, but if you want to go crazy you can more or less make as many as you like: As long as each level is downscaled by at least some constant factor of the more detailed level below it, you'll only have O(log(N)) overhead for O(N) chunks which is small even for very large N. Compare mipmapping, which is more or less the opposite of this process.