What approaches are there to blending multiple terrain types? [duplicate]

So for my university final assignment I’m doing a procedural world generator in unity. The idea is that different types of terrain are generated such as ocean, swamp, hills etc. I have the different biomes generating as chunks with different colours at the moment and the next step for me is to smoothly transition between them rather than drop off from one terrain type to another.

To do this I’m going to need to adjust the heightmap so that the edges join together rather than having gaps between them. The noise is continuous so biomes of the same type connect seamlessly. However with different biomes the height generated from any given noise is different, that way my mountains stick up without my ocean chunks being weird shapes. The result is like I said earlier, there are seams between my chunks that I need to stitch.

So my real question is what approaches are there currently to blend from one height map to another?