How to create more organic heightmaps?

Following a couple of tutorials on procedural generation I have coded a small project which creates a large piece of 2.5D terrain (divived into smaller chunks for performance) based on a perlin noise heightmap, and so far results look ok.



However, since the map is generated from a noise map it lacks the organic quality of real terrain with it's river beds and mountain ridges, so I am looking for suggestions on how to add this extra bit of credibility to my heightmaps.

(since this is a topic revolving around Texture2D usage I thought it would fit best in the Graphics forum)

 

It's a complex subject, most people stop at perlin noise in tutorial, in reality it ask you to master many techniques and understand the core of the techniques to do what you want. You won't find explicit answer to your question, it depend on a lot of factor. For example are the terrain infinite? Do you need just on time generation, do the generation need "locality" (ie don't depend on long dependencies relation), can raster gradient from primitive? etc ...

This is a good overview of perlin base only terrain.