Texturing large terrain

I already asked a smiler question a couple of month back when I wanted to texture a large building floor,and the solution was using generated(repeated) mapping.
But now I am texturing a large terrain (about 300x300 meters) and am running in a number problems:(
My main problem is making it high resolution. Since terrains normally don’t have just one texture but rather at least 10 textures or more.So I obviously can’t use generated mapping but I also can’t use a UV mapped image because it would have way to little detail(the terrain should be some what photo realistic).

Here is a the terrain (its not final yet as I don’t want to put in hard work if I don’t know how to texture it).It is going to be a real rocky environment with a small river.
So if any one could help me with a tutorial link or could tell me how to it,it would make my day:)!
Thank in advance.

I downloaded the .blend file but unfortunately the textures are not working because the source image/texture is not in the download.
But I learned how to make particle objects from the blend file:)…So even though It did not help with the original problem I had,it will help me in the future:)
So Great thanks any ways!