You cant and wont IMHO. Take a look at Swatsnipes enviros...hard yakka and lots of work. As a Surveyor...I map these things and they are not easy to replicate, hence my intense interest on what Swatsnipe does. DEM....or DTM in my lingo are great BUT they have a resolution limit. You CANNOT get a great res from the sky...I dont care what anyone tells you...you CANT. The best DTM I have EVER had from any design consultant was a 0.3m on a flat plane surface. This was achieved with aerial photography etc etc .

IF you want realism...its going to hurt. ALL rivers have fall etc towards a lower point...getting that right is a bitch. Personally I could show you the math but you probably already know it. Then you would have to use something like Realflow I suppose to make it work.

I have asked this question...I since stopped. This is not easy and will be very hard to do and complete. Once you add liquid to the equation, things change dramatically. Most people use an ocean shader etc...try a dynamic sim of a river...mate good luck. Im not being critical in any way...but if you pull this off I want to come and buy you a beer.

Lanscapes are easy...I build them....liquid? apart from the Rum I drink...simulation on an active hardscape is hard.

Cheers bullet