Hey tobspr, again some great work!
I tried to make such a program for months now, mine does still produce anything but the expected results. 
As I don’t know nearly enought about shaders to come up with something equivalent to your solution, I would like to expand your program into a fully functional terrain editor program.
Therefore, i have some Questions:
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which erosion model did you implement, is there a paper around that explains the underlying idea?
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Do you plan to do further work on this?
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I noticed that, altought calculation is done using floats, most images use an integer format. What advantages does this have?
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is your LUI system meant to replace DirectGui? When should I use which of them?
thanks in advance