Help needed about map making.

[rich2005]

It should work as Blighty describes

Using the more up-to-date Gimp 2.8 single window mode interface. Gimp menu -> Windows -> Single-Window Mode

Summary: You made your well blurred land mass (1) Added noise with layer mode Overlay (2)

Now you have to add a white layer, You can add a layer and fill with white or add it straight as white.
Give it a name while there (3)



Put that layer into Lighten only mode (4)
then Colors -> Levels and draw the Output Levels slider to the left (5)



Gives this (6) for the next step (whatever that may be)