I'm with Karro and Jykke, my rather amateurish experience has been that these lakes are either above or below sea level and that water would either rush in or out and open up a channel to the sea which then widens through tidal action. I have been quite skeptical that through noise alone can you model the coast line. As a first pass its fine but I think you either need to work on it with some gray matter guesswork or some math simulation of water flow from rivers or the sea. It would be interesting to see some satellite photos of some areas that have pics from about the 1970's through to present and to see an animation of them showing how its changing. Although I doubt that the movement would be all that much it might be just enough to see the underlying trends and model them.