Ground Textures Help!

[JSF72]

Hi guys!, Im trying to make a scenery but as you can see in the following picture, the costline is very diferent in FS9 than in real life, how can I change the shape of the costline?
I might have to add ground texture over where is now water and create some river over the land...
what programs should I use?
Thanks.

[Kaworu]

ALL of the coastlines in FS9 are terribly inaccurate. I think you can use the Terrain SDK to modify the bgl files.