Just a suggestion, but why not use a mixed material on the forested terrain, mixed with the beach material? That way you could adjust how far the beach material extends into the forest material with either a distribution map or using the slope and altitude effects tab. Shouldn't be too difficult to achieve a more realistic transition between the two terrains. There's an ultra basic tutorial about mixing materials at my site that may give you some ideas on what you are trying to achieve in Vue. http://niandji.com/html/tutorials.html