After doing some coding on a game of the same sort as Silversword I think I have found a way to make the map accessible to voiceover users.
As the game is already split into squares on a (x, y) grid, a table with rows and columns for corresponding axis of the grid could be made and as each new square is entered the corresponding cell in the table would hold text stating what was the: water, grass, wall etc. The idea isn't perfect but would increase the accessibility of the game.