It's probably about obsession. Obsession keeps the narrator from being able to erase this woman from his mind, even though he let her go because he didn't trust her. He decides all she was really after was being with him, and what he's saying in this song is that he will make sure she doesn't erase him either by writing more songs for her. The entire album can be interpreted to match with this idea, or with the threat of flooding, etc., but this song really doesn't work well with any other type of interpretation. It's very clear.
It's probably about obsession. Obsession keeps the narrator from being able to erase this woman from his mind, even though he let her go because he didn't trust her. He decides all she was really after was being with him, and what he's saying in this song is that he will make sure she doesn't erase him either by writing more songs for her. The entire album can be interpreted to match with this idea, or with the threat of flooding, etc., but this song really doesn't work well with any other type of interpretation. It's very clear.