For contrast with the young earth view.
My short response: he may not think the evidences presented are proof postive of a global flood, but they are consistent with that hypothesis. Much geologic data is equivocal, and can be used to support multiple hypotheses.
However, there are data presented in AiG's ongoing series on evidences for a young earth that are much less equivocal, especially the presence of C-14 and soft tissues in fossils presumed tens to hundreds of millions of years old by radioactive dating measures.
(The humorous image above is from the Geochristian's author information page: http://geochristian.wordpress.com/more-about-the-author/)