This information is available to the moderators at http://travel.stackexchange.com/admin/analytics#trafficSource. This page displays information about activity levels for various site activities, page views, traffic sources, and referrers. The page does have the headline
analytics data is intended for moderators only; please don't share the specifics of this data in public
so I can't tell you about the specifics. I can tell you that at Electrical Engineering, just around 10% of our traffic comes from direct visits (typing in the URL to my address bar, clicking a bookmark, etc), and 10% more comes from people following links posted on other (non-search-engine) sites, and the remaining 80% is search engine traffic. The month after we entered private beta, we had less than half of our present traffic levels, and about half of our traffic came from direct visits and links on the SE network.
This isn't something that you can fix by flipping a switch. The #1 best way to improve this statistic is to generate quality content - Answer and ask questions, edit and improve existing questions and tags, and generate a vibrant community with a high quality corpus of Q&A. Lots of people like to travel, and are searching for queries that should be on your site. Generate the answers to these queries, and your traffic numbers will improve.