By Editorial page staff, The Times-Picayune Original article at http://www.nola.com Hurricanes and floods are Louisiana's costliest disasters --which is hardly news for people who have lived through Katrina, Rita, Ike and Gustav since 2005. But that is why it's disconcerting that only about one in every three Louisiana households has flood insurance, and that the figure peaked in 2008 and dropped a bit in recent years. As hurricane season gets under way, Insurance Commissioner Jim Donelon is urging homeowners to apply to the National Flood Insurance Program. That's sound advice. Only 31 percent of Louisiana residents have flood insurance, or slightly more than 492,000 properties. That's a substantially higher number than the 380,000 properties that had insurance when Katrina hit in August 2005. After Katrina and Rita, many Louisianians purchased flood insurance, with the figure peaking at roughly 502,000 policies in 2008, the year Gustav hit. Since then, the f