Melbourne's weekend hail storm and south-west Queensland's one- in-a-hundred-year floods could cost the insurance industry close to one billion dollars.More than 40,000 claims are now expected from Victorians. Insurance industry executives are talking about total payouts 'easily sailing past half a billion dollars.'Damage in Melbourne was mostly caused by hail, wind, rain, and water run-off and will therefore be covered by standard home and contents packages.Insurers are also expecting extensive commercial claims to flow in from brokers. Losses relating to business interruption are expected to be significant.About eight thousand claims have already been received from south-west Queensland, with estimated costs totalling $120 million to date. Suncorp recently made flood damage standard in home and contents packages and will therefore pay out on many policies.Other insurers will await hydrology reports concerning the nature of the water damage before making decisions about payments under their home and contents packages.The Queensland premier Anna Bligh urged insurers not to quibble over technicalities.The technicality is the difference between a riverine flood - where water rises from a river over a flood plain -and water run-off from a storm or rain event that policy holders often refer to as a flood.A spokeswoman for the Insurance Council of Australia said that the ICA made application in early 2008 to the ACCC for insurers to voluntarily adopt a common definition for flooding, but that consumer groups had objected.The "super cell" hailstorm that hit Sydney's CBD and eastern suburbs on 14 April 1999 remains the costliest weather event in Australian insurance history, costing the industry about $1.7 billion in paid out claims.