While rain is arriving in torrents this winter, local mortgage lenders are dealing with a different kind of deluge -- home loan refinancings.Record-low interest rates are spurring an economy which, without the gangbuster housing market, could be on the verge of flatlining. Steve Shear, vice president of retail mortgage operations for Roseburg-based Umpqua Bank, has seen his lending offices flooded with refinance applications."I've been in the business since '75 and this absolutely is the best rate environment I've ever worked in," said Shear, who works out of Corvallis. "Honestly, this year my staff has been rode hard and put away …