(Gresham, OR)  --  Police are investigating a report of a sexual assault on the Springwater Trail in Gresham.  Authorities say a 22-year-old Portland woman reported being assaulted on the trail which she was traveling by bicycle off Southwest Highland Drive on March 18th.  The woman told investigators she was attacked by a man she had flagged down after her tire went flat.  Police say the suspect is described as a bald white man in his 40s, with a medium build, six-feet-two, clean shaven, and wearing a red jacket, blue jeans, and carrying a dark-colored backpack.