WASHINGTON — In the blazing heat they walked up and down Old Ellicott City’s flood zone — a group of young people sometimes trudging up the hills, sometimes dashing door to door to help residents hit by the flash floods that rushed though the city July 30. The teenagers, high school and college students volunteering with Centennial Relief, were pushing a wheelbarrow filled with fresh fruits and vegetables and bag lunches, which are all free to the families affected by the flash flooding. Many homeowners had recently returned to see basements and first floors filled with soaked furniture and carpets....