 None of the cities lies entirely within the watershed.In 2000, Johnson Creek and its tributaries drained 53 percent of Gresham, 42 percent of Milwaukie, 19 percent of Happy Valley, and 14 percent of Portland.The watershed covered only 1.2 percent of unincorporated Multnomah County and less than 1 percent of unincorporated Clackamas County.