The rain-swollen and brown South Umpqua River flowed around trees Wednesday afternoon as it rushed past Stewart Park. It was 4 feet below the height it reached after Sunday’s record rainfall, but was still an impressive sight. “I’m guessing it’s going about 30 mph,” said Zanna Wright, 19, of Roseburg, gauging the river’s speed against cars moving on the other side of the river. Evidence remained of how high the water had reached into the park. About 30 feet from the river, a line of leaves and twigs indicated the extent of the river’s rise this weekend, when it covered …