SEATTLE — Called by the sound of flowing water and ample trees, a family of beavers have moved into Carkeek Park, building a series of dams along the mouth of Pipers Creek. The largest dam — which incorporates a fixed park bench and two large trees — has widened and grown to the degree that water is spilling on to a walking trail nearby. The dam, reinforced with mud and branches, also may present a challenge for chum salmon, which are set to return and spawn at any moment, said David Koon, the salmon program director at the Carkeek Watershed Community Action Project. It's not clear yet how the...