FOURTEEN HUNDRED YEARS OF HISTORY AT THE DUWAMISH RIVER MOUTH

The north flowing Duwamish River at Seattle has a complex history. What tools can one find to sketch out its recent history? I am working on a high terrace on the east bank at the mouth of the Duwamish using stratigraphy of sediments, plant fossils, pollen and diatoms, as well as archival data to study the vegetation record during the last 1400 years. The research provides a better understanding of environmental changes locally, and adds to a large body of data relating to the major earthquakes of 1200 on the Seattle Fault. My data also help understand archeological excavations on the Duwamish No. 1 Site (Boas, Inc., 1987) directly across the river. The Duwamish people were there before and during these events. Archeological data document site-use change from a seasonal cottonwood fish-processing site to an upland Douglas-fir and permanent cedar-house site. Recent LiDAR photography and historical data suggest that the river bed tipped up at the mouth, approximately at the location of my study site. My fossils reflect ecological changes consistent with this theory, as they show change from a low salt marsh to a lower high marsh flora 1200 years ago. Another more recent habitat change from lower high marsh to upper high marsh taxa is evident, as is also suggested by subsurface data at Winslow marsh (Liu et al in press). My study demonstrates how interdisciplinary tools aid in understanding historical change.