Laserfiche WebLink
City of Tukwila My WebLink |HelpSearch Tips |About |Sign Out
2.0 Drainage Basin and Watershed <br />Characteristics <br />This section contains a description of the physical characteristics of the City of Tukwila. <br />Drainage, water quality, and aquatic habitat conditions are also presented. Appendix B <br />contains the detailed information in support of this Section 2. <br />2.1 General Description <br />The City of Tukwila encompasses approximately 9.7 square miles straddling the Green and <br />Duwamish Rivers (Figure 1). The climate is strongly influenced by the Pacific Ocean with <br />wet and mild winters with temperatures varying from 30 °F to 50 °F and dry and cool <br />summers with temperatures typically less than 80 °F. The average annual precipitation is <br />between 32 and 38 inches. <br />The Green and Duwamish Rivers and associated floodplains dominate the geography and <br />topography of Tukwila. Relatively flat and poorly drained floodplains exist adjacent to the <br />rivers and steep valley walls dominate the areas on the west side of Tukwila along the I -5 <br />corridor. Soils in the valley floor tend to be fine sandy loam and silty clay loam (Newberg <br />and Woodinville Series, respectively). The valley walls typically are comprised of soils from <br />the Alderwood Series (interbedded silts and clays) and are characterized by numerous <br />hillside springs and the accompanying potential for instability. <br />2.2 Drainage Basins <br />The City has been divided into nine drainage basins (Figure 2): <br />• Green / Duwamish River Mainstem <br />• Gilliam Creek <br />• Nelson Place - Long Acres <br />• P17 <br />• Riverton Creek <br />• Southeast Central Business District (CBD) <br />• Southgate Creek <br />• Johnson Creek <br />• Mill Creek <br />Portions of these basins are located outside City limits as shown in Table 1. The basin <br />boundary delineation was based on information from field visits, the City Geographic <br />Information System (GIS), and previously developed basin plans. The City of Tukwila has <br />finished an inventory and mapping of the drainage network. Basin boundaries should be <br />periodically re- visited to ensure the inventory is up to date. Appendix A to this Plan <br />includes a Surface Water map book, a summary of this inventory and mapping to date. <br />WBG031611103411SEA1 TUKWILASURFACEWATERCOMPPLANFINAL V2.DOCX 2 -1 <br />