Editing Willamette River

{{Short description|River in northwest Oregon, US}}
{{Use mdy dates|date=March 2025}}
{{Infobox river
| name               = Willamette River
| name_native        = 
| name_native_lang   = 
| name_other         = 
| name_etymology     = From a [[Clackamas people|Clackamas]] Native American village name<ref name="Bright"/>
<!---------------------- IMAGE & MAP -->
| image              = USACE Fremont Bridge Portland.jpg
| image_size         = 300
| image_caption      = The Willamette passing through [[Downtown Portland]] in the 1980s
| map                = Willamette_river_map_new.png
| map_size           = 300
| map_caption        = A map of the Willamette River, its drainage basin, major tributaries and major cities
| pushpin_map        = 
| pushpin_map_size   = 
| pushpin_map_caption= 
<!---------------------- LOCATION -->
| subdivision_type1  = Country
| subdivision_name1  = [[United States]]
| subdivision_type2  = State
| subdivision_name2  = [[Oregon]]
| subdivision_type3  = 
| subdivision_name3  = 
| subdivision_type4  = 
| subdivision_name4  = 
| subdivision_type5  = Cities
| subdivision_name5  = [[Eugene, Oregon|Eugene]], [[Corvallis, Oregon|Corvallis]], [[Albany, Oregon|Albany]], [[Independence, Oregon|Independence]], [[Salem, Oregon|Salem]], [[Newberg, Oregon|Newberg]], [[Wilsonville, Oregon|Wilsonville]], [[Portland, Oregon|Portland]]
<!---------------------- PHYSICAL CHARACTERISTICS -->
| length             = {{convert|187|mi|km|abbr=on}}<ref name="length">{{cite web |title=Facts About the Willamette River |publisher=[[Willamette Riverkeeper]] |url=http://willamette-riverkeeper.org/basicsfacts/ |access-date=November 16, 2016 |archive-url=https://web.archive.org/web/20161031083557/http://willamette-riverkeeper.org/basicsfacts/ |archive-date=October 31, 2016 |url-status=live}}</ref> 
| width_min          = 
| width_avg          = 
| width_max          = 
| depth_min          = 
| depth_avg          = 
| depth_max          = 
| discharge1_location= Morrison Bridge, Portland, {{convert|12.8|mi|km|1}} from mouth
| discharge1_min     = {{convert|4200|cuft/s|m3/s|abbr=on}}
| discharge1_avg     = {{convert|33010|cuft/s|m3/s|abbr=on}}
| discharge1_max     = {{convert|420000|cuft/s|m3/s|abbr=on}}
<!---------------------- BASIN FEATURES -->
| source1            = Confluence of [[Middle Fork Willamette River]] and [[Coast Fork Willamette River]]
| source1_location   = near [[Eugene, Oregon|Eugene]], [[Lane County, Oregon|Lane County]], [[Oregon]]
| source1_coordinates= {{coord|44|01|23|N|123|01|25|W|display=inline}}<ref name="gnis"/>
| source1_elevation  = {{convert|438|ft|abbr=on}}<ref name ="gnis"/>
| mouth              = [[Columbia River]]
| mouth_location     = [[Portland, Oregon|Portland]], [[Multnomah County, Oregon|Multnomah County]], [[Oregon]]
| mouth_coordinates  = {{coord|45|39|10|N|122|45|53|W|display=inline,title}}<ref name="gnis"/>
| mouth_elevation    = {{convert|10|ft|abbr=on}}<ref name="gnis"/>
| progression        = 
| river_system       = 
| basin_size         = {{convert|11478|sqmi|abbr=on}}<ref name="Oregon Encyclopedia">{{cite encyclopedia |last=Robbins |first=William G |url=http://www.oregonencyclopedia.org/articles/willamette_river/#.U3pB7iiorqw |title=Willamette River |publisher=Portland State University and the Oregon Historical Society |encyclopedia=The Oregon Encyclopedia |access-date=May 19, 2014}}</ref>
| tributaries_left   = [[Coast Fork Willamette River]], [[Long Tom River]], [[Marys River (Oregon)|Marys River]], [[Luckiamute River]], [[Yamhill River]], [[Tualatin River]]
| tributaries_right  = [[Middle Fork Willamette River]], [[McKenzie River (Oregon)|McKenzie River]], [[Calapooia River]], [[Santiam River]], [[Molalla River]], [[Clackamas River]]
| custom_label       = 
| custom_data        = 
| extra              = 
}}

The '''Willamette River''' ({{IPAc-en|audio=En-Willamette River.oga|w|ᵻ|ˈ|l|æ|m|ᵻ|t}} {{respell|wil|AM|it}}) is a major [[tributary]] of the [[Columbia River]], accounting for 12 to 15&nbsp;percent of the Columbia's flow. The Willamette's [[main stem]] is {{convert|187|mi|km}} long, lying entirely in northwestern [[Oregon]] in the United States. Flowing northward between the [[Oregon Coast Range]] and the [[Cascade Range]], the river and its tributaries form the [[Willamette Valley]], a basin that contains two-thirds of Oregon's population, including the state capital, [[Salem, Oregon|Salem]], and the state's largest city, [[Portland, Oregon|Portland]], which surrounds the Willamette's mouth at the Columbia.

Originally created by [[plate tectonics]] about 35&nbsp;million years ago and subsequently altered by [[volcanism]] and erosion, the river's [[drainage basin]] was significantly modified by the [[Missoula Floods]] at the end of the [[Last glacial period|most recent ice age]]. Humans began living in the watershed over 10,000&nbsp;years ago. There were once many tribal villages along the lower river and in the area around its mouth on the Columbia. Indigenous peoples lived throughout the upper reaches of the basin as well.

Rich with sediments deposited by flooding and fed by prolific rainfall on the western side of the Cascades, the Willamette Valley is one of the most fertile agricultural regions in North America, and it was thus the destination of many 19th-century pioneers traveling west along the [[Oregon Trail]]. The river was an important transportation route in the 19th&nbsp;century, although [[Willamette Falls]], just upstream from Portland, was a major barrier to boat traffic. In the 21st&nbsp;century, major highways follow the river, and roads cross the main stem on approximately 30 different bridges. More than half a dozen bridges not open to motorized vehicles provide separate crossings for bicycles and pedestrians, mostly in the Eugene area, and several others are exclusively for rail traffic. There are also ferries that convey cars, trucks, motorcycles, bicycles, and pedestrians across the river for a fare and provided river conditions permit. They are the [[Buena Vista Ferry]] between Marion County and Polk County south of Independence and Salem, the [[Wheatland Ferry]] between Marion County and Polk County north of Salem and Keizer, and [[Canby Ferry]] in Clackamas County north of Canby.

Since 1900, more than 15 large dams and many smaller ones have been built in the Willamette's drainage basin, 13 of which are operated by the [[United States Army Corps of Engineers|U.S. Army Corps of Engineers]] (USACE). The dams are used primarily to produce [[hydroelectricity]], to maintain reservoirs for recreation, and to prevent flooding. The river and its tributaries support 60 fish species, including many species of [[salmon]] and [[trout]]; this is despite the dams, other alterations, and pollution (especially on the river's lower reaches). Part of the [[Willamette Floodplain]] was established as a [[National Natural Landmark]] in 1987, and the river was named as one of 14 [[American Heritage Rivers]] in 1998.

==Course==
{{Main|Course of the Willamette River}}
[[File:Pan Voyager moored in the Williamette.jpg|thumb|alt=Pan Voyager moored in the Willamette|Ocean-going cargo ship anchored at the mouth of the Willamette]]
The upper tributaries of the Willamette originate in the mountains south and southeast of [[Eugene, Oregon]]. Formed by the confluence of the [[Middle Fork Willamette River]] and the [[Coast Fork Willamette River]] near [[Springfield, Oregon|Springfield]], the [[main stem]] Willamette meanders generally north for {{convert|187|mi|km}} to the [[Columbia River]]. The river's two most significant course deviations occur at [[Newberg, Oregon|Newberg]], where it turns sharply east, and about {{convert|18|mi|km}} downstream from Newberg, where it turns north again. Near its mouth north of downtown [[Portland, Oregon|Portland]], the river splits into two channels that flow around [[Sauvie Island]]. Used for navigation purposes, these channels are managed by the [[Federal government of the United States|U.S. federal government]]. The main channel, which is the primary navigational conduit for Portland's harbor and riverside industrial areas, is {{convert|40|ft|m}} deep and varies in width from {{convert|600|to|1900|ft|m}}, although the river broadens to {{convert|2000|ft|m}} in some of its lower reaches.<ref name="DeLorme"/><ref name="channel plan"/> This channel enters the Columbia about {{convert|101|mi|km}} from the Columbia's mouth on the Pacific Ocean. The smaller [[Multnomah Channel]], a [[distributary]], is {{convert|21|mi|km}} long, about {{convert|600|ft|m}} wide, and {{convert|40|ft|m}} deep. It ends about {{convert|14.5|mi|km}} farther downstream on the Columbia, near [[St. Helens, Oregon|St. Helens]] in [[Columbia County, Oregon|Columbia County]].<ref name="DeLorme">{{cite map |publisher=DeLorme Mapping |title=Oregon Atlas & Gazetteer |edition=1991 |section=41–43, 47–48, 53, 59–60, 66 |isbn=0-89933-235-8}}</ref><ref name="channel plan">{{cite web |url=http://www.portlandoregon.gov/bps/article/145503 |title=Willamette River Dredged Material Management Plan Project |publisher=City of Portland |author=Bureau of Planning and Sustainability |archive-url=https://web.archive.org/web/20161117144851/http://www.portlandoregon.gov/bps/article/145503 |archive-date=November 17, 2016}}</ref><ref name="topoquest multiple quads">{{cite web |author=U.S. Geological Survey |title=United States Geological Survey Topographic Map |publisher=TopoQuest |url=http://www.topoquest.com/map.php?lat=44.03988&lon=-123.02511&datum=nad83&zoom=4&map=auto&coord=d&mode=zoomin&size=m |access-date=June 29, 2010 |archive-date=October 13, 2012 |archive-url=https://web.archive.org/web/20121013014728/http://www.topoquest.com/map.php?lat=44.03988&lon=-123.02511&datum=nad83&zoom=4&map=auto&coord=d&mode=zoomin&size=m |url-status=dead}} Relevant map quadrangles include Eugene East, Coburg, Junction City, Harrisburg, Peoria, Riverside, Lewisburg, Albany, Monmouth, Salem West, Mission Bottom, Dayton, St. Paul, Newberg, Sherwood, Canby, Lake Oswego, Portland, Linnton, Sauvie Island, and Saint Helens.</ref><ref name="Multnomah Channel">{{cite web |title=Multnomah Channel |url=http://www.oregon.gov/OSMB/library/docs/WillametteRiverGuide-07/WillametteRiverGuidePDF-MultnomahChannel.pdf?ga=t |publisher=Oregon State Marine Board; Oregon State Parks Department |archive-url=https://web.archive.org/web/20140529052638/http://www.oregon.gov/OSMB/library/docs/WillametteRiverGuide-07/WillametteRiverGuidePDF-MultnomahChannel.pdf?ga=t |archive-date=May 29, 2014 |page=30 |url-status=dead}}</ref><ref name="Columbia project">{{cite web |url=http://www.sei.org/columbia/background_project.html |title=Background&nbsp;– Project |publisher=Sustainable Ecosystems Institute |work=Columbia River Project—Columbia River Channel Improvement Reconsultation Project |date=February 28, 2001 |url-status=dead |archive-url=https://web.archive.org/web/20111005050610/http://www.sei.org/columbia/background_project.html |archive-date=October 5, 2011}}</ref>

Proposals have been made for deepening the Multnomah Channel to {{convert|43|ft|m}} in conjunction with roughly {{convert|103.5|mi|km}} of tandem-maintained navigation on the Columbia River.<ref name="Columbia project" /> Between the 1850s and the 1960s, channel-straightening and flood control projects, as well as agricultural and urban encroachment, cut the length of the river between the McKenzie River confluence and Harrisburg by 65&nbsp;percent. Similarly, the river was shortened by 40&nbsp;percent in the stretch between Harrisburg and Albany.<ref>Laenen and Dunnette, p. 24</ref>

[[File:Multnomah Channel (Multnomah County, Oregon scenic images) (mulDA0081a).jpg|thumb|left|alt=The Multnomah Channel|The Multnomah Channel from the Sauvie Island Bridge]]

[[Interstate 5 in Oregon|Interstate 5]] and three branches of [[Oregon Route 99]] are the two major highways that follow the river for its entire length. Communities along the main stem include Springfield and Eugene in [[Lane County, Oregon|Lane County]]; [[Harrisburg, Oregon|Harrisburg]] in [[Linn County, Oregon|Linn County]]; [[Corvallis, Oregon|Corvallis]] in [[Benton County, Oregon|Benton County]]; [[Albany, Oregon|Albany]] in Linn and Benton counties; [[Independence, Oregon|Independence]] in [[Polk County, Oregon|Polk County]]; [[Salem, Oregon|Salem]] in [[Marion County, Oregon|Marion County]]; Newberg in [[Yamhill County, Oregon|Yamhill County]]; [[Oregon City, Oregon|Oregon City]], [[West Linn, Oregon|West Linn]], [[Milwaukie, Oregon|Milwaukie]], and [[Lake Oswego, Oregon|Lake Oswego]] in [[Clackamas County, Oregon|Clackamas County]]; and Portland in Multnomah and [[Washington County, Oregon|Washington]] counties. Significant tributaries from source to mouth include the Middle and Coast forks and the [[McKenzie River (Oregon)|McKenzie]], [[Long Tom River|Long Tom]], [[Marys River (Oregon)|Marys]], [[Calapooia River|Calapooia]], [[Santiam River|Santiam]], [[Luckiamute River|Luckiamute]], [[Yamhill River|Yamhill]], [[Molalla River|Molalla]], [[Tualatin River|Tualatin]], and [[Clackamas River|Clackamas]] rivers.<ref name="DeLorme"/><ref name="topoquest multiple quads"/>

Beginning at {{convert|438|ft|m}} above sea level, the main stem descends {{convert|428|ft|m}} between source and mouth, or about 2.3&nbsp;feet per mile (0.4&nbsp;m per km).<ref name="gnis">{{cite web |url={{GNIS 3|1158060}} |date=November 28, 1980 |title=Willamette River |work=Geographic Names Information System |publisher=U.S. Geological Survey |access-date=June 25, 2010}} Source and mouth elevation derived from [[Google Earth]] search using GNIS source and mouth coordinates.</ref> The gradient is slightly steeper from the source to Albany than it is from Albany to Oregon City.<ref name = "Benke 617">Benke, ''et al.'', p. 617</ref> At [[Willamette Falls]], between West Linn and Oregon City, the river plunges about {{convert|40|ft|m}}.<ref name = "Benke 617"/> For the rest of its course, the river is extremely low-gradient and is affected by Pacific Ocean tidal effects from the Columbia.<ref name = "Benke 617"/> The main stem of the Willamette varies in width from about {{convert|330|to|660|ft|m}}.<ref name = "Benke 617"/>

===Discharge===
{{Main|Course of the Willamette River#Discharge|l1=Discharge of the Willamette}}
With an average flow at the mouth of about {{convert|37400|cuft/s|m3/s}}, the Willamette ranks 19th in volume among rivers in the United States<ref name="USGSrivers">{{cite web |first=J.C. |last=Kammerer |url=http://pubs.usgs.gov/of/1987/ofr87-242/ |title=Largest Rivers in the United States |publisher=U.S. Geological Survey |date=May 1990 |access-date=July 2, 2010}}</ref> and contributes 12 to 15&nbsp;percent of the total flow of the Columbia River.<ref name="Benke 616"/> The Willamette's flow varies considerably season to season, averaging about {{convert|8200|cuft/s|m3/s}} in August to more than {{convert|79000|cuft/s|m3/s}} in December.<ref name = "Benke 617"/>

[[File:Oregon_Route_34_1717.JPG|thumb|alt=The Willamette at Corvallis|The Oregon Route 34 bridge across the Willamette River at Corvallis is a mid-valley highway crossing.]]

The [[United States Geological Survey|U.S. Geological Survey]] (USGS) operates five [[stream gauge]]s along the river, at Harrisburg, Corvallis, Albany, Salem, and Portland. The average discharge at the lowermost gauge, near the Morrison Bridge in Portland, was {{convert|33220|cuft/s|m3/s|0}} between 1972 and 2013. Located at [[river mile]] (RM)&nbsp;12.8 or river kilometer (RK)&nbsp;20.6, the gauge measures the flow from an area of {{convert|11200|sqmi|km2}}, roughly 97&nbsp;percent of the Willamette basin.<ref name= "Morrison Bridge gauge">{{cite web |title=Water-Year Summary for Site USGS 14211720 |publisher=U.S. Geological Survey |url=https://waterdata.usgs.gov/nwis/wys_rpt?dv_ts_ids=114384&wys_water_yr=2015&site_no=14211720&agency_cd=USGS&adr_water_years=2006%2C2007%2C2008%2C2009%2C2010%2C2011%2C2012%2C2013%2C2014%2C2015%2C2016&referred_module= |access-date=January 8, 2017}}</ref> The highest flow recorded at this station was {{convert|420000|cuft/s|m3/s|0}} on February&nbsp;9, 1996, during the [[Willamette Valley Flood of 1996]], and the minimum was {{convert|4200|cuft/s|m3/s}} on July&nbsp;10, 1978.<ref name="Morrison Bridge gauge"/> The highest recorded flow of {{convert|635000|cuft/s|m3/s}} for the Willamette at a different gauge in Portland occurred during a [[Great Flood of 1862|flood in 1861]]. This and many other large flows preceded the [[Flood Control Act of 1936]] and dam construction on the Willamette's major tributaries.<ref name="Flooding">{{cite web |url=http://140.194.76.129/publications/misc/un24/c-8.pdf |title=Willamette River Multi-Purpose Development in the 1930s |publisher=U.S. Army Corps of Engineers |work=Army Engineers and the Development of Oregon: A History of the Portland District U.S. Army Corps of Engineers |year=1983 |page=107 |archive-url=https://web.archive.org/web/20140221174430/http://140.194.76.129/publications/misc/un24/c-8.pdf |archive-date=February 21, 2014}}</ref>

The river below Willamette Falls, {{convert|26.5|mi|km}} from the mouth, is affected by [[tide|semidiurnal tides]],<ref>{{cite web |url=http://www.oregon.gov/DSL/NAV/Pages/tidally.aspx |title=Tidally-Influenced Waterways |work=Waterway Authorizations |publisher=Oregon Department of State Lands |url-status=dead |archive-url=https://web.archive.org/web/20121008131154/http://www.oregon.gov/DSL/NAV/Pages/tidally.aspx |archive-date=October 8, 2012}}</ref> and gauges have detected reverse flows (backwards river flows) below [[Ross Island (Oregon)|Ross Island]] at RM&nbsp;15 (RK&nbsp;24).<ref>{{cite journal |first=James M. |last=Caldwell |author2=Doyle, Micelis C |title=Sediment Oxygen Demand in the Lower Willamette River, Oregon, 1994 |year=1995 |journal=Water-Resources Investigations Report 95-4196 |publisher=U.S. Geological Survey |page=2 |doi=10.3133/WRI954196 |s2cid=129065743 |doi-access=free |hdl=2027/uc1.31210026451912 |hdl-access=free}}</ref> The [[National Weather Service]] issues tide forecasts for the river at the [[Morrison Bridge]].<ref>{{cite web |author=National Weather Service Forecast Office |location=Portland, Oregon |title=Local Tide Predictions and Water Levels |publisher=U.S. Department of Commerce |url=http://www.wrh.noaa.gov/pqr/tides.php |access-date=July 2, 2010}}</ref>

==Geology==
The Willamette River basin was created primarily by [[plate tectonics]] and [[volcanism]] and was altered by erosion and sedimentation, including deposits from enormous glacial floods as recent as 13,000&nbsp;years ago.<ref name="Wallick">Wallick, ''et al.'', pp. 495–97</ref> The oldest rocks beneath the Willamette Valley are the [[Siletz River Volcanics]].<ref name=orr2012>Orr (2012), pp. 188–89</ref> About 35&nbsp;million years ago, these rocks were [[Subduction|subducted]] by the [[Farallon Plate]] beneath the [[North American Plate]], creating the [[forearc]] basin that would later become the Willamette Valley.<ref name = "Wallick"/><ref name=orr2012/><ref name = "Benke 616">Benke, ''et al.'', p. 616</ref> The valley was initially part of the [[continental shelf]], rather than a separate inland sea.<ref>Orr (1999), p. 203</ref> Many layers of marine deposits formed in the forearc basin and cover the older Siletz River Volcanics.<ref name=orr2012/> About 20 to 16&nbsp;million years ago, [[Tectonic uplift|uplift]] formed the Coast Range and separated the basin from the Pacific Ocean.<ref name = "Wallick"/>

[[Basalt]]s of the [[Columbia River Basalt Group]], from eruptions primarily in [[eastern Oregon]], flowed across large parts of the northern half of the basin about 15&nbsp;million years ago.<ref name = "Wallick"/> They covered the [[Tualatin Mountains]] (West Hills), most of the [[Tualatin Valley]], and the slopes of hills farther south, with up to {{convert|1000|ft|m}} of [[lava]].<ref>Orr (1999), p. 206</ref> Later deposits covered the basalt with up to {{convert|1000|ft|m}} of silt in the Portland and Tualatin basins.<ref>Orr (1999), p. 208</ref> During the [[Pleistocene]], beginning roughly 2.5&nbsp;million years ago, volcanic activity in the [[Cascade Range|Cascades]] combined with a cool, moist climate to produce further heavy sedimentation across the basin, and [[braided river]]s created [[alluvial fan]]s spreading down from the east.<ref name = "Wallick"/>

[[File:Erratic rock Oregon.JPG|thumb|left|alt=Erratic Rock State Natural Site|The glacial Bellevue Erratic at [[Erratic Rock State Natural Site]]. The rock was transported to the Willamette Valley by the [[Missoula Floods]].<ref name="Erratic Rock">{{cite news |last=Hill |first=Richard L. |title=Project takes on story of region's ice-age cataclysms |newspaper=The Oregonian |date=November 29, 2000 |page=A19}}</ref>]]

Between about 15,500 and 13,000&nbsp;years ago, the [[Missoula Floods]]—a series of large outpourings originating at [[Glacial Lake Missoula]] in Montana—swept down the Columbia River and backfilled the Willamette watershed.<ref name = "Wallick" /> Each flood produced "discharges that exceeded the annual discharge of all the present-day rivers of the world combined".<ref name="Benke 616"/> Filling the Willamette basin to depths of {{convert|400|ft|m}} in the Portland region, each flood created a temporary lake, [[Lake Allison]], that stretched from Lake Oswego to near Eugene.<ref name = "Orr 1999 212-13">Orr (1999), pp. 212–13</ref> The ancestral Tualatin Valley, part of the Willamette basin, flooded as well; water depths ranged from {{convert|200|ft|m}} at Lake Oswego to {{convert|100|ft|m}} as far upstream (west) as [[Forest Grove, Oregon|Forest Grove]].<ref name = "Orr 1999 212-13"/> Flood deposits of silt and clay, ranging in thickness from {{convert|115|ft|m}} in the north to about {{convert|15|ft|m}} in the south, settled from this muddy water to form today's valley floor.<ref name = "Wallick"/> The floods carried Montana icebergs well into the basin, where they melted and dropped [[glacial erratic]]s onto the land surface. These rocks, composed of granite and other materials common to central Montana but not to the Willamette Valley, include more than 40&nbsp;boulders, each at least {{convert|3|ft|m|1}} in diameter.<ref name = "Orr 1999 214">Orr (1999), p. 214</ref> Before being partly chipped away and removed, the largest of these originally weighed about {{convert|160|ST|MT}}.<ref name = "Orr 1999 214"/>

The northern part of the watershed is underlain by a network of [[Fault (geology)|faults]] capable of producing earthquakes at any time, and many small quakes have been recorded in the basin since the mid-19th&nbsp;century.<ref name = "Orr 1999 215-219">Orr (1999), pp. 215–19</ref> In 1993, the [[1993 Scotts Mills earthquake|Scotts Mills earthquake]]—the largest recent earthquake in the valley, measuring 5.6 on the [[Richter magnitude scale|Richter scale]]—was centered near [[Scotts Mills, Oregon|Scotts Mills]], about {{convert|34|mi|km}} south of Portland.<ref>{{cite web |last=Ludwin |first=R. S. |author2=Qamar, A. I. |author3=Malone, S. D. |author4=Crosson, R. S. |author5=Moran, S. |author6=Thomas, G. C. |author7=Steele, W. P. |title=Scotts Mills Earthquake Summary |url=http://assets.pnsn.org/notable/ScottsMills/scottsmills.html |publisher=University of Washington Department of Earth and Space Sciences |date=October 11, 1996 |access-date=September 5, 2014 |archive-url=https://web.archive.org/web/20160628205405/http://assets.pnsn.org/notable/ScottsMills/scottsmills.html |archive-date=June 28, 2016 |url-status=live}}</ref> It caused $30&nbsp;million in damage, including harm to the [[Oregon State Capitol]] in Salem.<ref>{{cite web |title=Earthquake Education: Historic Earthquakes in the Pacific Northwest |url=http://www.oregongeology.org/earthquakes/HistoricEQs.htm |publisher=Oregon Department of Geology and Mineral Industries |archive-url=https://web.archive.org/web/20180529051931/http://www.oregongeology.org/earthquakes/HistoricEQs.htm |archive-date=May 29, 2018 |url-status=dead}}</ref> Evidence suggests that massive quakes of 8 or more on the Richter scale have occurred historically in the [[Cascadia subduction zone]] off the Oregon coast, most recently in [[1700 Cascadia earthquake|1700&nbsp;CE]], and that others as strong as 9 on the Richter scale occur every 500 to 800&nbsp;years.<ref>{{cite web |title=Hazard Mitigation Plan |publisher=City of Troutdale |url=http://www.ci.troutdale.or.us/documents/Hazard_Mitigation_Plan_Final.pdf |archive-url=https://web.archive.org/web/20140724064319/http://www.ci.troutdale.or.us/documents/Hazard_Mitigation_Plan_Final.pdf |archive-date=July 24, 2014 |pages=10–1–10–27 |date=October 25, 2010}}</ref> The basin's high population density, its nearness to this subduction zone, and its loose soils, which tend to amplify shaking, make the Willamette Valley especially vulnerable to damage from strong earthquakes.<ref name = "Orr 1999 215-219"/>

==Watershed==
[[File:Wpdms shdrlfi020l willamette valley.jpg|200px|right|thumb|Willamette Valley map showing main stem and major tributaries|alt=the Willamette valley watershed]]

The Willamette River drains a region of {{convert|11478|sqmi|km2}}, which is 12&nbsp;percent of the total area of Oregon.<ref name="Oregon Encyclopedia" /> Bounded by the Coast Range to the west and the Cascade Range to the east, the river basin is about {{convert|180|mi|km}} long and {{convert|100|mi|km}} wide.<ref name="Benke 616" /> Elevations within the watershed range from {{convert|10495|ft|m}} at [[Mount Jefferson (Oregon)|Mount Jefferson]] in the Cascade Range<ref name="Benke 616" /> to {{convert|10|ft|m}} at the mouth on the Columbia River.<ref name="gnis"/> Watersheds bordering the Willamette River basin are those of the [[Little Deschutes River (Oregon)|Little Deschutes River]] to the southeast, the [[Deschutes River (Oregon)|Deschutes River]] to the east, and the [[Sandy River (Oregon)|Sandy River]] to the northeast; the [[North Umpqua River|North Umpqua]] and [[Umpqua River|Umpqua]] rivers to the south; coastal rivers including (from south to north) the [[Siuslaw River|Siuslaw]], the [[Alsea River|Alsea]], the [[Yaquina River|Yaquina]], the [[Siletz River|Siletz]], the [[Nestucca River|Nestucca]], the [[Trask River|Trask]], and the [[Wilson River (Oregon)|Wilson]] to the west; the [[Nehalem River|Nehalem]] and the [[Clatskanie River|Clatskanie]] to the northwest, and the Columbia River to the north.<ref>Loy, ''et al.'', pp. 168–69</ref>

About 2.5&nbsp;million people lived in the Willamette River basin as of 2010, about 65&nbsp;percent of the population of Oregon.<ref name="hydrologic observatory">{{cite web |title=The Basins: About the Willamette River basin |url=http://pnwho.forestry.oregonstate.edu/site/index.php |publisher=Oregon State University |work=The Pacific Northwest Hydrologic Observatory |archive-url=https://web.archive.org/web/20141209051249/http://pnwho.forestry.oregonstate.edu/site/index.php |archive-date=December 9, 2014}}</ref> As of 2009, the basin contained 20 of the 25 most populous cities in Oregon.<ref name="DeLorme"/><ref name = "city populations">{{cite web |url=http://factfinder.census.gov/servlet/GCTTable?_bm=y&-geo_id=04000US41&-_box_head_nbr=GCT-T1-R&-ds_name=PEP_2009_EST&-_lang=en&-format=ST-9S&-_sse=on |title=Oregon&nbsp;– Place 2009 Population Estimates |publisher=U.S. Census Bureau |access-date=January 14, 2011}}{{dead link|date=June 2022|bot=medic}}{{cbignore|bot=medic}}</ref> These cities include Springfield, Eugene, Corvallis, Albany, Salem, Keizer, Newberg, Oregon City, West Linn, Milwaukie, Lake Oswego, and Portland.<ref name="DeLorme"/><ref name = "city populations"/> The largest is Portland, with more than 500,000 residents.<ref name = "city populations"/> Not all of these cities draw water in part or exclusively from the Willamette for their municipal water supply.<ref>{{cite web |url=http://www.corvallisoregon.gov/index.aspx?page=135 |title=Water Utility |publisher=City of Corvallis, Oregon |access-date=November 16, 2016}}</ref><ref>{{cite web |url=https://www.cityofalbany.net/images/stories/publicworks/water/wqr/2015-albany-wqr.pdf |page=3 |title=2015 Annual Water Quality Report |publisher=City of Albany, Oregon |access-date=November 16, 2016}}</ref> Other cities in the watershed (but not on the main-stem river) with populations of 20,000 or more are Gresham, Hillsboro, Beaverton, Tigard, McMinnville, Tualatin, [[Woodburn, Oregon|Woodburn]], and Forest Grove.<ref name="DeLorme"/><ref name = "city populations"/>

Sixty-four&nbsp;percent of the watershed is privately owned, while 36&nbsp;percent is publicly owned.<ref name = "Benke"/> The [[United States Forest Service|U.S. Forest Service]] manages 30&nbsp;percent of the watershed, the U.S. [[Bureau of Land Management]] 5&nbsp;percent, and the State of Oregon 1&nbsp;percent.<ref name = "Benke"/> Sixty-eight&nbsp;percent of the watershed is forested; agriculture, concentrated in the Willamette Valley, makes up 19&nbsp;percent, and urban areas cover 5&nbsp;percent.<ref name = "Benke"/> More than {{convert|81000|mi|km}} of roads criss-cross the watershed.<ref name = "Benke">Benke, ''et al.'', pp. 616–17</ref>

In 1987, the [[United States Secretary of the Interior|U.S. Secretary of the Interior]] designated {{convert|713|acre|ha}} of the watershed in Benton County as a [[National Natural Landmark]]. This area is the [[Willamette Floodplain]], the largest remaining unplowed native grassland in the North Pacific geologic province, which encompasses most of the Pacific Northwest coast.<ref>{{cite web |title=Willamette Floodplain |publisher=National Park Service |url=https://www.nps.gov/subjects/nnlandmarks/site.htm?Site=WIFL-OR |access-date=November 16, 2016 |archive-url=https://web.archive.org/web/20161117151813/https://www.nps.gov/subjects/nnlandmarks/site.htm?Site=WIFL-OR |archive-date=November 17, 2016 |url-status=live}}</ref>

==History==

===First inhabitants===
[[File:Willamette River at Molalla SP eb.jpg|thumb|right|180px|alt=The Willamette near the confluence with the Molalla|The Willamette River near the confluence with the [[Molalla River]]]]
For at least 10,000&nbsp;years, a variety of indigenous peoples populated the Willamette Valley. These included the [[Kalapuya people|Kalapuya]], the [[Chinook people|Chinook]], and the [[Clackamas people|Clackamas]].<ref name="removalexcerpt">{{cite journal |last=Spores |first=Ronald |title=Too Small a Place: The Removal of the Willamette Valley Indians, 1850–1856 |journal=American Indian Quarterly |volume=17 |year=1993 |page=172 |publisher=University of Nebraska Press |jstor=1185526 |doi=10.2307/1185526 |issue=2}}</ref> The territory of the Clackamas encompassed the northeastern portion of the basin, including the Clackamas River (with which their name is shared). Although it is unclear exactly when, the territory of the Chinook once extended across the northern part of the watershed, through the Columbia River valley. Indigenous peoples of the Willamette Valley were further divided into groups including the [[Kalapuyan languages|Kalapuyan-speaking]] [[Yamhill (tribe)|Yamhill]] and [[Atfalati|Atfalati (Tualatin)]] (both Northern Kalapuya), Central Kalapuya like the [[Santiam people|Santiam]], Muddy Creek (Chemapho), Long Tom (Chelamela), Calapooia (Tsankupi), Marys River (Chepenafa) and Luckiamute, and the [[Yoncalla language|Yoncalla]] or Southern Kalapuya, as well other tribes such as the Chuchsney-Tufti, [[Siuslaw people|Siuslaw]] and [[Molala]].<ref name="Oregon Encyclopedia" /><ref name="removalexcerpt" /> The name ''Willamette'' is of indigenous origin, deriving from the French pronunciation of the name of a Clackamas Native American village.<ref name="Bright">Bright, p. 567</ref> However, Native American languages in Oregon were very similar,<ref>Campbell, p. 120</ref> so the name may also be derived from Kalapuya dialects.<ref name="RG 3/18/10">{{cite news |first=Bob |last=Welch |title=A Bridge Too Far Along to Be Renamed |url=http://projects.registerguard.com/csp/cms/sites/web/opinion/24574689-41/bridge-pap%C3%A9-welch-commission-decision.csp |archive-url=https://web.archive.org/web/20220119115052/http://projects.registerguard.com/csp/cms/sites/web/opinion/24574689-41/bridge-pap%C3%A9-welch-commission-decision.csp |archive-date=January 19, 2022 |url-status=dead |newspaper=The Register-Guard |date=March 18, 2010 |location=Eugene, Oregon |page=B1}}</ref>
{{clear}}

[[File:Wilhamut.1.JPG|thumb|left|alt=A boulder engraved with the Kalapuyan word "Whilamut" "Where the river ripples and runs fast"|A boulder at [[Alton Baker Park]] in [[Eugene, Oregon|Eugene]] engraved with the Kalapuyan word "Whilamut" "Where the river ripples and runs fast"]]
Around the year 1850, the Kalapuya numbered between 2,000 and 3,000 and were distributed among several groups. These figures are only speculative; there may have been as few as eight subgroups or as many as 16.<ref>Thornton, p. 125</ref> In that time period, the Clackamas' tribal population was roughly 1,800.<ref>{{cite web |url=http://www.nationalgeographic.com/lewisandclark/record_tribes_084_13_22.html |title=Clackamas Indians |publisher=National Geographic Society |work=National Geographic |year=1996 |url-status=dead |archive-url=https://web.archive.org/web/20100208102759/http://www.nationalgeographic.com/lewisandclark/record_tribes_084_13_22.html |archive-date=February 8, 2010}}</ref> The [[United States Census Bureau|U.S. Census Bureau]] estimated that the Chinook population was nearly 5,000,<ref>Snipp, p. 344</ref> though not all of the Chinook lived on the Willamette. The Chinook territory encompassed the lower Columbia River valley and significant stretches of the Pacific coast on both the north and the south side of the Columbia's mouth. At times, however, the Chinook territory extended even farther south in the Willamette Valley.<ref>Ruby and Brown, p. 4</ref> The total native population was estimated at 15,000.<ref name="removalexcerpt"/>

The indigenous peoples of the Willamette River practiced a variety of life ways. Those on the lower river, slightly closer to the coast, often relied on fishing as their primary economic mainstay. [[Salmon]] was the most important fish to Willamette River tribes as well as to the Native Americans of the Columbia River, where white traders traded fish with the Native Americans. Upper-river tribes caught [[Rainbow trout|steelhead]] and salmon, often by building [[weir]]s across tributary streams. Tribes of the northern Willamette Valley practiced a generally settled lifestyle. The Chinooks lived in great [[Plank house|wooden lodges]],<ref name="Ruby and Brown, p. 16">Ruby and Brown, p. 16</ref> practiced [[slavery]], and had a well-defined [[caste]] system.<ref name="Ruby and Brown, p. 16"/> People of the south were more nomadic, traveling from place to place with the seasons. They were known for the controlled burning of woodlands to create meadows for hunting and plant gathering (especially [[Camassia|camas]]).<ref>Deur and Turner, p. 220</ref>

===18th century===
The Willamette River first appeared in written records in 1792, when it was observed by British Lieutenant [[William Robert Broughton]] of the [[Vancouver Expedition]], led by [[George Vancouver]].<ref name="Brochure">{{cite web |url=https://www.oregon.gov/OSMB/forms-library/Documents/Publications/WillametteRiverGuide07.pdf |title=Willamette River Recreation Guide |publisher=Oregon State Marine Board |date=December 2007 |access-date=November 16, 2016 |pages=1–3, 10 |archive-url=https://web.archive.org/web/20161117210929/https://www.oregon.gov/OSMB/forms-library/Documents/Publications/WillametteRiverGuide07.pdf |archive-date=November 17, 2016 |url-status=live}}</ref>

===19th century===
The 1805–1806 [[Lewis and Clark Expedition]] originally missed the mouth of the Willamette. On their return journey, only after receiving directions from natives along the [[Sandy River (Oregon)|Sandy River]] did the explorers learn about their oversight. [[William Clark (explorer)|William Clark]] returned down the Columbia and entered the Willamette River in April 1806.<ref name="Benke 616"/>

Fur trappers originally working for the [[Pacific Fur Company]] (PFC)) and subsequently for the [[North West Company]] (NWC) were next to visit the Willamette River and various tributaries.<ref>Mackie, p. 115</ref> The [[Siskiyou Trail]] (or California-Oregon Trail) originally developed by Indigenous people, was used to reach farther south. This trail, over {{convert|600|mi|km}} long, stretched from the mouth of the Willamette River near present-day Portland south through the Willamette Valley, crossing the [[Siskiyou Mountains]], and south through the [[Sacramento Valley]] to [[San Francisco]].<ref>Engeman, p. 63</ref>

In 1812, William Henry and Alfred Seton paddled up from [[Fort Astoria]] (PFC) on the [[Columbia River]] into the mouth of the Willamette, continued on until the falls portage (present-day [[Oregon City]]) and finished their journey at a flattening of both banks, the later site of [[Champoeg]]. A first trading post was established. By early 1813, William Wallace and John C. Halsey established a second outpost, [[Wallace House (fur-trade post)|Wallace House]], farther south, north of present-day Salem. 

By the end of the [[War of 1812]], the NWC acquired the PFC. Free trappers Registre Bellaire, [[John Day (trapper)|John Day]] and Alexander Carson hunted and traded furs during the winter of 1813–14 along the Willamette. About thirty NWC employees were stationed at the Champoeg post, now called the [[Willamette Trading Post]], along with freemen housed in two huts and Kalapuya nearby. [[Nez Perce]] and [[Cayuse people|Cayuse]] warned the NWC to stay out of the Willamette Valley hunting grounds. Skirmishes went on for several years over fishing and hunting grounds contended by several groups.

By the winter of 1818–19, [[Thomas McKay]] led a hunting brigade farther south towards the sources of the Willamette River and reached the upper [[Umpqua River]]. More violent skirmishes were fought. Most brigade members returned to Fort George (formerly called [[Fort Astoria]]). Louis LaBonté, [[Joseph Gervais]], [[Étienne Lucier]], Louis Kanota, and Louis Pichette (dit DuPré) remained in the Willamette Valley as free trappers.<ref>{{cite web |url=http://www.usgennet.org/usa/or/county/clackamas/timeline1.html |title=Clackamas County Oregon History, 1800 to 1843}}</ref> Meanwhile, in 1821 the HBC merged with the NWC. In 1825 a new [[Fort Vancouver]] headquarters was built on the north shore of the Columbia closer to the Willamette, and Fort George was closed. [[Alexander Roderick McLeod]] traveled up the Willamette in 1826 and 1827, to the [[Umpqua River|Umpqua]] and the [[Rogue River (Oregon)|Rogue]] rivers.

In 1829 Lucier established a land claim near the Champoeg trading post and started to settle, soon joined by Gervais (1831), [[Pierre Belleque]] (1833) and 77 French Canadian settlers by 1836. By 1843, approximately 100 newcomer families lived in the vicinity of the Willamette on a section referred to as [[French Prairie]].

By 1841, members of the [[United States Exploring Expedition]] came through the Siskiyou Trail. They noted extensive salmon fishing by natives at Willamette Falls, much like that at [[Celilo Falls]] on the Columbia River.<ref>Wilkes, pp. 341–74</ref>

In the middle part of the 19th century the Willamette Valley's fertile soils, pleasant climate, and abundant water attracted thousands of settlers from the [[eastern United States]], mainly the [[Upland South]] borderlands of Missouri, Iowa, and the Ohio Valley.<ref>Meinig, p. 71</ref> Many of these emigrants followed the [[Oregon Trail]], a {{convert|2170|mi|km|adj=on}} trail across western North America that began at [[Independence, Missouri]], and ended at various locations near the mouth of the Willamette River. Although people had been traveling to Oregon since 1836, large-scale migration did not begin until 1843, when nearly 1,000 pioneers headed westward. Over the next 25 years, some 500,000&nbsp;settlers traveled the Oregon Trail, to reach the Willamette Valley.<ref>{{cite web |url=http://www.isu.edu/%7Etrinmich/Introduction.html |title=Introduction |publisher=Idaho State University |work=The Oregon Trail |archive-url=https://web.archive.org/web/20100529081949/http://www.isu.edu/~trinmich/Introduction.html |archive-date=May 29, 2010 |url-status=dead}}</ref><ref>{{cite web |url=http://www.isu.edu/%7Etrinmich/routewest.html |title=The Route West |publisher=Idaho State University |work=The Oregon Trail |archive-url=https://web.archive.org/web/20100529081928/http://www.isu.edu/~trinmich/routewest.html |archive-date=May 29, 2010 |url-status=dead}}</ref><ref>{{cite web |url=https://www.octa-trails.org/articles/where-did-the-oregon-trail-go |title=Where did the Oregon Trail Go? Reaching Oregon's Willamette Valley |publisher=Oregon-California Trails Association |access-date=September 3, 2014}}</ref>

[[File:Oregon City and Willamette Falls, 1867.jpg|thumb|left|alt=Oregon City in 1867|Oregon City circa 1867, with Willamette Falls in the background]]

Starting in the 1830s, [[Oregon City]] developed near Willamette Falls. It was incorporated in 1844, becoming the first city west of the [[Rocky Mountains]] to have that distinction.<ref>{{cite web |url=https://sos.oregon.gov/blue-book/Pages/local/counties/clackamas.aspx |title=Clackamas County |publisher=Oregon State Archives |work=Oregon Blue Book |access-date=October 26, 2018}}</ref> [[John McLoughlin]], the Hudson's Bay Company (HBC) superintendent of the [[Columbia District]], was one of the major contributors to the founding of the town in 1829.<ref>Samson, p. 125</ref> McLoughlin attempted to persuade the HBC (which still held sway over the area) to allow American settlers to live on the land, and provided significant help to American colonization of the area, all against the HBC's orders.<ref>Holman, pp. 96–97</ref> Oregon City prospered because of the lumber and grist mills that were run by the water power of Willamette Falls, but the falls formed an impassable barrier to river navigation. [[Linn City, Oregon|Linn City]] (originally Robins Nest) was established across the Willamette from Oregon City.<ref>McArthur, p. 1022</ref>

After Portland was incorporated in 1851, quickly growing into Oregon's largest city, Oregon City gradually lost its importance as the economic and political center of the Willamette Valley. Beginning in the 1850s, [[steamboat]]s began to ply the Willamette, despite the fact that they could not pass Willamette Falls.<ref>Gulick, pp. 28–29</ref> As a result, navigation on the Willamette River was divided into two stretches: the {{convert|27|mi|km|adj=on}} lower stretch from Portland to Oregon City—which allowed connection with the rest of the Columbia River system—and the upper reach, which encompassed most of the Willamette's length.<ref>Gulick, p. 22</ref> Any boats whose owners found it absolutely necessary to get past the falls had to be [[portage]]d. This led to competition for business among steam portage companies.<ref>Timmen, pp. 14, 17, 27</ref><ref name="Alan Lewis">{{cite web |last=Lewis |first=Alan |url=http://www.willamettefalls.org/hislocks#!history-of-the-locks/c1tb3 |title=Conquering the Falls: The Willamette Falls Locks |publisher=Willamette Falls Heritage Foundation |work=History of the Willamette Falls |date=August 2006 |url-status=dead |archive-url=https://web.archive.org/web/20130517061950/http://willamettefalls.org/HisLocks#!history-of-the-locks/c1tb3 |archive-date=May 17, 2013}}</ref> In 1873, the construction of the [[Willamette Falls Locks]] bypassed the falls and allowed easy navigation between the upper and lower river. Each lock chamber measured {{convert|210|ft|m}} long and {{convert|40|ft|m}} wide, and the canal was originally operated manually before it switched to electrical power.<ref name="Alan Lewis" /> Usage of the locks peaked in the 1940s, and by the early 21st&nbsp;century, the lock system was little used.<ref>{{cite news |last=Balingit |first=Moriah |author2=Lednicer, Lisa Grace |url=http://www.willamettefalls.org/LocksNews |title=Living on Borrowed Time |work=The Oregonian |date=May 18, 2006 |archive-url=https://web.archive.org/web/20130521074956/http://willamettefalls.org/LocksNews |archive-date=May 21, 2013}}</ref> Since 2011, the Willamette Falls Locks have been inactive.<ref>{{cite web |url=https://www.nwp.usace.army.mil/willamette/locks/ |title=Willamette Falls Locks |publisher=U.S. Army Corps of Engineers |access-date=December 22, 2022}}</ref>

As commerce and industry flourished on the lower river, most of the original settlers acquired farms in the upper Willamette Valley. By the late 1850s, farmers had begun to grow crops on most of the available fertile land.<ref>{{cite web |url=http://www.opb.org/programs/oregonstory/farming/timeline.html |title=A Chronology of Farming in Oregon |publisher=Oregon Public Broadcasting |year=2000 |archive-url=https://web.archive.org/web/20160304055646/http://www.opb.org/programs/oregonstory/farming/timeline.html |archive-date=March 4, 2016 |url-status=dead}}</ref> The settlers increasingly encroached on Native American lands. Skirmishes between natives and settlers in the Umpqua and [[Rogue River (Oregon)|Rogue]] valleys to the southwest of the Willamette River led the [[Government of Oregon|Oregon state government]] to remove the natives by military force.<ref>Edwards and Schwantes, p. 61</ref> They were first led off their traditional lands to the Willamette Valley, but soon were marched to the [[Coast Indian Reservation]]. In 1855, [[Joel Palmer]], an Oregon legislator, negotiated a treaty with the Willamette Valley tribes, who, although unhappy with the treaty, ceded their lands to non-natives.<ref>Edwards and Schwantes, p. 62</ref><ref name="Jette">{{cite encyclopedia |last=Jette |first=Melinda |url=http://www.oregonencyclopedia.org/articles/kalapuya_treaty/ |title=Kalapuya Treaty of 1855 |publisher=Portland State University |encyclopedia=The Oregon Encyclopedia |access-date=June 6, 2010}}</ref> The natives were then relocated by the government to a part of the Coast Reservation that later became the [[Grande Ronde Reservation]].<ref name="Jette"/>

Between 1879 and 1885, the Willamette River was charted by [[Cleveland S. Rockwell]], a topographical engineer and cartographer for the [[United States Coast and Geodetic Survey]]. Rockwell surveyed the lower Willamette from the foot of [[Ross Island (Oregon)|Ross Island]] through Portland to the Columbia River and then downstream on the Columbia to [[Bachelor Island (Washington)|Bachelor Island]].<ref>U.S. Coast and Geodetic Survey, p. 76</ref> Rockwell's survey was extremely detailed, including 17,782&nbsp;hydrographic soundings. His work helped open the port of Portland to commerce.<ref>Stenzel, pp. 37–39</ref>

In the second half of the 19th&nbsp;century, the [[United States Army Corps of Engineers|USACE]] dredged channels and built locks and levees in the Willamette's watershed. Although products such as lumber were often transported on an existing network of railroads in Oregon, these advances in navigation helped businesses deliver more goods to Portland, feeding the city's growing economy. Trade goods from the Columbia basin north of Portland could also be transported southward on the Willamette due to the deeper channels made at the Willamette's mouth.<ref name=Willingham>{{cite encyclopedia |last=Willingham |first=William F |title=U.S. Army Corps of Engineers |url=http://www.oregonencyclopedia.org/articles/u_s__army_corps_of_engineers/ |encyclopedia=The Oregon Encyclopedia |publisher=Portland State University |access-date=September 14, 2011}}</ref>

===20th and 21st centuries===
[[File:Conveyor belt for Big Pipe project - Portland, Oregon.JPG|thumb|right|alt=The Big Pipe Project|Conveyor belt loading debris onto a barge as part of the Big Pipe Project]]
By the early 20th&nbsp;century, major river-control projects had begun to take place. Levees were constructed along the river in most urban areas, and Portland built concrete walls to protect its downtown sector.<ref name="Flooding"/> In the following decades, many large dams were built on Cascade Range tributaries of the Willamette. The Army Corps of Engineers operates 13 such dams, which affect flows from about 40&nbsp;percent of the basin.<ref name="Nature Conservancy">{{cite web |url=http://www.nature.org/cs/groups/webcontent/@web/@oregon/documents/document/prd_022483.pdf |title=Sustainable Rivers: Willamette Flow Management |publisher=The Nature Conservancy |archive-url=https://web.archive.org/web/20131111033206/http://www.nature.org/cs/groups/webcontent/@web/@oregon/documents/document/prd_022483.pdf |archive-date=November 11, 2013 |url-status=dead}}</ref> Most of them do not have fish ladders.<ref name="NOAA NRO">{{cite web |title=Willamette River Basin |url=http://www.nwr.noaa.gov/Salmon-Hydropower/Willamette-Basin/ |publisher=NOAA National Marine Fisheries Service, Northwest Regional Office |archive-url=https://web.archive.org/web/20120922022048/http://www.nwr.noaa.gov/Salmon-Hydropower/Willamette-Basin/ |archive-date=September 22, 2012 |date=June 28, 2012}}</ref>

With development in and near the river came increased pollution. By the late 1930s, efforts to stem the pollution led to formation of a state sanitary board to oversee modest cleanup efforts.<ref name="Oregon Encyclopedia"/> In the 1960s, Oregon Governor [[Tom McCall]] led a push for stronger pollution controls on the Willamette.<ref name="Williams, p. 131"/> In this, he was encouraged by [[Robert W. Straub|Robert (Bob) Straub]]—the state treasurer and future Oregon governor (1975)—who first proposed a [[Willamette Greenway]] program during his 1966 gubernatorial campaign against McCall.<ref>{{cite book |last=Johnson |first=Charles K. |title=Standing at the Water's Edge: Bob Straub's Battle for the Soul of Oregon |publisher=Oregon State University Press |year=2012 |location=Corvallis |page=125 |isbn=978-0-87071-669-0}}</ref> The Oregon State Legislature established the program in 1967. Through it, state and local governments cooperated in creating or improving a system of parks, trails, and wildlife refuges along the river.<ref name= "Brochure"/> In 1998, the Willamette became one of 14 rivers designated an [[American Heritage River]] by U.S. President [[Bill Clinton]].<ref>{{cite web |title=American Heritage Rivers News |publisher=U.S. Environmental Protection Agency |url=http://water.epa.gov/type/watersheds/named/heritage/10-5upda.cfm |date=November 19, 2009 |archive-url=https://web.archive.org/web/20110722002603/http://water.epa.gov/type/watersheds/named/heritage/10-5upda.cfm |archive-date=July 22, 2011}}</ref> By 2007 the Greenway had grown to include more than 170 separate land parcels, including 10 state parks.<ref name= "Brochure"/> Public uses of the river and land along its shores include camping, swimming, fishing, boating, hiking, bicycling, and wildlife viewing.<ref name= "Brochure"/>

In 2008, government agencies and the non-profit [[Willamette Riverkeeper]] organization designated the full length of the river as the Willamette River Water Trail.<ref name="Karas">{{cite news |last=Karas |first=Chisti |title=Peaceful Paddle with Beer Stops on Oregon's Willamette Water Trail |work=The Seattle Times |url=http://www.seattletimes.com/life/travel/peaceful-paddles-with-beer-stops-on-oregons-willamette-water-trail/ |date=July 24, 2015 |access-date=January 22, 2017}}</ref> Four years later, the [[National Park Service]] added the Willamette water trail—expanded to {{convert|217|mi|km}} to include some of the major tributaries—to its list of [[National Water Trail]]s. The water trail system is meant to protect and restore waterways in the United States and enhance recreation on and near them.<ref name=willamettewatertrail>{{cite web |title=Willamette River Water Trail |publisher=American Trails |url=http://www.nrtdatabase.org/trailDetail.php?recordID=3816 |access-date=March 31, 2020}}</ref><ref>{{cite web |title=National Water Trails System |url=https://www.nps.gov/subjects/nationaltrailssystem/national-water-trails-system.htm |publisher=National Park Service |access-date=March 31, 2020}}</ref>

A 1991 agreement between the City of Portland and the State of Oregon to dramatically reduce [[combined sewer]] overflows (CSOs)<ref name="nwconstruction">{{cite web |url=http://northwest.construction.com/features/archive/0311_Cover.asp |archive-url=https://web.archive.org/web/20130927191417/http://northwest.construction.com/features/archive/0311_Cover.asp |archive-date=September 27, 2013 |title=West Side Big Pipe |publisher=Northwest Construction |last=Bacon |first=Sheila |date=November 2003 |url-status=dead}}</ref> led to Portland's [[West Side CSO Tunnel|Big Pipe Project]]. The project, part of a related series of Portland CSO projects completed in late 2011 at a cost of $1.44&nbsp;billion,<ref>{{cite news |last=Slovic |first=Beth |title=Going Down the Tube, At Last |work=The Oregonian |edition=Sunrise |date=November 26, 2011}}</ref> separates the city's sanitary sewer lines from storm-water inputs that sometimes overwhelmed the combined system during heavy rains. When that occurred, some of the raw sewage in the system flowed into the river instead of into the city's wastewater treatment plant. The Big Pipe project and related work reduces CSO volume on the lower river by about 94&nbsp;percent.<ref name="portlandonlinecso2">{{cite web |title=Combined Sewer Overflow Control |publisher=City of Portland |url=http://www.portlandoregon.gov/bes/31030 |access-date=November 16, 2016 |archive-url=https://web.archive.org/web/20161117144756/http://www.portlandoregon.gov/bes/31030 |archive-date=November 17, 2016 |url-status=live}}</ref><ref name="oregonianpipe">{{cite news |title=A Big Pipe |newspaper=The Oregonian |date=December 11, 2007 |archive-url=https://web.archive.org/web/20121008111019/http://www.portlandonline.com/cso/index.cfm?a=180894&c=43918 |archive-date=October 8, 2012 |url=http://www.portlandonline.com/cso/index.cfm?a=180894&c=43918}}</ref>

In June 2014, Dean Hall became the first person to swim the entire length of the Willamette River.<ref>{{cite news |last=Hachmann |first=Cari |title=Dean Hall to Finish Willamette River Swim |url=http://portlandtribune.com/pt/9-news/225521-87105-dean-hall-to-finish-willamette-river-swim |work=Portland Tribune |publisher=Pamplin Media Group |date=June 27, 2014 |archive-url=https://web.archive.org/web/20140729120305/http://portlandtribune.com/pt/9-news/225521-87105-dean-hall-to-finish-willamette-river-swim |archive-date=July 29, 2014}}</ref><ref name=KPTV>{{cite news |last=Padula |first=Andrew |title=Man Battling Cancer Swims Entire Length of Willamette River |url=http://www.kptv.com/story/25892320/man-battling-cancer-si |work=KPTV Fox 12 |date=July 25, 2014 |access-date=March 11, 2017 |archive-url=https://web.archive.org/web/20140701165433/http://www.kptv.com/story/25892320/man-battling-cancer-si |archive-date=July 1, 2014 |url-status=dead}}</ref> He swam {{convert|184|mi|km}} from Eugene to the river mouth in 25 days.<ref name=KPTV/>

In 2017, [[Human Access Project]] partnered with [[Portland Parks & Recreation]] to open the city's first officially recognized public swimming beach, [[Poet's Beach]].<ref>{{Cite web |last=Labrecque |first=Jackie |date=July 6, 2017 |title=Poet's Beach will have life guards, swim rope along Willamette River's west banks |url=https://katu.com/news/local/beach-will-have-life-guards-swim-rope-along-willamette-rivers-west-banks |access-date=September 20, 2023 |website=KATU |language=en}}</ref><ref>{{Cite web |date=July 15, 2017 |title=Portland touts revived Willamette River |url=https://www.seattletimes.com/seattle-news/portland-touts-revived-willamette-river/ |access-date=September 20, 2023 |website=The Seattle Times |language=en-US}}</ref><ref>{{Cite web |last=Law |first=Steve |date=June 7, 2017 |title=Welcome to Portland's first pop-up beach |url=https://www.portlandtribune.com/news/welcome-to-portlands-first-pop-up-beach/article_17736473-41ad-5e4d-915d-be8f36458399.html |archive-url=https://web.archive.org/web/20231014045332/https://www.portlandtribune.com/news/welcome-to-portlands-first-pop-up-beach/article_17736473-41ad-5e4d-915d-be8f36458399.html |url-status=dead |archive-date=October 14, 2023 |access-date=September 20, 2023 |website=PortlandTribune.com |language=en}}</ref>

==Dams==
[[File:Oregon City Willamette Falls Paper Mill.jpg|thumb|right|alt=Oregon City Willamette Falls Paper Mill|The weir-type dam at Willamette Falls]]
There are more than 20 major dams on the Willamette's tributaries, as well as a complex series of [[Levee|levees]] and channels to control the river's flow.

The only dam on the Willamette's main stem is the [[Willamette Falls]] Dam, a low [[weir]]-type structure at Willamette Falls that diverts water into the [[Water wheel|headraces]] of the adjacent mills and a power plant.<ref name="LIHI">{{cite web |url=http://lowimpacthydro.org/lihi-certificate-33-willamette-falls-hydroelectric-project-oregon-ferc-2233/ |title=LIHI Certificate #33 – Willamette Falls Hydroelectric Project, Oregon |publisher=Low Impact Hydropower Institute |access-date=December 23, 2014 |archive-url=https://web.archive.org/web/20160402235823/http://lowimpacthydro.org/lihi-certificate-33-willamette-falls-hydroelectric-project-oregon-ferc-2233/ |archive-date=April 2, 2016 |url-status=live}}</ref> The [[Willamette Falls Locks|locks at Willamette Falls]] were completed in 1873. Elsewhere on the main stem, numerous minor flow-regulation structures force the river into a narrower and deeper channel to facilitate navigation and [[flood control]].<ref name="Brochure"/>

The dams on the Willamette's major tributaries are primarily large flood-control, water-storage, and power-generating dams. Thirteen of these dams were built from the 1940s through the 1960s and are operated by the [[United States Army Corps of Engineers]] (USACE).<ref name="basin dams">{{cite web |title=Willamette Basin Reservoirs |url=https://www.oregon.gov/OWRD/wrdpublications1/1998_04_Willamette_Brochure.pdf |publisher=Oregon Water Resources Department; U.S. Army Corps of Engineers |access-date=December 19, 2020}}</ref><ref>{{cite web |url=http://www.salmonrecovery.gov/BiologicalOpinions/WillametteBiOp.aspx |title=Willamette BiOp |publisher=Columbia River Basin Federal Caucus |access-date=July 26, 2012}}</ref> Of those 13, 9 produce hydropower.<ref name="basin dams"/> Flood-control dams operated by the USACE are estimated to hold up to 27&nbsp;percent of the Willamette's runoff. They are used to regulate river flows so as to cut peaks off floods and increase low flows in late summer and autumn, and to divert water into deeper, narrower channels to prevent flooding.<ref name="Brochure"/><ref name="Nature Conservancy" /><ref name="LIHI"/><ref name="valley locations">{{cite web |title=About Our Willamette Valley Locations |url=https://www.nwp.usace.army.mil/Locations/Willamette-Valley/ |publisher=U.S. Army Corps of Engineers |access-date=November 16, 2016 |archive-url=https://web.archive.org/web/20170118231645/http://www.nwp.usace.army.mil/Locations/Willamette-Valley/ |archive-date=January 18, 2017 |url-status=live}}</ref><ref>{{cite map |publisher=ACME Mapper |title=USGS Topo Maps for United States |cartography=U.S. Geological Survey |access-date=June 7, 2010 |url=http://mapper.acme.com/}}</ref> A relatively small of amount of the water stored in the reservoirs is used for [[irrigation]].<ref name=capitalpress>{{cite news |url=http://www.capitalpress.com/Oregon/20150610/ags-needs-from-willamette-basins-dam-reservoir-system-studied |title=Ag's needs from Willamette Basin's dam, reservoir system studied |author=Mortenson, Eric |work=Capital Press |location=Salem, Oregon |date=June 10, 2015 |access-date=February 16, 2016}}</ref>

[[File:USACE Detroit Dam Oregon.jpg|thumb|left|180px|alt=Detroit Dam|[[Detroit Dam]], the basin's second tallest]]
[[Cougar Dam]] on the [[South Fork McKenzie River]] and [[Detroit Dam]] on the [[North Santiam River]] are the two tallest dams in the Willamette River basin. Detroit Dam is {{convert|463|ft|m}} high and stores {{convert|455000|acre.ft|m3|lk=in}} of water.<ref>{{cite encyclopedia |last=Reinhardt |first=Bob |url=http://www.oregonencyclopedia.org/articles/detroit_dam/ |title=Detroit Dam |publisher=Portland State University |encyclopedia=The Oregon Encyclopedia |access-date=June 7, 2010}}</ref> [[Lookout Point Dam]] on the [[Middle Fork Willamette River]], forming [[Lookout Point Lake]], has the largest water storage capacity, at {{convert|477700|acre.ft|m3}}. The other 11 dams are [[Big Cliff Dam|Big Cliff]] on the North Santiam River; [[Green Peter Dam|Green Peter]] and [[Foster Dam|Foster]] on the [[Santiam River]]; Cougar on the [[South Fork McKenzie River]]; [[Blue River Reservoir|Blue River]] on the [[Blue River (Oregon)|Blue River]]; [[Fern Ridge Reservoir|Fern Ridge]] on the [[Long Tom River]]; [[Hills Creek Dam|Hills Creek]] and [[Dexter Reservoir|Dexter]] on the Middle Fork Willamette River; [[Fall Creek Lake|Fall Creek]] on [[Fall Creek (Middle Fork Willamette River)|Fall Creek]]; [[Cottage Grove Dam|Cottage Grove]] on the [[Coast Fork Willamette River]], and [[Dorena Reservoir|Dorena]] on the [[Row River]].<ref name="valley locations"/>

Due to these tall dams, [[Chinook salmon]] and [[Rainbow trout|steelhead]] are blocked from roughly half of their historic habitat and [[spawn (biology)|spawning]] grounds on the Willamette's major tributaries. Unable to live and reproduce as they once did, they have been "brought to the brink of extinction".<ref name="Kelly House">{{cite news |last=House |first=Kelly |title=As Willamette Project Dam Work Inches Along, Corps Works Out Deadline Extension |work=OregonLive |url=http://www.oregonlive.com/environment/index.ssf/2015/07/as_willamette_project_dam_work.html |date=July 9, 2015 |access-date=January 22, 2017}}</ref> Endangered species listings and a subsequent lawsuit by [[Willamette Riverkeeper]] led to a plan to improve fish passage and take other actions to help native fish recover in 2008.<ref>{{cite news |last=Learn |first=Scott |title=Getting Salmon Past Daunting Willamette Basin Dams Could Have a Big Price Tag—and a Big Payoff |url=http://www.oregonlive.com/environment/index.ssf/2011/09/detroit_dam_to_restore_wild_ru.html |work=OregonLive |date=September 8, 2011 |access-date=January 22, 2017}}</ref> Since then, work has proceeded slowly, and the Corps of Engineers, citing engineering difficulties and cost, may not meet the original agreed-upon deadline of 2023 for a system of effective remedies.<ref name="Kelly House"/>

Other major dams in the Willamette watershed are owned by other interests; for example, several hydroelectric facilities on the [[Clackamas River]] are owned by [[Portland General Electric]]. These include the [[River Mill Hydroelectric Project]], the [[Oak Grove Hydroelectric Project|Oak Grove]] project, and the dam at [[Timothy Lake]].<ref name="PGE">{{cite web |title=Clackamas River |url=https://www.portlandgeneral.com/corporate-responsibility/environmental-stewardship/water-quality-habitat-protection/clackamas-river |publisher=Portland General Electric |access-date=November 16, 2016}}</ref>

==Bridges==
[[File:HawthorneBridge-Pano.jpg|thumb|right|alt=The Hawthorne Bridge|The [[Hawthorne Bridge]] is the oldest remaining highway structure over the Willamette.]]
The 50 or so [[List of crossings of the Willamette River|crossings]] of the Willamette River include many historic structures, such as the [[Van Buren Street Bridge]], a [[swing bridge]]. Built in 1913, it carries [[Oregon Route 34]] (Corvallis–Lebanon Highway) over the river upstream of RM&nbsp;131 (RK&nbsp;211) in Corvallis. The machinery to operate the swing span was removed in the 1950s.<ref>Smith, ''et al.'', p. 287</ref><ref name="topoquest Corvallis">{{cite web |author=U.S. Geological Survey |title=United States Geological Survey Topographic Map: Corvallis, Oregon, Quadrangle |publisher=TopoQuest |url=http://www.topoquest.com/map.php?lat=44.56617&lon=-123.25734&datum=nad83&zoom=2&map=auto&coord=d&mode=zoomin&size=m |access-date=May 31, 2010 |archive-date=October 13, 2012 |archive-url=https://web.archive.org/web/20121013055343/http://www.topoquest.com/map.php?lat=44.56617&lon=-123.25734&datum=nad83&zoom=2&map=auto&coord=d&mode=zoomin&size=m |url-status=dead}}</ref> The [[Oregon City Bridge]], built in 1922, replaced a [[Suspension bridge|suspension span]] constructed at the site in 1888. It carries [[Oregon Route 43]] over the river at about RM&nbsp;26 (RK&nbsp;42) between Oregon City and [[West Linn, Oregon|West Linn]].<ref>Smith, ''et al.'', p. 96</ref><ref name="topoquest Oregon City">{{cite web |author=U.S. Geological Survey |title=United States Geological Survey Topographic Map: Oregon City, Oregon, Quadrangle |publisher=TopoQuest |url=http://www.topoquest.com/map.php?lat=45.357222&lon=-122.607222&datum=nad83&zoom=4 |access-date=June 1, 2010 |archive-date=October 13, 2012 |archive-url=https://web.archive.org/web/20121013055400/http://www.topoquest.com/map.php?lat=45.357222&lon=-122.607222&datum=nad83&zoom=4 |url-status=dead}}</ref>

The [[Ross Island Bridge]] carries [[U.S. Route 26 in Oregon|U.S. Route&nbsp;26]] ([[Mount Hood Highway]]) over the river at RM&nbsp;14 (RK&nbsp;23). It is one of 10 highway bridges crossing the river in Portland. The {{convert|3700|ft|m|adj=on}} bridge is the only [[Cantilever bridge|cantilevered deck truss]] in Oregon.<ref>Smith, ''et al.'', p. 78</ref><ref name="topoquest Ross Island">{{cite web |author=U.S. Geological Survey |title=United States Geological Survey Topographic Map: Portland, Oregon, Quadrangle |publisher=TopoQuest |url=http://www.topoquest.com/map.php?lat=45.50121&lon=-122.66454&datum=nad83&zoom=4 |access-date=June 1, 2010 |archive-date=October 13, 2012 |archive-url=https://web.archive.org/web/20121013055412/http://www.topoquest.com/map.php?lat=45.50121&lon=-122.66454&datum=nad83&zoom=4 |url-status=dead}}</ref>
[[File:SteelBridgePano1.jpg|thumb|left|200px|alt=The Steel Bridge|The lower deck of the Steel Bridge can be raised independently of the upper deck.]]
[[Tilikum Crossing]] is a {{convert|1720|ft|m|adj=on}} [[cable-stayed bridge]] that carries public transit, bicycles, and pedestrians, but no cars or trucks, over the river.<ref>{{cite web |last=Lum |first=Brian |title=Tilikum Crossing: Set Apart by Design |url=http://howweroll.trimet.org/2015/08/21/tilikum-crossing-set-apart-by-design/ |date=August 15, 2015 |publisher=TriMet |archive-url=https://web.archive.org/web/20150924160112/http://howweroll.trimet.org/2015/08/21/tilikum-crossing-set-apart-by-design/ |archive-date=September 24, 2015}}</ref> It opened for general use on September 12, 2015, becoming the first new bridge built across the river in the [[Portland metropolitan area]] since 1973.<ref name=factsheet-aug13>{{cite web |title=Portland–Milwaukie Light Rail Bridge Fact Sheet/August 2013 |date=August 2013 |publisher=[[TriMet]] |url=http://trimet.org/pdfs/pm/Fact-sheets-timelines/PMLR_Bridge_Fact_Sheet_Aug2013.pdf |access-date=April 19, 2014 |archive-date=February 3, 2014 |archive-url=https://web.archive.org/web/20140203020137/http://trimet.org/pdfs/pm/Fact-sheets-timelines/PMLR_Bridge_Fact_Sheet_Aug2013.pdf |url-status=dead}}</ref><ref name=rose2>{{cite news |url=http://www.oregonlive.com/portland/index.ssf/2011/06/construction_begins_thursday_o.html |title=Construction Begins on New Light-rail Bridge in Portland That Will Go Up 'Piece by Piece' |last=Rose |first=Joseph |author-link=Joseph Rose (journalist) |work=OregonLive |date=June 30, 2011 |access-date=June 30, 2011}}</ref>

Farther downstream is the oldest remaining highway structure over the Willamette, the [[Hawthorne Bridge]], built in 1910.<ref>Smith, ''et al.'', p. 115</ref> It is the oldest vertical-lift bridge in operation in the United States<ref name = "Wortman">{{cite book |last=Wood Wortman |first=Sharon |author2=Wortman, Ed |title=The Portland Bridge Book |edition=3rd |publisher=Urban Adventure Press |year=2006 |pages=61–68 |isbn=0-9787365-1-6}}</ref> and the oldest highway bridge in Portland. It is also the busiest bicycle and [[Transportation in Portland, Oregon|transit]] bridge in Oregon, with over 8,000 cyclists<ref>{{cite web |url=http://www.portlandoregon.gov/transportation/article/386265 |publisher=Portland Bureau of Transportation |title=2011 Bicycle Counts Report |page=4 |access-date=April 24, 2013}}</ref> and 800 [[TriMet]] buses (carrying about 17,400 riders) daily.<ref name = "Wortman"/>

[[File:St. Johns Bridge, Portland, OR - March 2012.JPG|thumb|right|120px|alt=The St. Johns Bridge|The St. Johns Bridge in northwest Portland]]
Another historic structure, the [[Steel Bridge]], farther downstream, was "the largest telescoping bridge in the world at the time of its opening" in 1912.<ref name="Smith 208">Smith, ''et al.'', p. 208</ref> It carries trains on its lower deck, [[MAX Light Rail|MAX]] (Metropolitan Area Express) [[light-rail]] trains and motorized vehicles on its upper deck, and foot and bicycle traffic on a cantilevered walkway attached to the lower deck.<ref>Wortman and Norman, pp. 39–44</ref> When small ships must pass under the bridge, its double vertical-lift span can raise a lower railway deck without disturbing traffic on the upper deck. Operators can raise both decks as high as {{convert|163|ft|m}} above the water. The Steel Bridge is "believed to be the world's only double-lift span that can raise its lower deck independently of the upper deck."<ref name ="Smith 208"/>

The [[Broadway Bridge (Portland, Oregon)|Broadway Bridge]], slightly downstream of the Steel Bridge, was the world's longest double-leaf [[Bascule bridge|bascule]] drawbridge at the time of its construction in 1913.<ref name = "Smith 116">Smith, ''et al.'', p. 116</ref> Farther downstream, the [[St. Johns Bridge]], a steel suspension bridge built in 1931, replaced the last of the Willamette River [[ferry|ferries]] in Portland.<ref name = "Smith 113">Smith, ''et al.'', p. 113</ref> At about RM&nbsp;6 (RK&nbsp;10), it carries the [[Special routes of U.S. Route 30#Portland bypass|U.S. Route 30 Bypass]].<ref name = "Topoquest St. Johns">{{cite web |author=U.S. Geological Survey |title=United States Geological Survey Topographic Map:Linnton, Oregon, Quadrangle |publisher=TopoQuest |url=http://www.topoquest.com/map.php?lat=45.58508&lon=-122.76477&datum=nad83&zoom=4 |access-date=June 5, 2010 |archive-date=October 13, 2012 |archive-url=https://web.archive.org/web/20121013055422/http://www.topoquest.com/map.php?lat=45.58508&lon=-122.76477&datum=nad83&zoom=4 |url-status=dead}}</ref> The bridge has two [[Gothic architecture|Gothic towers]] supporting the span.<ref>{{cite web |publisher=Center for Columbia River History |title=St. Johns Bridge Dedication |url=http://www.ccrh.org/comm/slough/primary/stjbridge.htm |archive-url=https://web.archive.org/web/20160509122844/http://www.ccrh.org/comm/slough/primary/stjbridge.htm |archive-date=May 9, 2016 |url-status=dead}}</ref> The adjacent park and neighborhood of [[Cathedral Park, Portland, Oregon|Cathedral Park]] are named after the [[Gothic Cathedral]]-like appearance of the bridge towers. It is the tallest bridge in Portland, with {{convert|400|ft|m|adj=on}} tall towers and a {{convert|205|ft|m|adj=on}} navigational clearance.<ref name = "Smith 113"/>
{{Panorama 
|image=File:WillametteRvrPano.jpg
|fullwidth=7073 
|fullheight=1100 
|height=180 
|caption=The Willamette as it passes through Portland. The bridges seen, from left to right, are the Fremont, Steel, Burnside, Morrision, Hawthorne, Marquam, Ross Island and Sellwood.  The Tilikum Crossing bridge was not built at the time of this 2007 photo.
|alt=The bridges, from right to left, are the Sellwood, Ross Island, Marquam, Hawthorne, Morrision, Burnside, Steel (the black bridge that is partially obscured), Fremont (the arch bridge at far left). The mountains, from right to left, are Mount Hood, Mount Adams (only the tip is visible) and Mount Saint Helens.
}}

==Flooding==
[[File:Willamette River 1996 flood aerial.jpg|thumb|alt=Flooding in 1996|An aerial view of the 1996 flooding]]
Due to the volume and seasonality of precipitation in western Oregon, the Willamette River has often flooded. Heavy rains and mountain snows are common in winter, and snowpack in the Cascade Range can rapidly melt during warmer winter storms.<ref name="Oregon Encyclopedia"/><ref name="1861flood">{{cite web |last=Allen |first=Cain |url=http://oregonhistoryproject.org/articles/historical-records/the-great-flood-of-1861/ |title=The Great Flood of 1861 |publisher=Oregon Historical Society |work=The Oregon History Project |year=2004 |access-date=June 17, 2016 |archive-url=https://web.archive.org/web/20160827132826/https://oregonhistoryproject.org/articles/historical-records/the-great-flood-of-1861/ |archive-date=August 27, 2016 |url-status=live}}</ref> The greatest Willamette River flood in recorded history began in 1861, well before the construction of dams in the watershed.<ref name="1861flood"/>

Rainstorms and warm temperatures in December 1861 combined with a well-above-average snowpack in the Cascades created the largest Willamette River flood in recorded history. An observer of the flood wrote, "The whole Willamette valley was a sheet of water".<ref name="1861flood"/> From Eugene to Portland, thousands of acres of farmland were washed away, and many towns in the valley were damaged or destroyed. The "[[Great Flood of 1862|Great Flood]]", as it is sometimes called, was massively destructive to human development because most of that development was located on the river's floodplain, which provided rich soils and ready access to water transportation. The 1861 flood peaked at {{convert|635000|cuft/s|m3/s}}—more than the [[Mississippi River]] usually discharges in the 21st&nbsp;century—and inundated some {{convert|353000|acre|km2}} of land.<ref name="Flooding" /><ref name="1861flood"/><ref>{{cite web |title=Mississippi River Anatomy: How Much Water Does the Mississippi Handle? |url=http://www.americaswetlandresources.com/background_facts/detailedstory/MississippiRiverAnatomy.html |publisher=America's Wetland Foundation |access-date=August 27, 2013 |date=June 1, 2012 |archive-url=https://web.archive.org/web/20160514051844/http://americaswetlandresources.com/background_facts/detailedstory/MississippiRiverAnatomy.html |archive-date=May 14, 2016 |url-status=live}}</ref> This flood destroyed the town of [[Linn City, Oregon|Linn City]]. When the flood ended on December 14, only three homes remained standing in Linn City. No one died in the Linn City flood, but the destruction was too significant for the town to recover, and it was abandoned. Today the city of [[West Linn, Oregon|West Linn]] stands about where Linn City once was.<ref name="BLM">{{cite web |last=Thomas |first=Mike |title=Linn City, Oregon: A Victim of Nature's Wrath |publisher=Bureau of Land Management |url=http://www.blm.gov/wo/st/en/res/Education_in_BLM/Learning_Landscapes/For_Kids/History_Mystery/hm3/linn_city.html |archive-url=https://web.archive.org/web/20160930010910/http://www.blm.gov/wo/st/en/res/Education_in_BLM/Learning_Landscapes/For_Kids/History_Mystery/hm3/linn_city. |archive-date=September 30, 2016 |url-status=dead}} 
</ref>

Significant flooding recurred in the winter of early 1890.<ref name="philadelphia record">{{cite news |title=The Floods and the Storm |url=https://news.google.com/newspapers?id=U8tVAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=4553%2C5634916 |access-date=July 2, 2011 |newspaper=The Philadelphia Record |page=1 |date=February 9, 1890}}</ref><ref name="great floods">{{cite news |title=Oregon's Great Floods |newspaper=The New York Times |date=February 7, 1890 |url=https://timesmachine.nytimes.com/timesmachine/1890/02/07/103228176.pdf |access-date=July 2, 2011}}</ref> Portland's main street was completely submerged, communication over the Cascades was cut off, and many rail lines were forced to shut down.<ref name="great floods" /> Another major flood occurred on the Willamette in 1894, and although it too caused much damage, it was not as large as that of 1861.<ref name="Flooding"/>

[[File:Aerial view of vanport flooded.jpg|thumb|left|alt=flooded Vanport in 1948|The remains of Vanport City in June 1948]]

Throughout the 1940s the Willamette continued to flood its valley. It washed out five bridges in Lane County in December 1942,<ref name="vancouver sun">{{cite news |title=Floods Wash Out Oregon Bridges |url=https://news.google.com/newspapers?id=F_ZlAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=6691%2C1835508 |access-date=July 2, 2011 |newspaper=The Vancouver Sun |date=December 1, 1942 |location=Vancouver, British Columbia |page=1}}</ref> caused seven deaths in Portland and evacuations in Eugene in January 1943,<ref name="RG 1-2-43">{{cite news |title=Lower River Areas Hit by Flood Crest |url=https://news.google.com/newspapers?id=W7BWAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=4605%2C2872262 |access-date=July 2, 2011 |newspaper=The Register-Guard |location=Eugene, Oregon |date=January 2, 1943 |agency=Associated Press |page=1}}</ref><ref name="flood peril">{{cite news |title=Flood Peril Wanes in Ohio Valley |url=https://news.google.com/newspapers?id=t1wiAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=3694%2C861829 |access-date=July 2, 2011 |newspaper=Reading Eagle |date=January 1, 1943 |agency=United Press International |location=Reading, Pennsylvania |pages=1, 18}}</ref> flooded Corvallis in November 1946,<ref name="SDC 1946">{{cite news |title=Willamette River Is Nearing Crest of Flood Stage |url=https://news.google.com/newspapers?id=RONXAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=7328%2C7090518 |access-date=July 2, 2011 |newspaper=The Spokesman-Review |date=November 28, 1946 |agency=Associated Press |location=Spokane, Washington |page=2}}</ref> contributed to the destruction of [[Vanport City, Oregon|Vanport City]] and the death of about 15 of its residents in May 1948,<ref>{{cite web |url=http://www.portlandoregon.gov/parks/finder/index.cfm?&propertyid=34&action=ViewPark |title=Delta Park |publisher=Portland Parks & Recreation |access-date=November 10, 2013}}</ref><ref>{{cite news |url=https://news.google.com/newspapers?id=miwfAAAAIBAJ&pg=4282,5836489&hl=en |title=After the Flood: Portland State Pays Tribute to Vanport Pioneers |newspaper=Daily Record |location=Ellensburg, Washington |date=October 4, 2001 |first=Landon |last=Hall |agency=Associated Press |page=B3 |access-date=August 26, 2013}}</ref> and nearly flooded parts of Salem in December 1948.<ref name="Salem flooding">{{cite news |title=River Flood Waters Reach Oregon Capital |url=https://news.google.com/newspapers?id=dsBkAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=1317%2C5881058 |access-date=July 2, 2011 |newspaper=Telegraph Herald |date=December 14, 1948 |agency=Associated Press |location=Dubuque, Iowa |page=16}}</ref>

Although the Willamette was, by the mid-20th century, heavily engineered and controlled by a complex system of dams, channels, and barriers, it experienced severe floods through the end of the century. Storms caused a [[Christmas flood of 1964|major flood]] that swelled the Willamette and other rivers in the Pacific Northwest from December 1964 through January 1965, submerging nearly {{convert|153000|acre|km2}} of land.<ref name="FEMA">{{cite web |last1=Gregory |first1=S. |last2=Ashkenas |first2=L. |last3=Jett |first3=S. |last4=Wildman |first4=R |url=http://www.fsl.orst.edu/pnwerc/wrb/Atlas_web_compressed/3.Water_Resources/3e.flood&fema_web.pdf |title=Flood Inundations/FEMA Floodplains: Floods and Floodplains in the Willamette River |publisher=Corvallis Forestry Research Community, Oregon State University |work=Willamette River Basin Atlas (2nd edition) |access-date=June 6, 2010 |archive-url=https://web.archive.org/web/20171209104055/http://www.fsl.orst.edu/pnwerc/wrb/Atlas_web_compressed/3.Water_Resources/3e.flood%26fema_web.pdf |archive-date=December 9, 2017 |url-status=dead}}</ref> Before dawn on December&nbsp;21, 1964, the Willamette reached {{convert|29.4|ft|m}}, which was higher than the seawall on its banks in Portland. By this time, about 15 people had died as a result of the flooding, and about 8,000 had been forced to evacuate their homes.<ref name="rampaging river">{{cite news |title=Portland Threatened by Rampaging River |newspaper=Tri-City Herald |date=December 21, 1964 |location=Kennewick, Washington |page=20}}</ref>

On December 24, 1964, President [[Lyndon B. Johnson]] ordered federal aid for the flooded areas as the Willamette continued to rise.<ref name="spoiled holiday">{{cite news |title=Floods Spoil Holiday in Oregon, California |url=https://news.google.com/newspapers?id=Nq4RAAAAIBAJ&dq=willamette%20flood%20-wiki&pg=7350%2C2520105 |access-date=June 29, 2011 |newspaper=The Spokesman-Review |date=December 25, 1964 |page=2 |location=Spokane, Washington}}</ref> In the next couple of days, the river receded, but on December&nbsp;27, it was at {{convert|29.8|ft|m}}, which was still nearly {{convert|12|ft|m}} above the flood stage.<ref name=reprieve>{{cite news |title=Portland Gets Reprieve from a Big Flood Threat |url=https://news.google.com/newspapers?id=-JUfAAAAIBAJ&dq=portland%20gets%20reprieve%20from%20a%20big%20flood%20threat&pg=1976%2C5832349 |access-date=June 29, 2011 |newspaper=The Nevada Daily Mail |date=December 27, 1964 |location=Nevada, Missouri |page=1}}</ref> The river continued to pose flood threats through January 1965,<ref name="pittsburgh press">{{cite news |agency=United Press International |date=January 30, 1965 |title=1000 Flee Flood in Northwest; Nation Shivers |newspaper=The Pittsburgh Press |url=https://news.google.com/newspapers?id=iF4bAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=6917%2C4443507 |page=1 |access-date=July 2, 2011}}</ref> and more stormy weather occurred along the Pacific Coast.<ref name="lewiston daily sun">{{cite news |agency=Associated Press |date=February 6, 1965 |title=Eastern Deep Freeze Eases, but Rain Brings Flood Fears to West |newspaper=The Lewiston Daily Sun |location=Lewiston, Maine |page=1 |url=https://news.google.com/newspapers?id=GsZGAAAAIBAJ&dq=willamette%20river%20flood%20-wiki&pg=6981%2C2178938 |access-date=July 2, 2011}}</ref>

{{quote box|align=right|width=33%|quote = The river crested at one town after another—at Corvallis 3½ feet above flood stage, Oregon City 18 feet above, Portland 10.5 feet above—much like a meal moving through a boa constrictor.|source= —Associated Press, February 10, 1996<ref name="Deseret News">{{cite news |agency=Associated Press |date=February 10, 1996 |title=Swollen River Spares Downtown Portland |newspaper=The Deseret News |location=Salt Lake City |page=A4 |url=https://news.google.com/newspapers?id=X_BHAAAAIBAJ&dq=the%20river%20crested%20at%20one%20town%20after%20another%20like%20a%20meal%20moving%20through%20a%20boa%20constrictor&pg=6510%2C5004315 |access-date=June 25, 2011}}</ref>}}

In February 1996, heavy warm rains driven by a subtropical [[jet stream]] fell on a deep snowpack in the Willamette watershed. These conditions, similar to those that caused the 1861 flood, caused [[Willamette Valley Flood of 1996|some of the costliest flooding in the river's recorded history]].<ref>{{cite web |last=Taylor |first=George H. |url=http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/6134/SR%20no.%20970_ocr.pdf?sequence=1 |title=The Great Flood of 1996: Its Causes and a Comparison to Other Climate Events |publisher=Oregon State University |date=November 1996 |page=2 |access-date=August 3, 2011}}</ref> An [[Associated Press]] journalist reported, "The river crested at one town after another—at Corvallis 3½ feet above flood stage, Oregon City 18 feet above, Portland 10.5 feet above—much like a meal moving through a boa constrictor."<ref name="Deseret News"/> The flood was serious enough to interrupt the progress of Oregon's growing economy,<ref>{{cite news |last=Barnard |first=Jeff |agency=Associated Press |title=Flood Spreads in Economy Like Muddy Water |url=http://nl.newsbank.com/nl-search/we/Archives?p_product=RM&p_theme=rm&p_action=search&p_maxdocs=200&p_topdoc=1&p_text_direct-0=0EB4E49FC4CAF785&p_field_direct-0=document_id&p_perpage=10&p_sort=YMD_date:D&s_trackval=GooglePM |access-date=June 26, 2011 |newspaper=Rocky Mountain News |date=February 25, 1996 |location=Denver}}</ref> but the inundated acreage was smaller than in 1964—only about {{convert|117000|acre|km2}}.<ref name="FEMA"/>

About 450 concrete flood-protection walls in Portland that had been constructed during the February flood, each weighing about {{convert|5500|lb|kg}}, were removed in April 1996.<ref>{{cite news |title=Flood Wall Comes Down Today in Portland |url=https://news.google.com/newspapers?id=ZEdWAAAAIBAJ&dq=willamette%20river%20flood%201996%20-wiki&pg=5507%2C82622 |access-date=June 26, 2011 |newspaper=The Register-Guard |date=April 1, 1996 |location=Eugene, Oregon |page=3C}}</ref> In October, they were replaced by a larger steel wall that cost the city about $300,000. The new wall had {{convert|0.25|in|mm|adj=on}} removable steel plates designed to better prevent future flooding.<ref>{{cite news |agency=Associated Press |date=October 14, 1996 |title=Flood Wall Readied for Next Time |newspaper=The Register-Guard |location=Eugene, Oregon |page=5C |url=https://news.google.com/newspapers?id=MUxWAAAAIBAJ&dq=willamette%20steel%20plates%20-wiki&pg=1859%2C3852913 |access-date=June 27, 2011}}</ref>

==Pollution==
[[File:FleetWeekRoseFestival.jpg|thumb|340px|alt=The Tom McCall Waterfront Park|The [[Tom McCall Waterfront Park]] is named after the Oregon governor who led a cleanup of the river.]]
Since as early as 1869, with the introduction of a federally funded "snag puller" designed to keep the waterway clear, human habitation has affected the [[ecology]] of the river basin. Domestic and industrial waste from the cities built up along the river "essentially [turned] the main-stem river into an open sewer by the 1920s."<ref name="Oregon Encyclopedia" /> The construction of large federal dams on the Willamette's tributaries between 1941 and 1969 damaged the spawning grounds for spring [[Chinook salmon]] and [[Rainbow trout|steelhead]].<ref name="Oregon Encyclopedia" /> <!-- 1-2 more sentences summarizing changes in more recent decades? -->

A 1927 [[City Club of Portland]] report labeled the waterway "filthy and ugly" and identified the City of Portland as the worst offender. The Oregon Anti-Stream Pollution League brought a pollution-abatement measure before the [[39th Oregon Legislative Assembly]] in 1937. The bill passed, but Governor [[Charles Martin (Oregon politician)|Charles Martin]] vetoed it. The [[Izaak Walton League]] and the Oregon affiliate of the [[National Wildlife Federation]] countered the governor's veto with a ballot initiative, which passed in November 1938.<ref name="Oregon Encyclopedia" />

Governor [[Tom McCall]], shortly after he was elected in 1966, ordered water quality tests on the Willamette, conducted his own research on the water quality, and became head of the [[Oregon State Sanitary Authority]]. McCall learned that the river was heavily polluted in Portland. In a television documentary, ''Pollution in Paradise'', he said, "The Willamette River was actually cleaner when the Oregon Sanitary Authority was created in 1938 than it was in 1962."<ref name="Williams, p. 131">Williams, p. 131</ref> He then discouraged tourism in the state and made it harder for companies to qualify for a permit to operate near the river. He also regulated how much those companies could pollute and closed plants that did not meet state pollution standards.<ref name="Williams, p. 132">Williams, p. 132</ref><ref name="Sarasota">{{cite news |title=Oregon Sets Pace in Improving Environment |url=https://news.google.com/newspapers?id=8pscAAAAIBAJ&dq=tom%20mccall%20willamette%20river&pg=7577%2C366713 |access-date=July 17, 2011 |newspaper=Sarasota Herald-Tribune |date=April 17, 1973 |agency=Los Angeles Times/Washington Post News Service |location=Sarasota, Florida |page=20A}}</ref>

Despite earlier cleanup efforts, state studies in the 1990s identified a wide variety of pollutants in the river bottom, including [[toxic heavy metal|heavy metals]], [[polychlorinated biphenyl]]s (PCBs), and [[pesticide]]s along the lower {{convert|12|mi|km}} of the river, in Portland.<ref>{{cite web |title=Portland Harbor Cleanup Sites |url=http://www.deq.state.or.us/lq/cu/nwr/portlandharbor/docs/PortlandHarborMap.pdf |publisher=Oregon Department of Environmental Quality |date=February 17, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110930213739/http://www.deq.state.or.us/lq/cu/nwr/portlandharbor/docs/PortlandHarborMap.pdf |archive-date=September 30, 2011}}</ref> As a result, this section of the river was designated a [[Superfund]] site in 2000,<ref name="van der Voo">{{cite news |url=http://portlandtribune.com/component/content/article?id=88851 |title=History of a Superfund Cleanup Bid |last=Van der Voo |first=Lee |work=Portland Tribune |date=July 2, 2007 |archive-url=https://web.archive.org/web/20160304032118/http://portlandtribune.com/component/content/article?id=88851 |archive-date=March 4, 2016 |url-status=dead}}</ref> involving the [[United States Environmental Protection Agency|U.S. Environmental Protection Agency]] (EPA) in cleanup of the river bottom.<ref>{{cite web |title=Portland Harbor Superfund Site |publisher=Oregon Department of Environmental Quality |url=http://www.deq.state.or.us/nwr/PortlandHarbor/ph.htm |archive-url=https://web.archive.org/web/20061216212032/http://www.deq.state.or.us/nwr/PortlandHarbor/ph.htm |archive-date=December 16, 2006}}</ref> The area to be addressed stretches from the Fremont Bridge almost to the Columbia – spanning nearly 11 river miles.<ref>U.S. EPA, Record of Decision, January 6, 2017, p. 88</ref> Reducing risk from the pollutants in this stretch will involve removing contaminated sediment from the river bottom and efforts to contain contaminated sediment by placing clean sediment on top (known as "capping").<ref>U.S. EPA, Record of Decision, January 6, 2017, p. 144</ref> Pollution has been exacerbated by combined sewer overflows, which the city has greatly reduced through its [[West Side CSO Tunnel|Big Pipe Project]].<ref>{{cite web |title=The Willamette River: A Renaissance in the Making |url=http://www.americanrivers.org/assets/pdfs/reports-and-publications/chapter_6e1f9.pdf |publisher=American Rivers |archive-url=https://web.archive.org/web/20160411155812/http://www.americanrivers.org/assets/pdfs/reports-and-publications/chapter_6e1f9.pdf |archive-date=April 11, 2016 |page=140 |url-status=dead}}</ref> Farther upstream, the pressing environmental issues have mainly been variations in pH and dissolved oxygen.<ref>{{cite web |title=Processes Controlling Dissolved Oxygen and pH in the Upper Willamette River Basin |publisher=U.S. Geological Survey |year=1994 |url=http://or.water.usgs.gov/pubs_dir/Pdf/95-4205.pdf |access-date=February 12, 2008 |archive-url=https://web.archive.org/web/20161222135305/http://or.water.usgs.gov/pubs_dir/Pdf/95-4205.pdf |archive-date=December 22, 2016 |url-status=live}}</ref> The Willamette is nevertheless clean enough to be used by cities such as Corvallis and [[Wilsonville, Oregon|Wilsonville]] for drinking water.<ref>{{cite web |first1=Mark |last1=Knudson |first2=Libby |last2=Barg |title=Drinking the Willamette: the Power of Public Education |url=http://www.pnws-awwa.org/uploads/PDFs/conferences/2008/Drinking%20the%20Willamette.pdf |publisher=Pacific Northwest Section of the American Water Works Association |access-date=December 24, 2012 |page=2 |date=May 1, 2008}}</ref>

Since pollution concerns are primarily along the lower river, the Willamette in general scores relatively high on the Oregon Water Quality Index (OWQI), which is compiled by the [[Oregon Department of Environmental Quality]] (DEQ). The DEQ considers index scores of less than 60 to be very poor; the other categories are 60–79 (poor); 80–84 (fair); 85–89 (good), and 90–100 (excellent).<ref>Oregon Water Quality Index, p. 6</ref> The Willamette River's water quality is rated excellent near the source, though it gradually declines to fair near the mouth. Between 1998 and 2007, the average score for the upper Willamette at Springfield (RM&nbsp;185, RK&nbsp;298) was 93. At Salem (RM&nbsp;84, RK&nbsp;135), the score was 89, and good scores continued down to the Hawthorne Bridge in Portland (RM&nbsp;13, RK&nbsp;21) at 85. Scores were in the "fair" category farther downstream; the least favorable reading was 81 at the Swan Island Channel midpoint (RM&nbsp;0.5, RK&nbsp;0.8). By comparison, sites on the [[Winchuck River]], the Clackamas, and the North Santiam all scored 95, and a site at a pump station on Klamath Strait Drain between [[Upper Klamath Lake]] and [[Lower Klamath Lake]] recorded the lowest score in Oregon at 19.<ref name ="OWQI 7-10">Oregon Water Quality Index, pp. 7–10</ref>

==Flora and fauna==
[[File:Osprey mg 9605.jpg|right|upright|thumb|alt=Osprey|Osprey are among bird species often seen along the Willamette River.]]
Over the past 150 years, a significant change for the Willamette River has been the loss of its floodplain forests, which covered an estimated 89&nbsp;percent of a {{convert|400|ft|m|adj=on}} band along each river bank in 1850.<ref name="Benke 619"/> By 1990, only 37&nbsp;percent of this zone was forested; the rest had been converted to farm fields or cleared for urban or suburban uses.<ref name="Benke 619"/> The remaining forests close to the river include stands of [[Populus trichocarpa|black cottonwood]], [[Fraxinus latifolia|Oregon ash]], [[willow]], and [[Acer macrophyllum|bigleaf maple]].<ref name="Benke 619">Benke, ''et al.'', p. 619</ref> The central valley—a former perennial grass prairie interspersed with oak, [[Douglas fir]], [[Pinus ponderosa|ponderosa pine]], and other trees—is devoted almost entirely to farming. Douglas fir, [[Tsuga heterophylla|western hemlock]], and [[Thuja plicata|western red cedar]] dominate the forest on the Coast Range side of the basin. Forests to the east in the Cascade Range are predominantly Douglas fir, [[Abies amabilis|Pacific silver fir]], western hemlock, and western red cedar.<ref name="Benke 617" /><ref name="Benke 616"/>

Fish in the Willamette basin include 31 native species, among them [[Coastal cutthroat trout|cutthroat]], [[Bull trout|bull]], and [[rainbow trout]], several species of [[salmon]], [[Catostomidae|sucker]], [[minnow]], [[sculpin]], and [[lamprey]], as well as [[sturgeon]], [[stickleback]], and others. Among the 29 non-native species in the basin, there are [[Brook trout|brook]], [[Brown trout|brown]], and [[lake trout]], [[Largemouth bass|largemouth]] and [[Smallmouth bass|smallmouth]] bass, [[walleye]], [[carp]], [[bluegill]], and others. In addition to fish, the basin supports 18 species of amphibians, such as the [[Pacific giant salamander]]. [[Beaver]] and [[North American river otter|river otter]] are among 69 mammal species living in the watershed, also frequented by 154 bird species, such as the [[American dipper]], [[osprey]], and [[harlequin duck]]. [[Garter snake]]s are among the 15 species of reptiles found in the basin.<ref name="Benke 620-21"/>

Species diversity is greatest along the lower river and its tributaries. Threatened, endangered, or sensitive species include spring Chinook salmon, winter steelhead, [[chum salmon]], [[Coho salmon]] and [[Oregonichthys|Oregon chub]].<ref name="Benke 620-21">Benke, ''et al.'', pp. 620–21</ref> In the central valley, several projects have been done to restore and protect wetlands<ref>{{cite web |title=Willamette Valley Projects |url=http://www.ohjv.org/projects/willamette.html |publisher=Oregon Habitat Joint Venture |archive-url=https://web.archive.org/web/20160313132319/http://ohjv.org/projects/willamette.html |archive-date=March 13, 2016 |date=November 14, 2001 |url-status=dead}}</ref> in order to provide habitat for [[bald eagle]]s, [[Fender's blue butterfly]], Oregon chub, [[Lomatium bradshawii|Bradshaw's desert parsley]], a variety of [[Erigeron decumbens|Willamette fleabane]], and [[Lupinus sulphureus|Kincaid's lupine]].<ref>{{cite web |title=Threatened & Endangered Species |url=http://www.fws.gov/refuge/William_L_Finley/Wildlife_and_Habitat/T_E_Species.html |work=William L. Finley National Wildlife Refuge |publisher=U.S. Fish and Wildlife Service |archive-date=July 15, 2015 |archive-url=https://web.archive.org/web/20150715014856/http://www.fws.gov/refuge/William_L_Finley/Wildlife_and_Habitat/T_E_Species.html |url-status=dead}}</ref><ref>{{cite web |url=http://www.fws.gov/refuge/Baskett_Slough/wildlife_and_habitat/T_and_E.html |title=Threatened & Endangered Species |work=Baskett Slough National Wildlife Refuge |publisher=U.S. Fish and Wildlife Service |archive-date=July 15, 2015 |archive-url=https://web.archive.org/web/20150715021656/http://www.fws.gov/refuge/Baskett_Slough/wildlife_and_habitat/T_and_E.html |url-status=dead}}</ref><ref>{{cite news |last=Zaveri |first=Mihir |title=In Oregon's Willamette Valley, the Race to Save the Endangered Fender's Blue Butterfly |url=https://www.oregonlive.com/environment/2011/06/a_research_team_studies_the_en.html |newspaper=The Oregonian |date=June 17, 2011 |access-date=December 21, 2022}}</ref><ref name=federalregister>{{cite web |url=https://www.federalregister.gov/documents/2023/01/12/2023-00037/endangered-and-threatened-wildlife-and-plants-reclassifying-fenders-blue-butterfly-from-endangered |title=Endangered and Threatened Wildlife and Plants; Reclassifying Fender's Blue Butterfly From Endangered to Threatened With a Section 4(d) Rule |date=January 12, 2023 |author=U.S. Fish and Wildlife Service |work=Federal Register |publisher=National Archives |access-date=May 29, 2023}}</ref> In the early 21st&nbsp;century, osprey populations are increasing along the river, possibly because of a ban on the pesticide [[DDT]] and on the birds' ability to use power poles for nesting.<ref name="Benke 621">Benke, ''et al.'', p. 621</ref> Beaver populations, presumed to be much lower than historic levels, are increasing throughout the basin.<ref name="Benke 621"/>

==See also==
{{Portal|Rivers|Oregon}}
* [[List of crossings of the Willamette River]]
* [[List of longest streams of Oregon]]
* [[List of rivers of Oregon]]
* [[Steamboats of the Willamette River]]
{{clear}}

==References==
{{reflist|colwidth=30em}}

==Works cited==
{{refbegin}}
{{div col}}
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* Laenen, Antonius; Dunnette, David A. (1997). ''River Quality: Dynamics and Restoration''. Boca Raton, Florida: CRC Press. {{ISBN|978-1-56670-138-9}}. {{OCLC|34885999}}.
* Loy, Willam G.; Allan, Stuart Allan; Buckley, Aileen R.; Meecham, James E. (2001) [1976]. ''Atlas of Oregon'' (2nd ed.). Eugene, Oregon: University of Oregon Press. {{ISBN|978-0-87114-101-9}}. {{OCLC|228223337}}.
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* {{cite book |last=Meinig |first=D.W. |title=The Shaping of America: A Geographical Perspective on 500 Years of History, Volume 3: Transcontinental America, 1850–1915 |year=1998 |publisher=Yale University Press |location=New Haven, Connecticut |isbn=978-0-300-08290-6 |oclc=60197763 |url-access=registration |url=https://archive.org/details/shapingofamerica00dwme}}
* Orr, Elizabeth L.; Orr, William N. (1999). ''Geology of Oregon'' (5th ed.). Dubuque, Iowa: Kendall/Hunt Publishing Company. {{ISBN|978-0-7872-6608-0}}. {{OCLC|42944922}}.
* Orr, Elizabeth L.; Orr, William N. (2012). ''Oregon Geology'' (6th ed.). Corvallis, Oregon: Oregon State University Press. {{ISBN|9780870716812}}. {{OCLC|794227917}}.
* {{cite book |last1=Ruby |first1=Robert H. |last2=Brown |first2=John A. |year=1976 |title=The Chinook Indians: Traders of the Lower Columbia River |url=https://archive.org/details/chinookindianstr00ruby |url-access=registration |series=Civilization of the American Indian |location=Norman, Oklahoma |publisher=University of Oklahoma Press |isbn=978-0-8061-2107-9 |oclc=1958350}}
* Samson, Karl (2010). ''Frommer's Oregon''. Hoboken, New Jersey: Wiley-Blackwell. {{ISBN|978-0-470-53771-8}}. {{OCLC|671277501}}.
* Smith, Dwight A.; [[James B. Norman|Norman, James B.]]; Dykman, Pieter T. (1989) [1986]. ''Historic Highway Bridges of Oregon'' (2nd ed.). Portland, Oregon: Oregon Historical Society Press. {{ISBN|978-0-87595-205-5}}. {{OCLC|20362124}}.
* Snipp, C. Matthew (1989). ''American Indians: The First of This Land''. New York, New York: Russell Sage Foundation. {{ISBN|978-0-87154-822-1}}. {{OCLC|19670797}}.
* Stenzel, Franz (1972). ''Cleveland Rockwell: Scientist and Artist, 1837–1907''. Portland, Oregon: Oregon Historical Society. {{ISBN|978-0-87595-037-2}}. {{OCLC|333762}}.
* {{cite book |last=Thornton |first=Russell |year=1990 |title=American Indian Holocaust and Survival: A Population History Since 1492 |location=Norman, Oklahoma |publisher=University of Oklahoma Press |series=Civilization of the American Indian |isbn=978-0-8061-2220-5 |oclc=263150623}}
* {{cite book |last=Timmen |first=Fritz |title=Blow for the Landing |year=1973 |publisher=Schiffer |location=Atglen, Pennsylvania |oclc=38286714}}
* {{cite book |author1=U.S. Coast |author2=Geodetic Survey |name-list-style=amp |title=Report of the Superintendent of the U.S. Coast and Geodetic Survey Showing the Progress of the Work during the Fiscal Year Ending with June 1886 |year=1887 |publisher=Government Printing Office |location=Washington, D.C. |oclc=28937852}}
* {{cite book |last1=Wallick |first1=Jennifer Rose |last2=Grant |first2=Gordon E. |last3=Lancaster |first3=Stephen T. |last4=Bolte |first4=John P. |last5=Denlinger |first5=Roger P. |chapter=Patterns and Controls on Historical Channel Change in the Willamette River, Oregon, USA |chapter-url=https://www.fs.usda.gov/research/treesearch/33121 |year=2007 |title=Large Rivers: Geomorphology and Management |editor-last=Gupta |editor-first=Avijit |publisher=John Wiley & Sons |location=Chichester, England |isbn=978-0-470-84987-3 |access-date=December 22, 2022}}
* {{cite book |last=Wilkes |first=Charles |title=Narrative of the United States' Exploring Expedition, During the Years 1838, 1839, 1840, 1841, 1842: Condensed and Abridged |url=https://archive.org/details/bub_gb_o3AFAAAAQAAJ |publisher=Whittaker and Co |location=London |year=1845 |oclc=602918838}}
* {{cite book |last=Williams |first=Travis |title=The Willamette River Field Guide |year=2009 |publisher=Timber Press |location=Portland, Oregon |isbn=978-0-88192-866-2 |oclc=243601804}}
* Wortman, Sharon Wood; Wortman, Ed.; Norman, James B. (2006). ''The Portland Bridge Book'' (3rd ed.). Portland, Oregon: Urban Adventure Press. {{ISBN|978-0-9787365-1-4}}. {{OCLC|76928209}}.
{{div col end}}
{{refend}}

==External links==
{{Commons|Willamette River}}
* [http://www.portlandoregon.gov/citycode/article/72561? City of Portland River Renaissance Strategy]
* [https://web.archive.org/web/20130525094401/http://www.opb.org/thinkoutloud/shows/guiding-willamette/ Guiding the Willamette] [web archive], ''Think Out Loud'' radio program on [[Oregon Public Broadcasting]], April 1, 2009
* [http://www.oregongeology.org/pubs/ll/p-poster-willamette.htm Historic river channels between Albany and Monmouth]&nbsp;– Oregon Department of Geology and Mineral Industries [[lidar]] poster
* [https://web.archive.org/web/20070505061622/http://www.deq.state.or.us/lq/cu/nwr/PortlandHarbor/index.htm Portland Harbor DEQ cleanup]&nbsp;– Oregon State Department of Environmental Quality
* [http://www.willamette-riverkeeper.org Willamette Riverkeeper]&nbsp;– Non-profit environmental organization

{{AHR}}
{{Portland, Oregon, watersheds}}
{{featured article}}

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[[Category:Willamette River| ]]
[[Category:American Heritage Rivers]]
[[Category:Ferries of Oregon]]
[[Category:Oregon placenames of Native American origin]]
[[Category:Rivers of Benton County, Oregon]]
[[Category:Rivers of Clackamas County, Oregon]]
[[Category:Rivers of Lane County, Oregon]]
[[Category:Rivers of Linn County, Oregon]]
[[Category:Rivers of Marion County, Oregon]]
[[Category:Rivers of Multnomah County, Oregon]]
[[Category:Rivers of Washington County, Oregon]]
[[Category:Rivers of Yamhill County, Oregon]]
[[Category:Rivers of Columbia County, Oregon]]
[[Category:Rivers of Oregon]]
[[Category:Tributaries of the Columbia River]]
[[Category:Willamette Valley]]