Floods and Flows - Augerot and Bach


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Presentation by Xan Augerot of the Marys River Watershed Council and Leslie Bach of The Nature Conservancy

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  • Big mountains, big water. 11,476 sq mi basin is home to 2.5 million peopleRain-driven hydrology, but largest events are rain on snow
  • Big water, 13 big dams designed for flood control, water storageThey were located,designed& operated primarily for flood control. Other authorized purposes include hydropower production, recreation, fish and wildlife, water quality, and storage of water for municipal and industrial water supply and irrigation. Some of those purposes benefit from having the water in storage in the reservoirs...while others benefit from the timed release of water to meet downstream needs.
  • Prior to the construction of Lookout Point Dam, flood flows greater than 30,000 cfs were not uncommon in the fall and winter. That is twice the peak flood flow of the mid 1990s, even during the 1996 flood. We have taken the tops off of winter floods, and increased stream flows in the summer months.
  • Beyond the loss of upstream spawning habitat for salmonids:Loss of winter rearing habitat in inundated areas downstreamDecrease in supply of large wood, sediments and channel-forming flowsLoss of population connectivity for species such as Oregon chub
  • Troy will share the inundation model for the Willamette, developed by River Design Group.
  • Leslie will explain the TNC-ACOE ecological flows planning, and describe opportunities for restoration of mainstem Willamette habitat function.
  • Just after Fall Creek drawdown, which you will hear about from Greg.
  • Engineered large wood structures providing slack water winter habitat for cutthroat trout and other fishes and amphibians, depositing sediments, creating channel complexity and high quality habitats.Mainstem restoration work to reconnect channel to floodplain in the Marys and other tributaries is limited by the base elevation of the Willamette, which has declined with the impoundment of sediments behind dams.
  • Floods and Flows - Augerot and Bach

    1. 1. Xan Augerot (MRWC) and Leslie Bach (TNC) Within Our Reach Oregon State University Alumni CH2M Hill Center 6 December 2012
    2. 2. Willamette Basin Project,USACE:13 Multi-Purpose Dams & Reservoirs132 miles of navigation channel100 miles of revetments © USACE © Leslie Bach/TNC © USACE © USACE
    3. 3. Observed Flow of Middle Fork Willamette River at Jasper, Oregon
    4. 4. Lateral Dimension
    5. 5. Loss of complex off-channel and floodplain habitatWillamette River Planning Atlas (PNW Ecosystem Research Consortium)
    6. 6. Willamette past, present and … 1890 Flood1890 Willamette FloodOregon State Archives, Marion Co Historical Society, MJON0209 1943 Flood Oregon State Archives, Oregon Water Resources Department, OWR0085 © Leslie Bach/TNC © Leslie Bach/TNC © USACE
    7. 7. Future: flows shaped and targeted for habitat and floodplain restoration © Leslie Bach/TNC (Tharme and King 1998; Postel and Richter 2003)© Rick McEwan
    8. 8. January 2012: it all comes together High flows scoured side channel, and backwatered onto floodplain© RaptorViews Philip Bayles psb@efn.org 25000 Middle Fork Willamette at Jasper 20000 15000 Flow (cs) 10000 5000 0 9/1/2011 10/1/2011 11/1/2011 12/1/2011 1/1/2012 2/1/2012 3/1/2012© Chris Orsinger
    9. 9. And after three floods on the Marys…Photos J. Beathe, Starker Forests