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
Xan Augerot (MRWC) and Leslie Bach (TNC) Within Our Reach Oregon State University Alumni CH2M Hill Center 6 December 2012