Abstract Title

Session S-06F: Elwah River Restoration: Evolution of Habitats and Ecosystems During a Dam Removal Project

Keywords

Restoration

Location

Room 602-603

Start Date

1-5-2014 1:30 PM

End Date

1-5-2014 3:00 PM

Description

Concurrent removal of Elwha and Glines Canyon dams on the Elwha River, Washington, is the largest dam removal and related sediment release ever undertaken. The project began in fall 2011, and the older, smaller Elwha Dam was removed by spring 2012, while Glines Canyon dam is still being demolished. Repeat aerial surveys are capturing river and shoreline changes at a temporal and spatial scale that allows tracking the effects of sediment pulses released by dam drawdown and storm events. The Elwha PlaneCam, a low-cost aerial survey platform developed during the project, is collecting aerial imagery at 10-15 cm ground pixel resolution over more than 30 river km on a weekly-to-monthly basis along the shoreline and river from the mouth to the reference reach in Geyser Valley above the project. Structure-from-Motion surface reconstruction techniques are used to build high-resolution orthoimagery and digital surface models to calculate sediment erosion volumes from reservoirs, and to map geomorphic change in the river, including parameters such as deposition, erosion, braidedness, wood density, and sediment composition. These aerial survey data provide a uniquely detailed picture of the complex changes unfolding as the Elwha river and shoreline transitions from a sediment-starved to sediment-rich system. By fall 2013, more than 6 million cubic meters of sediment have been eroded from the two former reservoirs, dramatically altering river, estuarine, and nearshore plan and profile forms. Riverine changes include progressive transition from pool-riffle to braided channel type and initial aggradation followed by degradation driven by a large sediment wave moving through the system. At the river mouth, new estuarine and shoreline habitat is evolving following deposition of more than 8 m at the river mouth as the delta prograded over 300 m.

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May 1st, 1:30 PM May 1st, 3:00 PM

The Elwha PlaneCam: A novel and affordable aerial survey method tracking river and shoreline evolution in high spatiotemporal resolution during the largest dam removal in history

Room 602-603

Concurrent removal of Elwha and Glines Canyon dams on the Elwha River, Washington, is the largest dam removal and related sediment release ever undertaken. The project began in fall 2011, and the older, smaller Elwha Dam was removed by spring 2012, while Glines Canyon dam is still being demolished. Repeat aerial surveys are capturing river and shoreline changes at a temporal and spatial scale that allows tracking the effects of sediment pulses released by dam drawdown and storm events. The Elwha PlaneCam, a low-cost aerial survey platform developed during the project, is collecting aerial imagery at 10-15 cm ground pixel resolution over more than 30 river km on a weekly-to-monthly basis along the shoreline and river from the mouth to the reference reach in Geyser Valley above the project. Structure-from-Motion surface reconstruction techniques are used to build high-resolution orthoimagery and digital surface models to calculate sediment erosion volumes from reservoirs, and to map geomorphic change in the river, including parameters such as deposition, erosion, braidedness, wood density, and sediment composition. These aerial survey data provide a uniquely detailed picture of the complex changes unfolding as the Elwha river and shoreline transitions from a sediment-starved to sediment-rich system. By fall 2013, more than 6 million cubic meters of sediment have been eroded from the two former reservoirs, dramatically altering river, estuarine, and nearshore plan and profile forms. Riverine changes include progressive transition from pool-riffle to braided channel type and initial aggradation followed by degradation driven by a large sediment wave moving through the system. At the river mouth, new estuarine and shoreline habitat is evolving following deposition of more than 8 m at the river mouth as the delta prograded over 300 m.