Image of the Week – Elwha River Dam Removal

In September 2011 the largest dam removal project in U.S. history began. Two dams built on the Elwha River in the early 1900s created two reservoirs in northwestern Washington. They also greatly reduced the amount of sediment flowing to the rivers delta and blocked salmon migration upstream into Olympic National Park. A 2011 image from Landsat 5 shows the river before the dams were removed. The Lake Mills and Lake Aldwell reservoirs are visible along the river. After dam removal images from Landsat 8 using shortwave infrared and near-infrared imaging reveal sediment blanketing the beds of the former lakes. Closer views show the river changing course over time. With the dams gone the river deposits more sediment at the delta. Natural color images show sediment flowing into the ocean. A USGS animation shows the changing Elwha River delta. The animation is based on shaded relief elevation maps from summer topographic and bathymetric surveys.

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