Characterization of seafloor photographs near the mouth of the Elwha River during the first two years of dam removal (2011-2013)

We characterized seafloor sediment conditions near the mouth of the Elwha River from underwater photographs taken every four hours from September 2011 to December 2013. A digital camera was affixed to a tripod that was deployed in approximately 10 meters of water. Each photograph was qualitatively characterized as one of six categories: (1) base, or no sediment; (2) low sediment; (3) medium sediment; (4) high sediment; (5) turbid; or (6) kelp. For base conditions, no sediment was present on the seafloor. Low sediment conditions were characterized by a light dusting of sediment; medium sediment conditions were characterized by a layer of sediment that covered all rock surfaces but did not obscure the relief of the seafloor; high sediment conditions were characterized by a layer of sediment that covered all rock surfaces and obscured the relief of the seafloor. During turbid conditions, suspended sediment in the water column obscured the view of the seafloor, and during kelp conditions, blades of kelp covered the camera lens, blocking our view of the seafloor.