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Surficial sediment data on the North Fork Stillaguamish River and State Route 530 landslide near Oso, Washington

October 30, 2017

These tables document grain-size distributions of sediment collected as part of a study on the geomorphic impacts of the March 2014 State Route 530 Landslide near Oso, Washington. This includes samples of material from the landslide deposit itself, covering a range of distinct facies present in the landslide, and samples of sand and gravel at various locations along the North Fork Stillaguamish River both upstream and downstream of the landslide. Grain size distributions of landslide material were distinguished between outwash material, till, and lacustrine material, distinct facies all present in the landslide deposit. Material coarser than 4-16 mm (sample dependent) was sieved and weighed in the field, and fine material was retained and analyzed at the Cascade Volcanoes Observatory Sediment lab. Bulk densities were measured for a subset of the samples. Grain size data for the North Fork Stillaguamish was collected via surficial pebble counts. All samples from 2014 and 2015 were collected by USGS. All samples prior to 2014 were collected by the Stillaguamish Tribe of Indians and provided to the USGS.