Landsat-8 images of Washington State landslide site

March 23rd, 2014 |
Landsat-8 0.59 µm panochromatic visible image of the Washington State landslide site

Landsat-8 0.59 µm panochromatic visible image of the Washington State landslide site

Kudos to Russ Dengel of the SSEC RealEarth web map server development team for spotting this: a relatively cloud-free overpass of the Landsat-8 satellite which revealed the site of the massive landslide/mudslide near the small town of Oso in northwestern Washington State (north of Seattle). The animation shown above was made using RealEarth to zoom in with the Google Maps base layer, and then toggle between the base map and an overlay of 15-meter resolution Landsat-8 0.59 µm (Band 8) panochromatic visible imagery at 19:03 UTC or 12:03 PM local time on 23 March 2014. It can be seen that debris from the landslide — which occurred a day earlier — covered one mile of State Road 530, cutting off access to the town of Darlington (located east of the landslide site); it also blocked the North Fork of the Stillaguamish River, leading to fears of localized flooding both upstream and downstream of the landslide site.

The Landsat-8 visible image is shown below. The landslide was blamed on ground saturation due to heavy rainfall in the region over the past month (30-day total rainfall | depature from normal).

Landsat-8 0.59 µm panochromatic visible image

Landsat-8 0.59 µm panochromatic visible image

===== 01 April Update =====

Landsat-8 0.59 µm panochromatic visible image on 01 April

Landsat-8 0.59 µm panochromatic visible image on 01 April

14 days later, there was another overpass of the Landsat-8 satellite; it could be seen on the 0.59 µm panochromatic visible image (above) that the mudslide still covered a significant portion of State Road 530. The 1.61 µm near-IR image (below) revealed that the mudslide had altered the course of the North Fork of the Stillaguamish River, and highlighted areas where some localized flooding was occurring due to a widening of the river (water is a strong absorber at the 1.61 µm wavelength, so it appears dark on the near-IR image).

Landsat-8 1.61 µm near-IR image on 01 April

Landsat-8 1.61 µm near-IR image on 01 April