New LiDAR Maps Reveal Skagit County's Geologic Landscape

LiDAR mapping – the process of methodically using pulsed lasers from a plane/helicopter to map aerial-view landscape features – helps communities plan for landslide hazards, understand potential floodplains, and learn about geologic features previously unknown. Because LiDAR penetrates through tree canopies, it produces much greater detail and precision than typical aerial maps. So, when new LiDAR maps are released (particularly in areas with heavy tree cover, thus meaning much longer lead times to create new maps) – it is a cause for excitement in the earth science and geographic information system (GIS) communities.

Skagit County just finished a year-long LiDAR mapping project of the county and produced a great new story map that reveals features--including a prehistoric landslide near Cultus Mountain – that were not apparent on the previous aerial maps.

The region’s first generation of LiDAR maps was a tremendous advancement over the aerial photo-based survey maps that had been used for generations. While very useful, the limitations in quality of the older LiDAR was most apparent in steep and heavily vegetated areas – frustrating because those are exactly the areas where you most want the best data. The greater detail and accuracy of this new generation of LiDAR maps presents a leap forward in resolution and ability to survey these important areas. 

 Compare the quality of the 2006 LiDAR map of Guemes Island (left) to the new version (right)

Compare the quality of the 2006 LiDAR map of Guemes Island (left) to the new version (right)

The new generation also frequently includes “green light LiDAR”, a method with the ability to penetrate water and reveal the bathymetry of shorelines, streams, rivers, and other shallow water bodies.  Both of these improvements greatly improve our ability to rely on the new LiDAR maps for interpretation of geomorphic features and active processes, and detect natural and human-caused changes in the environment. 

Take a look: Skagit Lidar Map Journal