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Mapping Puget Sound bluffs and beaches

Our Coastal Monitoring & Analysis Program (CMAP) conducted a series of boat-based Lidar surveys at 16 sites spanning about 135 miles of shoreline and more than two dozen drift cells from 2013 through 2016. This critical work collected high-resolution, topographic data about Puget Sound beaches and bluffs.

Mapping strategy

The boat-based Lidar and GPS topography data were used to produce 0.5-meter digital elevation models for beaches and bluffs at each of the survey sites. These models provide afford us the opportunity to inventory and characterize the shoreline landscape affecting the nearshore ecosystem such as:
  • Feeder bluff activity
  • Beach slope and width
  • Armoring position, length, and elevation relative to the back shore
Boat-based Lidar provides a more advantageous point of view of the bluff face compared to airborne Lidar. This results in much higher resolution data needed to gain insight about bluff failure and erosion mechanisms as well as corresponding sediment transport processes. In addition, the near-horizontal look angle of the laser successfully collects data that lies under overhanging vegetation and over-water structures.

Using the data

In the future, repeat surveys will enable us to analyze changes in quantifying bluff sediment supply and marine riparian vegetation to gain a better understanding about the linkages between physical and ecological processes.
Satellite image of shoreline with houses compared to LIDAR point cloud of the same site showing the accuracy of the LIDAR scan.

Top image: Aerial photo of shoreline at Three Tree Point.  Bottom image: Boat-based LIDAR point cloud of same shoreline rotated to view from top-down

The drift cells were selected based on a geospatial analysis of bluff-backed beaches:

  • With a high potential for significant bluff sediment to supply intact shorelines.
  • Containing suitable habitat for forage fish, eelgrass, herring, and shellfish.
  • In which previous investments have been make for beach restoration projects.
  • That have potential for future shoreline armoring and habitat loss based on population growth scenarios.
For these reasons, the surveyed drift cells are top candidates for implementing bluff protection and restoration strategies.