Monday, June 24, 2013

Surveying Dungeness Spit

The view landward from the lighthouse on the end of Dungeness Spit.

Randy Johnson, now at the Jamestown S'Klallam Tribe, has called the Strait of Juan de Fuca the "Land of Large Spits"...the ready sediment supply (primarily from eroding bluffs) combined with highly oblique wave energy in the Strait of Juan de Fuca create ideal conditions for spit evolution. Ediz Hook and Dungeness Spit in particular are fascinating features that dominate the shoreline of the Central Strait of Juan de Fuca. While they are similar in so many ways, Ediz Hook and Dungeness Spit have "grown apart" in a way over the past 100 years or so...Ediz Hook is highly modified, with a mill, a road, power, water and sewer lines plus armoring that runs nearly its entire length. By contrast Dungeness Spit is nearly pristine from a morphologic standpoint...few modifications to either the spit itself or the adjacent bluffs that are the source of some or all of the sediment to the spit.

The sign at the end of the spit...a suitable reminder regarding how far you've come

Spits are particularly vulnerable to climate change (via sea level rise, changes in wave climate, or other factors) and/or changes in sediment supply from up-drift sources (like eroding bluffs or, in some cases, rivers). In the case of Ediz Hook and Dungeness Spit, both features are incredibly important to coastal communities - Ediz Hook as a barrier for Port Angeles Harbor, and Dungeness Spit as a wildlife refuge and shallow water habitat. As a result I wanted to include both features in a shoreline monitoring program that I've been working on developing over the past year. On Saturday, in partnership with the University of Washington MeSSAGE program we finally had the opportunity to get out and survey the end of Dungeness Spit.

A student from the UW MeSSAGE program collecting grain size samples on the end of Dungeness Spit

The goal was to establish baselines for proposed morphology (primarily beach profiles) and beach grain size monitoring that would occur twice a year for the next few years at least. The idea is to build a dataset that would allow us to address unresolved questions like, "how does sediment supply from adjacent bluffs influence the morphology of the spit?", "what are the implications of sea level rise on spits?", and "What are the patterns of spit migration relative to wave climate, sea level variability, or other factors". I also was interested in doing some basic morphology characterization to compare to the results found by Maury Schwartz and his students during their field work in the 1980's...still the only peer-reviewed work on shoreline morphology from Dungeness Spit.

A student form the UW MeSSAGE Program conducts a topography survey with a backpack-mounted RTK-DGPS system

As a preliminary survey the day was hugely was a big operation, and we ran into the inevitable logistical hurdles, but in the end we walked away with thorough coverage for the end of the spit. The goal now is to compare our topo data to existing LiDAR data, run our grain size samples, and then prepare for the next survey...

topographic survey data coverage for our one-day survey

A huge thank you to the staff of the Dungeness Spit National Wildlife Refuge for permitting and logistical support. Also, this project simply wouldn't have happened without equipment support provided by the US Geological Survey and Peninsula College.

1 comment:

Jassen L. Bowman said...

I just moved to Port Angeles a few days ago, and just wanted to say thanks for sharing all your field research experiences. I'm neither geologist or marine anything, but science is science, and I'm fascinated with the local topology and interaction between the Oly mountains and marine environs... It's all good stuff. Thanks for sharing all this!