Erosion and (beach, but not bluff) recovery at Kalaloch

12 March 2021 photo of the eroded access stairs below Kalaloch Lodge

Through support from Washington Sea Grant, the North Pacific Coast Marine Resources Committee, and with a research permit from Olympic National Park, I've been prioritizing every-other-month trips out to the beach around Kalaloch Creek to collect beach profiles and other shoreline morphology information.  This post is intended to be a bit of a summary of observations I've made to date.  So first off, some profiles going back to 2017 from the southern edge of my study area, just south of the lodge/cabins:

So these plots have three sub-panels - at the top are all of the profiles collected along a particular transect, and the location of the transect is shown in red in the map at lower left.  The plot at lower right is a time-series of the position of the Mean High Water contour on the transect through time.  In this particular figure note two things - first off the annual cycle in the position of the beach shown in the time-series at lower right.  This seasonal cycle has to do with on-shore and off-shore movements of sand that are associated with seasonal changes in the wave climate, and its a common feature of high energy sandy beaches.  The envelope of variability for the profiles at this site are also huge...the elevation of the beach changes by ~6 feet each year, suggesting that a truly massive weight of sand (something like 300,000-400,000 tons of sand if I did my math right) is potentially being pushed back and forth each year on and off the beach under Kalaloch Lodge. 

The other thing to note in these data is that there is no obvious chronic erosion going on on the beach over this 4 year time-frame (check this out for a bit more on that).  In other words, each year the winter erosion that happens on the beach is countered by accretion in the spring and summer.  Zooming in on data from the last three surveys perhaps illustrates this better, as beach recovery is already occurring after erosion that happened between October and January:

At Kalaloch, though, chronic erosion IS occurring on the bluff.  Since I survey with an RTK-DGPS system I'm not able to survey most of the bluff face, but I can generally collect data on the location of the toe of the bluff, and these bluffs are generally pretty vertical.  The rates of bluff erosion are fastest to the north, nearer to the creek, and have been dramatic this winter:

This erosion is also readily apparent in photos, and has impacts.  The photo at the top of this post comes from the northern section of the beach near to the creek, and the access stairs to the beach here have been closed for a few months.  Here is photo, from a different perspective, of this section of bluff taken on 2 September 2016:

 and more or less the identical location and perspective from just a few days ago, on 12 March 2021:

Its important to note that, unlike beaches, bluffs can't recover naturally.  In other words bluffs don't have any natural mechanism by which erosion is counter-acted.  This has really important implications in regards to attempts to manage bluff erosion using defensive approaches...its incredibly hard and expensive, and failure of the structure over time is more or less assured.