Storm impacts on the beach: 27 November 2019

I had a chance to poke around Ediz Hook and Port Angeles Harbor a bit around high tide on 27 November 2019, during a strong northeast wind that coincided with high tide.  Waves were breaking over the coastal defenses on Ediz Hook (video above shot from the Coho ferry), as well as on to the Olympic Discovery Trail:



and not surprisingly, led to a bit of damage along the trail:



Beaches exposed to the northeast were also impacted.  I just happened to collected a few beach profiles on the east side of the Elwha River delta the day before this storm, so went back out afterwards to re-occupy those transects, one collected about here:

 and another a bit further east here:

Both of these beach profiles definitely show the impact of that event on the beach.  In both cases the upper beach eroded landward by anywhere between a fraction of a meter (a few feet), and up to roughly 3 meters (~10 feet).  I don't typically have the opportunity to capture this kind of event-driven change, and in fact these sorts of quantitative characterizations of event-driven change on the shorelines of Puget Sound and the Strait of Juan de Fuca are pretty rare...so I'm glad the opportunity came up. 

The anatomy of this particular storm was interesting to me.  The tide itself wasn't particularly high.  The tide gauge in Port Angeles maxed out at about 0.3 m (~ 1 foot) above MHHW:

and there was no storm surge associated with this event.  In fact, the high tide was suppressed a little bit, probably by the outward flow of air in the Strait (since the air pressure was low-ish during the high tide).  A water level of 0.3 m (~1 foot) above MHHW is nothing - we typically hit 0.3 m above MHHW multiple times a year.  What really made this event tick was wind, and in particular the strong flow of air out of the Strait, that led to sustained winds measured in Port Angeles harbor of 20 to 25 knots from the northeast.  The wind kicked up waves with significant wave heights exceeding 1.5 meters at the NOAA buoy in the Strait of Juan de Fuca, which is big, but not huge, for the Strait in November.  And this is really where we get to what made this event so interesting...it was the direction of the wind and waves...from the northeast...directed straight into Port Angeles Harbor, and straight at the end of Ediz Hook and the east side of the Elwha.

The waves breaking over the rip-rap on Ediz Hook (in the video at the start at this post) also provide an important bit of context.  I know from my survey work out there that the crest of the rip-rap sits at an elevation of roughly 2.5 meters (~8 feet) to 3.0 meters (~9.5 feet)  above MHHW.  Since we know that the water level at the time, as measured at the tide gauge, was 0.3 meters (~1 foot), we also know that water was being pushed 7 feet or more above the water level at the time, up and over the crest of the rip-rap.  So wave-related process, like wave run-up and set-up, were really important in making this event exciting.  Furthermore, we can actually use the event to characterize the magnitudes of those processes during an extreme event...and those sorts of observations are also relatively rare in Puget Sound and the Salish Sea.

Elwha sand hits Ediz Hook (maybe)

Looking at Ediz Hook from the west, September 2013

When I present about Elwha I frequently get asked about if, and how much, Elwha River sediment has made it to Ediz Hook.  I've also addressed this question in a previous blog arguing at the time (summer of 2016) that I didn't see evidence for any Elwha influence on Ediz Hook.  This year, though, I started answering that question with a bit more confidence - I think it is likely that Elwha sediment has made it to Ediz Hook in quantities adequate to lead to measurable changes on the beach.  I'm going to lay out some preliminary evidence for an influence on the beach of Ediz Hook in this blog.

First off, what is the shoreline response that I'm looking for?  I've framed the expected response to dam removal on the shoreline along the Elwha littoral cell as the "X-hypothesis".  Essentially I am measuring two things - the location of the beach profile, and the grain size of the beach.  When the dams came down we expected to see something like this:

in which a previously coarse eroding beach becomes finer and starts to move seaward.  We definitely saw this pattern on the Elwha delta, and in fact just published a paper focused in particular on the beach profile position part of the story (the red line in the conceptual model above).

We also expect this response to move alongshore, driven by alongshore transport processes.  So, essentially, the profile response and grain size response should sort of propagate alongshore with time, something like:

One of the most interesting insights from that paper is that we took a crack at estimating the RATE that the dam removal response moved alongshore, at least on the Elwha River delta nearest to the river mouth...and came up with an estimate of 1 meter per day.  If we extrapolated that rate to Ediz Hook, which is 8.5 km from the Elwha River mouth, we wouldn't expect a response there for quite some time...around 2033.  The evidence I'm going to lay out below suggests the possibility that Ediz Hook is seeing a response now.  Other evidence suggests faster response rates than our paper came up with as well.  The Coastal Watershed Institute, for example, published this account of beach accretion east of the delta in 2014...suggesting early slugs of sediment propagating along that shoreline that may have influenced Ediz Hook in some way.

So what is the evidence on Ediz Hook?  I'm going to show summer annual beach profiles dating back to 2012, and oblique photos of the beach from three locations dating back to 2014, the first being the transect that I survey at the very base of Ediz Hook.  So here, the evidence that I see is in the beach profiles:

So what I think I see here is a fairly stable beach between 2012 and 2016, but then a period of accretion between 2016 and 2018.  Its not huge...the beach moved seaward by a handful of meters...but it is out of character for this beach at least based on the limited data we have.  The grain size story at this site isn't quite as compelling.  Here is an oblique from 2014:

and 2016:

and then 2017, in which if you focus on some of the rip rap material in the far field you can really see the beach accretion

and 2018 in which we seem to see a finer beach face:

and finally this year (2019), in which overall we continue to see a relatively finer shoreline:

So lets turn our attention a bit further east, and further out on Ediz Hook.  This site sits just past the mill, and just about a kilometer from the site above.  The story once you get to the mill and beyond is complicated, and the evidence isn't strong.  But it may be there.  Here are the profile data:

Erosion from 2012 to 2016, then a big bump seaward by the summer of 2017 associated with a cobble nourishment project (more on that below), erosion again between 2017 and 2019, but then, critically, a movement seaward between 2018 and 2019.  Lets look at the oblique photos, starting in 2014:

then 2016:

2017...this is the cobble nourishment:

2018...amazing how quickly that cobble is eroded from the site:

and 2019:

The story at this site is complicated by cobble nourishment, placed very 5 years or so under contract with the Army Corps of Engineers.  Ediz Hook was nourished in this way, and at this site, in 2011 and again in 2017.  However, one of the things that seems clear to me looking at these photos and profiles though is that the nourish material erodes very rapidly after it is placed, and the beach probably continues to erode until the next nourishment.  The summer of 2017 photo above, for example, is a very visual example of what this beach looks like just before nourishment - coarse and heavily eroded.  So the evidence that I see here for an Elwha influence is that between 2018 and 2019 the beach didn't erode...it grew, apparently (based on the photos), because of an influx of sand and gravel.  Scant, I know...but something.

The final site is right around the middle of Ediz Hook.  Here are the profile data:

Its hard to see in this profile view, and the MHHW time-series plot isn't really working here, but you can see the influence of the 2011 nourishment in this profile, and then erosion through 2018 (interesting that there is no obvious influence of the 2017 nourishment in this profile, though there might be in the grain size)...but then a little accretion between 2018 and 2019.  Here are the photos, starting with 2014:

then 2016:

2017:

2018:

and 2019:

So here the summer of 2017 stands out for how coarse the beach substrate was, perhaps reflecting alongshore transport of cobble that was placed near the mill in early 2017.  That nourishment, though, based on the profile data, didn't really add too much volume to the beach.  However, between 2018 and 2019, as at the last location, we see an increase in beach volume driven by sand and gravel (based on the photos).

So is there an Elwha influence on Ediz Hook?  I think so.  I think the profile and grain size data support it, and while its conceivable that there is another source of sediment at play here (bluff erosion for example), I don't think that the rate of erosion on the Elwha bluffs accounts for what we see in these profiles.  As always, looking forward to next year's survey data.

Beach dynamics make the West End Natural Resources News

The North Pacific Coast Marine Resources Committee publishes a great annual newsletter highlighting natural resources issues and projects in the "West End" of the Olympic Peninsula.  I was given the opportunity to write up a little summary of my year-long shoreline dynamics study that I pulled off with MRC funding (along with support from Olympic National Park and Peninsula College), which is available here in the July 2019 edition.  But I'm going to reproduce the article here...enjoy:

The Olympic Coast is an extraordinary place - one needs to only try to find a trailhead parking spot on a summer weekend to find visceral proof of that. People travel from around the world to visit.  Drill down further though, and focus only on the narrow boundary between the land and sea, and the shoreline of the Olympic Coast becomes even more extraordinary still.  Most people who visit the coast with this sort of focus tend to dwell on the diverse and colorful intertidal marine community of the rocky shorelines.  But, through the support of the North Pacific Coast MRC and my employer, Washington Sea Grant, I’ve had the opportunity to study the dynamics and behavior of Olympic Coast beaches for the last year, and will describe a bit of what I’ve found.

The broad sandy beach at Kalaloch, one of two study sites for this project.  Photo from April 2018

 My study focuses on two beaches – Rialto and Kalaloch – though it is likely that the lessons I’ve learned are the same up and down the stretch of the Olympic Coast from Pt. Grenville to the south to Cape Flattery in the north.  The beaches along this stretch of coast are alive and dynamic, molding themselves each day to the changing behavior of the unruly North Pacific Ocean, and the geologically-tortured lands of the western fringe of the Olympic Peninsula.  Sandwiched between these two restless bodies, Olympic Coast shorelines literally shape-shift in an effort to hold a line.

Map of the Olympic Coast, which I define as stretching from Cape Flattery to the north, and Point Grenville to the south.  My two study sites, Rialto and Kalaloch Beaches, are marked on the map.

Let me start first by describing what I do on the beach.  I use survey equipment to measure, with great accuracy, location and elevation on the beach.  Collected along transects that cut across the beach, the raw GPS data can be converted into what are called beach profiles.  The figure below is an example from a single transect at Rialto Beach.  You learn something from a profile from a single day – you can easily calculate, for example, the slope of the beach, the width of the beach, or the elevation of the berm at the top of the beach.  All are useful for understanding what sort of habitat a shoreline may provide. 

Three beach profiles, from three different days, collected at Rialto Beach, Olympic National Park.  Beach profiles represent a slice through the intertidal beach

But for me, the really interesting stories emerge by looking at these profiles over time, which is exactly what this project focused on.  I visited Rialto and Kalaloch every other month, developing a picture of the seasonal behavior of both beaches over the course of a year, and was able to calculate and plot a time-series of the position of the beach.  My take-away?  Both beaches are alive, never standing still.  Rialto over that time period moved almost 60 feet seaward between March 2018 and January 2019, and then promptly retreated 45 feet back in just the two months following January 2019.  Kalalaloch followed a similar pattern, except its back and forth movement, first landward and then seaward, exceeded 150 feet, and it ended the year with a final yo-yo back seaward of over 100 feet. 

Time-series of beach position at both Rialto and Kalaloch beaches from approximately Spring 2018 to Spring 2019.  Where the slope of the time-series line is positive the beach is accreting.  Where the slope is negative the beach is eroding.

What makes beaches dance this way?  If we imagine these beaches dancing to music, it is a complex composition.  Different factors like the range of tides, the source and supply of beach-building sediment, the presence or absence of large wood, and even the movement of groundwater certainly play a role in the behavior of beaches.  From a sediment stand-point, for example, both of these beaches are quite different; Kalaloch is a broad sandy beach along a relatively straight stretch of coast, while Rialto is a narrow mixed sand and gravel beach, positioned near a large river mouth.  If I had to guess, though, these beaches are mostly moving according to the seasonal tempo set by ocean waves.  At a basic level, beaches are controlled by the energy delivered to the shoreline by waves, which indeed does vary dramatically over a typical season on the Olympic Coast.

Surveying Rialto Beach during a winter storm, February 2018

I was also able to fit the beach profiles collected over the year into a larger study focused on long-term trends at both beaches; in essence I’m trying to determine if the beaches of the Olympic Coast are eroding over many years, accreting, or just staying put.  The reasons for doing this may not be obvious, but they are important.  Beaches often serve as barriers that protect human infrastructure from the astonishing energy of the ocean.  Indeed, both Kalaloch and Rialto serve this function for things that we’ve built behind them.  Erosion of beaches in and of itself is a natural process, but if that erosion compromises things that we value it becomes a hazard.  The outlook for damaging erosion of shorelines all over the globe isn’t great; a rising average sea level can prompt beach erosion, as can a change in the energy carried by waves across the ocean’s surface, and both are observed to be happening all over the world. 

Example summer profiles from Kalaloch Beach from 2014 and 2018, and a time-series of summer beach position (bottom panel), also from Kalaloch Beach.

Profiles collected every year in the summer, limited though they are to the last 5-6 years, start to paint a picture of a possible long-term erosion trend at both beaches.  It is difficult to conclude too much from the erosion trends that are emerging from my data…it is simply too short of a record to evince a great deal of confidence.  But perhaps these data are a reminder that we live in a time of change, and these beaches that we enjoy may be increasingly stressed by changes in the North Pacific Ocean.  We, as a society, may have some hard decisions to make regarding how to respond to that in the future.

Sea-star wasting is still at work in the sub-tidal environment of the central Strait of Juan de Fuca

A map showing most of our long-term sub-tidal monitoring sites around the Elwha River Delta.  We've got a few additional sites closer to Freshwater Bay, and Green Point.

I was able to join up again this summer with a team of divers from the US Geological Survey and Lower Elwha Klallam Tribe to collect sub-tidal ecology data at a series of sites along the central Strait of Juan de Fuca.  We are basically limping along a program that we started way back in 2008, that at the time was focused solely on understanding how dam removal would influence the coastal marine ecological community near the Elwha River mouth.  We published our opus on that question in 2017.  Since 2017, though, we've continued each summer to cobble together just enough support to visit at least some of our sites.

Nancy Elder (diver in far field) and Steve Rubin (diver in near field) from the US Geological Survey survey a transect at site E2 on 6 August 2019

Our focus has broadened a bit, now, and we are developing an expanded set of goals for this work:

1. Continue to try to understand how habitats that were altered by dam removal evolve over longer-time-scales
2. Use some of our sites that were less altered by dam removal to understand overall trends in ecological conditions, and patterns of annual variability
3. Understand patterns and trends related to loss and recovery of sea stars due to Sea Star Wasting Syndrome (SSWS)

Its #3 that I want to focus on briefly here, because SSWS is still at work in these sub-tidal environments of the Strait of Juan de Fuca.  How do we know?  We saw it:

The arm of a Pycopodia helianthoides on the sea-floor at Site GP1 on 25 July 2019.  Wasting probably proceeds very quickly, so it is likely that this star was probably roaming the sea-floor looking healthy just the day before. 

We did see a few other healthy-looking P. helianthoides across the sites that we visited. This star, for example, was at the same site on the same day:

One of the larger stars we observed at our sites this summer...maybe a bit in excess of 30cm.  Site GP1, 25 July 2019.

But clearly their numbers are still very depressed from what we used to see prior to the onset of disease in 2014.  In 2008, for example, P. helianthoides was the 5th most abundant invertebrate at our sites (see p. 148 here).

The star in the photo above was also notable for its relatively large size.  In general, most of the P. helianthoides that we've observed at these sites since 2014 have been less than 30 cm in diameter, whereas in the past we regularly observed larger specimens:

A large star catching a ride on the back of Steve Rubin, USGS, at a site near Freshwater Bay, 9 September 2009.

To end on a hopeful note - I did recently observe some larger specimens at a site in Port Angeles harbor this year...the first I've seen in "the wild" since 2014.  Maybe the subject of a future post.

The ocean is WARM

A 2005 satellite image of Cascadia.  We live in a landscape that is wedded to the ocean.

I've got a backlog of posts on my to-do list, but not a lot of time these days.  So this one will be short and to the point.  The ocean lapping Washington's coast is warm again...like possibly record-setting warm.   One of the longer ocean temperature records that I am able to access in its entirety is from NOAA's Cape Elizabeth buoy, which sits about 40 miles off of Taholah.  There are a couple of ways to visualize these data, but I like this approach, where the daily average temperature observations are laid over each other by year:

Daily average temperature dating back to 1987 from NOAA's Cape Elizabeth buoy.  This year's data are bolded in green.

This is a nice way to get a sense for the usual range of variability in temperature at this site across the entire record.  The data from this year aren't complete in this plot (that may be a problem with my download script - haven't checked) but the most recent summer data are there, and are shown with the bold green line.  The period right around the 200th day of the year (19 July this year) appears to be a record.  Its gotten a bit cooler since then, but we are still definitely on the upper end of the range of variability at this site.  Its warm.

By the way, I'm assuming that odd spike in the red line around the 270th day of the year is spurious...haven't checked that out yet...but based on how it looks compared to the rest of the record I don't think it is real.

The Cape Elizabeth buoy is some distance off-shore.  Is this warmth evident closer to the coast?  It appears so.  Here are temperature data form the tide gauge in La Push.  While this is a much shorter record, dating back to only 2005, it also appears as if some new temperature records were set at La Push in the middle of July:

Daily average temperature dating back to 2005 from NOAA's tide gauge in La Push, Washington.  This year's data are bolded in blue.

Again, I'm assuming that weird spike in yellow from around the 120th day of 2007 is spurious.

This does appear to possibly be something not affecting the inland sea.  Here is the same plot from Friday Harbor:

Daily average temperature dating back to 1992 from NOAA's tide gauge in Friday Harbor.  This year's data are bolded in red.

It is warm...the most recent observations from Friday Harbor are almost 14C, or almost 57F (yes, that is warm for the inland sea)...but nowhere near the record highs set in the summer of 1997 (the light blue line in the plot above).

A new sea level rise impact assessment hits the news...but may not be newsworthy

A few days ago the Center for Climate Integrity released quite an interesting study intended to try to estimate the cost of protecting the nation's coastlines against sea level rise using shoreline armoring approaches.  I was interviewed for a response, as were other colleagues within the Washington Coastal Resilience Project, and collectively I think we pushed a few key points in response to this study:

1.  On the plus side:  The overall benefit of studies like this, from my standpoint, is to both remind us that there are impacts to things we care about from sea level rise, and to come up with comparative cost/impact estimates for sea level rise across some area of interest (the United States, Washington State, etc.).  Put another way, studies like this can provide us with ways to prioritize different adaptation actions over some area we care about.  An example of a similar study is Zillow's real estate exposure analysis analysis from a few year's ago.  I didn't look at Zillow's analysis as a real prediction of real estate impacts, but I DID see it as a useful way to evaluate relative vulnerability to sea level rise across the country, and across Washington State.  That is useful.

2.  Also on the plus side:  They do a good job focusing on the near-term.  They emphasize in their results that they are using a sea level rise scenario that is likely by 2040.  That is very much within contemporary planning horizons.  That is useful.

3.  Now, on the negative side:  This study SHOULD NOT lead anyone to imagine though that armoring is the only, or the most desirable, way to address sea level rise.  Lest you imagine that we were alone in this response, my friend and colleague Rob Young in North Carolina had the same response.  There are a variety of possible responses to sea level rise, including adaptating vulnerable infrastructure, or pulling it back from the coast, or soft-shore armoring options, that may very well be cheaper AND more effective than traditional armoring for reducing risks from sea level rise.

3.  And also, on the negative side:  There may be some flaws in this study.  I didn't outright say this in my interview, mostly because at the time I had barely had a chance to review the report.  But now that I've had a chance to dig into it a bit more I can't really figure out where they got the numbers they did.  Setting aside the question of how accurate the dollar values are, this  also compromises the usefulness of this study as a way to assess relative vulnerability along the coast.  To be clear, the methods they outline seem sound...but let me illustrate my concerns.

Here is a map of the contemporary Mean High High Water shoreline of Port Angeles, snipped from the NOAA Sea Level Rise Viewer:

So the blue areas are those that are currently flooded at the current average high tide.  I chose Port Angeles to focus on for two reasons:  First, this is where I live, so I know the shoreline really well.  Second, Port Angeles pops out in their analysis as one of the most exposed communities on Washington's coast, requiring 15 miles of seawalls to provide protection by 2040, under the scenario that they considered.

Okay, so lets dig into that a bit.  First, 15 miles is a lot.  Measuring the length of shorelines is hard and you get different numbers doing it different ways.  BUT, I did a quick and dirty assessment of the TOTAL shoreline length for the city of Port Angeles using Google Earth and came up with...12.5 miles.  Total:

I don't get all of the tiny little wiggles and such, but I do include the bluff backed shoreline to the east of Port Angeles.  So at first blush 15 miles of seawall "required" by 2040 seems quite a lot. .

I also mapped, again using the NOAA Sea Level Rise Viewer, their chosen scenario for their analysis, a 50th percentile sea level rise projection for 2040 under RCP 4.5 (I came up with 5 inches) and a 1-year return frequency storm surge event (1.5 feet)  Here is the map:

Compare this carefully with the map above and look for differences.  See any?  There are a few but they are VERY slight.  There is a good physical reason for this...we have a steep shoreline, and we already get plenty of events the push water 2 feet above MHHW.  As a consequence, there isn't much built in that zone.  How did their model translate this into a change into a changed flood exposure that "requires" armoring the entire coast of Port Angeles? 

Before I look to a study like this as a useful way to assess relative vulnerability to sea level rise on Washington's coast I have to understand that.

The winter ocean doing strange things

Hourly water temperature, parsed by year, from the NDBC 46041 buoy off of Washington's coast

I was going through some wave metrics from the Cape Elizabeth buoy and noted this interesting water temperature pattern, and though I would throw up a quick blog about it.  The figure above shows each year's temperature data by day of the year.  The bold red line is this year, 2019.  Water temperature plunged about 2C in a matter of days...a fairly rare thing for the winter when temps tend to be fairly uniform.  

I've highlighted two years in the record when something similar seems to have happened this time of year...in 2014 (the sort of reddish bolded line) and in 2018 (the purplish bold line).

Monthly average water temperature from the Cape Elizabeth buoy (blue line), and the anamoly from the 1999-2008 average (red line).

Its also worth noting that up to that point the ocean was pretty warm.  The figure above shows the anamoly from the monthly average, and we are still in this phase of warm winter ocean water that kicked off in 2015.  In fact at Cape Elizabeth there have been only two warmer Januaries, in 2003 and 2016.

Hourly water temperature, parsed by year, from the Port Angeles tide gauge

 Just out of curiosity I also downloaded the water temp data from the Port Angeles tide gauge...shorter record, same idea.  Same pattern here.  Perhaps its not a coincidence that at about the time that this water temperature plunge started it got really cold here in Port Angeles.

Anatomy of a coastal storm: December 20

December 20, 2018 photo of flooding in the Three Crabs area.  Photo from the Peninsula Daily News

The storm on December 20, 2018 brought some coastal flooding with it...notably in the Three Crabs area on the Dungeness River delta, and locations in Port Townsend.  I'm going to focus this post on the Three Crabs flooding.  Shortly after the event a set of aerial photos shot by John Gussman of Doubleclick Productions began to make the rounds, and a few things caught my attention.  First, this was a still water flood - there was little wave action associated with this event at this location (in contrast to areas exposed to south wind, like in Port Townsend).  As a result, we might be able to learn something interesting about the processes driving this event from tide gauge data.  Second, it was very localized near the mouth of Meadowbrook Creek, which suggested to me the possibility of a river component to the event.  I grabbed those photos, and a few published by the Peninsula Daily News (above) and headed out with an interest in seeing if I could get some flood elevation data.  I had a particular question in mind - was this flood driven entirely by coastal processes, or was there a river component to it?

Debris line left by flooding on December 20, 2018, Three Crabs area on the Dungeness River delta.  Photo collect 18 January 2019

So first, the flood elevation data.  I didn't really need the photos...there were plenty of places where a debris line was still evident, a month after the flood (photo above).  I ended up collecting 52 estimates of the elevation of the flood waters using Peninsula College's ProMark 200.

Location of 52 flood elevation estimates from the Three Crabs area

I'm going to report elevations here in meters relative to NAVD88, to facilitate comparison to tide gauge data collected in Port Angeles (at this location, based on VDatum, NAVD88 is 2.09 m BELOW Mean Higher High Water).  So here are two presentations of the flood elevation data:

Flood elevation estimates based on surveys of debris lines, or water lines from photos, in meters relative to NAVD88, for the December 20, 2018 flood at Three Crabs.

The top panel show the data plotted against longitude, since I was interested in whether there was any elevation variation in the flood that might suggest a fluvial component to the flooding.  There is a bunch of scatter, and its too hard to say.  The points at larger longitudes do seem to be a bit higher in elevation, but that is the opposite that I would expect if Meadowbrook Creek was a source, since Meadowbrook Creek is in the opposite direction.  I'm going to call this inconclusive.

The histogram in the bottom panel provides a sense for the range in the elevations I collected.  The mean of these values is 2.94 m NAVD88, which equates to 0.85 m (2.8 ft) above Mean Higher High Water at this location.  There is a total range in the values of 0.35 m, or just over a foot...with is most likely a reflection of trying to estimate a flood surface elevation from a pile of debris on the side of a road.  

So lets move on to comparing the flood elevations at Three Crabs to tide gauge data collect in Port Angeles.  For this purpose I'm going to compare to the mean flood elevation value from the data I collected, 2.94 meters NAVD88.  Here are the data collected at the Port Angeles tide gauge that day:

The tide gauge in Port Angeles recorded a maximum water level of 2.98 m NAVD88 at 11:36 am that day, driven by the combination of a high tide (predicted to be 2.32 m NAVD88, just above Mean Higher High Water), and a 0.66 m non-tidal residual, or "storm surge".  In this case the "storm surge" was probably driven mostly by low atmospheric pressure.  My conclusion though?  The flooding at Three Crabs very well could have been entirely driven by coastal processes - specifically the combination of a relatively large non-tidal residual co-occurring with a high tide.  

Lets dig a bit further to address two other questions.  First, where does this water level rank in the record collected in Port Angeles dating back to 1975?  Turns out that this was indeed a pretty high water level...but not the highest.  Three other events have driven coastal water level higher in Port Angeles.  The record for that tide gauge was set on 2 January 2003 by an event that was very similar - a high tide co-occurring with a storm surge of 0.66 m or so.  The big difference was in the timing of the tide...the predicted tide on 2 January 2003 was almost 0.10 m higher, and hence the record water level on that date was 3.07 m.  Two other events, one on 31 December 2005 and another on 27 January 1983 also both exceeded this December 20 event, if only barely.  Both of these events were characterized by lower non-tidal residuals, but higher astronomical tides than the event on December 20.  I'm curious about what happened in the Three Crabs area during those events.  

The next question...how bad could it be?  Coastal flooding is a game of chance, with the worst events happening when the astronomical tide is high, and the non-tidal residual is also large.  It gets even worse when we add in winds from the right direction...but lets ignore that here.  So the highest astronomical tide on record for Port Angeles was 2.63 m NAVD88 on 30 December 1986.  Pretty darn impressive astronomical tide!  The maximum non-tidal residual?  That occurred on 1 January 1997 when water level hit 0.9 meters above the predicted water level associated with a notable winter storm.  Fortunately on that day two things happened that kept water level relatively un-exciting (the tide gauge peaked out at a maximum water level of 2.79 meters NAVD88); first, the predicted high tide wasn't that high, and second the peak of the non-tidal residual didn't correspond with the peak of the high tide. 

So how high could it be?  Well what if that highest astronomical tide of 2.63 m NAVD88 corresponded with that maximum non-tidal residual of 0.9 meters?  A peak water level of 3.53 meters, fully 0.55 meters, or almost 2 feet higher than the December 20 event.  Now that would have been unpleasant in the Three Crabs neighborhood.  Fortunately for us the odds of those two things co-occurring are pretty darn low...but we are certain to get higher than we did on December 20...its only a matter of when.