Wednesday, November 25, 2015

Poking around at FW Bay

Every year for my Peninsula College Oceanography Class I offer an optional field trip in which we head out to FW Bay during a winter low tide, and poke around for an hour or two. This year's trip happened during last night's beautiful low tide, with cold but crystal clear conditions and a bright moon. This year's trip happened just 6 days after Tuesday's storm, which featured high tides and substantial must have really rocked the intertidal. We seemed to see it - many crabs missing legs, everything coated with a layer of silt...

As with last year's trip, there were two groups of animals that really seem to dominate the FW Bay intertidal:

The porcelain crabs, and the:

the gunnels

Both occurred, often in large numbers, under nearly every rock we looked under.

As with last year, we also came across a brooding female Red Rock crab, but unlike last year this one was alive and well:

Perhaps most unlike last year, we stumbled across a nice size Sunflower Star (photo at top), and a full-size Pisaster ochraceus:

in addition to many Leptasterias hexactis (which we typically see there), and a blood star.

Wednesday, October 14, 2015

Moorings away!

Step 1: Start with a table full of line, tape, zip ties, buoys and weights...

Back at teaching my Peninsula College oceanography class again, and earlier this week the class designed and built their temperature and light moorings. This continues to be one of my favorite activities with my class - getting to throw stuff in the ocean for science just never seems to get old. Next year I am hoping to take the next step, and build at least some of the sensors we deploy.

Step 2: Pay careful attention to the mount for the sensors...this is the crux of the assignment

Step 3: Make sure all knots are good, sensors are turned on, and the water depth and tides are properly accounted for

Step 4: Over the side

Friday, September 25, 2015

Vegetating the old beach at Elwha

I was struck this morning, during my monthly shoreline survey on the Elwha River delta, by the profusion of what I presume is Beach Pea (Lathyrus japonicus) growing directly on top of what was, just a few years ago, the active beach face east of the Elwha River mouth. Check out this before/after series from a site just a few hundred meters east of the Elwha River mouth:

There is also some alder and American Dunegrass (Leymus mollis) in there. Its a phenomenal transition to witness...from a coarse high(ish) energy beach to a stable backshore lagoon type system.

Thursday, September 17, 2015

El Nino and the Washington Coast

Coastal erosion along the California coast associated with the 1997-1998 El Nino winter

We are experiencing El Nino conditions now, which are very likely to continue...with forecasts pointing towards a strong peak in late fall or early winter. What does a strong El Nino mean for the Washington coast?

The scientific literature exploring the coastal impacts of El Ninos on the west coast of the US suggest that we should expect above-average erosion and property damage. BUT, most of this literature focuses on impacts in California...and in California there is no doubt that El Nino winters are a big deal. In California the cost of coastal damage from both the 1982-1983 El Nino and the 1997-1998 El Nino was measured in the millions of dollars. There is quite a bit less available regarding how previous El Nino winters have played out on Washington's Pacific coast. The one analysis that I could find (which includes as a co-author Washington State Department of Ecology's own George Kaminsky) looking at erosion along the west coast during El Nino winters that INCLUDED shorelines in SW Washington was unclear. El Nino years WERE erosive on the SW Washington coast...but so were lots of other years not associated with El Nino conditions.

This paper, though, shows how multiple mechanisms exist that can conspire to create potentially erosive conditions on Washington's Pacific coast during El Nino winters. At play are three primary factors: Elevated average winter sea level, above-average wave size, and a change in the average wave direction over the winter season.

Average sea level is definitely elevated during strong El Nino winters on Washington's coast. Here are monthly average sea level data from Toke Point, Washington (on the coast in the mouth of Willapa Bay):

Note in particular the "spikes" in the plot above, marking months in which average water level measured at this tide gauge was >0.3 m (~ 1 foot) above the long-term average for that month. The first is centered on Feb 1983, and the other on February 1998.

But its not just about water level. On the open ocean coast above-average waves and changes in mean wave direction play a major role in driving patterns of erosion and damage to infrastructure during El Nino winters (see references here and also this paper). What to expect in the inland waters of Washington where ocean waves aren't much of a factor? Here there is virtually no documentation that I could find regarding any unusual coastal impacts associated with the 1997-1998 winter. In fact, I spoke to Hugh Shipman, Coastal Geologist with the Washington Department of Ecology regarding his recollections from 1997-1998...and mostly he talked about other years, especially 1996-1997 when heavy precipitation drove coastal bluff erosion and failure around Puget Sound:

A home in Seattle after heavy precipitation in the winter of 1996-1997.

All that being said, El Nino years definitely do drive elevated average sea level in Puget Sound. Here is the monthly average sea level for Seattle:

again, with those large "spikes" in average water level during the winter of 1982-1983 and 1997-1998, identical to those observed in Tokeland. In fact, the highest water level ever recorded in Seattle happened on January 27, 1983 - during a strong El Nino winter.

But unless those elevated water levels are associated with some heavy winds/waves, or maybe some heavy precipitation, they may not lead to much in the way of damage. Instead, it can lead to some coastal "nuisance" flooding - definitely a problem, but typically not extraordinary in terms of damage. But should we expect stormier conditions this winter in the inland waters of Washington associated with a strong El Nino, that could couple up with elevated water level and really cause some damage?

There is an apparent relationship between El Nino winters and a reduced frequency of storms specifically associated with north wind and colder than average temperatures (Nick Bond, personal communication). This is perhaps consistent with the observation from past El Nino winters of higher than average winter temperature:

Temperature anomalies during El Nino winters versus a long-term average. Courtesy of Nick Bond.

But what about general storminess? Based on a very preliminary analysis I am going to go out on a limb and say that there likely isn't much connection between El Ninos and heavier-than-usual wind or lower pressure (associated with storms) in the inland waters of Washington State. To arrive at this conclusion I collated hourly observations from the Seattle tide gauge from 1991-2001, and looked at patterns for the winter months (October - March). Here are those data for wind speed expressed as a box plot for each winter, where the red line is the median value, the edges of the box represent the 25th and 75th percentiles, and the "whiskers" cover approximately between the 1st and 99th percentiles of the distributed data. I didn't include outliers here, since my interest was in average winter condition:

So as you can see the winter of 97-98 really doesn't look too different than the 3 or 4 winters that preceded it (though it looks like those winters were windier, on average, than those at the beginning and end of the decade).

Wind direction tells a similar story:

with the winter of 97-98 really not looking all that different as compared to the 3 or 4 winters before, as well as the winter of 98-99...though all of those winters collectively look to have had a bit more south wind than the winters at the beginning of the decade (and the beginning of the 00's).

and finally, pressure is generally a good indicator of storminess, with lower pressure equating to a stormier winter. In seattle, there isn't much distinction, on average, across the winters I looked at:

And what about precipitation? Generally for our area El Nino winters are associated with less precipitation than normal. Here, for example, is a look (courtesy of Nick Bond) at how precipitation has varied nationally during El Nino winters since 1957 (strong and weak), as compared to the long-term average:

Indeed, that is the forecast for this winter (20 August 2015 update).

So all in all, what to expect? There seem to be two stories - one for the Pacific Ocean coast favoring an increased chance for erosion and damage due to the combination of higher-than-average water level, higher-than-average wave heights, and a shift in the average wave direction. And another for the inland waters, favoring some elevated water level and perhaps enhanced nuisance flooding...but possibly not much else, at least that would be unusual as compared to any other winter.

Monday, August 17, 2015

Mt St Helens

Visited Mt St Helens for the first time in at least 20 years last week during a week-long vacation with my family. While the focus was checking out a volcano with a trio of young boys, I couldn't help but marvel at how important the mountain, and its eruption in May 1980, has been to how we view perceive, study, and prepare for natural hazards.

We spent the entirety of our two days on the north side of the volcano, in the areas directly affected by the massive landslide that preceded the blast, the pyroclastic flow that characterized the eruption itself, and the lahar that swept down the Toutle River in the hours after the eruption, and visited both the Johnston Ridge Observatory and Weyerhauser's Forest Learning Center. The Forest Learning Center, in particular, was a surprise hit for both its diverse and innovative interpretive materials, and its awesome playground (which Theodore found particularly appealing):

Our first stop, though, was the buried A-frame alongside the Toutle River, some 25 miles downstream from the volcano. While this place is, at its heart, a classic American road-side also really helps to transport you back to mid-day during the eruption, when mud enveloped the entire floodplain:

McHenry and my nephew Silas staring into the second floor window of a house buried by the lahar that followed the eruption

Part and parcel of the story of the Toutle Valley lahar was getting to view and grapple with the management implications of the massive quantity of sediment injected into lowland watersheds during the eruption. The management of that sediment is an on-going issue, and includes a dam purpose built to retain sediment in the upper Toutle River valley. Here is a view looking downstream along the Toutle Valley:

The Toutle was transformed by the massive dump of sediment from the eruption, and its floodplain, 35 years later, still gives every appearance of trying to work through the massive sediment supply. It is generally poorly vegetated, highly braided, and very broad.

Up at the volcano itself, the geology is absorbing. We walked the Hummocks Trail through the landslide area just down valley from the mountain, through giant piles of debris, most of it composed of angular chunks of the mountain itself.

An angular rock carried down valley by the massive landslide that preceded the eruption, as the whole north flank of the mountain collapsed.

One of the hummocks, huge piles of dust, angular boulders, and ash, associated with the massive landslide that came off of Mt St Helens on the morning of May 18

However, I found myself focusing on the stories that provided insight into how people at that time viewed and responded to the risk of an eruption. Some of the interpretive materials at the Johnston Ridge Observatory and the Forest Science Center really helped me to understand how difficult the days leading up to the eruption were for scientists, local and state decision-makers, and emergency managers. The scale of the devastation, even 35 years later, makes it hard to believe that many doubted the advice provided by scientists working on the project...but some died as a result of that doubt.

Indicators of destruction: The remnants of trees at Johnston Ridge, ripped from their stumps

Those that died. Front and center is the name of David Johnston, a USGS scientist that died in the line of duty during the eruption, manning a volcano observation post, on what is now called Johnston Ridge. The landslide that preceded the eruption swept over this ridge within seconds of it breaking loose from the flank of Mt St Helens.

Monday, July 20, 2015

Short-term beach change on Dungeness Spit

The study site - approximately Mile 3 on Dungeness Spit. This view is looking north-east towards the light house.

Our beaches are extraordinarily dynamic, and as I go about doing the work that I do I hear countless stories about big changes to the morphology of beaches that happen over very short time-scales. I don't always get the chance to really address that kind of variability since most of my shoreline monitoring sites are typically re-occupied only once or twice a year. Two of my sites, though, are unique. Both Ediz Hook and Dungeness Spit take two tidal cycles to finish, and so for this year's Dungeness Spit survey I collected some data on both of my survey days (8 June and 1 July) along an area around the 3 mile mark on the spit in order to assess how much change occurred over that time period. The conclusion - more than you might expect for a few relatively calm weeks in the summer.

Lets start with the profile data from three transects. In all cases change is occurring below Mean High Water (MHW). Here is the most landward one first:

Here is appears that the beach has accreted, or grown over that two week period, over almost the entire profile below MHW. Interestingly, though, this accretion doesn't appear to dramatically change the grain size composition of the beach face. Here is an example photo taken at 1 meter above MLLW on 8 June:

and then another taken at the same elevation on 1 July, after beach accretion:

Here is another example from lower down on the beach (at Mean Lower Low Water) that does suggest a sandier substrate associated with the accretion suggested by the profile data. First the photo from 8 June:

and then here is the photo from 1 July, again shot at MLLW:

Moving to the next transect to the northeast, the patterns was reversed, with the profile data suggesting erosion on the lower part of the beach over the three week period:

and finally the next transect to the east (and the last that I overlapped) suggests a bit of a mix of erosion on the lower part of the beach, and some accretion on the upper beach (around 3m):

This seems to be supported by oblique photos collected at that site. Here is the one from 8 June:

and if you compare that carefully to the oblique from 1 July:

you will note the addition of some large woody debris high up on the profile, which is often associated with beach accretion.

What were the factors that conspired to drive these changes? Thats a tough one, but we can be sure that, despite it being summer, there was plenty of energy delivered to the beach. Here is a summary of water level data (bottom panel, from Port Angeles, referenced to MHW) along with significant wave height and dominant wave period from the Hein Bank buoy:

In particular the early part of the period, between maybe June 10 and June 19, was characterized by pretty high water (0.5 m or so above MHW during the high tides), and multiple occurrences of waves with heights > 1 m. The high correlation between the average wind speed (middle panel), and wave heights suggest that these are primarily locally generated wind waves rather than swell energy from ocean - not at all surprising for the summer season in the Strait of Juan de Fuca (see Chapter 3 in my dissertation for a description of seasonal wave patterns from Elwha). If I had to guess, I would think that those profile changes, at least on the upper profile (above MHW) on the last transect, happened in that time period.

Tuesday, June 9, 2015

Back out to the Spit

The view from the end of Dungeness Spit

For the third year I was able to arrange with the US Fish and Wildlife Service to collect beach morphology data on Dungeness Spit for my shoreline monitoring program. This is such a special survey to me - its the most difficult logistically, but provides a chance to collect some data on what is really a spectacular coastal feature:

A view of the lighthouse from the end of the Spit, with the Olympics in the background.

Spits are really such important coastal features. In the case of Dungeness Spit it creates a very unique and productive shallow water habitat in its lee. And its "sister", Ediz Hook, creates what many argue is the best harbor in the region. In my view, we simply need to do a better job at understanding what makes these sorts of coastal features work. One surprise, at least based off looking at the preliminary data, is that the end of the Spit appears to have retreated a bit, at least over the last few years:

Again, these data are very preliminary, and just one profile doesn't tell the whole story...but given the average rates of growth reported by Maury Schwartz this is an interesting finding. Part of the story could be related to the migration of the top of the Spit, but it clearly is a complicated story. These profiles cutting through the bulge at the end of the spit for example, suggest the possibility (again, using the caveat that just one set of profiles per year doesn't a convincing story make) that erosion on the seaward side of the spit was associated with accretion on the landward side between 2012-2014:

But that pattern didn't hold up in 2015.

More to come - I will head out to finish the long skinny part of the Spit later this month or next, and then hopefully continue annual surveys for at least another two years.