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.
Friday, September 25, 2015
Thursday, September 17, 2015
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:
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
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 attraction...it 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
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
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.
Wednesday, May 27, 2015
A few weeks back I gave the webinar above on a new approach we are using to project future sea level in a climate change adaptation planning project I am involved in focusing on Clallam and Jefferson Counties in Washington State. The approach takes advantage of a new synthesis of sea level rise projections published last year.
Despite struggling with how to most effectively communicate probabilistic sea level rise projections, I'm really liking this new approach, and its got me thinking about how to do an even better job of incorporating and communicating the current and future hazard related to sea level processes. In the webinar, though, I highlight a few outstanding needs - gaps in research or data needs that are limiting our ability to be as rigorous we can possibly be with assessing contemporary and future hazards related to sea level and coastal impacts.
As an example, consider that these sea level rise projections are meant to get at the "still water level" (i.e. ignoring waves). In general we've viewed that as an okay first-order approximation of the hazard in the inland waters of Washington State...but is it?
First consider the photo above, which comes from Cliff Mass's Weather Blog (check out the specific blog here), but that he attributes to the West Seattle Blog. This photos was taken on 17 December 2012, when the water level, as measured by the NOAA tide gauge in Seattle, reached 14.47 feet relative to MLLW:
This water level was just shy, by a whisker (0.01 feet to be exact) of the record water level measured in Seattle on 27 January 1983.
Next consider this photo, taken at the same exact spot by Melissa Poe of Washington Sea Grant on 29 November 2014:
On this day, still water level reached just 13.11 feet:
Well shy of the near record water level of 14.47 feet associated with the event from 17 December 2012...yet the flooding extent is essentially the same. The obvious difference? A local wind storm generating waves:
So what this tells me is that the data that we derive from tide gauges, and that we use to assess the coastal flooding hazard now and in the future only tells us part of the story, and we need better information on waves in order to take things to the next level. This is nothing new, Peter Ruggiero and others have been telling us for years that we need to account for "total water level"...including the influence of waves. But largely that message has focused on the substantially more energetic wave climate of the outer coast of the Pacific Northwest. Clearly we need to account for waves in the inland waters as well. Now, if only we had data...
Wednesday, April 29, 2015
Make sure you make room for the 2016 film festival in your schedule!
I help to organize this event because I think we are entering this great age of small-scale film-making, enabled by digital technologies. And that means that, more and more, we are seeing perspectives and views into other peoples lives and experiences that we've never had before. The River and Ocean Film Festival is designed to showcase films about the west end of the Olympic Peninsula, but I've also been tracking films about coastal science and hazards. A few that have come up lately:
Here is a nice little series I found just last night, by the St. Petersburg (Florida) Coastal and Marine Science Center of the USGS. I love this!:
While I am a giant fan of the USGS Coastal and Marine program, I think that from the standpoint of nerdy videos about coastal geology and geomorphology, that this video series from Ireland takes the grand prize. Here is an example:
I love this stuff!
A bit closer to home, is this piece by Oregon Sea Grant focused on the coastal effects of climate change, part of a series (find them all here):
and there are also some really nice coastal videos at the Science Earth youtube channel. Here is an example:
And then we get into the one-offs. As an example, here is an interesting film by The Verge focused on design strategies for protecting Manhattan after Hurricane Sandy: