Andrea, Emily, and Steve Rubin (USGS)—with help from Ian Miller (WA Sea Grant)—made a successful rapid response cruise to the Elwha Delta, following a day of heavy rain. The goal was to collect surface water samples from the river plume. Given sufficiently high sediment concentrations, these samples will be usable for grain-size and concentration analyses.

Collecting these samples has been on the to-do list for a long time, but this winter has been particularly dry (= low river flow). The January 11^th rainstorm did not flood the river, but still made for a pretty exciting day on the water and a truckload of great samples. Emily is currently processing these in the lab – sediment will be allowed to settle for about a week, and after a series of dilutions, will be processed using the Sedigraph. The goal is to determine size distributions of disaggregated particles in the plume.

Back to watching the weather for the next big one! With any luck, we’ll see a pineapple express (http://www.komonews.com/weather/faq/4307577.html) sweep through western Washington this winter.

Winter at the Elwha – this was the edge of the surface plume a day after heavy rains. Nice sediment samples!

An interesting mix of grain sizes in this bed sample

Samples! (Photo by Ian Miller)

As part of our ongoing study of sediment dispersal offshore of the Elwha River, we made two scheduled research cruises in late 2013 (August and November). The goal of both cruises was to service two seabed instrument systems (tripods) and survey the sediment plume, water column, and seabed across the subaqueous delta.

Instrument servicing was overall a success, though a couple unlucky instruments were returned to the shop rather than the ocean. We retrieved some nice data on advection of muds both during the summer dry season and a couple fall rainstorms. One of the photos shows Dan Nowacki and Niall Twomey hard at work in our favorite workspace, the Port Angeles harbor. Hooray for no rain in both August and November!

The ship-based surveys were also successful. In November we made our first Kasten coring attempt since the project began. The most successful site yielded about 40 cm of mud, which represents a huge change from the gravelly substrate seen on many other cruises. A new sandy/muddy deposit is growing outward from the river mouth into Freshwater Bay, while other parts of the delta remain coarse (gravel, sand and the occasional boulder).

The cruises were made possible by help from our dedicated lab crew, including Andrea, Chuck, Emily, Dan, Rip, Aaron, Katie, visiting international students Suzan and Wenhua (their first cruises in Washington State!), Kevin, Julia, and Niall, and also Nicole Harris from Western Washington University (who researches Elwha nearshore changes)—and of course the great crew on the R/V Barnes (Ray, Greg, and Bob). Looking forward to another great cruise in April!

Members of the Sediment Dynamics Group recently returned from a three-week stint in Brazil, where we completed fieldwork on the Amazon River and its associated sedimentary environments.

Our first field site was along the Amapá coastline north of the mouth of the Amazon River.  The mangroves that flank the coast here are bathed in Amazon River sediment that is transported northward after exiting the mouth.  We undertook a pilot study along the Rio Calçoene, downstream of the town of Calçoene.

View Map on Google Maps

Near Calçoene, the river has relatively little suspended sediment, and the water appears quite clear.

Rio Calcoene near Calcoene

Closer to the mouth, suspended sediment concentrations are much higher, and the river starts to resemble chocolate milk.  Almost all of this sediment is likely from the Amazon River, the mouth of which is some 250 km to the south.

Near the mouth of the Rio Calcoene

In addition to making measurements and collecting samples along the river itself, we did work in a few small channels that incise the mangrove forests that characterize this part of the Brazilian coastline.

A small channel at low tide incising mangrove forest

A closeup of a channel at low tide

Wow–what a whirlwind.  The second half of our fieldwork was a frenzy of activity.  We finished the second 25-hour transect and completed the third quickly and efficiently.  With over 75 hours of continuous ADCP measurements (3, 25-hour station occupations), 230-plus CTD (conductivity-temperature-depth) casts, over 100 sediment samples, and about 150 water samples, we have a lot of data on our hands waiting to be analyzed.  Right now we’re in Seoul airport waiting for our flight back to Seattle.  Look for another post or two with some more great photos and perhaps a few data plots describing what exactly it is we did on the river.  For now, we’re headed to our gate, so here a few photos.

A night view from the bow of Aaron filtering

Rip doing creating a manual vacuum while we repaired our vacuum pump

Sunrise on the Mekong

We’re just past half way through our second 25-hour transect, this one about 15 km farther upstream from our first transect location.  Things have been going well overall, though the hours are long and the weather decidedly un-Seattle-like with temperatures in the mid-to-upper 90s.  We’ll finish this transect around 9 pm tonight and then everyone will get some well deserved rest before starting our third and final transect bright and early tomorrow morning.

Loading up with more water for the showers and toilets

Sand barge on the river

Major shoreline erosion

Tri and one of the captains

On the bow

Yesterday we spent our first day on the river, loading gear, testing equipment and getting settled in to our home and work space for the next few days.  From Dai Ngai we transited along Cu Lao Dung island on our way to our first 25-hour transect location near the mouth of the Mekong.  We started the transect at 5 am today and are about 13 hours in at the time of this writing.  The kinks have mostly been worked out and the science team and boat crew are getting in to a good groove.

Loading up

We’ll finish the transect around 6 am tomorrow and then a few folks will explore some mangrove areas for potential future work.  Then we’ll have some much-needed down time and transit to our next transect location farther up river.

Aaron and Dan setting up the ADCP.

So far the data we have collected look promising.  Check back for some preliminary results in the coming days.

Aaron, Dan, and Rip reflected on a stanchion on board the VLC.

Today we made the 3.5 hour journey from Saigon to Can Tho, where we met colleagues from Can Tho University.  From there we headed to Dai Ngai where we met the vessel we’ll be using for research:  the Vinh Long Cruiser.

Vinh Long Cruiser

The Cruiser is very much a vessel of opportunity but it should work out well for the types of work we’ll be doing over the coming week.  Tomorrow morning we’ll load up and start setting up equipment.  For now it’s dinner time, a much-needed shower, and our last night of sleep on dry land for a while.

We spent most of today purchasing more supplies and testing equipment in preparation for traveling to the Mekong tomorrow.  Our route will take us through Can Tho where we will meet up with colleagues from Can Tho University.  Then we will spend the night in Soc Trang before meeting the boat on Tuesday morning.

Check out a few photos from today in the gallery below.

Because we packed our gear within the confines of airline luggage, we are assembling here in Vietnam some of the larger equipment needed for our field work.  The video below shows stainless steel pipe being cut at a storefront in Saigon’s District 11, which is also Chinatown.  We will bolt the pipe to a flanged mounting bracket (that was small enough to fit in luggage) built by UW Oceanography engineering services.  Fully assembled, this mount will support our ADCP–acoustic Doppler current profiler–which measures water velocity from a moving boat and which we will use extensively on the Mekong River in the coming days.