Saturday, October 17, 2009
Saturday, October 10, 2009
Its been a surprisingly exhausting summer, and feels doubly so as I write this at night in a San Diego hotel as we wrap up our last day of field work. For me, its the last day of field work of an intense summer, that included a total of about 30 days in the field in Washington, and another 20 or so here in San Diego. Added on top of a visit to my folks, it meant that I've been at home very little this summer. Not that I'm complaining. The chance to work on interesting projects in coastal environments is part of why I signed on to graduate school. But I must confess that the travel was exhausting this year.
A few photos from San Diego. The project down here is Jon Warrick's, and is focused on understanding the movement and eventual fate of about 1500 dump truck loads of mixed sand and silt dumped on the beach just north of the Mexican border. The dumping of this sediment was an experiment - in the U.S. we typically only allow sand to be dumped on beaches, not fine material like silt. The state park in the Tijuana River estuary wrestles with what to do with sediment that collects in catchement basins and marshes, and have to pay to get rid of it. The idea of using it as nourishment on beaches is attractive, and it was that idea that spawned this project.
For me the project involved daily morning trips in a small boat to the ocean just off-shore of the beach, where we collected data on temperature, salinity and sediment concentration at 18 sites, and collected a water sample from each site. We try to get back in by noon or so before the wind comes up, and then head out to the beach to collect yet more water. Tomorrow we drive back to Santa Cruz with boat in tow and a whole bunch of bottles of water. Looking forward to getting home...
Monday, October 5, 2009
Its interesting that coverage of the Samoan Tsunami of September 29th has largely been overshadowed by the Indonesian earthquake, which resulted in greater loss of life. Surprisingly, though, the Samoan tsunami did show up on the west coast and, for that reason, was of particular interest to me. Thankfully, it didn't show up in a BIG way.
When the tsunami struck Samoa I was working in San Diego and found myself extremely intrigued by the tsunami warning that was released for the west coast. It is no surprise that waves generate and travel over entire ocean basins, but I found this one particularly exciting, if only because I was in an ideal position to watch it propagate around the globe, and am now surrounded by people at USGS who get REALLY into these things.
At about 8:30 pm on the 29th I went to NOAA's Tides and Currents site (http://tidesandcurrents.noaa.gov) and pulled up real-time water level data for San Diego, Monterey and Port Angeles. By about 9:00 pm the waves were visible in the data stream in San Diego, showing up as waves with an amplitude of about 1/2 a foot and a wavelength of about 30 minutes. The same wave signature showed up shortly after in Monterey, CA and just after midnight in Port Angeles.
USGS scientists Andy Ritchie (who, as an aside, is from Port Angeles) was in Santa Cruz on the bridge over the harbor and reported: "at around 9:26 the first (negative) wave appeared. The water surface dropped by about 50 cm over a period of five minutes or so, then rose about 1.4 m from the low over about the next 7.5 minutes. I watched this through another two waves, when the amplitude began to decrease somewhat. It looked like maximum water velocities were somewhere around 4 m/s - which was pretty impressive to me. Other than some surprised-looking gulls and slightly distraught pelicans zipping back and forth on the current, and some impressive turbidity getting kicked up, it seemed like everything stayed put. There were some curious (brave? foolish?) folks in a rowboat that rowed out of sight before the tsunami came, and I imagine they felt a bit like the seagulls and the pelicans."
I was particularly delighted to find the signature of the tsunami in NOAA's water level data from Port Angeles, which you can see here. I can't help but wonder if these relatively small events have any impact whatsoever on geomorphology or coastal habitats on the west coast.