John Porter (VCR)
In mid-November 2009, extratropical storm (formerly hurricane) Ida visited the VCR/LTER bringing with it sustained high winds and tides. During the storm we were able to monitor a variety of conditions on isolated Hog Island (20 km from our lab) using our wireless network. See graphs and webcam images in the attached PDF file.
How serious was Ida? In Norfolk, just to the south of our site, it set a new record for storm surge – exceeding both Hurricane Isabel (2003) and two major hurricanes in 1933, and came in fourth for overall flooding (surge plus tide) ( http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1383). On Hog Island, winds on the top of the Machipongo Station (an old Coast Guard Station, now run by The Nature Conservancy), sustained winds of more than 50 mph were observed. On the ground, and surrounded by vegetation, winds were more moderate, topping out at about 25 mph (11 m/s). However, an important aspect of Ida was its duration. Most nor'easters have a duration of 1-2 days, but Ida had sustained winds for more than 4 days in a row – all coming from approximately the north. This led Ida to pile up water in the coastal bays resulting in extremely high tides over an extended period. This in turn led to extremely high ground-water levels as the less-dense freshwater floated on top of the tidally-driven salt water.
As several LTER sites have found, extreme events often provide novel stresses on monitoring equipment. Unlike Hurricane Isabel in 2003, when we lost several stations to flooding, almost all our equipment stayed dry enough to function throughout the storm. Our closest call came at a flux tower located on a salt marsh. We had recently raised all the equipment an additional 45 cm due to concerns about storm flooding. Nonetheless, the outer equipment box did flood, but the internal NEMA boxes safely floated, preserving expensive instruments, computers and data loggers. A solar controller was less fortunate – its NEMA container was wedged so it couldn't float and salt water caused a small, electrical fire that destroyed the controller. We also had some problems with a tide sensor, when an intermediate junction box partially flooded, causing a several day outage. One webcam also had problems during the height of the storm, but returned to normal operation following the storm, allowing a rapid assessment of overwash in the vicinity of the camera. However, our other main webcam stayed up throughout the storm.