Race to a spectacular beginning (overwash experiments conclude, for now)

Today was my last on the SAFL shop floor. What a spectacular visit this has been. I’m grateful to both the NCED2 program and the British Society for Geomorphology for the opportunity to work here in Minneapolis these past two weeks. Rich discussions, incredible facilities, and so much enthusiasm from so many people – not just about the experiments I was trying run (and in a two-week window before AGU and Christmas, run is the operative word), but about morphodynamic problems of all sorts.

Perhaps it’s a good time to include some natural examples of overwash patterns – always food for thought. In the gallery below, the pictures I’ve gleaned from various corners of the Internet give way to photos I’ve taken in the past few days.

NC Outer Banks (via USGS repository).

Near Southampton, NY.

NC Outer Banks (via PSDS).

Bottom: Long Beach Island, NJ, 1962.

An advancing wetting front – this is how each trial starts.

Initial results – overwash lobes distributed “alongshore.”

Scanning the topography during a trial.

Initial topography (top), final topography (middle), difference (bottom).

After a run, when the water has drained.

These little channels set their own spacing.

Chris Ellis set up a webcam!

Effects of a forcing template in the topography?

Post run, draining the tank.

Competition among lobes for flow capture.

Scanning the final trial.

Lobe in the foreground starved out the others – runaway flow capture.

Initial results look very promising, galvanizing, exciting. More on that to come, including some animations of topographic change we were able to capture with the laser scanner set to “continuous.” (I might try a sneak preview in a follow-on post.)

Whatever papers emerge from this research, the acknowledgements will require an appendix.

Lots of folks stopped by the tank – or were forced to by this desperate highwayman. (I was a man on a deadline.) Tour groups snaking their way through the building labyrinth came to peer over the edge and watch the laser scanner do its passes. Unsuspecting graduate students who’d wandered too far from their desks suddenly found themselves holding a socket wrench and a tape measure, adjusting T-nuts on the screed and readying the barrier for the next trial. I commandeered staffers and undergraduate students working at SAFL with some apology and less mercy – “Hey, uh, can I borrow you for a second?” (I’m in their debts.) Postdocs in Chris Paola‘s group haunted the floor with me, equally busy with their own eclectic materiel: tape, corrugated cardboard, thin sheet metal, plexiglass plates, a sediment feeder, sacks of industrial salt, pumps, hosing, a mop and bucket ringer, plastic grit, a trout-fishing net, a six-foot-long galvanized washtub caked with leaves where it had been frozen into the December ground. Chris and Vaughn Voller checked in on the proceedings. Chris Ellis kept a weather eye on the works, and Jim Mullin, too (the senior engineers).

Thank you, again, to SAFL & NCED2 and all those who make this place what it is. I hope you’ll have me back.

– EDL