Samhain Waxing Thanksgiving Moon
Once in a while it’s bracing to throw yourself in the deep end and I did that today. I went to a conference titled Experiments on Rivers: the Consequences of Dams. I realized how little consideration I’d given to dams by the end of the day. I’ll just give you one example and it came in the first three minutes of the conference in a presentation from Efi Foufoula-Georgiou, Director of the National Center for Earth-Surface Dynamics, headquartered at the St. Anthony Falls Laboratory, location of the conference. After four slides and a technical explanation, Efi told us that of the 40 large river deltas in the world surveyed in a recent scientific study, 27 of them had much less sediment than the same deltas had before the construction of dams begun largely in the 1950’s.
What’s the big deal? Well, it turns out that all deltas are subsiding, that is, sinking. The thing that keeps the deltas and the land forms dependent on or within them from getting inundated is the build up of sediment; sediment now significantly blocked in 27 cases by upstream dams. Think global sea level rise, then put the two together. Efi’s crowd predicts that without solving the sediment deposit drought New Orleans (why does everything focus on the Big Easy?) will be gone by 2100. Whoa.
I’ll drop other information in throughout the week so I don’t overload ancientrails with dam related topics.
The St. Anthony Falls Laboratory*, created in 1938, has run continuously since then, churning out (ha, ha) hydraulic studies for dams, transportation studies and much, much more. The tour of the wind tunnel (also a from of hydraulics), delta modeling and stream and river bed modeling was worth the time to attend the conference. This is real science done with made up tools, including a pipe cleaner forest and a wooden and plexiglass model of downtown Minneapolis.
*SAFL is the world’s only fluid-mechanics laboratory that uses a natural waterfall as its prime water source. For over 70 years researchers from around the world have been visiting our unique location on an island in the Mississippi River to conduct research for developing innovative and sustainable engineering solutions to major environmental, water resources, and energy-related problems. We would like to extend our warmest invitation to visit our facilities and talk with our research staff and students.