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Global Skywatch

surveying the East Fork

East Fork surveyor 1Not because the world has some screaming need I am fulfilling, but merely because I want to… I slipped on my 14″ dairyman boots to walk across a river varying in depth from 10″ – 18″. If your math skills are average or better, you will correctly guess those boots were quite full of water in short order.

During last year’s low tide, in my first iteration, I staggered out with rattle cans and tape measure in a backpack to paint marks on the center support of Conner Cutoff Road over the East Fork Bitterroot. You can see the close-ups of this river-height gauge at river is a-risin’ and “river running by” from last May.

East Fork surveyor 2A major shortcoming of that design appeared when I most wanted the information. With the river really flowing (4′ and above) the bow wave upstream of the support obscured my marks. Additionally, I had no measure of width or depth and, thus, quantification of volume was impossible.

Thanks to the knowledge my first experiment gives me and that my mobility is no longer hampered with a back injury, I began a more thorough surveying project. Yesterday I found a rather consistent 1-foot depth across a 52-foot width. Also just for fun, I measured a downstream flow around 45-feet in 15-seconds or about 135 cubic feet per minute … passing by our cabin around the lowest flow of the year … except, that is, when almost all Bitterroot moisture is being locked up in snow and ice.

I will soon be using my sight-level, a handy tool from my grading and pond-building days, to set stakes up the bank towards our cabin in 1-foot-vertical increments. Noting the horizontal width at each, I will then have a depth/width measurement at every river level reached on the near shoreline.