Last week, I (Matthew Goslin) ventured out to the Middle Fork John Day River where we are investigating effects on channel morphology of the native plant, Carex nudata (aka torrent sedge). A key methodology are the arrays of erosion pins (steel rods) I’ve set out in river banks with and without C. nudata fringes. We measure the length of the pins three times a year in transitions between summer/fall, winter/spring and spring/summer in order to capture different erosion processes. The post-river ice/pre-spring peak flows measurement is one of the most important: it will allow us to distinguish between winter freeze/thaw processes which may cause erosion or, more problematically, push the pins outward and the fluvial erosion caused by spring snowmelt-driven peak flows. It’s also the trickiest because there’s a short window of time when the river is wadeable between the ice melt and rise in flows.
For reference, discharge at the nearest gage to our site is 20-60 cfs in summer and peak flows range from 600-900 cfs. Last year, we measured pins while flow was around 120 cfs, a level we found barely wadeable. This year, as soon as the ice melted, flows jumped to 600 cfs and then declined to 120 cfs. I got my team ready as flows declined, but that window lasted only 4 days. One night of rain and flows climbed and leveled at around 290 cfs, conditions in which we had never tried to work. We forged ahead, finding dry suits to borrow from fish snorkel surveying friends. We knew we would have to immerse ourselves in frigid water to get these measurements.
Arriving at Oxbow Conservation Area, we were surprised to still see a patchwork of snow, bare in some places and 1-2 feet deep in others. The first couple hours led me to despair: almost all of the pins were under water with turbidity and sediment making them invisible. We would have to do this almost entirely by feel. Mission impossible? Flows were too strong to cross the river, but we could work in the less powerful velocities near the edges. We pushed ourselve to try and find and measure pins. We soon discovered we had a rhythm, it wasn’t impossible. By the end of the trip, we had measured about 90% of the pins. Working in the frigid snowmelt water left us feeling miserable and elated all at the same time as we pushed through the challenge. Jame Major (Pat McDowell’s undergrad research assistant) and Emily Erickson (a recent grad and summer river crew alum) were fantastic assistants, as was volunteer, Emily Davis of the Confederated Tribes of the Warm Springs.
It was awe-inspiring to work in this snow melt landcape with water running (or just standing!) across surfaces everywhere, everything we learn about snowmelt-driven hydrology in action.