To provide accurate and reliable information on sediment near the Fargo-Moorhead metropolitan area, the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers conducted a study in the spring (March-May) of 2010 and the spring of 2011 to examine sediment concentrations, loads, and particle-size distributions at nine selected sites in the Red River and its tributaries. Samples of suspended sediment, bed material, and bedload were collected at the nine sites at various time intervals during the high-flow events.
Suspended-sediment concentrations varied spatially during the 2011 spring high-flow event sampling period. Most tributary streams had substantially higher suspended-sediment concentrations compared to suspended-sediment concentrations in the main stem of the Red River, especially at the Sheyenne River sites. Suspended-sediment concentrations on the Red River ranged from 45 to 126 milligrams per liter near Christine, North Dakota and from 49 to 197 milligrams per liter near Fargo, North Dakota. In comparison, the suspendedsediment concentrations ranged from 239 to 1,180 milligrams per liter at the Sheyenne River above Diversion and from 199 to 1,130 milligrams per liter at the Sheyenne River below Diversion. The Buffalo River had the lowest concentrations among the sites; suspended-sediment concentrations in the Buffalo River ranged from 21 to 61 milligrams per liter. Peak measured suspended-sediment concentrations were slightly higher in 2011 at the Red River near Fargo, Sheyenne River above Diversion, and Sheyenne River below Diversion compared to measured suspended-sediment concentrations in 2010. Peak measured suspended-sediment concentrations were lower in 2011 at the Red River near Christine, Maple River, and Wild Rice River compared to measured suspendedsediment concentrations in 2010.
Total sediment loads measured during the 2011 spring high-flow event at the Red River and its tributaries near the Fargo-Moorhead metropolitan area were mainly composed of suspended sediment and were greatest at the Sheyenne River above Diversion compared to the loads at the other eight sites. The calculated total sediment load during the entire event ranged from 3,040 tons at the Lower Branch Rush River (April 7-21) to 188,000 tons at the Sheyenne River above Diversion (April 8 to May 16). The peak daily total sediment loads calculated for the 2011 spring high-flow event ranged from 825 tons per day in the Lower Branch Rush River to 13,209 tons per day in the Sheyenne River above Diversion
More than 90 percent of the measured suspended sediment was composed of fine-grained material less than 0.062 millimeters in most of the suspended-sediment samples collected during the 2011 spring high-flow event, except for the Sheyenne River. Samples from the Sheyenne River above Diversion had 19 to 43 percent of the suspended sediment with particle sizes greater than 0.062 millimeters and the Sheyenne River below Diversion had 10 to 30 percent of the suspended sediment with particle sizes greater than 0.062 millimeters.
Most of the bedload samples had particle sizes in the 0.5 to 1 millimeter and 0.25 to 0.5 millimeter ranges from the Maple River, Wild Rice River, Rush River, Buffalo River, and Red River sites. The Rush and Lower Branch Rush Rivers also had a greater portion of larger particle sizes in the 1 to 2 millimeter range. The Sheyenne River sites had a greater portion of smaller particle sizes in the bedload in the 0.125 to 0.5 millimeter range compared to the other sites. The bed material in samples collected during the 2011 spring high-flow event demonstrated a wider distribution of particle sizes than were observed in the bedload; the coarsest material was found at the Red River near Christine and the Lower Branch Rush River and the finest material at the Sheyenne River sites.