The Need for Long‐Term Monitoring When Assessing Sediment Production of the Black Vermillion River in Northeast Kansas

Tuttle Creek Reservoir provides flood control, water supply, wildlife habitat, and recreation for approximately 40% of Kansas residents and has lost 50% of its capacity to sedimentation since 1960. A 2012 study that focused on sediment contributed by the Black Vermillion River (BVR), monitored 18 study banks and 18 cross sections within three BVR subwatersheds (Main Stem [MS], North Fork [NF], and Irish Creek [IC]) between 2007 and 2010. A subsequent study in 2017 estimated future BVR sediment production using the 2012 data. In 2021, this study resurveyed 14 cross sections and 7 study banks at seven of nine study reaches of the 2012 study. It was hypothesized that average annual erosion rates for the entire study period (2007–2021) would differ from previous studies due to a high number (14) of bankfull flows between 2007 and 2010 and channel stabilization since 2010. Between 2007 and 2021, the average annual study bank retreat rate (0.19 m) and increase in top‐of‐bank cross‐sectional area (0.69 m 2 ) of all study reaches were less than between 2007 and 2021 (0.38 m and 1.84 m 2 , respectively). Geomorphic change varied significantly between the three subwatersheds from 2007 to 2021, with some reaches having decreased erosion rates, some having increased, and some experiencing deposition. These differing patterns of change highlight the need for long‐term monitoring of individual river channels to better understand channel succession and estimate sediment production.