Large river systems provide many services, including water resources, barge transport, and sand and gravel (S&G) for mining. However, unlike damming, the impacts of channel dredging and S&G mining are poorly monitored. We quantify these impacts on the Lower Arkansas River, U.S.A., where anthropogenic processes are well documented. The construction of dams caused a 98% reduction in suspended sediment discharge (Q_ss). Since dam construction, fluvially-transported Q_ss and suspended sand discharge (Q_sand) varied on the decadal scale, but the average of Q_ss (4.4 ± 0.5 Mtyr^-1) and Q_sand (1.1 ± 0.1 Mtyr^-1) at Van Buren are of the same order as sediment removal rates by dredging (1.2 ± 0.1 Mtyr^-1) and S&G mining (1.7 ± 0.1 Mtyr^-1). During 1975-2019, the cumulative sediment deficit caused by dredging and S&G mining (1.7 Mtyr^-1) outpaced the cumulative post-dam fluvial sediment deficit (0.7 Mtyr^-1), indicating sediment extractions are now essential parts of rivers’ sediment balance.