Estimating Suspended Sediment Loading Rates for Rivers and Streams

The Streambank and Wetland Restoration Team, NRCS National Water Management Center (NWMC) located in Little Rock, Arkansas, is currently writing new procedures incorporating old technology to estimate suspended sediment loading rates, suspended sediment rating curves, and annual sediment budgets for gauged or modeled rivers, streams, and/or creeks.  The technology first published in 1953 is coupled with Rosgen’s Stream Classification System to enhance stream classification, stream assessment, and channel evolution/succession scenarios.  Streams that carry sediment loads adjust channel geometry and slope to match available water and sediment discharges.  Therefore, by analyzing changes in hydraulic channel geometry measurements and comparing these rates of changes to stratified Rosgen stream types, suspended sediment loading rates can be estimated for un-gauged rivers, creeks or streams. This is another mathematical tool to help quantify sediment loads and to compare different streams, when conducting a comprehensive watershed assessment.

The mathematical method compares the in-channel hydraulic geometry for any gauged or modeled stream or river with unknown sediment loads to a reference stream with similar in-channel hydraulic geometry and known sediment characteristics.  Inferences of the suspended sediment characteristics of the watershed upstream from the gauged stream or modeled river reach (i.e. tributaries) can also be made.

Applications of this technology include improved geomorphic assessments, identifying and targeting unstable stream types, predicting future sediment responses, develop watershed management strategies to reduce loads into reservoirs, extend design life of flood control structures, and ways to restore streams to lower sediment loading rates.
Your contact is NRCS hydraulic engineer Thomas J. Garday at 501-210-8905.