Sediment Transport Monitoring and Assessment
GMA Hydrology conducts a wide variety of sediment transport studies on both dam controlled and free flowing rivers. GMA emphasizes an empirical approach which provides reliable information for calibrating existing transport formulae or applying curve-fitting techniques with larger, empirically derived sediment-transport data sets. GMA specializes in measuring both suspended and bedload components of total sediment discharge during the high flow events which transport most of an annual sediment load.
Over the past 20 years, we have developed techniques which allow us to safely collect sediment transport data in extreme conditions: from conventional wading and bridge techniques; to constructing and operating bank-operated cableways; to deploying highly-specialized cataraft-based sampling platforms attached to temporary cableways where no bridge or BOC exist. To our knowledge, GMA is the only consulting firm to operate extensive cataraft-based sediment data collection programs that operate on large rivers in high velocity conditions. GMA has successfully sampled on the Trinity River to 11,000 cfs, the Tuolumne River to 7000 cfs, the Smith River to 35,000 cfs, the Sandy River to 8,000 cfs, and Clear Creek to 5,000 cfs using this equipment.
GMA Hydrology is actively collaborating with agencies, universities, and other research groups to investigate surrogate technologies for measuring sediment transport. GMA conducts experiments using apparent bed velocity (using acoustic Doppler current profilers) and total acoustic energy (using passive hydro-acoustic systems) as surrogates for bedload transport. Some projects utilize ISCO pump samplers, which trigger during rapid increases of stage or turbidity, allowing us to sample suspended sediment at remote sites automatically. We operate numerous continuous turbidity stations and regularly compute suspended sediment discharge using turbidity as a surrogate for suspended sediment concentration.