There is considerable difficulty and expense in sediment measurement. Some of the expense is due to the fact that streams carry more than 50% of their total sediment transport during flood events. Since these large flows often occur at night and are hard to predict, it is difficult to obtain sediment samples unless some type of automated measurement system is used. Even under good conditions, however, the time and labor inherent in sediment sampling add to its expense. In addition, traditional forms of sediment measurement where sediment samples are taken in the field and analyzed in a laboratory may accumulate errors in sampling and computation as large as 20%. These ex-situ techniques also modify the particle size distribution since aggregates are often broken up in sample collection and handling. On the other hand, allowing the particles to settle may allow the creation of more aggregates than existed in the original sample.

Non-intrusive, automated techniques with good temporal resolution are needed for the measurement of suspended-sediment concentration in fluvial environments. These requirements can be met using high-frequency acoustic techniques. There has been some success in measuring suspended-sediments in marine environments, but more work is needed before effective measurements can be made in fluvial settings. The broad particle size distributions and large ranges of sediment concentration in riverine systems make acoustic measurements challenging.

Research at the National Center for Physical Acoustics focuses on the development of ultrasonic pulse-echo techniques for measuring suspended-sediment concentration and size distributions.