Applying Measurements of Cohesive Soil Erodibility

Project ID: 6226
Principal Investigator: Tony Wahl
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2010
Keywords: None

Research Question

Through Dam Safety Office research funding ($188,000 in fiscal years [FY] 2007-2008), Reclamation has recently developed the capability to quantitatively evaluate the erodibility of cohesive soils using two methods, the submerged jet erosion test (JET), and the hole erosion test (HET). This scoping project would attempt to identify applications for these test methods beyond the dam safety arena. Likely candidates are efforts to model streambank erosion and the erosion of deposited sediments from reservoir areas following dam removal or during periods of significant reservoir drawdown.

Need and Benefit

Erosion of cohesive sediments is a fundamental physical process that is important in a variety of application areas, including: dam overtopping, erosion of earthen spillway channels, and stream channel evolution and geomorphology. A multitude of factors affect the erodibility of cohesive materials, which can vary over several orders of magnitude. The relative influence of most factors is poorly understood--making it difficult to analytically predict the erodibility of any given material. For this reason, tests that can measure erodibility in a quantitative way (relating erosion rate to applied hydraulic stress) are very important to those attempting to model cohesive sediment erosion.

Until recently, Reclamation had very limited ability to measure the erodibility of cohesive soils. Flume-type tests developed in the 1980s were difficult to perform and not standardized, and the unique equipment developed by Reclamation had been surplused. During the last decade, other groups have developed simpler tests that have been standardized to varying degrees and are now seeing widespread use. Two in particular are the JET (ASTM-D5852) developed by the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) and the HET, developed in Australia. The JET has been used extensively in the study of spillway headcut erosion and dam overtopping erosion, and there has also been some investigation (outside of Reclamation) of its use for streambank erosion modeling. An ASTM standard does not yet exist for the hole erosion test, but it has been used extensively in the study of piping and internal erosion, and it is a key component of Reclamation's internal erosion risk toolbox. Both tests can be performed in the laboratory using remolded or undisturbed tube samples, and the jet test can also be performed in situ.

Through Dam Safety Office research funding ($188, 000 in FY 2007and FY 2008), Reclamation has recently made significant improvements to our HET facilities and has studied the correlation between JET and HET results. This work has brought us to a point where both tests could now be valuably applied to a variety of cohesive sediment erosion modeling problems in Reclamation, but their utility has only been demonstrated thus far in applications related to dam safety.

The primary benefit of applying these tests would be an improved accuracy and reduced uncertainty of results obtained from erosion and sediment transport modeling efforts. The availability of these tests would allow analysts to measure erodibility instead of predicting it by correlation with other variables.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

A comparison of the hole erosion test and jet erosion test (final, PDF, 488KB)
By Tony Wahl
Publication completed on June 27, 2010

The hole erosion test (HET) and submerged jet erosion test (JET) were compared and evaluated for their ability to determine the erodibility of cohesive soils typically encountered in the modeling of embankment dam erosion and breach processes. The tests were applied to a set of remolded soil specimens prepared in parallel for each test, representing a range of cohesive soils. The methods ranked the relative erodibility of soils similarly...

Relating HET and JET test results to internal erosion field tests (final, PDF, 509KB)
By Tony Wahl
Publication completed on June 27, 2010

Three soils used in a series of embankment dam piping erosion and breach tests at the Agricultural Research Service's (ARS) outdoor hydraulics laboratory in Stillwater, Oklahoma were analyzed to determine their erodibility. Erosion indices were determined using the hole erosion test (HET) method, and the submerged jet erosion test (JET) method. Tests were performed in the laboratory on three series of remolded specimens...

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Last Updated: 6/22/20