Sediment Erosion Characteristics in the Anacostia River.

Four in situ experiments on sediment erosion characteristics were conducted at the Anacostia River that runs through Washington, D.C. Supplemental erosion rate data were also obtained by carrying out five laboratory experiments using sediment samples collected at the field. In laboratory experiments, the sediment samples were mixed with tap water and placed in the flume to form beds for finding the difference in terms of erosion characteristics caused by different sediment composition among the five samples. This approach enables the finding of erosion characteristics for the entire tidal Anacostia River with limited resources. The in situ measured critical bed-shear stresses τ_cr for erosion at the water-sediment interface z=0 varies from 0.03 to 0.08 Pa. Field results indicated that τ_cr(z) increases with the depth z and becomes more than 0.6 to 0.7 Pa with an erosion thickness of less than 1 cm. Sediment beds prepared at a laboratory appear having an upper limit on how much τ_cr(z) can be developed. [ABSTRACT FROM AUTHOR]