Work completed by Texas Transportation Institute in 2004 on NCHRP Project 24-15 and published in NCHRP Report 516 using the SRICOS (Scour Rate In COhesive Soils) method demonstrates that erosion rates for cohesive soils can be lower than for cohesionless soils. The scour depth in cohesive soils is also dependent upon the duration of the flow. The testing that this work is based on was done in Texas and one site on the Potomac River near Washington D.C. These results may be valid for cohesive soils in South Dakota, but no verification has been completed to confirm that this method is acceptable for use in South Dakota.
The SRICOS Method could provide potential cost savings and increased confidence levels if testing was done on cohesive soils in South Dakota. The method should also be examined with small water sheds and ungaged streams. Sensitivity analysis needs to be conducted to determine the critical input parameters.