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Rock scour research conducted for National Cooperative Highway Research Program Project No. 24-29 used a modification of the conventional slake durability test to develop a geotechnical scour number (equivalent scour depth divided by equivalent stream power) for degradable weak rocks (Keaton and Mishra, 2010). The physical difference between weak rock and strong soil can be minor; therefore, the modified test should be applicable for cohesive and weakly cemented soil materials. Cohesionless soils would not survive the sample preparation process for the test. Durable coarse sand or gravel fragments in some soils can dominate the retained weight during the modified test, as well as tend to pulverize the soil matrix. Highly plastic clay could adhere to the drum or each other. The objectives of this paper are to describe the modified test procedure and discuss its applicability for soil materials, with a hypothetical example based on Hortons (1945) belt of no erosion.