Earthen dams are often built into bedrock abutments and on bedrock foundations. Bedrock joints naturally occur in bedrock materials. These bedrock joints create voids for ground water to pass through. Historically earthen dams were sometimes built in direct contact with the bedrock joints, causing a contact point between the soil of the dam and the flowing water. It has been engineering practice to place grout into exposed bedrock joints for some time now. However, soil is not always cleaned out of bedrock joints before they are grouted, which leaves a weakness for water to push through. The purpose of this study is to understand the point at which water flowing through bedrock joints will erode soil from the earthen dam embankment. The information of how much soil is eroded away in an amount of time is also crucial to the scope of this study. The goals of this study were accomplished by building a physical model or apparatus of an earthen dam embankment on top of a simulated bedrock joint. Different soil types were tested in the apparatus to start a database of information about erosion rates of the soil along the bedrock joint and embankment interface. These results will be used to start a database for organizations that assign probabilities of dam failures. The purpose of the study is not to indicate when dams will fail, but to help with assigning probabilities of the likelihood of a serious problem being caused from this type of mechanism presented in this study.