Abstract
Check-dam stability is heavily influenced by local scouring processes, such that structure undermining and failure can occur if scour depth is not adequately accounted for. Therefore, the foundation depth of grade-control structures is generally assigned to equal the maximum scour depth in clear-water conditions. The present chapter will first present an overview of the physical processes taking place in local scour phenomena due to overfalls and then a state-of-the-art of the prediction of the maximum scour depth at single and sequence-forming check-dams. Differences between the two cases will be highlighted, and the complex interaction between closely-spaced structures will be addressed.