Block ramp failure mechanisms: critical discharge estimation

Stream rehabilitation structures such as block ramps or rock chutes can be subjected to different levels of instability that produce morphological variations. To ensure ramp functionality, it is important that the rocks remain stable during design flood events. Analysis of the failure mechanisms that can occur is thus of considerable interest for river engineers. Experimental results indicate four main failure phases - incipient motion, local failure, global failure and ultimate failure. All these instability mechanisms are qualitatively described. Simple novel relationships are given in order to evaluate the critical discharges corresponding to each failure phase.