Scour Protection for Locks and Dams 2-10, Upper Mississippi River. Hydraulic Model Investigation.

A 170-scale physical model of a typical spillway section of the locks and dams on the Upper Mississippi River was used to determine the probable cause of the scour that has occurred at these projects. It was determined that single-gate opertion on the spillways created hydraulic conditions conducive to scour. A 142-scale model was used to develop suitable riprap protection. Two gradations of fill material were found suitable and two gradations of riprap were adequate for protection downstream of the tainter gates and roller gates at these structures. The geometric layout of the riprap depended upon the slope of the scour hole to be repaired. Lock and Dam 2 was studied separately because of its unique stilling basin configuration and operation schedule. Riprap protection similar to the other projects was devised for Lock and Dam 2.