One of the keys to a successful flume installation is bracing (or cribbing) the flume during the installation process.  Failing to brace or insufficiently bracing a flume can result in the sidewalls / floor deforming.  This is particularly true of larger flumes or flumes with either flat floors or vertical sidewalls (Parshall, Cutthroat, Montana).  

Here the contractor has only placed minimal bracing in the throat of the Parshall Flume.  While this flume didn't distort, there was a strong likelihood that it could have.