The Bonnet Carre Spillway discharges water from the EAST bank of the river through Lake Ponctchartrain to the EAST to Mississippi. Apparently the decision was made that was to place to construct the spillway to protect the grater New Orleans area flooding. From a land building standpoint I think the best place would have been on the west bank of the river just east of St. Charles and discharge to the gulf through Lake Salvador. That is a little bit further downstream from the current location of the Bonnet Carre.