downstream beds were at the same level. Inpractice downstream beds may be eroded by the flowover the weir leading to unequal bed levels.Using laboratory models, this study examined thedischarge over submerged weirs with unequal beds. Theresulting flow pattern was shown to be different tothat of the equal bed case. The approach channelFroude Number differs from that of the equivalentequal bed case. The standard formulas derived forsubmerged equally bedded weirs were shown to giveincorrect values.The existing standard formulas for calculatingdischarge over submerged thin plate weirs treatsubmerged flow as a variation of the free modularflow. The later part of the study treats flow over asubmerged thin plate weir as a separate flowcondition and proposes an initial form of a newdischarge formula.

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