The pontons(o) were anchored in several ways, usually a cable was stretched on the "Up" side from shore to shore with lines tied into & then down to the ponton. That worked better than The anchors that were available. Maintenance of the cable was a 24 hour task. Adjustments to the cable & lines was continious. The bridges bowed in the middle, the critical point, & could not exceed about 10deg. At times boats with motors pulled the bridge to the up side. Pontons are uncovered "Boats", pontoons have a top on them !!! Engrs. used mostly pontons. The 540th bridge across the Rhine is a ponton bridge. Who knows what the Rule of Thumb "Seven UP" means???
Floating bridges of any sort were a pain in the neck. The larger ones were especially tough, dangerous and harder to work on. WE had several near drownings, many broken hands and fingers from the unstable work place. Floating baileys were the worst, only one built by the 48th. WE built the one ponton bridge across the Neckar in Heidelberg on about 1 April 45. The high banks of the river made the approach & exit of the bridge especially tough. I'm sure the flow was much less than The Rhine (540) bridge. After construction of floating bridges it would take the supply sergeant several days to write "droppage reports" for the tools lost. Yes We had to account for all tools at all times.