At the time of the flood I looked at the map but there's no indication of which is high ground and so on so it doesn't help but I think mink's right. Charlie and Adam came across the blockage and wanted to make the road passable for the milk tanker.
I very much hope Charlie isn't involved in the blocking in the first place but I don't think so. That's something Rob went off in the boat to do and I'm surprised David didn't ask Stefan when exactly he saw Rob stuffing the culvert.
I believe Charlie has realised that a blocked culvert would bring blame on BL/Damara and the general state of the ditches seems to have been poor so he hired Ed to do a clear up and told him to be discreet.
Charlie might well suspect Rob of doing it but Charlie almost died so the likelihood is that he is covering up sloppiness rather than deliberate wrong-doing.
(It is odd that the outfit which got the maintenance contract that Adam lost seems not to be mentioned at all these days.)
The kiss is a secret because Helen doesn't want Ian hurt but the silly bint told Rob so the SWs must have some idea of Rob using the info at some point. If his back is to the wall he'll use any weapon he has.
One other thing puzzles me and that's the design of Berrow which is state of the art and new. Why was it built in such a way that the cattle pens would be flooded by the culvert? Have planning laws been broken when it was built and is that why Charlie risked his life and wouldn't want attention drawn to it?
That might be Rob's ultimate blackmail material.
Did Rob save the lives of hundreds of cows that night at the expense of the village?