I am finding this a very interesting thread as some of the things done elsewhere in the world would just be a complete no no in my books here in Australia.Firstly would be a definite no to knocking out a gap in the bank to drain the water you would have make sure the soil that went back in was the same and compacted the same etc. otherwise first big storm and it could be gone.Totally agree with you scrub on silt scoops as to why more aren't used.I owned one myself for many years a three section one which is even more effective then a single scoop as in the pictures as it can go up and down contours banks etc. and not lose its load of silt.The other thing with cleaning with this method lose very little water out of the dam and also,in my experience, within days the water will, in some cases be clearer than before desilting and cattle will drink it no trouble.I have tried to desilt dams with just a dozer but amongst the the obvious problem of getting the machine bogged, you have the keep a very close eye on the tracks, because if you dont keep the mud away from the tracks then they will bind up that tight that it will make it hard for the machine just to move let alone push silt.I sold the silt scoop only a couple of years ago, why I don't know, could have used it half a dozen times at least since.