I used gabion baskets as retaining walls; but not as a dam. For retaining structures it very undesirable to retain water behind the wall because it adds up more load to the lateral soil pressure.
Haven't used gabions for a temporary dam but have used precast jersey barriers with a membrane. You may alos want to check out PortaDam water retaining structures.
Never tried it, but it sounds good to me. - You will need to do something to stop the membrane getting punctured.
How are you thinking of building it? - Front part (downstream) then membrane then rear gabions? If so could you leave the membrane exposed to ease future repairs?
Gabions, with a waterproof coating, are used as the "impervious core of a earth dike". See page 424, in Chapter 13, of "Handbook of Steel Drainage & Highway Construction Products". Here is a link to the free .pdf download
Well done my friend! Your knack to find references and the speed you do it is very well appreciated by me. I am sure other colleagues appreciate it as well.
