In many situations, there is no point in overcomplicating rigs, but there is one key feature to my barbel rigs and that is the use of an anchor point.
My go-to barbel rig for most conditions consists of a fluorocarbon hooklink attached to a Uni-Link Swivel and short section of supple braid to which I attach the hook. The key component to finish off the rig is an anchor point, in this case, a blob of putty moulded around the swivel. This not only holds the final few inches to the bottom, but it also helps to ensure the hook is pulled down when a barbel picks up the bait ensuring a good hook hold.
When I am fishing in floodwater conditions, I will fish Tungsten Loaded all the way through to the hook and instead of using putty, I will simply pinch on a large shot. Also, during floodwater conditions, I will opt to fish a much longer hooklink with 4-5ft being a good starting point as it would be impossible to use a backlead in these conditions. The long hooklink not only reduces the chances of a barbel flanking the taught mono that is coming up from the lead. But, it also ensures that any debris caught up around the lead does not mask the hook.