Dealing with tunnels is a long term challenge for the Engineers in the IDF. They really should develop some technology/special weapons/demolitions for quickly and safely clearing and thoroughly disabling tunnels. They will likely have to do it repeatedly, and will typically have small windows in which to get the maximum job done.
How about wheelbarrow-sized robots to run a flamethrower through it, and then follow with demolition charges and/or a line charge? Maybe a small motorized platform that a guy in an EOD-like suit could weild a high volume grenade laucher, so the pieces could be carried down stairs or lowered down ladders by soldiers when needed.
Flooding leaves the tunnels intact to be pumped out later, but flooding with fuel for a clearing fire can be followed up with demolition the next day.
If you have enough water and strong enough pumps you could clear tunnels with water and then demolish conventionally, but that is probably only rarely feasible. If you can emplace demolitions with scuba equipment though, flooded tunnels would provide excellent tamping for the charges.
Just some thoughts. Counter tunnel tactics is unlikely to have escaped Israeli attention, so I hope they have some innovative weapons and tactics.
bump