What effect would floods have on modern military forces?

And avalanches along with all the other things natural objects can bury you under.

I know the infantry forces are screwed. Everyone knows that.

But what about the tanks? The aircraft (that isn't in the air)? The mecha? Artillery? Armored cars? APCs? etc.

Many dams were actually destroyed in WWII to slow down enemy movements. It worked well enough for what it did. The Danish are still recovering.

The tanks will get slooshied with water, probably rendering its components water-logged. I think same goes for the artillary and APCs and whatnot. If they're not waterproof..

How big a flood are we talking? Tsunumi sized?

One that's large enough to completely cover the vehicles.

Unless you're working with futuristic or fantastic-level technology, I say this will definitely slow this shit down, to the brink of breaking things. Some of the vehicles will be irreparibly damaged beyond repair, and the lucky ones that do survive will need two or more days' worth looking at.

edited 20th Jan '11 12:30:24 PM by QQQQQ

Would the force of the flood/avalanche/whatever be strong enough to actually push these things back?

Depends primarily on the terrain they are on. Low friction terrain (ice, sleet) and the vehicles will be shoved aside and maybe over. Murky, unstable terrain will have the vehicles sink down into the sopping ground (think bog and quicksand).

edited 20th Jan '11 12:37:04 PM by QQQQQ

Would also depend on how close they are to where the flood starts. I think.

The easiest way to block up a mountain pass to armored vehicles along a road is detonate an avalanche onto it. (IIRC, this tactic has been used before against both infantry and armor foes.)

Get an armored vehicle caught in an avalanche like a skier and it'll be pretty busted up if it works at all assuming you can recover it in the first place.

Aircraft are even worse in shape. Say you have a mountainside airfield/helicopter airfield and you drop an avalanche on it, every aircraft and helicopter hit by the avalanche is going to be out of commission either way.

Armored personnel carriers, infantry fighting vehicles, light vehicles like trucks will all be knocked out in an avalanche.

Flooding is much different. Some vehicles are designed to be amphibious and thus are not affected by a flood unless it's like a flash flood on a slope and it washes the vehicle onto its top or over a cliff/down a hard to travel slope.

A flood is not usually enough in and of itself to immediately create boggy ground out of previously solid ground. That usually takes a relatively long period of soaking.