Water finds a way. It might be a basement, a beach, or a bridge, but water finds a way. Its power comes from a life-giving combination of cohesion, polarity, and fluidity, not to mention weight. A specific arrangement of atoms gives water heft—enough water to fill seven milk jugs weighs more than 62 pounds. Just six inches of it can lift an SUV off the street. Two hydrogen atoms and one oxygen molecule describe this molecular wave that can toss ships, stop fatal car crashes, and undermine embankments.

Screen Shot 2013-01-21 at 8.50.28 PMWe brick and mortar ourselves away from nature. The outside world is behind glass, underneath a slab of concrete, running through PVC. Our steel and concrete are suitable enough until nature comes knocking. And when she wants to get in, nothing can stop her.

In the attempt to dodge rivers and streams, nature ultimately determines when we can pass. Her toll is simple: if you engineer the bridge correctly, you can pass. If you don’t, this happens:

Scour is the largest cause of highway bridge failures in the United States. During years of service, or during a large event like a flood, the river or stream’s molecular soup carries thousands of pounds of sediment and debris with it. This detritus builds up in the channel and at the piers of the bridge, changing the way the water flows around it. This change in flow, if unanticipated by the engineers, gives the water a new plan of attack: blast away supporting material.

LocalScourImage via the USGS

In the case of the video above, the flow of the water is blocked, but the flow must continue. Churning and swirling water caused by the obstruction removes material from the base of the embankment. The water can’t go over, so it eats a hole through. You can see the exact point (around 25 seconds in) when enough material has been removed for the water to take a different path. The path takes the support of the embankment with it. Without support, the bridge collapses spectacularly.

Engineer as we might, we are only a few extra molecules away from realizing that far from controlling nature, we merely endure it.