Got 3 minutes? Learn why rivers change their courses

Rivers. They’re pretty amazing things. They provide humans with water for drinking, irrigation, and sanitation. They give us fish and other aquatic animals for food. They can be harnessed to power grind our grain, run our looms, and even power our cities. Their seasonal floods can bring rich silt to our fields or destruction and devastation to our lives. Sometimes, with just a little bit of help, they can even catch on fire. It’s no mistake that the first major human civilizations – Egypt, Mohenjo-Daro, Sumeria – developed along the banks of the world’s great rivers.

But rivers are much more than servants of (wo)man. They are dynamic ecosystems rich with biodiversity that shape and are shaped by the world around them. Any entity that can literally carve the Grand Canyon is pretty damn powerful.

And so rivers change. They top their banks, meander downstream, shift their paths. Sometimes, rivers even stop, turn around, and travel in the opposite direction. Rivers are not the static, shaped bodies that we encounter, but living, breathing systems.

It’s exactly this dynamism that humans don’t seem to like. We don’t like things that are beyond our control. We like to make things knowable, predictable, manageable. So we applied the logic of urban planning to one of the most complex systems in the world. We filled in urban rivers and sent them through channels and culverts. We built artificial banks out of concrete and steel to keep rivers contained. We constructed elaborate systems of dykes, dams, canals, and sluice gates so that we could regulate the seasonal pulses of the Mississippi and the Nile. We even dreamed up cockamamie schemes to make crooked rivers straight. These efforts to regulate rivers have created their own severe side effects – riverbank erosion, declining biodiversity, reduced silt delivery, sedimentation, and altered flood risks. We’re only beginning to face up to these unintended consequences.

So we know that, left to their own devices, rivers will constantly change. But have you ever wondered how and why? Well, wonder no more, thanks to this new video from Minute Earth. If you have three minutes to spare, you can learn a lot about fluid dynamics, fractals, and how muskrats decorate their dens.

(Cross posted from timkovach.com)