A Mile Wide and an Inch Deep

One of the great waterways of the continent is the Platte River, which flows through and drains the area seen below:

Permission is granted to copy this image under the GNU free documentation license.  This map is by Shannon1, a prolific photographer and cataloger of rivers in North American and around the world.

While not among the largest drainage basins out there, the Platte is significant in that it has long served as something of a natural oasis of water and tree cover on the otherwise open prairies of the Great Plains.  Cranes and other waterbirds would take shelter and rest here during their great annual migrations north and south along the Central Flyway, a bird travel route that largely follows the guiding north-south geographical features of the Rockies, the eastern coast of Mexico, and the Plains themselves.  

The term oasis can be a bit of a misnomer, however, as the Platte is not your typically palatable river for human use.  She carries quite a lot of sediment with her, both from the Rockies and the surrounding Plains, especially in parts of Wyoming and Nebraska that are a bit sandier and slightly more arid that the rest of the central Plains.  The Arkansas to the south also carries a similar load of sediment, but owing the a larger drainage basin and the fact that it is probably a bit older than the Platte (which probably really only got underway as the melting, thicker Rockies glaciers of the last ice age helped it out), it tends to have a bit more volume and thus water quality to it.  The title of this post is a tribute, in fact, to the running joke that past Americans have long made about the very shallow and braided river. 

Looking downstream from eastbound I-80 on the Platte near Ashland, Nebraska.  Though braided, the spring rush will actually fill the river enough to make it look a bit deeper.  When it's like this, though, you can walk across it!

 Still, the water is not exactly terrible either.  The birds enjoy it, the cottonwoods, ashes, and willows grow in abundance along its banks, and it once boasted an extremely healthy population of brook trout which thrived in the cool waters in the narrower channels and along the margins shaded by the dense forests.  The river, in this condition, actually served as an inviting passage for migrants seeking to get to the lands of California, Oregon, and Utah.  Given the choice between the vast, somewhat mysterious Plains and the familiar waters and forests that made up the Platte oasis, travelers from the eastern United States tended to follow the river. They fished from it, let their animals drink from it, and used the trees for fuel, so much so that the place became something of an exposed wasteland in a matter of mere years.  

The trout declined, the forests disappeared, and the river further eroded the nearby land and became even more of what the running joke mocked it as.  Native oral traditions and the written records of French traders do not leave us much of history of what the Platte was once like, but the presence of brook trout, which normally like clear or tannin stained waters, tend to convince me that it was once a bit different.  It probably was still braided, especially near its mouth at the Missouri, but it might also have been a bit more stabilized and purified by an abundance of shoreline vegetation.  Some of the crossings of I-80, for example, have spans which cross several channels nearly on top of each other, all of which are now covered in thick vegetation.  Research into former wildfire patterns indicates that this is not necessarily the result of modern prevention of fires, but because the forests did not experience significant burns in comparison to the surrounding grasslands.  The forests might only have seen significant burns a century or so apart, which would have been more than enough time for cottonwoods to keep a good cover over stabilized braid islands, which is what those crossings of I-80 pretty much are.  This could mean that we are seeing some of this river habitat fully restored.  Hopefully I can get a good shot of this sort of thing the next time I am there.

In any event, I-80 follows the Platte in what is one of the more verdant crossings of the Plains.  If all one does is look straight on to the road, in fact, one might not even guess they have entered the great grasslands until well into Nebraska.  Looking out to the sides, however, a traveler can see the great vistas open up in rolling hills at the edge of the Platte valley edges, often many miles distant.  The edges close in more the further west one goes, and the Plains take on the appearance of small mountains, having been well eroded over the centuries.  Grass can hold soil in place, but it is no substitute for trees.

Eventually the ashes and willows start to give way, and even the cottonwoods start getting a bit stunted up on the High Plains in Wyoming.  The river gets a bit more of a "mountain glacier green" to its waters by the time it gets to Ft. Laramie:

Taken in May of 2010 at Fort Laramie National Historic Site.

By this point it has long since divided into two main tributaries, both of which are named Platte, both of which live up to this French name meaning "flat".  Both tributaries emerge from the Front Range of the Rockies and take on a less than flat appearance as they pour out of the Continental Spine.  Here they leave behind the cottonwoods and eastern survivors and meet the forests of the west.  In both nature and history, the Platte has long served as a bridge between two different worlds, sort of like a North American Nile (which connected tropical Africa to the Mediterranean world).