The state and national borders that had been historically dictated by a river's path may聽come into question聽when that river changes direction. 聽CU Boulder Geology Professor Dr. Greg聽Tucker understands this issue all too well. 聽Tucker explains that,聽"Rivers and streams often appear to be fixed and more or less permanent features聽of the natural landscape. 聽Yet as聽the recent [September 2013] flooding in Boulder illustrates, they are often quite dynamic." 聽Indeed, as a drive up US 36 will quickly tell you, the St. Vrain River now runs in different places than it did just a year ago before the Fall 2013 flooding, which left a lasting impact on the surrounding community.
In 2013, Tucker received an ASSETT Development Award to create an animation about a changing river system.聽聽"I used the ... award to hire a professional scientific illustrator to work with me to聽create a short animated movie depicting river meandering." 聽The illustrator is Dr. Cheryl McCutchan of .聽McCutchan made the river animation聽in Adobe Flash. 聽Watch it聽here:
Tucker says, "The animation illustrates the way a river can carve a floodplain聽by eroding and widening the valley聽through聽time." 聽The white along the river in the animation represents,聽"... Point bars ... fresh sediment ... that grow outward over time," he says. 聽The darker green along the river represents the older flood plain. 聽Tucker explains that, "The meandering process leads to fascinating patterns in river valleys, with the channel following a convoluted path that winds back and forth across its valley, and with striking features such as long, curving lakes known as oxbow lakes." 聽Oxbow lakes form when a river floods and changes to a straighter direction, leaving fresh new shoreline between the new straighter river聽and the former curve of the river, now an isolated lake in the shape of the letter U, or an oxbow.
Why Use Animation, and How?
Tucker and McCutchan explain that animation can better illustrate changes to a landscape over time聽than would聽just looking at static images in a textbook. 聽Tucker says, "By creating an animated movie of a hypothetical meandering stream as it evolves over time, creates channel cutoffs, and forms oxbow lakes, we provide students with a means of visualizing the dynamics at play." 聽McCutchan agrees:
Illustrations that show three points in the formation of a stream meander or ox bow lake don't give students a sense of how these structures form. 聽Our goal was to animate the evolution of a stream channel over several millennia as the channel widened ....
However, the animation was not created overnight. 聽Tucker says that the process took about a year to complete. 聽He found a聽computer simulation that a Post-Doctoral聽student had written聽several years聽prior. 聽Tucker shared the simulation聽with McCutchan to give her specific聽information about exactly what happens when a river changes course. 聽Tucker says:
Starting with these images, together with photographs, maps, and satellite images of real meandering rivers, [McCutchan]聽used the Adobe flash聽animation program to create a series of animation frames that show a river in the context of its valley and floodplain.
McCutchan explains that she chose Flash intentionally because it can create transition between a few frames to convey the illusion of continuous flow of movement: "Flash is an incredibly powerful program that allows the animator to draw only a few key frames. 聽Flash then interpolates how the objects change between those two scenes ..."
Tucker ultimately intended to show the animation to his聽Introductory Geology students because, "One of the challenges in teaching Introductory Geology is helping people appreciate that the Earth is always changing," but that changing process is often, "slow and intermittent," over hundreds or thousands of years. 聽He聽wants his students to walk away from his Introductory Geology聽course with some practical knowledge about changing landscapes聽and, "Have them leave the course聽appreciating that change is normal in river systems, so that when they聽go out and buy a house, they appreciate聽what it means to be on a floodplain."
Tucker聽plans聽to share this animation on the , which聽is a National Science Foundation-funded site that offers聽share-able scientific images and animations to the public. 聽After all, he says, "As a scientific community, we should be sharing [information]."
Next, McCutchan and Tucker are planning to聽collaborate on a second animation that would use a聽cross sectional view to聽show how river sediment changes over time.
