Saturday, April 18, 2009

Stream Restoration

My posting has been sporadic here of late. I've been swamped, trying to finish everything I can for school before it's technically due. And, in fact, I have succeeded in that. I've only one large project to go, Advanced Hydrology, a graduate Capstone presentation to a review panel, and a few other presentations to give. Thus, practically all of my actual work is finished for the semester. Now I just have to present this stuff.

So, with that, I have volunteered to do some GIS work for the Stream Institute at the University of Louisville. The Stream Institute is a group that works with stream restoration and wetland development throughout Kentucky, and also some other states. I am in the class currently. Ultimately the goal is to restore a man-made stream into something natural looking. Doing this will lower shear stresses throughout the channel, thus reducing erosion and flooding only things that are meant to be flooded.

The project I'm doing actually sounds pretty cool. I have 60 digital aerial photos of the stream that is being researched. These images are circa 1970 and black & white. I am to import them into ArcMap, georeference them, and process them. Then, I am to import topo maps and compare the stream's position to the topo maps. Finally, I am to bring in current (2006) aerial photography and compare the stream.

Imagine a jigsaw puzzle. The black & white photos are the pieces. I have a topo map that serves as the box cover, letting me know what my goal is to look like. I am working with a mostly urban landscape. However, in the 70s it wasn't as urbanized. For me, I get to see, literally, how the land changed in 30 years.

The difficult part is actually finding where the pieces go. See, the topo map includes the entire county, and some of the neighboring county. The images may not all go adjacent, and most definitely will not fill the county. It's like having 60 jigsaw pieces to a 200 piece puzzle.

Once I get everything imported and processed, I'm essentially done. By learning how much a stream has moved over a given time, we can calculate how much sediment was deposited. I don't fully understand the rationale, but sediment deposits are officially counted as a pollutant.

It really is dramatic to see how much a stream has changed over the course of time. A well-intentioned farmer 10 miles downstream may have straightened out a channel to keep his farmland from flooding. Straightening a channel is never natural. In doing so, a headcut develops (usually) and works its way upstream, tearing through the soil like any normal person going through a Dairy Queen blizzard. The headcut is a destructive force in the stream, and can only be stopped with the appropriate amount of pool and riffle sequences, or if the headcut meets a culvert, etc.

Overall, the project seems like it will be interesting. I'm trying to finish as quickly as possible, but it seems like it'll take a while. On a related note, the 60 images were .TIFF files, huge image files that took up around 5 gigs. A friend recommended using irfanview to convert these .TIFFs to .JPEGs. I brought 5 gigs down to just over 700 megs, keeping the same quality and functionality. If you have image files, movie files, or sound files you need to convert, you should check it out.

I read the news today, oh boy, about a lucky man who made the grade...

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