...A mini lesson in hydrology by Emily and Nena! Click "Read More" for sweet movies!
I apologize in advance: This is not a post about kayaking... It is, however, related to the outdoors and water.
Last fall I took a really interesting class called "Watershed Engineering," in which we analyzed and designed water control structures (dams, culverts, channels, etc). One of our projects was to analyze the Virgil Creek earthen dam. For some unknown reason, a few of us fell in love with the dam, and have been back to visit (and camp out...) a few times... The slope of the dam makes a perfect angle for watching meteor showers...
Around the outside there's also an "emergency spillway" (see above) which would hypothetically route extra water around the dam, should the flood be greater than a 100 year flood. If water over-tops an earthen dam, the dirt will erode quickly, and the entire dam will disintegrate in minutes, causing an incredibly destructive wave to go down and upstream from the site. Ok, enough background. Today Emily and I (we missed our other watershed engineering friends who have moved on from Ithaca!) went to the dam to see what happened after 5 inches of rain fell in one day. We didn't know what to expect. There was a LOT of water.
Scroll down to see the Google air photo of the dam!
Below are some comparison photos of the dam.
Click to enlarge.
The dam is a "dry dam", which means it only holds back water when there is a large rainfall event. It was designed after a storm in 1981 that cause massive flooding in the town of Dryden.
Construction was completed in 1998. It was made to handle a 100-year flood, which means it can hold a LOT of water. The metal gates in the photo to the left keep the gradient of the stream from being too steep, slowing down the water and preventing excess erosion. Today there was so much water that we couldn't even see these gates!
The movie on the right is only 1 minute long and shows the outflow of the dam. It's crazy! Normally there is just a calm trickle of water... This movie shows you the energy dissipator in full force -- it forces the water to churn intensely and get rid of some of its energy so it won't scourge the sides of the creek and cause massive erosion.