In Wisconsin, United States
Size:  (not chosen)
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Very easy access to this earthcache. Easily wheelchair accessible. The parking coords are for one spot that does not have a specific sign prohibiting your parking. Also, I have permission from the Lauderdale Lakes Lake Management District for cachers to park here for the few minutes that should be required to complete this cache. But please do not linger parked there TOO long. :)
D A M S -- the science
When the flow of a river or stream is obstructed, the water will build up behind that obstruction. Beavers know this and have used it for eons to control their environment.
Like the beavers, it seems that man is never satisfied with his surroundings. We build dams to control water flow in order to create ponds, create lakes, change the course of rivers, or to harness the energy of the water we are holding back.
In our pursuit of control, we often change the earth around us to a large degree. While at this site STAY ON THE NORTH SIDE OF THE DAM OR ON PAVEMENT. DO NOT TRY TO GO NEAR THE DAM ITSELF OR OVER THE FENCE!!!
The site of a dam requires some pretty specific geological properties. The dam itself requires a solid foundation. So the stream or river that is to be dammed needs to be flowing through a place that is just above rock, or at least a VERY solid base. The builders need to be able to clear away the top soil and set their steel and concrete directly on a solid foundation to ensure that the dam will last.
In the case of this dam, that's one reason it was later rebuilt back away from the lake itself. The shore of a lake is too susceptible to erosion. So they set the dam back where the creek is in this deeper ravine that has a lot of rock, gravel, and clay in the soil. It is easier to dam the river and not allow it to erode around the dam. If you look at the downstream (east side)of the dam where the creek flows on and under the road, you'll see that the ravine originally cut by the stream is a bit deep. Clearly they felt that ravine would serve their purpose.
In the case of a big river like the Snake River out west, the dam must be set directly into the bed rock in order to prevent erosion. A dam like the Hoover Dam clearly must be set solidly to hold back the millions of gallons of water so completely. In comparison, a little creek like this one does not necessarily need to get to bedrock. A good solid base in tough dirt, rock, gravel, and clay will suffice.
Just like building the foundation of a house, the builders here put a foundation down deep enough to get below the frost line in order to prevent problems from freezing. They also set the dam far enough into the surrounding banks of the river so that the water cannot go around it.
Besides the construction of the dam as far as its foundation goes, the geological location of the dam is important, too. Naturally, the dam must be on a stream or river. It needs to be located where the water behind the dam has room to back up without flooding anything real important.
When the dam is put in place, the water will want to back up to the height of the dam. since this will raise the natural level of the lake (or in some places, CREATE a lake), a good survey of the entire upstream area must be made to figure out how the added level of the lake will impact the shoreline. This is a relatively small dam so the lake was probably only raised by a few feet. It's hard to imagine what the lake area would look like if the lake were a few feet lower, but we can clearly see two large affects:
We can see the small pond that exists between the lake and the dam; and we can take a look downstream. The little mill pond we see here would not exist without the dam. The lake would simply flow out the culverts under the road and down the stream. Then take a look to the east of he dam -- the downstream side. We don't really see much there.
With the dam holding back so much water, we wonder what the stream would look like if the dam were not there. The flow of the water would be uninterrupted from the lake. So the water flowing downstream would undoubtedly be much more and it's level would be higher. The stream we see here would be flowing perhaps twice the size. Take a walk up to where the stream passes under the highway. If you look on the far side of the highway you will see some wetlands. If the lake were not being held back by the dam, would we perhaps see another lake over there rather than just wet lands?
H I S T O R Y -- of this site
Originally, the dam was where you are standing. It was built in 1839 by Amasa Bigelow to provide power for a sawmill. That mill produced much of the lumber used to build homes on Lauderdale Lakes in its early days. An interesting note: Every evening when he closed he would add boards to the top of the dam so it would hold back extra water over night. The lake's level would actually rise. When he came to work the next morning he would remove those extra boards. The extra water held up over night was needed to get the big wheel of the mill moving.
In 1907 the mill ceased its lumber operation. The dam was used for a while after that to provide electricity for the Sterlingworth Hotel which stood right nearby. The generator turned out to require too much maintenance as it would often clog with branches and seaweed. So the generating equipment was emoved. The original dam was removed and the new one placed where you see it today. It's only use now is to help control the level of the lake. The pond you see before you is also used as a place for fire trucks to pick up water to fill tankers.
Many thanks to the Lauderdale Lakes Lake Management District (Don in particular) for their cooperation in placing this earthcache.
V E R I F I C A T I O N of your visit
To claim this cache, go to the coords above. You will be on a public roadway that is little used but please be very careful. DO NOT GO DOWN TO THE POND, NEAR THE FENCE OR TRY TO GET TO THE WATER AS IT IS PRIVATE PROPERTY. STAY ON THE PAVEMENT!!!
Once at the coordinates, please accomplish three tasks and e-mail me your answers:
1) How many sluiceways are there? (The sluiceway is the concrete path the water takes over the dam)
2) About how wide is each sluice in feet?
3) If, during regular water levels, this dam is flowing 25 gallons of water per minute per foot of width, about how much water flows over this dam each hour? (your answer to #1, times your answer to #2, times 25 times 60)
(#1) x (#2) x 25 x 60 = your answer
E-mail me the answer to those three questions for satisfaction of the tasks. Look around our environment. Dams are actually pretty prevalent. Imagine what the world might look like without them.
(No hints available.)
Last Updated: on 1/18/2015 11:13:47 PM (UTC-08:00) Pacific Time (US & Canada) (7:13 AM GMT)
Coordinates are in the WGS84 datum