Creating a Lake

   / Creating a Lake #2,061  
Then why are gravity dams shaped the way they are?
 
   / Creating a Lake #2,062  
Then why are gravity dams shaped the way they are?

Because they work (are successful.) The height of the material above water serves to compress the material below water and make it more resistant to washout. All too often folks who don't understand this sufficiently will decide to change the overflow to get greater water depth and not have so much dam sticking up in the air being wasted.... OOPS!!! Another dam washes out!

The angle of repose is a consideration as is resistance to wave action. The USDA has some good guidelines on pond dam construction.

Again, the angle of either side of the dam does nothing to the static forces such as the head of pressure at whatever depth. The lateral force of water on any portion of a dam is a function of depth and is not changed by the slope of the dam.

Pat
 
   / Creating a Lake #2,063  
Then why are gravity dams shaped the way they are?

Because they work (are successful.) The height of the material above water serves to compress the material below water and make it more resistant to washout. All too often folks who don't understand this sufficiently will decide to change the overflow to get greater water depth and not have so much dam sticking up in the air being wasted.... OOPS!!! Another dam washes out!

The angle of repose is a consideration as is resistance to wave action. The USDA has some good guidelines on pond dam construction.

Again, the angle of either side of the dam does nothing to the static forces such as the head of pressure at whatever depth. The lateral force of water on any portion of a dam is a function of depth and is not changed by the slope of the dam. If you wanted to calculate the force of the water on the dam you'd divide the pressure at the bottom of the dam by 2 to get the average PSI and multiply that times the vertical area of the dam (ignore slope, just go with vertical area, i.e. width times vertical height.) So, you are multiplying Pounds per unit area times effective area of the dam and you end up with pounds.

Pat
 
   / Creating a Lake
  • Thread Starter
#2,064  
I got lucky the other night. It had just rained and the sky was still making all kinds of noise. The clouds looked interesting, so I drove the Mule down to my favorite spot to take sunset pictures and waited. It was a pretty decent show of color in the sky, then all of a sudden, it got VERY GOOD!!!! Just as quickly, it faded.

Eddie
019.jpg
 
   / Creating a Lake
  • Thread Starter
#2,065  
After months of delays, I was able to pour concrete today. My parents where here to help me, and we got it done in a couple of hours. Total was five yards for $647. I had estimated 7 yards, which proves that I can't do math and it's very hard to estimate concrete!!! :confused:

I'm going to let it sit for two weeks, and then pull the forms. The rest is pretty easy now, just a matter of taking it one step at a time and not being in a rush.

Eddie
003.jpg
 
   / Creating a Lake #2,066  
I got lucky the other night. It had just rained and the sky was still making all kinds of noise. The clouds looked interesting, so I drove the Mule down to my favorite spot to take sunset pictures and waited. It was a pretty decent show of color in the sky, then all of a sudden, it got VERY GOOD!!!! Just as quickly, it faded.

Eddie
View attachment 274720
Eddie,
You need to try selling these photos to Texas Highways or Texas Parks and Wildlife magazines.
They are awesome photos.
hugs, Brandi
 
   / Creating a Lake #2,067  
The spillway looks great, Eddie. But when are you gonna cut the weeds?;) :laughing:

The back side of my dam is grown up with Johnson grass and cockleburs. I told my grandson that all those weeds would cut down on erosion and they are good.:D
 
   / Creating a Lake #2,068  
I got lucky the other night. It had just rained and the sky was still making all kinds of noise. The clouds looked interesting, so I drove the Mule down to my favorite spot to take sunset pictures and waited. It was a pretty decent show of color in the sky, then all of a sudden, it got VERY GOOD!!!! Just as quickly, it faded.

Eddie
View attachment 274720

Beautiful photo. Wish I had that to look at iin the evenings around here.
Very nice. I agreee you should either list these photos with a stock photo agency or
maybe print up some and sell them. You might place them in a local resturant framed
with a price tag and see what happens. Not much to loose.
 
   / Creating a Lake #2,069  
Any progress Eddie? I'd like to make a suggestion to you. I know you are relying on vegetation to keep erosion from occurring where the water leaves the concrete pad. However, I think you could reduce the chance of erosion from happening by making a shallow energy dispersion pool out of your concrete pad. Gravity is going to increase the water speed a lot where the water falls off the cinder block wall and just hitting the concrete is not going to slow that very much before reaching the edge of the concrete. By making a pool of water on that pad of 3" to 6" deep, the water will loose most of the energy produced by the fall by hitting the shallow pool. Use bricks or block to make a small dam across the end of your pad about 6" to 12" from the edge. That way the water leaving the pool over the top of the bricks will still hit concrete before gently entering the soil bottom spillway. You could even leave a few gaps between the blocks so the water eventually completely drains to avoid a mosquito raising pool. You just need to trap some water there while there is a lot of flow coming over your block wall.
 
   / Creating a Lake
  • Thread Starter
#2,070  
Thank you for the nice comments of my pictures. I might enter that one in the County Fair, but will do a test on facebook first. What I like isn't always what everyone else likes!!!!! Mostly I take the pictures and post them on facebook to remind my clients that I'm out here and for them to think about me. Oscar, my pig, does that for me too. It's blatent marketing that has proven to be very effective for keeping me busy and increasing my rates.

I just got back from Peru today and haven't been down to see the pond yet. Hopefully tomorrow I'll be able to see how it looks and get the forms off. If not, it will be this weekend.

The reason the spillway is where it is, is because the land has a VERY GENTLE slope. It's almost level, the water flows very slowly over the grass until it gets to the creek. I'm 99% sure that once I get it smoothed out and planted in Bermuda grass again, there wont be any errosion. My only concern is where the concrete ends and the grass begins. This might develop into an area that I'll have to add some river rocks to. Worse case scenerio is that I create a hole or depression in the ground there. Even if there is massive errosion, it's virgin soil that has nothing to do with the dam, so I'm good either way. My only concern is how will it look and how hard will it be to maintain.

Pics as soon as I get some!!!

Eddie
 

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