patrick_g said:
Eddie, The pressure at any given depth is equal in all directions and the slope of the dam doesn't work the way you reconveyed the comments you heard. There are a lot of folks who can build a dam and lake that don't understand the physics. Bumble bees aren't aerodymanicists but they fly.
Earthen dams are "gravity dams" and require enough dirt in the air to provide enough weight to keep the submerged dirt held firmly in place. A slope as you suggest is a good practice, just not quite for the reason you were told. Bottom line is if the lake is what you want and the dam holds under all conditions of stress/overflow it doesn't matter why it works just that it does work. I have 10 ponds noiw and plans for some more but most are under 2-3 acres.
Pat
Thanks Pat, but you lost me on this. If a a dirt dam requires dirt above the water to hold it in place, wouldn't it have to be more dirt than water?
I'm confused on this because I would think the water far outweights the dirt by a overwhelming amount. If I understand what your saying, than the wouldn't I have to have more dirt than water? If the water was to rise to the top of the dam, would that cause the dam to fail?
I've seen poorly designed dams that didn't have a spillway and the water just flowed over the top. After awhile, erosion wears through the dam and the water flows out, leading to more erosion and more water comeing out faster and faster until it's all gone or there's no more dirt to erode.
I've never heard of a dam failing because of too much weight of the water, or not enough dirt holding it down. Of course, I'm not very knowledgable on these things and I'm just trying to understand it so it makes sense in my brain.
Another point that I'm confused is on the inner slope of the dam. If the slope doesn't affect the preasure of the water, why does it need to be 2:1 or more? Mine is 3:1 because I thought this would make it even stronger. Is this simply a formula to create enough weight to hold the dirt in place?
I know there is a formula for how thick the dam should be based on the height of the water when full, but again, I thought that was to hold back the water with the thickness of the dam. If I understand what you're saying, this is in fact to create enough weight to hold the water back.
Is the water presure determined by the height of the water on the dam alone? Wouldn't the large amount of water create more preasure? I'm really lost here. One acre foot would weigh so much, so would that weight have a certain amount of preasure on the dam? If so, would 4 acred feet have more preasure than one acre foot?
Thank you, this is very confusing.
Eddie