How ever you want to say it is the most important part of the pond system.
Picture your worst rain storm where the ground was covered in water 2” deep or more.
Or maybe a hurricane dumps rain that you have never seen before.
The over flow pipe does it’s job the best it can but can be over whelmed with too much rain. The over flow pipe can only handle so much water, what it can’t handle will continue to fill the pond until one of two thing happen, one the rain stops or 2 there is an emergency spillway to release the excess water level to protect the dam.
Second the rain keeps coming and the water goes over the dam. Water over the dam can equal close to perpetual motion, when the water keeps flowing over the dam the water will cut into the earth and erode the earth away and will continue eroding until there is no more water left in the pond.
The spillway is what can save the dam when done properly.
Wide and shallow works best to remove the most amount of water faster with a maximum flow rate and less fish loss. Do Not screen the spillway to try and save fish. It is better to lose a few fish than lose the dam.
The construction of the the spillway can be seeded for grass, the grass will help prevent erosion from the water running thru it. The spillway can also made from all cement with no chance of eroding or lay down anti erosion screen and put rock and stone on top. These stone and rock are found when the pond was being dug.
The erosion screen will prevent erosion and the rock will help to break up and slow down the water flow along with a nice rock way.
From the top of the dam to the bottom of the spillway should be 1′ then from the bottom of the spillway to the top of the over flow tube 1′.
The width of the spillway depends on the size of pond and the acreage of water shed flowing into the pond. For an example a ½ acre pond with two acres of water shed make the spillway 8-12′ wide.
This is another case of bigger is better. Do it right, do it big so when your at work or away on vacation you can rest easy knowing your pond will still be there when you get home.
Think of it as an insurance program.
Tornadoes, thunder storms and hurricanes may not effect your area but if they do you should be prepared with the spillway. Take a look at the pond construction page for more information.
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