Currently Building a pond- going to put a spillway in to handle water overflow- it’s not an emergency spill way. I will have no Pipe in the dam.

The question I have is - is it a horrible idea to put the riprap spillway at the middle of the dam? It’s tallest section?

I see most spillways are on one side of the pond.

The reason for wanting to put the spill way in center is for looks - nothing more

Thanks

You want it on the side so you can cut the spillway into the virgin soil where the dam ties in. The virgin soil won't washout nearly as easy as your fresh packed dam.

Spillways aren't usually used for the primary way to remove excess water from the pond because they have a tenancy to wash out due to the amount of water that they would typically see during the normal pond life. The emergency spillways are used because they don't see water flowing through them frequently and will "usually" stay in place.

Without having to go look up the information, I know that there is a maximum flow rate in feet per second that you want a spillway to see so it doesn't wash out.

Many thanks to all- so if a soul ways isn’t preferred due to washout. What other options exist? I was trying to avoid a vertical pipe . And also didn’t want a potential leak issue with a pipe. All thoughts appreciated

Spillway not soul way- lol

Overflow pipe installation really poses little leak issue threats if installed properly with seep collars, the most problems people have had over the years I think, are from iron pipes that eventually rust out, I know that some still use them but I am not a fan of them when you have the pvc pipe option that are pretty much deterioration proof. I done think a spillway for all excess water expulsion would be desirable in the long run, unless you have very little water flow that just barely keeps your pond full and very little excess runoff.

The other option is a siphon drain, you can put that through the dam at a much higher level than a typical overflow pipe and the great thing about them is that you can suck water out from the bottom of the pond instead of surface water.

My spillway will be right in the center of my damn. It's the place where my new damn meets the original damn. Right now I'm hoping we dont get a toad strangler and wash it out.

I have a pipe through the dam. No problem. However, it is pretty low mileage due to my lands aversion to rain.

You need to consider some sort of controlled drain system. IF my 1/4 acre pond, with excessive watershed, did not have a simple drain pipe...it would not have a dam today. You want to size the drain system to handle as much water as your pond is expecting to see in the larger rain events and then have the Emergency Overflow off to the side, preferably in virgin soils (like Bob said). My example, 1/4 acre pond with 20+ acres of water shed (about 10 times more than it should for my area), has a 15" diameter pipe through the dam, and a low path (emergency spillway) where the dam met the original landscape. We could not place the emergency spillway in completely virgin soils so we added freeboard to the dam that allows water to build up 3 foot above full pool before going over the dam. To date (going on 4 years), the emergency spillway has not seen water, but the water has risen to 2 foot above full pool. Without the through pipe...I am sure the spillway would have needed some maintenance at a minimum.

It's purely my opinion that a pond that can exist without a drain pipe is one that would have a hard time filling and staying at a reasonable filled level. This would be one with inadequate watershed for it's size.

Something else to consider. Try to put the spillway where it will have the least amount of slope on the back side. The less the water path drops per foot, the lower the water speed and the less it will erode.