Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Exit of overflow pipe

Looking for some advice. I have a little over an acre pond that has a 15 inch smooth walled corrugated pipe for overflow with a spillway that works if the pipe gets over ran. With the water runoff I have the pipe handles it perfectly. Usually is 3/4 full when we have a downpour. My question is at the exit of my pipe. There is a large hole from erosion that keeps opening up when the water flows out with a lot of force. I'm trying to figure out what is the best solution to control this washout and a way that I can divert the small amount of trickle that comes out of the tube when we have light rain. From the exit of the pipe to the ditch it drains to is 175 feet. I can't really afford to buy 180 feet of 15 inch pipe. Was thinking of burying a 6 inch pvc pipe to carry all the small amounts of water that flows from the pipe to help with erosion. Any advice would be great

Welcome to PBF C72!

If I understand your problem correctly, you are trying to control erosion from the end of your overflow to a ditch that is 180 feet away. FWIW I was faced with a similar problem but on the inlet side of my pond. I have a huge watershed and there are two "rivers" of water that enter the pond when it rains much. I took a suggestion from Snrub, a member here, and made the waterways into the pond wider, to slow the flow, and filled them for 100 feet or so with rip rap. I went from losing a foot or two of soil in a big rain to losing none and my pond is no where near as muddy looking now after rain either! I'm thinking you could do the same thing from your overflow pipe to the ditch. IMO the rip rap under the pipe exit will prevent the "hole" as well. Here's a pic of one of the waterways.

Good Luck. Hopefully, there will be some pros along soon to offer more suggestions.

Bill D.

Edit: As Snrub pointed out to me when he made this suggestion, that rip rap may fill in with soil over time and even end up with grass on it but, the rip rap will still be there preventing the heavy erosion.

As Bill says, Put some big rocks in. Small rocks can/will wash away and gravel is pretty useless.. Been there; done that. About to redo mine.

As mentioned, some large rock (4" minimum but 6" better) for the water to hit on.

Another possibility is bags of "Quickcrete" concrete mix laid in like big bricks. When it rains they will set up into large rocks.

Or just mix up some Quickcrete and put a concrete pad for the water to hit. Similar idea to the concrete or plastic things you would put under a gutter downspout on your house.

You need not only something right where the water exits the pipe and hits the rocks, but also around it and sloped upward around the edges to contain the water and keep it from eroding to either side or end of where you put the rock.

One way to go about it is just fill the current hole with rock and or concrete and see where it washes out. If it washes out around the sides fill in with some more rock. That would be a way to approach it if you could find some rip-rap on a construction site, rocks in a farmers field, etc. In other words just fill in the hole as it develops. This would be a "fix it over time as the problem develops" project.

The other quicker way but more work up front is to get a backhoe and dig the hole out to a shape where you could deposit the rock so the sides sloped up like the banks of a creek or waterway and landscape it to handle the water. This could be a once and done project if done properly.

Keep in mind, whatever you put in the bottom of the hole to diffuse the water, the water will now diffuse outward. So the sides need to have rock lining also or the water will just erode a new hole around the existing rock.

Numerous ways of accomplishing what you need. Just depends on how much money you want to put into it and how manicured/rough you desire the finished look to be. A formed concrete trough would look really nice but unless you can do it yourself, a contractor is going to cost quite a bit to do it. A backhoe and a truck load of rock would make a nice channel out far enough but again requires the cost of the backhoe and rock. Filling in the existing hole with rock gathered free someplace and more put in as time goes by and the hole expands is cheap but takes time and effort on your part and is going to look like a farm fix and not something a person would want next to his million dollar home.

So it depends.

There are at least 2 solutions. 1) Line with something that will not wash away. 2) Spread the water out to reduce velocity. A wide, laterally flat, and gently sloping decent for the water will greatly reduce erosion, especially if lined with flat-bladed grass that will lay over during flooding. Longer term. weeping willows will develop a fibrous root mat on the surface where water runs. I have used the "concrete bag" method on washes successfully. Be aware that the protection is upstream of the bags because the water upstream slows. The water will often dig downstream if it runs over the bags more rapidly than without them.

Thanks for the responses. I did notice that my grade is slightly elevated near the exit of he pipe. Im going to fix the grade and apply rip rap 10 feet around the pipe. I think this will hel slow the a tee coming out of the pipe and save erosion. Great advice from all