Pond Boss Forums INTRO Questions & Observations overflow design for streamfed pond

I have a 3/4 acre stream-fed pond which has had major problems with the overflow spillway over the last 7 years. The original spillway was eroding, so we attempted to have a new one cut into the bank, but shortly afterwards, the old spillway partially blew out after 13" of rain in 4 days. The old spillway was filled in again, but the new spillway never really handled the overflow adequately - it just was not cut into the bank low enough to take the water and instead, the water gradually eroded the soil at the original spillway. There is a good stretch of rip rap in the new spillway - 50'x 10' but it sits up too high and is barely being used.

With the recent hard rains during the last several weeks, the original spillway has opened up and now has continuous flow; the pond level is nearly 6" below the vertical drainage pipe in the pond. To compound the problem, the overflow floods across the gravel driveway because the 2 24" drainage pipes are not enough to handle the volume of water in a flood. I've lost a portion of the driveway as a result. The excavator that did the work the first 2 times didn't get it right, so someone else is scheduled to do the repair work. Any suggestions as to how to best address the spillway design and the drainage issues?? We're looking at: building up the bank at the outlet so the water level rises to original level; widening the spillway to 10'-12' -to include the original and new spillways; cutting into the bank so that the spillway level will take water across entire stretch; and adding at least 1 more 24" pipe under the driveway to accommodate the volume during floods. What do folks think of these proposed solutions? Do any of these ideas sound like they'll adequately address the problems? Any suggestions would be greatly appreciated.

Kathleen, Wecome to the forum! I'm sure sorry to hear that such a large problem is how you found us.

Mike Otto will surely see this post and offer some expert advice. You may want to contact him directly to have a telphone consult.

Pictures will help everyone have a better idea of your situatuion---every pond is different. I wouldn't be a fan of cutting into a bank because of erosion concerns. Widening of the spillway is a givin along with increasing the capacity at your road. Any bottleneck will raise the water level to overflow something, somewhere.

I would contact the local NRCS agent at your county USDA office. If your county has a good agent, they will determine the size of your watershed and let you know how big and what styles of spillways will work best for you. Often they will supervise the repairs to make certain it is done correctly. A relatively low priced altenative discharge system is a siphon system. These can withdraw a huge volume of water through small diameter pipe.

Best suggestion I can offer is to contact the NRCS right away to help develop a plan before your contractor shows up. Changes in design made once the equipment is running often means large increases in cost to cover wasted work.

Kathleen, you might consider an automatic siphon. Go the Pond Dam Piping website and click on siphons. The start when the water rises and stop when it drops.

Oh yeah, welcome to Pond Boss.

Not sure if it helps but I have continuous flow coming out of my trout pond, albeit it's at a much smaller flow apparently than your pond. I'm moving almost 60,000 gallons a day into and out of the pond which is about 45 gpm. I use regular drainage pipe with at least one collar close the pond and another farther away to keep water from working under the pipe and eventually the entire length of the pipe, which it will if you don't use a collar.

I used to be a believer in an emergency overflow type of overflow lined with stone (ditch at the top of the dike),and fed into a culvert pipe in the next pond in the series, but I'm rethinking that. Problem was I've had star faced moles digging holes in the sides of the emergency overflow and down 2 to 4 feet into the dike. And they were digging under the pipe the water flows into at the end of the emergency overflow. If I would not have caught this it was just a matter of time before I had some serious problems.

One more thing I've learned from the school of hard knocks: Don't under size your drainage pipe. It's always better to go bigger than smaller.

How many acres are you draining through your pond?

I think she said "stream fed" didn't she?

Yes but I have a year round steam flowing through my property and it drains about 700-900 acres. Your drainage area can be just a few acres and still have a live spring with running water year round. If my land was just a little further upsteam flow would be the same but drainage acreage would be drastically different.

Makes sense.