Pond Boss Forums POND CONSTRUCTION Building a dam Dam height above water level

I had a dam built last year and the pond is finally almost full (drought last summer). While talking to another excavator about some work he asked how I intended to keep the water side of the dam mowed? Following advice on this forum and other sources, I had the dam built with 4-5 feet of freeboard at full pond. This guy suggests lowering that to 2' freeboard. This could be done in two ways...raising the overflow pipe by a foot or two or cutting the top of the dam off, which would make the dam much wider across its top. The later option is most attractive to me as I want to use the dam top as a driveway to our future house. The top is currently about ten feet wide, and cutting two feet off would add at least 8' (likely closer to 12') to that width.

My first thought was nope, I've heard too many experts on pondboss suggest 4-5' of freeboard. Then I started looking around at other dams in the area and noted that many of them only have about 2' of freeboard. What are your thoughts?

Chris

I PERSONALLY think you would be OK with 2 ft. Three ft might make me sleep better at night. Do you have a natural overflow area in case of a 100 yr flood? If not, I wouldn't do it.

If you decide to raise the water level, just put a PVC piece on the top that goes up at 90 degrees.

There is an emergency overflow that was cut into otherwise undisturbed ground to the side of the dam. The pond is about two acres and the overflow is about thirty feet wide. The emergency overflow is 12-18" above full pond, and is well established in grass. I focused on getting a healthy stand of grass on all parts of the dam to avoid erosion last year.

Your answer should be based on watershed and existing pipe. If they can handle emergency flow regime and with the good spillway sounds like ok.

I'd think more is better.. But if you need more width on top for a driveway I would think driving 2' from watersedge would be kinda spooky..

Treefarmer,where are you located in Va.? If you got grass to do well you are not around my place as it was really dry. Good luck with your pond!

The lake is ten miles west of Lynchburg. I was able to get the grass established in March...also put down some good fertilizer and lime.

Assuming that your emergency is 12 to 18 inches above current full pond, you can't raise the level without also raising the emergency overflow. Since it was cut into undisturbed ground, I would leave things as they are.

Dave...good point. I hadn't thought about that as another reason to leave the lake level as is. What about cutting the top off of the dam, so that it is say thirty inches above water level? This would give me a wider roadway across the dam and make it easier to maintain. Does your first post still seem ok?

I think I would probably be OK with that IF IT WERE MINE.

I would want at least a foot of the emergency overflow area to be below the top of the dam. Maybe even a little more,. Packed loam used in a dam is, IMO, never going to be as bullet proof as the natural ground.

I think it looks about right.