Pond Boss Forums Thread Like Summary - "pondering" a pond site

I love the idea of ponds being irregularly shaped; where from one spot, you can't see another spot on the water. I think about paddling into coves. My property has several ravines that in my mind would make very cool ponds shapewise.
I am not finding a whole lot of instances on here of folks successfully or otherwise, damming ravines.
Is this an absolutely dumb idea?

IMO, they are surprisingly accurate! Although they are certainly not perfect.

Do you own a backhoe or mini-excavator? I frequently rent a mini-excavator for work at our property. They are very cheap to rent over the weekend, and you can learn the controls very quickly.

Dangerous rookie mistakes (that I am aware of):

1.) Must call your underground locator services and abide by their notifications exactly. Electric lines and product pipelines will kill you!

2.) Must be an expert to traverse steep slopes.

3.) Must be an expert to operate on rocky slopes.

On flat ground, you can easily dig multiple test trenches in the areas you are considering for your dam. You can also test for clay content. (If you can make a "snowball" from a moist sample - good. If you can roll a "snake" between your palms - better!) You can also determine depth to bedrock. Finally, you can also assess if you have abundant groundwater. (Your trenches should show water within a few minutes to hours. But this will then stabilize at the water level of your local aquifer.)

P.S. You can also do the rest of the things on your chore list. Like dig out some stumps, install that culvert under your driveway that your wife wanted, etc.

P.P.S. There is a chance your NRCS office or a state agency may have a service available to drive a soil probe rig into your property and get you some samples. (The rigs I have seen for samples down to 25' are more difficult to move through your forest than a mini-excavator.) There is even a chance a governmental agency will provide planning or even financial services to help you build a pond. Definitely do a search on your state agencies.

You also need to contact your conservation agent at your local NRCS. There is one for every county in the U.S. My guy is very knowledgeable, and a good one can guide you to all of the available resources.

There's a lot that goes into an impoundment actually holding water. If you built a correctly constructed damn across a ravine, you would then have to contend with if the 'walls' of the ravine held water, or leaked. The other consideration would be how much water inflow was there to counteract leakage or natural seepage.

Damming ravines is not a dumb idea at all. I love the u-shaped ponds where people have dammed two ravines and have a "connector" section of pond combining them.

However, there are generally two problems to be addressed when damming a ravine.

1.) If the ravine is cut into bedrock rather than soils, you will need to pin your dam and core trench to rock. This creates a leak point and "slide point".

Ravine ponds are more likely to be narrow and deep. Imagine a small pond that is 20' deep at the base of the dam. That is a lot of hydrostatic pressure trying to push some water through the base layer between the bedrock and the clay core of your dam. Further, most tall earthen dams contain a "keyway" to lock the dam in place. The massive load of impounded water on only one side of the dam creates a force that tends to move the dam laterally in the downstream direction. You can't create a keyway over bedrock. (However, you can install pilings, etc.)

2.) The other problem is TOO MUCH water! Ravines generally form where the slope of the land gathers a large area of watershed into a single axis of water flow. During a big rain event, that can create an entire small creek of rapidly flowing water. If that flow ever exceeds the capacity of your primary drain and the emergency spillway of your pond, then it will overtop your dam and quickly cut through it like a hot knife through butter.


Now that I have said some of the bad stuff, I still like your idea to consider making a pond using your ravines. I would definitely recommend going out to your property during a frog strangler rain and observe how much water is passing through your ravine. You need to place a marker in the flow and observe the level for a period after the rain ends, because your ravine will "crest" at some time AFTER the peak rate of rain.

That amount of water, plus some safety margin, will control the sizing and design of your pond outlets. It is also frequently more difficult/costly to build your emergency outlet on steep terrain. Passing a large volume of water for an hour over a grassy terrain with a very gentle slope can be achieved without erosion. On a steeper slope, you need a more complex armored system.

I am just throwing out some problems for you to consider. Your eyeballs on the exact location will be a much more effective measuring tool!

There are a lot of ponds constructed in my area right where the ravine empties into a flatter portion of the property. If there are clay soils available at that location, plus easy low-slope terrain for the dozers/excavators to traverse, you can cost-effectively create a nice pond there. If there is a secondary slope break, then perhaps you can build a larger u-shaped pond and connect two ravines without busting your budget.

Good luck on your new pond project!

Where in Central Indiana? I was in Martinsville on Sunday doing a pond evaluation/consultation.

Is the 20' height a county requirement? The way you drew it, the dam shouldn't be more than 16' tall if I'm reading it correctly. Yes, you have to dig back into the sides of the ravines to get to good clay soil. A core trench or core "key" is mandatory as is proper slope and compaction of the dam and key. Go to your local NRCS office to talk to them about how many acres of watershed would feed into the pond, and how big the primary and emergency overflow needed to be to cope with 500 year flood events.