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!