Pond Boss Forums POND CONSTRUCTION Selecting a site "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?

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!

Well, you guys didn't totally poo poo the idea, so that's a bit encouraging.
I am examining two different ravines as possibilities. The first would be my ideal pond. Visible from a planned home site, about 2 acres in size, and a few branches to it. Below is the property.

I guess it's more of a ravine system. I'm looking at the 810 contour. For a frame of reference, that picture is roughly
700 x 700 ft. or a bit over 11 acres.
There are several limitations I've learned. The first is this part of the ground is enrolled in a state forest and wild lands program, and I am limited to under 2 acres that can be modified into a water feature (pond). That's fine by me, as I stated 2 acres in my mind is ideal. The next limit is dam height. If my dam remains under 20ft in height, then no state gov. involvement is required. That sounds like a worthwhile goal too!
Then of course are the soil limitations. As both you guys noted, soil and bedrock need to be accounted for. Around the 780 contour, bed rock is exposed, as FishinRod guessed. Looks like a siltstone, and quite fractured. I'd probably try to stay above the 790 ft level because of that?
I am going to play around a bit with some software and info; it looks pretty powerful mapping this stuff out.

I would also examine the satellite view of the areas adjacent to your property. If you see abundant small ponds, then the odds of favorable circumstances on your property are probably pretty good.

You might even check the elevation of the dams in your area. In regions where the bedrock has a low stratigraphic dip (slope), the elevation of the bedrock will be nearly uniform across the area. For example, if there are essentially no dams constructed where the ground level is 760' to 780', then that might mark a 20' thick bed of fractured siltstone that would be a nightmare for dam construction.

Great points! I have seen several ponds in the area. I'll pay more attention the elevations. I wonder how accurate the USDA soil maps are?

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 are several nice ponds within a half mile of me, all in the 800-820 level, except one is at 785. Bodes well.

As stated, I like the thought of a pond following the shape of a ravine. I've come to realize its going to be difficult to get the pond surface area size I'd like, with the ravines I have. The problem is to stay under a 20ft dam height, I have to move the dam upstream, making the surface area smaller than I hoped. So I try different surface contour levels and dam locations to try and maximize the surface area, and minimize the dam height.

Here's a pond at the 804-contour level in my ideal ravine:


The problem is at the 804 level, its still pretty low in the ravine, as you can see by the remaining contour lines. These contours are in 1 foot increments:

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.

I'm west central, Greencastle area.
The 20 ft dam height is a state thing. It's the point where you transition from a private to state monitored and regulated dam in Indiana.
The 1 ft contour lines are a bit difficult to see in the map I posted. The way I understand the rules, is that a dam's height is measured from the lowest point of the creekbed at the centerline of the dam.
In the case of my map, the dam midline crosses the ravine creekbed at the 787ft contour (804 ft pond surface -17 ft depth) So I was really pushing the limit with a 20ft dam (17ft depth plus 3 ft freeboard). I'd shoot for 6 inches lower to stay under the state radar.
This shows the the 804 and 787 lines:


As far as watershed, this is close but not totally accurate, as I had to move my dam upstream a bit, (I had to back off my original 810 ft level with about 2 surface acres.) since this watershed calc. was run. The new shed is probably a couple acres smaller, maybe 27 total instead of the stated 28.2:


I've read a little about dam construction so far, but not really focused on it yet.