I had a gentleman drop by the office to ask about removing trees off his pond’s dam and how to fix some major erosion on the backside of the spillway. Ponds built in watersheds are common in East Texas. It seems like every piece of rural property has a pond.
To ensure that your pond continues its longevity, we must learn how to inspect and protect it from erosion and, worst of all, failure of the dam. While an all-out “dam-break” may be a rare occurrence, a leaking dam that requires an expensive rebuild is not uncommon.
The reason a pond exists is because some areas with a watershed had a dam built to hold back the water. Whether your pond is for livestock, fish production, or simply aesthetics, these dams hold an enormous force of water behind them. Both old and newly built dams are subject to failure if not maintained.
Let’s review the main problems to look for when inspecting your pond’s dam. First, we want the dam to shed water. If it has low spots where the ground has settled and water puddles, that excessively wet soil over time can weaken the core structure. Ruts from vehicles or cattle trails across the dam can expand over time to increase problems.
Next, we’ll study the grass coverage on all sides of the dam. Anywhere the grass only thinly covers the soil or where the soil is bare, that site is ripe for erosion. Reseed with a perennial grass seed that will develop a permanent sod.
Finally, we’ll look for slumping, eroding edges, or areas that have collapsed. An eroding edge can simply occur from erosion caused by waves. This undercuts the bank and can grow unseen and weaken the dam. Worse is animal burrows and tunnels that go unnoticed. A tunnel right into the core of the dam is like punching a hole right through the very structure that you depend upon to hold back the water.
As you inspect the pond, remember that there are two slopes or “faces” to your pond’s dam. Simply walking to the top of the dam will not give you a good indication of any problems. It will be necessary to walk the top and both faces thoroughly. Grass can easily hide any smaller eroded areas and entrances to animal burrows. To be confident, one must not only walk along the top of the dam but also the upstream and downstream sides of the dam.
What about trees on the dam? Earlier this week a good acquaintance of mine, Joe, asked whether he should leave his trees on the dam. As a rule, trees should not be allowed to grow on dams. A tree that blows over or dies will leave a hole from the root ball or will have a mass of decaying roots that will greatly weaken the dam’s structure. According to one state Extension website, downed trees and decaying tree roots are the leading cause of dam failure.
So how should trees be handled? If they are small, mow them down or kill them with an approved herbicide. If they are large, their removal may leave a rotting root mass that will weaken a dam. With either a taproot or a shallow root ball, both root types can cause problems. If you have any large trees, many choose to let them be and reap any repercussions, if any, years later. If you do have concerns, this is the time to find, and likely hire, expert advice.
If you find a burrow that needs filling, one possible repair method for small burrows is a thick slurry mix made from 90 percent soil and 10 percent cement. Be cautious not to make the mix too watery. We want just enough water in the mix to allow the slurry to flow into the burrow. To aid the slurry in reaching deep into the hole, insert a metal stove or vent pipe into the burrow entrance, seal the area around it well, and then use it to funnel the mix into the burrow.
Some larger collapsed areas on your dam may need rebuilding. These typically require digging out and repacking with good clay soil.
Spillways need the same attention as erosion could compromise this important area. While the water is meant to travel over a spillway during heavy rains, this area may need its own maintenance and repair over time. A good grass covering the soil is essential for protection. Refilling large areas of erosion with clay, or a mixture of stone to help the water slow down and fill up the cracks with sediment may also be of help.
I’ve seen ponds that are incredibly old for our part of the state and have survived generations just fine. I’ve also seen newly built ponds with terrible erosion problems from bare soil or seepage from improper construction. Expert advice from Extension, USDA-NRCS, and some very qualified private pond management companies can all be of tremendous help.
