Culverts are tunnel-like structures, typically installed underneath roadways or driveways to funnel water underneath, whether it's stormwater or an established stream. If there is a drainage ditch or stream running along the roadway perpendicular to your home, you'll need to install a culvert in order for your driveway to pass over it. As water runs through the pipe culvert, it wears down the soil at either end and results in heavy erosion over time. Not only is this a fish passage barrier for fish swimming upstream, but it can also cause the entire culvert to wash away in the event of a storm or flood, washing out the road and causing serious damage. Luckily, there are a few things you can do to stop erosion around culverts.
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5 Ways to Stop Erosion Around Culverts
1. Install the Right Size Culvert
If your culvert is too small, it will quickly cause significant soil erosion. Consider how much water and debris your culvert will need to carry through it to determine how big your culvert should be to prevent erosion. The pipe should also be big (and strong) enough to handle any traffic driving over it. Most driveway culverts measure 12-15 inches in diameter. Check your local building codes to determine the appropriate size for yours. You should also make sure the pipe is long enough so it extends past either end of the bank or roadway.
2. Dig Deep
Excavate and install the culvert deep enough so that the bottom of the pipe is level with the bottom of the stream or drainage ditch. Install the pipe at an angle so that the upstream portion is slightly higher than the downstream portion. This will allow water to flow through the pipe somewhat naturally without a major drop-off as it flows out of the pipe and heads downstream.
3. Backfill With Dirt
After you've placed your pipe culvert into the ground, add backfill to secure it in place and help prevent erosion. Using the same type of soil that occurs in the area naturally, backfill dirt over and around the pipe. Cover it by at least 12 inches and pack the dirt in as firmly as you can.
4. Plant Vegetation
A completely natural way to prevent erosion around a culvert is to plant vegetation around it. Plant the vegetation along the bank. Once rooted, they will help hold in the soil and prevent it from getting washed away as water flows through the culvert.
5. Add Rocks or Rip-Rap
Place rocks around the openings on either end of the culvert. This will help stabilize the slope, preventing erosion.
If your erosion problems persist, consider further packing in the bank with rip-rap, which is a man-made rocky material used to stabilize slopes.