Digging a drainage trench may be the best option to move water around your yard. Drainage trenches are also handy around the homestead because God has a sense of humor and will often give you too much water in the wrong place at the wrong time.
Drainage trenches can get dug by hand or machine. No, you are not unearthing the Grand Canyon! But you will probably have more dirt than expected from a 12-inch wide by a 24-inch deep trench. And quite a bit of it will need a new home.
Getting started is tricky unless you have a handy trench-digging guide. No worries. We made one for you.
Here it is!
- Digging a Trench for Drainage In Five Easy Steps
- How Long Will it Take to Dig a Drainage Trench?
Digging a Trench for Drainage In Five Easy Steps
We have tons of experience with muddy yards, snow and storm runoff, and water drainage issues. That’s why we’re passionate about the following five-step trench-digging game plan.
- Step 1. Plan and Design Your Drainage Ditch
- Step 2. Calculate Ditch Depth and Ditch Slope
- Step 3. Gather Your Trench Digging Equipment
- Step 4. Digging Your Trench
- Step 5. Drainage Ditch Finishing
Let’s also examine these five trench-digging steps in closer detail.
Here’s how to plan, design, and dig your trench right the first time!
Step 1. Plan and Design Your Drainage Ditch
You probably know your yard well – where the water gathers and where you would like it to go. Before getting started, make a plan. If you have a natural low spot where you can direct the drain without causing problems? Then aim for that.
A level is necessary to get the proper drainage slope in the trench when you dig. And using a 6-foot level (or a laser level) to map out the lay of your drainage area may surprise you. There may be more or less slope than you think. Having this information allows you to plan your drain efficiently.
Another quick way to find elevations is to run string lines between solid pegs. Then hang string line levels from them. Once all the lines are level, it becomes a matter of measuring from line to ground. This measuring process will tell you the natural fall of the area.
Your trench does not need to be straight. You can design it with curves to pass through areas you want to drain – as long as the slope remains consistent. You should aim for at least a one-inch slope for every ten feet of run.
I know that sounds like a very shallow fall, but keep in mind that if you start 12 inches deep and have a 120-foot-long trench, you end up 24 inches deep. Run a string line along one edge of your proposed trench hole to help guide the dig.
Editor’s Note! Throughout most of the US and Canada, one call or website will get all the local utilities to your place to mark out underground pipes, wires, and drains. DO IT – even if you know where and how deep everything is. Driving your trench
Step 2. Calculate Ditch Depth and Ditch Slope
Digging your drainage ditch trench is the most critical part! However, it’s also easy to get wrong. Let’s take things slow and look at trench depth and slope – before we dig!
How Deep to Dig Your Drainage Trench
Drainage trenches are usually about 12 inches wide and 18 to 24 inches deep. Most drains use a 4-inch meter pipe. In other words, a 12-inch-wide-trench leaves you room for gravel and fill. A minimum 18-inch depth allows room for a gravel bed, piping, rock gravel, and topsoil if you choose.
What Fall (Slope) Do You Need for Drainage?
Your trench or pipe should slope at least one inch for every 10 feet of run. More slope equals a deeper trench hole. You will be at least 10 inches deeper at the outlet end of a 100-foot run. And 20 inches deeper if you want a 2-inch slope. More dirt to move. More gravel to fill.
As long as the pipe in your drain is perforated, it should not freeze up, regardless of how deep the frost line is or how shallow the slope is.
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Step 3. Gather Your Trench Digging Equipment
Whether you are trenching by hand or machine, you will need equipment. Some things you will probably need for either type of trench include the following.
- Level. To make sure the slope remains consistent.
- Wheelbarrow. To haul in gravel and haul out excess dirt.
- Spade. For removing dirt from the trench. For throwing the stone gravel or rock into a trench cavity. For replacing dirt and sod.
- Hoe. To smooth out the drainage trench and rock gravel.
- Tape Measure. A 25-foot tape measure (with at least a 1-inch blade) and a 100-foot for measuring depths and lengths.
- Work Gloves. Mine are roping gloves for rodeo and working ranches. I love roping gloves! Fewer seams = fewer blisters.
Tools You Need to Dig a Trench by Hand
- Trench Shovel. Narrow and sharp. Trench shovels also fit into the trench and cut through the soil.
- Grub Hoe (Pick Mattock). Pick ends to break up hard-packed ground soil. Mattock ends for roots.
- Flat Bottom
Shovel. These are handy tools for cleaning the trench and keeping the bottom layer flat and smooth.
Mechanized Trenching Options
- Walk-Behind Trencher. You should be able to rent one of these. Probably not worth it for anything under 100 inches.
- Backhoe. If you own a backhoe, have access to one, or have a friend with one, this is the quickest and easiest way to dig a trench, put in the gravel, and close it up. It is also a bit overkill for a short drainage trench.
Step 4. Digging Your Trench
Now that we’ve planned our drainage trench, it’s time to get our hands dirty. Let’s begin digging our trench by hand!
Once all the preparations get made, it is time for a strong back! While you are digging, check your slope regularly. I would use a 6-foot level. Anything shorter, and you risk building a seesaw bed.
Another option is to leave your line level on one side of the trench and measure down to the trench bed every few feet.
(You can also consider mechanized trench digging using heavy-duty equipment.)
Editor’s Note! If the area is dry, digging is much easier if you water it for about an hour the night before.
Step 5. Drainage Ditch Finishing
Before we finish, we should consider how to ensure the best possible drainage. Consider these finishing touches for your trench-digging operation!
Once your trench is complete, you can three-quarters fill it with gravel or rock. Cover the gravel or rocks with topsoil and plant grass. Another option is filling the trench to ground level with garden or terrain rocks. Doing so will provide a walkway through the garden or a feature in the yard.
You may also consider lining the trench with landscaping cloth before pouring gravel or rock. The landscaping cloth retards weed growth and prevents landscaping rocks from sinking into the bottom of the drainage trench. (The landscaping cloth should save you from having to top off the pesky trench rocks every couple of years!)
Gravel and Pipe Drain
A gravel and pipe drain is essentially the same as a pure gravel drain with a 4-inch perforated pipe incorporated into the construction to carry water. Put 3 or 4 inches of gravel or rock into the trench (with or without landscape cloth) and lay your pipe.
Cover the sides and top with 3 or 4 inches of rock. You now have the option of filling the trench with rock – or filling it with dirt and seeding. If you have used landscaping cloth, wrap it over the gravel fill before finishing the drainage trench. Doing so keeps dirt from washing through the rocks and plugging the pipe.
Any drainage ditch goes perfectly with a barrel. Instead of draining into a low spot, dig a hole at the end of your trench. Make the hole big enough for a 55-gallon barrel. Drill holes in the barrel to allow water to drain into the surrounding soil. Set it in the trench hole on a 4-inch bed of gravel. Fill between the barrel and trench soil with more gravel.
Don’t forget the cover.
How Long Will it Take to Dig a Drainage Trench?
If you are in reasonably good shape and have operated spades, shovels, picks, and hoes – you can figure on a rate of about 10 feet per hour. The soil type, depth, and several obstacles (rocks) will change the time requirements.
Editor’s Note! Your teenager will be nowhere close to 10 feet per hour. We’re not scolding them. We’re not that fast, either! 🙂
Our part of the world is gifted with natural springs. When we built the house, we found a couple that ran into the basement. We solved the problem by digging a roughly 4-foot deep trench along the back and two sides, adding about 2 feet of gravel, filling it, seeding it, and leaving it as a swale to protect the house. The system carries any spring water around the house and into the ditch out front.
We know that digging a trench for drainage isn’t the most fun outdoor project.
But proper water management can turn your muddy backyard into a much less-mucky paradise.
We hope our backyard trench-digging strategies helped you.
If you have questions about trench digging or water management tips, please share them!
And thanks for reading.
Have a great day!