Portland landscape design expert in the forest

Westside & Portland drainage. With DIY tips.

Estimates available (after consultation)

Copyright 2004 - 2013 by Mario D. Vaden / Header context: Largest Coast Redwoods

If you need an estimate for installation of a yard drainage system or French drain in the Portland area, please see the contact page, and review estimates. Before estimates, be certain to scroll down this landscape drainage page and find the photo of the root growing through a drainage pipe ... installed by another licensed landscaper. The root in the drainage pipe is just one of a few things that were wrong, and about 1 year later we replaced that, plus the entire back lawn. This drainage stuff can take a lot of experience to decipher.

We help homeowners near Portland, Oregon, westside including Beaverton, Tigard, Sherwood, Wilsonville, Hillsboro, Tualatin, Lake Oswego, West Linn and Tualatin with advice or improvements. With every 100 sq. ft. of local ground exceeding 2000 gallons of rain each year, Portland drainage is important to all of us.

drainage near Portland at Beaverton residence, with French drain, pipe and drain rock

M. D. Vaden has experience with drainage and soil from years of country club, university campus and landscaping work since 1988.

Images: click to see - landscaping design and drainage project from August 2003, done from scratch. Shown here 9 years later, November, 2012. The dry creekbed behind the water feature is actually a horizontal cistern to catch runoff from the big driveway.

Portland drainage and dry creekbed combination routed around water and rock in landscape

The small photo is from 2003 and shows the week of installation prior to planting. Solid drainage pipe was diverted around the water feature, which itself merely recycles it's self-contained water and has nothing to do with the drainage line.

There's 1000's of ways to design a dry creekbed with different shapes, layouts and plants.

About 1 of 3 people who call us about drain line, do not need French drains as expected. For many of them, the real solution involves soil, lawn or other changes. And drainage work tends to involve residual problems that have been ignored or undiscovered for years. Drainage can range from simple French drains to dry creek beds or decorative rock areas that offer cosmetic and aesthetic appeal. Sometimes it is better to collect and remove the water, and other times it may be better to divert water and slowly release it on the property where soil can handle moisture.

drainage and soil grade raised in Portland suburb of Tualatin to remove water

Click this Rock image to view another project.

We raised grade, slightly convex with a custom soil blend, replaced lawn, added French drain, and edging, increased useable area.

Tips ... DYI

Various suggestions below should give a head start if you want to tackle it yourself. Also, Soil Care and Compaction is very important to be aware of, especially in rainy areas like Portland has, were rain erodes or lubricates soil. So here are 3 related pages that may help ...

Read: Soil Care

Read: Soil Compaction

Read: Auger and Drainage

The DIY drainage and French drain advice may help you avoid installing drainage that you don't need. Certainly you want to get rid of your problems, and sometimes a French drain is not the solution.

Basically, just like the illustration to the right and down the page a little, a French Drain is more or less just a perforated pipe in a trench. Eventually covered with porous material like pea gravel or landscape stone. The simplicity vanishes when it comes to customizing the design for your site. How can the soil affect the drain line lifespan? Where are the trees and shrubs, and what will happen with the roots? Could the rock become a projectile near a lawn? Can a pathway with flagstone become a drainage component too?

Heavy rain can trigger material shortages in a matter of hours. Postponing drainage projects until the rainy season can leave people with plenty of water and no pipe to move it. Don't wait until rain storms to install your drainage project.

Extra example

french drain in Portland back yard plus liner and rock for drainage

Click Liner to the left to view another project.
Liner was used for an area where a deck will be installed later.

Portland Drainage pipe and trench illustration

Typically, French drains will include pipe near the bottom of a trench, with gravel or sand on top. If sand is used, a fabric cover or sleeve for the pipe will be essential. The pipe is normally perforated to collect or release water or solid to move water. Drain lines can be built with a combination of perforated and solid drain pipe: perforated drainage where we want to gather water and solid where we want to move it from point A to point B.

Image at right: Digging drainage trench walls at an angle can be morestable, potentially reducing collapse of the edge. But this is not essential. Straight walls can work too. Angled walls mean a wider top, and that can be impractical.

Solid pipe can be preferred near tree roots. If perforated pipe is located near trees or big shrubs, roots can grow into the gravel and drain line through perforations. There is little reason to use perforated pipe where the drain line passes areas where water will not be flowing into it.

Success depends on a variety of solutions and materials. Several of these images are from one back yard drainage project where several techniques were used. Perforated pipe was used to collect water. Pea gravel was used to fill most of the trench, but some areas near the surface were back-filled with sand to spare damage to lawn maintenance equipment like aerating equipment tines that need to punch soil.

Portland Oregon French drainage preparation through back landscaping lawn

Image right: Preparing to route non-perforated pipe segment under lawn for discharge. Discharge trenches that are not perforated need no sand or gravel. In this yard, water was collected elsewhere in low spots using catch basins, open trenches and perforated pipe. With careful diggging, sod can be replaced.

Sometimes site conditions don't offer a way for water to flow away in a pipe, and boring with an auger may help significantly, providing holes which are basically tiny circular drywells. The same basic concept can be done by digging a big submerged cavity to be filled with gravel - called a drywell. This option depends on whether or not the soil beneath the surface will allow water to naturally drain-away or seep out in the days following.

A boring method shown in one image on this page with the small auger. Sometimes used near trees, other than drainage, is called "vertical mulching" since holes may be filled with amendments like compost. For trees, the goal is often aeration.

Knowledge of soil & compaction may save installing a needless drain line. Here is a story ...

Years ago, a friend asked about installing drainage at his home near Beaverton, Oregon. 2 professional Portland area drain installers said he should install drainage, and that there was a "high water table". The real problem ... a mushy lawn with standing puddles after rain from surface soil compaction ... was not from a high water table. I pointed-out the old Oregon oak trees and Ponderosa Pines on his lot. Those would not flourish for 50 to 100 yrs. in a to-the-surface high water table. He was convinced, and we corrected soil conditions instead of wasting money on a French drain line. Spent one day for a new lawn, and saved a ton of money. To fix the problem, we removed the old sod, ammended the soil and rototilled it. Then planted grass seed. Problem solved: no mushy lawn, no standing water. And as the trees indicated, there was no high water table.

Functional dry creekbeds: another technique for drainage, is putting a drain line, or drain lines underneath a dry creekbed - the entire dry creekbed. You can put several sections of perforated pipe next to each other parallel, and even layered one row of pipe on top of one another. This turns a dry creekbed into a holding cistern to control runoff or allow rain to seep into the property. Sort of a flat drywell.

Drainage solution in NE Portland with river rock, ADS pipe and French drain

Image right: concave collection - It may not be evident from the 50mm photo's shallow depth of field, but the rock shown covers almost 6 x 20 feet, or 120 square feet. Portland gets 3 feet of rain per year, so this recontoured part of the yard with pond liner beneath the stone has potential to capture 360 cubic feet of water (3 x 120). Each cubic foot has almost 7.5 gallons of water. So 360 x 7.5 = 2700 gallons. That's how much water can be collected and released from part of a property and making it look decorative like a dry creek bed. Plants were added later. Drainage solutions are not limited to French drains.

A French drain trench is typically best with the rock exposed, enabling surface water to run into the trench. It may be concealed partially, such as when grass is allowed to grow into its surface gravel, rarely clogging it, as long as thick thatch does not accumulate. Then the water flows through the trench and away to an opening.

Several suggestions on this page - below - can extend the life of French drains and drain lines. Each idea will require extra time or extra money. But these ideas and methods are inexpensive for the average residential drainage project.

Some French drains fail due to clogging. So, some of this information is geared for preventing clogging. In fact, if your trench will be deep (1.5 feet to 4 feet, or deeper), you should consider lining the wall of the trench with a fabric to prevent soil from dislodging into the rock fill and clogging the upper trench.

Drainage line illustration for Portland Oregon climate French Drain illustration for Portland type soil

1. Many French drains can fail because the soil on the surface presses inward and seals the top of the trench. A way to avoid this is to slope the sides of the trench so that the top of the trench is wider than the bottom of the trench. Basically, this provides a “V” shape trench opening. When this is done, pressure on the top of the trench pushes energy down and outward on the sidewalls of the trench. If it's not feasible, don't worry too much about it.

2. Consider laying a landscape fabric in the trench before installing the drain line and gravel (or sand). This landscape fabric layer can provide a layer that also hinders trench wall soil from pressing inward into the gravel and drain line. Be sure the fabric is porous. This is not an essential technique.

3. Dig the trench a little deeper, and lay one, two or a few inches of gravel on the bottom underneath the drain pipe. No matter how well a drain line is built – a French drain – it probably will get clogged in the future whether 10 years down the road or 50 years from now. Every rain storm will move some silt into the drain line. If the drain pipe is laid on the bottom of the trench, it will start to get plugged with sediment from the first time it functions. But if a few inches of gravel are laid under the drain tile, this gravel base will be what starts to accumulate the initial sediments. This can extend the life of the French drain.

French drain pipe near SW Portland, with roots growing and starting to block drainage

4. The finer the gravel used to fill the trench, the better for preventing collapse of the trench walls. If large rock is used to fill a French drain – like 2” to 3” diameter river rock – it’s easier for soil to move inward into the cavities between the rocks from the side walls of the French drain trench. Consider using pea gravel or fine gravel like ¼ - 10 crushed gravel. Sand can be used to fill the trench, but a fabric mesh must be used to keep sand from washing through the tiny drain tile openings and clogging the drain line.

Image at right: take roots for example - Near Tigard / Lake Oswego, we replaced a so-called French Drain that another landscape contractor installed about 1 year earlier. Where they also installed new sod lawn that covered all the trenches (one more flaw). When we removed the perforated pipe they installed, fine roots had already grown through trench fabric and other fabric wrapping the pipe, and perforation holes. IThat was merely a year after install. The image to the right shows a view inside a section removed. The roots entered skinny and branched out. Given time, roots can engulf the entire inside diameter.

5. Use washed gravel. Don’t get crushed gravel like ¼ minus that has a lot of dirt. Get gravel or rock like pea gravel or ¼ - 10 crushed rock that has been washed. You don’t need a bunch of dirt washing from gravel and filling your drain with sediment.

6. Gypsum has a tendency to chemically aggregate soil ... that’s good. It can help open up the soil structure and make it more permeable. Gypsum is inexpensive. It can be sprinkled on top of the finished trench and gravel and allowed to wash down.

7. If the trench will go by tree and shrub roots, consider inserting segments of solid drain line in those areas. If perforated drain tile is near roots, those roots penetrate small openings and grow inside the drain line. The root mass will block water and render the drainage system ineffective.

Drain line in Portland Oregon

8. Root barriers are available. If you need a drain to draw water from near trees , consider placing a layer of root barrier against the trench wall between the tree roots and the drain line. Root barriers can be available from bamboo supply businesses, some nurseries and garden centers. Another source is tree or arborist supply. And I find pond liner to function reasonably well for this too.

Adding root barrier may be good if only to keep the roots from expanding and crushing the drain pipe someday. Any, or all these ideas combined can extend the life of your French drain. The right procedures and proper planning will prevent or significantly postpone this kind of clogging.

Image right: drainage can be improved in some areas by using a small auger, or a large auger, to bore holes past compacted layers of surface soil. The holes can be filled with sand for for a porous filling. The only drawback in some yards is a difference in color. But if your lawn is not a pristine A Grade area, this could be a good alternative