Not every drainage problem announces itself with a flooded basement. Most start quietly: a section of lawn that never quite dries out, mulch that keeps washing away from the same bed, or a soft spot that shows up in the same place every winter. By the time the damage is obvious, it’s been building for months or years.
Portland’s combination of 43+ inches of annual rainfall and clay-heavy soil makes drainage problems more common here than in most cities. Here are five signs your yard has a drainage issue, what’s causing each one, and what it takes to fix it.
1. Standing Water That Lasts More Than 24 Hours After Rain
If puddles sit in parts of your yard for a full day or more after a storm, the ground either can’t absorb the water or has no path to move it away. In Portland, the usual cause is a low spot where grading traps water with no outlet, combined with clay soil that’s already saturated from weeks of rain.
Small, isolated puddles in one corner of the yard sometimes respond to regrading alone. Persistent standing water across a larger area usually requires a French drain or catch basin system to collect the water underground and route it to a discharge point. The fix depends on whether the problem is surface water (grading issue) or subsurface saturation (clay soil issue), and it’s often both.
2. A Lawn That Stays Soft, Spongy, or Muddy
You walk across the grass and your shoes sink in. The lawn feels spongy even when it hasn’t rained in a few days. Some areas stay mud-brown while the rest of the yard greens up in spring. These are signs that the soil beneath the turf is holding water it can’t drain.
Portland’s clay soil is the primary culprit. Clay particles are so tightly packed that water moves through them at a fraction of the speed it moves through sand or loam. Once the clay is saturated (which happens early in the rainy season and persists into May or June in many neighborhoods), every additional drop of rain sits at or near the surface.
The fix usually involves a French drain or E-Z Flow drain installed beneath the soggy section to intercept water before it reaches the root zone. In some cases, soil amendment combined with regrading is enough to improve drainage without pipe. If the lawn is too far gone, you may need to address the drainage first and then install new sod once the ground can support healthy grass. We see this combination frequently on properties in Beaverton, Milwaukie, and Gladstone.
3. Water Stains, Damp Spots, or Moisture on the Foundation
If you notice water marks on the exterior foundation, damp spots on basement walls, moisture or musty smells in the crawl space, or efflorescence (white mineral deposits) on concrete, water is reaching your foundation and staying there long enough to cause problems.
The most common cause is improper grading. The ground around many Portland homes has settled over the years, and what was once a slope away from the foundation has become flat or even reversed. Downspouts that discharge directly against the house make it worse by concentrating thousands of gallons of roof runoff right at the foundation during the wet season.
Foundation drainage is one of the most urgent reasons homeowners call us. The fix typically involves regrading the soil away from the house, routing downspouts into underground pipe that discharges away from the foundation, and in many cases installing a French drain along the affected side. The cost of fixing foundation drainage is a fraction of what foundation repair or mold remediation costs if the problem is ignored. For more on how we approach this, see our drainage solutions page.
4. Mulch, Soil, or Gravel Washing Out of Beds
If you keep replacing mulch in the same bed, or you notice soil moving downhill after every storm, or gravel migrating from a path onto the lawn, water is flowing across the surface faster than the landscape can absorb it. This is surface erosion, and it’s especially common on sloped Portland properties in neighborhoods like West Linn, Lake Oswego, Happy Valley, and the West Hills.
Surface erosion means water is moving too fast, and it needs to be slowed down, redirected, or both. Solutions range from simple regrading to drainage swales and dry creek beds that channel surface water to a controlled discharge point. On steeper slopes, a retaining wall may be needed to create level terraces that break the slope and eliminate the erosion path entirely.
For a deeper dive into evaluating erosion and slope issues on your property, check out our Drainage and Grading Guide.
5. Water Pooling Near Patios, Walkways, or Driveways
Hardscape surfaces don’t absorb water. Every drop that lands on a patio, walkway, or driveway needs somewhere to go. If the surface is graded toward the lawn, the house, or a low spot instead of toward a drain, water collects at the edge and sits there.
Settling over time can change the slope of an originally correct surface. Concrete slabs are especially prone to this in Portland because freeze-thaw cycles (20 to 30 per winter) cause the slab to shift on clay subgrade. Pavers handle this better because individual units flex with the ground, but even pavers can develop pooling issues if the base wasn’t properly compacted or graded.
The fix is usually a catch basin or channel drain installed at the low edge, combined with regrading the adjacent soil to direct surface water toward the drain instead of toward the house or lawn.
When to Call a Professional
If you’re seeing one or more of these signs, the best time to investigate is during a heavy rainstorm between November and January, when the soil is fully saturated and water has nowhere to hide. Walk the property during the rain and note exactly where water is collecting, which direction it’s flowing, and where it’s coming from. That information makes the consultation faster and the diagnosis more accurate.
We provide free on-site drainage assessments throughout the Portland metro area. We’ll walk the property with you, identify the source of each problem, and give you a detailed written estimate with line-item pricing for the recommended solution.
Call (503) 847-9110 or request your free estimate online.
Learn More About Drainage
Backyard Drainage and Grading Planning Guide — How to evaluate your yard and understand your options before calling a contractor.
How Much Does a French Drain Cost in Portland? — 2026 pricing by project type and what drives cost.
French Drain vs. Catch Basin vs. E-Z Flow: Which Is Right for Portland? — A side-by-side comparison of the three most common drainage systems we install on Portland properties.
Do You Need a Permit for Drainage Work in Portland? — What triggers a permit and who handles it.
Can You Install a French Drain Yourself? — What’s involved, what goes wrong, and when to hire a pro.
