Why You Have Standing Water (7 Oregon Causes)

Standing Water Always Has a Reason

A puddle that lingers for days isn't bad luck. It's a symptom, and behind it is a specific cause — usually one of a handful that show up again and again on Oregon properties. Treating the puddle without finding the cause is how people end up installing a drain that doesn't fix anything. Diagnose the cause first, and the right solution becomes obvious.

Here are the seven causes behind nearly every standing-water problem in Oregon, and what each one points toward. For the full set of drainage solutions, see our Oregon drainage guide.

1. Clay Soil

Much of western Oregon sits on heavy clay and silt loam. These soils drain painfully slowly — water hits the dense layer and stops, so a yard can stay soggy days after the rain ends. Clay is the single most common reason Willamette Valley yards hold water.

The catch with clay: a deep French drain often underperforms because water can't migrate through the clay to reach it fast enough. The better answers are usually surface-first — regrading, swales, and shallow area drains. Our draining Oregon clay soil guide covers what actually works.

2. Soil Compaction

Compacted soil acts a lot like clay even when it isn't. When the ground is packed tight — by construction traffic, parking, foot traffic, or heavy equipment during a build — the pore spaces that let water soak in get crushed closed. Water then sits on the surface with nowhere to go.

New construction is a frequent culprit; the soil around a recently built home is often heavily compacted from the building process. The fix ranges from aeration and soil amendment for mild cases to regrading and drainage for severe ones.

3. Negative Grade

Sometimes water pools simply because the ground slopes the wrong way. If the yard tilts toward a low spot — or toward the house — water naturally collects there. Negative grade near a foundation is especially serious because it sends water against the building. The standard target is a 6-inch drop over the first 10 feet away from the foundation.

Regrading to establish positive slope is the fix, and it's often the highest-value first step. Our negative grade foundation fix guide covers it.

4. High Water Table

In valley-floor and coastal areas of Oregon, groundwater can sit close to the surface — especially in the wet season. When the water table rises near grade, there's simply nowhere for surface water to drain down to, because the ground below is already saturated. The yard floods from below as much as from above.

A high water table calls for different tools: curtain drains to intercept groundwater, sump-and-pump systems, or raised beds that lift planting above the saturated zone. A standard French drain can fill from below and fail to help.

5. Clogged or Failed Drainage

Sometimes the standing water is new, appearing where the yard used to drain fine. That often means an existing drainage system has clogged or failed. A French drain silted up from missing filter fabric, a catch basin full of debris, a crushed pipe, or a buried outfall — any of these turns a working system into a backed-up one.

Here the fix is repair, not new installation: diagnosing the existing system, clearing or rebuilding what failed, and restoring the outfall.

6. Downspouts and Roof Runoff

Roofs collect an enormous volume of water and concentrate it at the downspouts. If those downspouts dump right at the foundation or into a low spot, they create standing water all on their own — and they overwhelm whatever drainage is nearby. A single downspout can deliver hundreds of gallons during one Oregon storm.

The fix is often simple: extend the downspouts well away from the house on solid pipe, to a place that can handle the flow or to a proper outfall. It's one of the cheapest, highest-impact drainage moves there is.

7. Hardpan and Subsurface Layers

Some Oregon soils have a hardpan — a dense, cemented layer below the surface that water can't penetrate. The topsoil may look fine, but a foot or two down, an impermeable layer traps water on top of it, creating a perched water table that keeps the surface wet. This is sneaky because the surface soil seems to drain until it saturates and the hardpan stops everything.

Addressing hardpan may mean breaking through it where feasible, or working around it with surface drainage and raised areas. A soil investigation reveals whether hardpan is the hidden cause.

Often It's More Than One

Real yards frequently combine causes — clay soil and compaction, negative grade and a downspout dumping at the low point. That's exactly why diagnosis matters more than jumping to a solution. A site assessment identifies which causes are in play, in what combination, so the fix targets the actual problem instead of guessing. Our yard drainage cost guide covers what solutions run.