Diagnose Where the Water Is Coming From After heavy rain, standing water usually signals one of two problems. Either water is moving across the surface or it is soaking up from below. A French drain is a buried trench filled with gravel and a perforated pipe that collects subsurface water and carries it away. A surface swale is a shallow, vegetated channel that intercepts, slows, and encourages runoff to soak into the ground. This post helps you diagnose which problem you have, compares performance, cost, and typical installation, and explains when a hybrid approach makes sense. We'll also call out local factors for Rogers County, OK. For a quick side‑by‑side, see our earlier comparison on the Greenman blog French drain vs. surface swale . Step‑by‑step signs and a simple perc test to tell surface runoff from subsurface saturation Want to know whether water is running across your yard or coming up from below? Watch your property during and right after a heavy rain. Experts at TruGreen recommend noting where water pools, how long it stays, and whether the lawn feels spongy. Key signs to note during and after storms Standing water that lasts more than 24 to 48 hours usually means poor drainage and possible subsurface saturation. A soggy or spongy lawn after the storm points to water held in the soil rather than surface runoff. Erosion rills or obvious channels show fast surface runoff that could be managed with a swale. Cracks in patios, driveways, or foundations and musty basement odors suggest water pressure under or against the house. Very green, over‑lush strips of grass can reveal hidden saturated flows or a failing underground outlet. How to run a simple percolation (perc) test at home A perc test tells you how fast water soaks into the soil. Use this quick method before planning drainage work. Dig a hole about 12 inches wide and 12 inches deep in the problem area. Fill the hole with water and let it soak in overnight to fully saturate the surrounding soil. Next day, refill the hole and measure the drop in water level every hour until it drains. Repeat the test a few times in nearby spots for a reliable average. Interpretation examples from perc guidance: faster than four inches per hour drains very quickly. One to four inches per hour is generally good. If the hole takes more than six to twelve hours, infiltration is poor and soil holds water. How Oklahoma soil and slope change the likely fix Oklahoma yards often have clay‑dominant soil that swells and holds water. Oklahoma State Extension notes clay soils increase pooling and hydrostatic pressure. Surface swales work best when visible runoff follows slopes and you have room to channel water. French drains work better when soil stays saturated or water is pressing at foundations. Decision checkpoints: swale vs. French drain If you see fast-moving surface flow and erosion rills, choose a swale to slow and redirect runoff across the yard. If the lawn feels spongy, pools linger more than 48 hours, or basements smell musty, plan for a French drain to remove subsurface water. If perc tests show very slow infiltration, subsurface drainage is likely required rather than a surface channel. When both surface runoff and saturated soil occur, combine a swale to collect water with a hidden French drain to carry it away. If you feel unsure after these checks, document what you see during a storm and consult a drainage pro for a site assessment. Pick the right fix fast: capacity, cost, and installation compared Not sure whether to bury a pipe or reshape the yard? Start with how the system moves water. French drains collect water below the surface and carry it away through perforated pipe and gravel. Surface swales catch, slow, and spread runoff so it soaks in along a shallow vegetated channel. How much water each handles and how fast it clears Guidance from the PNNL stormwater resource shows French‑drain capacity varies by pipe size, slope, and trench size. Small 4‑inch setups move roughly 5 GPM. Larger 6‑inch and deeper gravel configurations can reach 37 to 75 GPM or more. That same guidance notes properly sized French drains often clear pooled yards in 12 to 36 hours after heavy rain. Swales are sized to design storms and to drain within one to two days. Core installation steps and typical materials French drain installs start by routing to an outlet, digging a sloped trench, lining it with nonwoven fabric, adding gravel, and placing perforated pipe before wrapping and backfilling. Swale construction marks contours, excavates a shallow channel, builds a downslope berm with excavated soil, shapes gentle side slopes, and establishes dense vegetation. You can add an underdrain if soil won’t infiltrate. Typical timelines, costs, and quick tradeoffs French drains usually take a few days to install on a typical yard. Residential costs commonly run about $10 to $35 per linear foot for exterior systems, with deeper or interior projects costing more. Swales often install fa
