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Yard Drainage & Erosion Control in Phoenix, AZ

Quick answer

Drainage problems in Phoenix come from monsoon and winter storms dumping water on hard, dry ground, roofs without gutters, and caliche that keeps water from soaking in. Common fixes are regrading toward retention areas, gutters or downspout lines, swales, rock-lined channels and water-harvesting basins. Check before changing a lot's retention area or working near a wash.

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It seems odd to worry about drainage in a place that averages around 7 inches of rain a year, but Phoenix-area yards get their water in bursts. Summer monsoon storms and occasional winter storms can drop a lot of rain in a short time on hard, dry ground that sheds it. The result is water running against foundations, decomposed granite washed across driveways, rock beds scoured into channels, and pools of water that sit on caliche.

Signs you have a drainage problem

  • Water pooling against the house or block walls after storms
  • Rock or DG washed onto walks, driveways or into the street
  • Channels cut through gravel beds or bare slopes
  • Soil eroding out from under a patio, wall footing or sidewalk
  • Areas that stay soggy long after irrigation runs, often a sign of caliche or a leak

Retention basins and drainage easements

Many Valley lots and subdivisions were built with on-lot retention areas, shallow depressions designed to hold storm water, and some have drainage easements along walls. Filling a retention area, building in it, or changing grading so water goes elsewhere can break the subdivision's drainage plan and create problems for you or your neighbors. Check your plat, your HOA and your city before you change grading in those areas.

Common solutions

  • Regrading: reshaping soil so it falls away from the house toward a retention area or approved outlet.
  • Gutters and downspout extensions: many Valley homes have no gutters, so roof water drops right at the foundation. Gutters, splash blocks or buried lines can help.
  • Swales and rock-lined channels: guide surface water around the house to where it should go.
  • Dry creek beds and rip rap: larger rock set in channels to slow water and resist scour.
  • Stabilized DG and edging: keep paths and seating areas from washing out.
  • Water harvesting basins: small planted depressions that catch runoff for trees and shrubs, a common desert technique.

Caliche and soggy spots

Caliche is a cemented layer of calcium carbonate common in desert soils. Where it sits close to the surface, irrigation and rain can't soak down, so water perches above it. Fixes range from breaking through the layer in planting holes to adjusting irrigation so it doesn't overwhelm the soil. If an area stays wet even in dry weather, check for an irrigation or pipe leak first.

Washes and floodplains

Homes near natural washes, especially in the foothills of north Phoenix, north Scottsdale and north Peoria, can see fast-moving water during storms. Work inside a wash, a floodplain or a protected natural area may need city or county approval, and in parts of Scottsdale, natural area open space easements bar grading entirely. Check with your city or the county flood control district before building or grading near a wash.

Before you hire

  • Take video during or right after a monsoon storm showing where water enters, flows and collects.
  • Note where roof water lands and whether gutters exist.
  • Ask the contractor where the water will end up and how they'll keep it from eroding the outlet.
  • Make sure Arizona 811 is contacted before trenching. Irrigation lines, gas and electric often run through side yards.

Read our guide to getting a Phoenix yard ready for monsoon season. If water is threatening a foundation, wall or driveway, mark your request as urgent and request a drainage company.

See how it works

How a French drain carries water away from a yard. Press the buttons to run each step and see what happens inside. Made with Colorfigures ·
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Frequently asked questions

Can I fill in the retention basin in my yard?

Not without checking first. Many Valley lots have retention areas that are part of the subdivision's approved drainage plan. Ask your city and HOA before filling or building in one.

Why does my rock wash away every monsoon?

Concentrated runoff, often from a roof without gutters or a slope, moves small rock and DG. Larger rock in channels, stabilized DG, edging and redirecting the water usually solve it.

Why is one spot always soggy?

Often it's caliche below the surface trapping water, or a leaking irrigation line or valve. Rule out a leak first, then look at soil and irrigation run times.

Sources and further reading

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