Gravel Driveway Washing Out on a Slope: How to Stop It

A gravel driveway washing out on a slope is almost always a water problem first and a stone problem second. Rain that runs down the driveway picks up speed, follows the wheel tracks, carries the fines away and then the stone. Fixing it means getting water off the driveway in short distances, then using stone that locks together.

Driveway slope calculator →

Read the damage first

Gullies down the wheel tracks mean water is running the length of the drive instead of crossing it.
A fan of stone at the bottom means water has a long, uninterrupted run.
Washouts at one spot often trace back to a downspout, a neighbor's runoff or a blocked culvert; see downspout washing out the driveway edge.
Loose, rolling stone everywhere points to round stone or stone with no fines.

Step 1: shape the surface so water crosses it

A crown (high in the middle) or a cross slope to one side lets rain leave the surface before it builds into a stream. On a hill, a cross slope toward the uphill ditch is common so water does not spill over the downhill edge. Driveway cross slope and putting a crown in a driveway cover the how-to. Grading with a box blade or land plane restores the shape after storms.

Step 2: break up long runs of water

Water bars or broad dips. A low, angled hump or a shallow dip across the driveway turns water off to the side. Several small diversions work better than one big one at the bottom.
Open-top culverts. A channel set flush across the drive catches water and sends it to the side. They need clearing after leaf fall.
Ditches and outlets. Diverted water has to go somewhere stable, such as a grassed swale or a riprap pad, not a neighbor's yard.
Culverts under the drive. Where the driveway crosses a natural drainage path, a properly sized pipe keeps water from flowing over the top; see driveway culvert.

Step 3: use stone that stays put

Angular crushed stone with fines packs into a crust that resists water far better than round stone. Products such as crusher run, dense grade aggregate, Class 5 or Item 4 are typical. Avoid deep layers of pea gravel on a hill. Compact the stone after spreading; loose stone washes first.

Step 4: consider grids or paving on the steepest part

Cellular confinement grids hold stone in place on grades where loose stone keeps moving; see geocell for a soft driveway. On very steep sections, paving only the hill is sometimes cheaper over time than replacing stone after every storm. Steep asphalt driveway and asphalt millings on a hill weigh those options.

Replacing washed-out stone

Measure the damaged stretch and estimate the depth lost. A 12 by 60 foot section that lost 2 inches needs about 4.4 cubic yards, or about 6 tons at 1.4 tons per yard. The base calculator handles other sizes. Fix the drainage before you buy stone, or the next storm takes it.

When to get help

Large culverts, work near streams or wetlands, and drainage that crosses property lines may need a permit or an engineer. Your county soil and water conservation office or road department can often point you in the right direction.

Questions people ask

Why does my gravel driveway keep washing out?

Usually because water runs down the length of the driveway instead of crossing it. Without a crown, diversions and stable outlets, flowing water carries fines and stone downhill.

What is a water bar on a driveway?

A low, angled hump or dip across the driveway that turns running water off to the side so it cannot build speed down the slope.

What gravel is best for a sloped driveway?

Angular crushed stone with fines, such as crusher run or dense grade aggregate, packs tight and resists washing. Round stone like pea gravel tends to roll and wash.

Should I pave the steep part of my gravel driveway?

If stone keeps washing out despite good drainage, paving the steepest section can cut maintenance. Compare that cost with yearly stone and grading.

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