RipRap for Ohio Banks, Culvert Outlets and Lake Shore

The mistake this stone gets bought to undo is nearly always the same: water was allowed to land on bare ground and it took some of that ground with it. A pipe discharges onto clay and cuts a hole under its own outlet. A creek in the southeast hills runs hard after a downpour and shaves another foot off a bank. A lake shore lot loses a strip to early spring storm waves. By the time riprap is ordered, the soil is already moving, and the job is to put a cover over the places where moving water is doing that work.

The material here runs 4 inches to 12 inches and up. It is large, heavy stone, and the weight is what keeps it where it was placed.

Choose riprap when water is moving soil, and skip it when water only sits

Order it where flowing or breaking water meets erodible ground: a stream or ditch bank that is scouring, the apron below a culvert or pipe outlet, a pond edge taking wave chop, the toe of a slope in the hill country after a wet spell has set it slipping, the shoreline of a lake frontage lot.

Leave it alone where the problem is standing water rather than moving water, where you want something to walk on, and where the fix is a graded surface. Weight is its whole value, and weight is the wrong tool for most yard work.

Three jobs it gets ordered for by mistake

A shed or garage pad is the most common one. A pad needs a flat, compacted surface that spreads load evenly, which 12 inch rock cannot give you at any depth; that is a job for 304 aggregate base built in lifts and rolled.

A downspout splash area is second. The volume off a roof valley looks dramatic but it is a trickle against a creek in flood, and heavy rock there looks out of scale and traps leaves. River rock over a small stone bed handles a downspout run and still looks like part of the garden.

Retaining wall backfill is third. Backfill behind a wall is about letting water drain out so it stops pushing, and that wants clean stone in a consistent size. #57 limestone does that; big irregular rock leaves voids the soil falls into.

Armoring a scouring creek bank against a lake shore edge

The two situations look alike and behave differently. On a creek or ditch bank in the southeast hills or along a till-plain waterway, the force arrives in short violent events after heavy rain, traveling along the bank. The stone has to extend below the scour line at the toe, because water undercuts from the bottom and the bank slides into the gap. Carry the cover up the face to above the level the water reaches in a big storm, and tie the ends into stable ground so the flow cannot get in behind the edge.

On a lake frontage or a pond, the force arrives as waves and, in a hard winter, as ice, and it works up and down the same strip of bank all season. That calls for the cover to run above the highest water line rather than just above the normal one, and for bigger stone than a quiet inland ditch needs. Early spring storms are the worst of it on the lake.

On a hillside in the unglaciated southeast, remember what is actually failing. Slips there are usually about saturated clayey slope debris losing strength, not about surface scour, and putting weight on top of a moving slope can make matters worse. Stone belongs at the toe and in the channel, and the rest of the answer is getting water off the slope.

Filter stone first, heavy rock second

Heavy stone placed straight onto soft clay does not stay put for long. Water works through the gaps between the pieces, carries fine soil out from underneath, and the rock settles into the holes it has made. A filter layer stops that. #4 crushed stone is the local answer here, used as filter stone beneath rip rap, and on fine clay soils geotextile is often laid under that.

Placement matters as much as the layer. Set the pieces so they bear on one another rather than tipping them down a slope and hoping. The cover should be more than one stone deep, so that losing a single piece in a storm does not open the soil beneath. Fill the gaps between the large pieces with smaller ones so there is no straight path through to the ground.

Yards for a 40 foot creek bank

Take a hypothetical stretch of bank, 40 feet long, with a sloping face measuring 8 feet from toe to top, covered 12 inches thick.

• Face area: 40 x 8 = 320 square feet
• Depth: 12 inches = 1 foot
• Volume: 320 x 1 = 320 cubic feet
• Cubic yards: 320 / 27 = 11.9 cubic yards

Order 12 cubic yards and a little over for the toe, which always takes more than the drawing suggests. Tonnage depends on the density figure the site applies to this material, so run the same measurements through the rip rap calculator rather than converting by guesswork.

A smaller hypothetical, the apron below a culvert at 12 feet by 10 feet and 12 inches thick, works out as 12 x 10 = 120 square feet, 120 x 1 = 120 cubic feet, 120 / 27 = 4.4 cubic yards. On the weight this site publishes for rip rap, about 3,100 lb per cubic yard or 1.55 tons per yard, that is approximately 18.4 tons for the bank and 6.8 tons for the culvert apron.

Work at a stream bank or along a shoreline can involve approvals, so check what applies at your site before the stone is ordered.

Getting a heavy load onto an awkward site

Delivery is arranged at checkout from the ZIP code you enter, and you pick the quantity and date on this page. Large stone cannot be wheelbarrowed, so the staging spot needs to be somewhere a machine can reach it and work from. Give the truck a clear approach and room to raise a bed, and do not plan a drop at the bottom of a steep wet lane in March.

Measure the face, run the yards, then pick your quantity and date above. If the bank is an odd shape or the toe sits under water, send the measurements through the contact page and Ohio Rock Supply can work the quantity out with you.