Turfgrass Sod vs. Other Erosion Control Methods (A Cost / Benefit Analysis)

Studies show that turfgrass sod stops erosion immediately… unlike grass seed, mulch or blankets. Erosion control eliminates the cost of erosion control failures.

Cost / Benefit Analysis of Turfgrass Sodding for Control Erosion

As early at 1986, a U.S. Geologically Survey funded project at The Pennsylvania State University documented that grassed areas established with turfgrass sod are up to 15 times more effective in controlling runoff than seed established grass, even after three years.

More recently, a University of Maryland team of scientists testing the “Runoff and Sediment Losses from Natural and Man-made Erosion Control Materials” found, “Sod offers superior performance when compared with straw in retarding the initiation of runoff, reducing runoff rates and reducing total soil losses. None of the man-made materials effectively extended the time for runoff initiation.”

While these and other scientific studies have documented the effectiveness of turfgrass to control erosion, there continues to be a debate regarding the costs and associated benefits of various methods of turfgrass establishment. The purpose of this paper is to examine all of the associated considerations, costs and benefits of the more popular grassing methods so that those who are responsible for making recommendations, or the actual decision making, will have a strong basis in fact for that action.

—- Time Of Year —-

(With or without Hydro or Blanket Methods):

• Not recommended for winter or summer due to extreme temperatures.

• Possible in spring, best in fall for most areas; however, rains needed for germination and establishment may also cause severe washout failures on the site, decreasing overall erosion control effectiveness.

Turfgrass Sodding:

• Year-round installation is possible, even on frozen ground.

• Recommend installation during an area’s wet season to minimize the amount of applied water that would be required.

• Summer installations require high levels of attention to water application needs, as newly installed sod will dry out rapidly, suffering significant set-back or total loss.

—- Soil Preparation —-

(With or without Hydro or Blanket Methods)
and Turfgrass Sodding:

• Regardless of grassing method, identical soil preparation is required, including tilling, adding or amending soil to meet soil test recommendations, leveling and grading.

—- Seed / Material Quality —-

(With or without Hydro or Blanket Methods):

• Must select species and varieties recommended for specific site(s).

• Extreme variability can be caused by germination rates, weed and foreign matter content.

• Must ensure uniformity of distribution.

• Must determine and ensure proper application rates.

Turfgrass Sodding:

• Certified (or elite) quality sod typically begins with Certified (or elite) quality seed or vegetative materials used to initiate sod production.

• Mixtures or blends are grown to suit area needs and specific uses.

• Sod can be custom grown to particular specifications and locations.

• Utility or Field grade turf is less costly than Certified and the quality may be acceptable for a particular site requirement.

• Thickness of cut can be significant: thinner soil layers allow faster rooting after installation; however, thin soil layers dry out quicker.

• Size of harvested sod pieces can vary from widths of 12 to 48 inches (30.5 to 122 cm) and lengths of two to 100 feet (.61 to 30.5 m)

Mechanical installation of big rolls reduces labor requirements, number of seams and joints, and the tendency for the pieces to move.

  —- Water Requirements —-


• Requires very high quantities of water to achieve germination and establishment; multiple daily applications are needed to maintain moisture because bare soil will dry quickly.

• If dependent only on natural rainfall, germination may be delayed and establishment questionable.

• For best results, water lightly at least once a day for three to four weeks; after first mowing, apply one inch of water weekly.

Hydro or Blanket Method:

• Water needs are moderate, as mulch will preserve some moisture.

• For best results, water to maintain moist surface three to four weeks; after first mowing, apply one inch of water weekly.

Turfgrass Sodding:

• Lowest overall water requirements; at installation, water to depth of six inches (15.2 cm); then light watering of next two to three weeks.

—- Weed Control —-


• Usually requires multiple applications of herbicides to combat competitive weed invasions until turf is well established.

• Care must be taken to avoid run-off of herbicides from virtually bare soils or void areas until turf cover is fully established.

Hydro or Blanket Method:

• Herbicide requirements are somewhat lessened because of mulch; however, invasive weeds require multiple herbicide treatments.

Turfgrass Sodding:

• Minimal–if any–herbicide treatment should be necessary for two to three years because density of turf will out-compete weedy plants.

—- Uniformity of Coverage —-


• Varieties, rates, germination times, washouts, traffic, feeding birds and rodents can create spottiness or severe void areas requiring repairs, delaying overall completion and erosion control effectiveness.

Hydro or Blanket Method:

• Mulch layer will reduce–but probably not eliminate–problems similar to seeded areas.

Turfgrass Sodding:

• 99% to 100% uniformity is achieved with installation.

• Care required at installation to ensure sod pieces are not stretched and are properly butted to avoid gaps.

—- Runoff / Erosion—-


• Rains–particularly heavy or prolonged downpours, and on sloping areas–wash away seed, chemicals and silt, creating a need for repair.

Hydro or Blanket Method:

• Mulch layer slightly reduces level of problems similar to seeded areas.

Turfgrass Sodding:

• Withstands heavy and prolonged rains at time of installation, without erosion or damage; steeply sloped surfaces may have to be pegged to soil until roots are established.

—- Visual Impact —-


Leaves rough texture and open soil.

Hydro or Blanket Method:

Colored mulches can help camouflage soil appearance but, over time, will fade and reduce appearance.

Turfgrass Sodding:

Provides finished landscape appearance at time of installation.

  —- Usability —-

Seeding/Sprigging/Stolonizing and
Hydro or Blanket Method:

Zero use allowed for one to two months; low traffic use two to four months, and normal to high use only after first year.

Turfgrass Sodding:

Low traffic allowed immediately after installation.

Normal, high traffic levels permitted within two to three weeks.

—- Maintenance Requirements —-

Seeding/Sprigging/Stolonizing and
Hydro or Blanket Method:

• Requires multiple applications of herbicide and fertilizer for first two to three years.

• Washout repairs–dependent upon many factors–should be expected.

• Requires large quantities of water initially and during early phases of grow-in.

• Increases wear and tear to mowing and maintenance equipment due to dust, rocks and debris.

Turfgrass Sodding:

• Requires minimal–if any–herbicide or fertilizer for first two to three years.

• After establishment period, natural rainfall should be adequate for properly selected species and varieties.

• Mowing and maintenance equipment will not suffer wear from dust, rock or debris, although some additional mowings will be needed because of almost immediate maturity of grass.

Project cost calculations will vary with each site; however, the use of the following chart will assist in capturing significant elements to make comparisons realistic and meaningful.
Cost Factor Turfgrass Sod Seed / Sprig Hydro / Blanket
Soil Preparation ———————————— same for all ————————————
Fertilizer ———————————— same for all ————————————
Amendments ———————————— same for all ————————————
Planting Material $ $ $
Mulch / Blanket n / a n / a $
Installation Labor $ $ $
Washout Repairs n / a $ $
Water Cost (1 year) $ $ $
Water Application (1 year) $ $ $
Herbicide (2-3 years) n / a $ $
Fertilizer (2-3 years) n / a $ $
Application Labor n / a $ $
Mowing Labor $ $ $
Equipment Depreciation $ $ $
Project Total $ $ $

(While fictitious, the following article could easily be real.)

Erosion Officials Face Angry Environmentalists, Possible Federal Charge

Angry environmentalists and federal inspectors today joined distraught Mill Creek area homeowners at a pubic hearing today to confront area erosion control officials who allegedly cut costs in their failed effort to stop runoff and silt from fouling the picturesque stream.Public records and personal notes revealed at the hearing that Smith’s Erosion Control, Inc., was awarded a contract six months ago to plant grass and control erosion on a mile-long (1.6 km), 3:1 slope embankment that runs into Mill Creek. Following what was described as “standard industry practices,” the company carefully followed the contract and took three days to prep the site and put down the specified seed/mulch combin-ation. They were paid in full within 30 days of billing.

Heat, Then Downpours

Weather records show that in the first few weeks that followed, the temperatures rose to nearly 100 and there was no rain. Later, light rains were followed by several severe downpours and then high temperatures returned. Photo-graphs showed that a month after installation vegetation was nearly a foot high and turning brown; however, coverage was not uniform. A thorough inspection of the site was not made despite residents’ calls that silt was washing into the creek and some dead fish had been noticed.

Efforts to mow the area were apparently abandoned for safety reasons because of rutting that got progressively worse further down the slope. Recently, a killing frost revealed not only how sparse the grass coverage actually was, compared to the more visible weeds, but also how severely eroded the embankment had become. From sheet erosion at the top, federal inspectors reported that the situation had deteriorated to severe gully erosion at the creek’s edge, clogging the creek with untold amounts of silt.

Camouflage, Not Control

Environmentalists claimed that erosion had not been controlled, it has simply been camouflaged. They were outspoken in their concern about the loss of wildlife habitat and endangerment to the many species of plants, animals and fish that were native to the area.Residents are demanding that the project be totally redone, including removal of silt and debris from the creek. Rather than re-seeding the area and facing a repeat of the same problem, they were encouraging the use of turfgrass sod, stating that it would result in immediate beautification of the area, and would provide known erosion control benefits.

Significant Fines Possible

Federal officials said they were gathering evidence to determine if there may have been violations of the U.S. Environmental Protection Agency’s National Pollutant Discharge Elimination System or Clean Water Act. Significant fines could result from such findings.

Environmentalists said losses were multiple: money spent on the project was virtually wasted; the creek and its wildlife inhabitants were seriously damaged; and, down-stream pollution and siltation were severe. They maintain that efforts to correct the resultant problems and actually control the embankment’s future erosion will be much more expensive than had other methods been originally used.

The public hearing is scheduled to continue tomorrow and may be extended for several days.

Issues to Address With All Potential Erosion Control Contractors

1. How will the effectiveness of the erosion control project be determined or measured?
A. Percent of ground cover to be achieved?
B. Sediment losses to be no greater than?

2. Who will be responsible for monitoring and measuring the control achieved?

3. When can erosion control efforts be initiated at the site?

4. How long after initiating work at the site will the erosion control objectives defined in question one be achieved?

5. For how long after the initial site work is completed will this firm assume responsibility for site conditions and grow-in?

6. What maintenance steps must be taken to ensure continued and consistent erosion control?

7. For those areas accessible to the public, how long after project initiation will there be use restrictions? What level of use restrictions will be necessary?

-Turf Resource Center Trade Info

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