Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Technical Brief 18: Protecting Archeological Sites on Eroding 

Shorelines: A Hay Bales Approach 

Robert M. Thorne, Pickering Environmental Consultants, Inc., Jackson, MS 

Published by the DOI Departmental Consulting Archeologist/NPS Archeology Program, 

National Park Service, Washington, DC, July 2004. 

Introduction 

Federal laws and regulations encourage preserving archeological sites in place when they are 

threatened by roadbuilding, reservoir construction, and the like.1 However, proactive managers 

favor the idea even when sites are not immediately at risk. Excavation is costly, with the curation 

of artifacts adding appreciably to the expense. A resource-specific conservation plan, carefully 

designed and implemented, substantially reduces management costs. At the same time, the plan 

can be aesthetically pleasing while serving to enhance other aspects of the surroundings. 

Figure 1. An Army Corps (WES) stabilization project using logs cabled in place and revegetation planted on 

bankline. Lake Sharpe, South Dakota, June 1994. 

There are many alternatives one can employ to stabilize sites and shorelines (Thorne 1991). A 

modeled approach to developing a stabilization strategy has been devised that can be applied to 

any setting (Thorne et al. 1987; Thorne 1988a, 1989, 1990, 1991). In many cases, however, funds 

are severely restricted, and factors such as environmental compatibility and aesthetic appeal come 

into play. 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Figure 2. A beach development zone behind hay bales put in place in 1991. Lake Sharpe, South Dakota, June, 

1994. 

An experimental program, described here, addressed these and other issues in reversing the 

severe erosion at South Dakota’s Lake Sharpe, which was caused primarily by wind-blown waves 

and the annual freeze-thaw cycle. The lack of stabilizing vegetation in the unconsolidated 

glacially deposited soil also contributed to the erosion. 

The approach, devised by the U.S. Army Corps of Engineers, uses hay bales in concert with 

revegetation to abate erosional forces. While not suited to every situation, this cost-effective 

alternative may be a low-cost solution for conservation planning. 

The Plan–A Case Study at Lake Sharpe 

Lake Sharpe was created by Big Bend Dam, constructed in 1963 to generate electricity. Over the 

course of a year, the water level fluctuates less than two feet, creating a near-constant ring of 

erosion around the lake. Lake Sharpe is shallow, which contributes to the severity of the waves. 

Ice reaches a thickness of almost three feet, and during thaw the wind drives large floes into the 

bank. 

As might be expected, the setting dramatically tests any stabilization technique other than riprap, 

which would be inappropriate and too expensive for the entire lakeshore. The violent combination 

of wind, waves, and ice undercuts the entire shore. Given the area to be protected and the almost 

constant loss, a cost-effective approach is essential. 

To armor the bank and its 200 archeological sites, the Corps instituted a stabilization program, 

ongoing since 1987. Though the overall program is still experimental, the efficacy of its hay 

bales/revegetation component has been amply demonstrated. 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Figure 3. A farm where hay bales were put in place Sept/Oct of 1993. Note the height of the vertical 

cutbanks in the background, which are common to the entire lake. Lake Sharpe, South Dakota, June, 1994. 

Stabilizing a shoreline with an archeological site differs very little from stabilizing a shoreline 

without one. The site does create a set of limiting factors, however, that may affect the stabilizing 

techniques, materials, and machinery as well as the vegetation and schedule. 

At Lake Sharpe, the main goal of the bales was to act as a barrier. A second goal was to create a 

basin to trap sediment washing down from the bank and in from the lake. Eventually, the 

sediments solidify. Since the bales are short-lived, they must then be supplemented with other 

stabilization measures. Revegetating the sediment-filled basin is the least expensive and most 

practical. 

The revegetation effort at the lake–designed and directed by Hollis Allen–had already proved 

successful, alone and in combination with driftwood trees (Figure 1). The use of bales, which was 

untried previously, also proved effective. But the test setting–a relatively well protected bank 

sloping gently to the water’s edge–was not representative of conditions at Lake Sharpe (Figure 2). 

The revegetation techniques were common (e.g., Thorne 1990); their efficiency was really never 

in doubt. The primary purpose was to test the bales in actual conditions. 

Acquiring the Bales 

Hay bales are easy to acquire. As might be expected, the quality varies. Protecting an eroding 

shoreline does not require feed-quality hay, but not every kind of bale will do the job. During 

initial tests, the bales often contained large weed stems and small sticks along with the feed grass. 

In some cases, the relatively poor quality reduced the weight of the bales as well as the strength 

of the ties holding them together. 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Figure 4. Commercially manufactured hay bale tongs for a crane. Were these actually attached to a crane, 

they would be hydraulically operated from inside the cab. Lake Sharpe, South Dakota, June, 1994. 

Army Corps researchers quickly recognized a bale’s ideal characteristics. Clearly, a heavy, tight 

bale will withstand waves better than a light, loose one. The quality of the bale depends on a 

number of factors–the intent of the baler, the type of equipment, and the kind of binding. The 

densest bales are bound with plastic ties or wrapped in plastic mesh, but twine is better for bales 

in a visually and environmentally sensitive site such as this one. Tight bales resist aging and the 

weather, shedding water like a thatched roof. Only the outer layer gets wet during snow and rain, 

so rotting is less of a problem. Loose bales are more prone to come apart as they are hauled and 

lifted into place. 

Some machines roll a four-by-four foot bale, which weighs around 800 pounds; the five-by-five 

foot bales in our tests, which weighed 1,000 pounds, were produced by newer equipment. A 

bale’s weight, and stability, increases in water, depending on the depth and the amount of 

absorption. 

The bales that individual ranchers produce are generally not as good as those produced by 

commercial operators. This is probably because commercial bales must stand up to frequent 

handling. Ranchers ultimately grind their bales into feed, so less attention is paid to density and 

tight binding. Depending on the setting of the project, the local economy can sometimes be used 

advantageously. In the case of Lake Sharpe, local farmers who lease Army Corps land 

contributed bales as part of their lease agreement. 

Placing the Bales 

Most of the bales at Lake Sharpe were placed slightly opposite vertical banks, up to six feet high 

(Figure 3). Because of the near constant water level–and the lack of ebb and flow–there were few 

beaches to use as staging areas. Initially, the bales were lifted from the top of the banks by a crane 

or a dragline fitted with a clamshell bucket or specially designed clamp (Figure 4). 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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To create the basin trap, the bales were placed away from the bank. This also left space for the 

vegetation. The bales need not be a specific distance away; placement usually depends on 

practical rather than technical considerations. At Lake Sharpe, they were usually placed about six 

feet out. To some extent, the distance depends on the stability of the shore and the type of 

equipment available. Light equipment can be used if the area fronts a dry beach; heavy machinery 

needs a more stable surface. 

There is no recommended spacing between bales but eight to twelve inches is common. This 

allows the small, suspended particles of sediment to flow in from the lake and bind with the larger 

particles washing down from the bank. 

Figure 5. An Army Corps "shop built" barge for use with an airboat to place bales. Lake Sharpe, South Dakota, 

June, 1994. 

For the Lake Sharpe project, a barge was designed to place bales in areas not accessible from the 

bank. This small, light, shallow-draft vessel, which was transported easily by trailer, also could be 

pushed or towed by boats with small motors (Figure 5). People wading alongside maneuvered it 

into position; a hydraulic lift dumped the bale in front of the vessel. 

Revegetation 

Buffering is only the first step in stopping the undercutting and slumping of the bank. Since the 

bales are short-lived, they must be supplemented and ultimately replaced. Vegetation is the best 

option in terms of cost, effectiveness, and compatibility with the natural environment. The merits 

of vegetation management have been discussed elsewhere (Jones–Thorne 1990), along with 

various field techniques (Allen and Klimas 1986, Gray and Leiser 1989, Schiechtl 1980). 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Figure 6. A stabilization at the Fort George Game & Fish Commission (with no Army Corps involvement) 

attempted to use tractor tires and hay bales. Note the sand buildup behind the center bale. Lake Sharpe, South 

Dakota, June, 1994. 

The choice of species should be appropriate to the setting, and frequently must follow preexisting guidelines. In most cases, indigenous vegetation is preferred because it will not outcompete existing species. Gathering plants locally can reduce the costs, and failed transplants are 

easily replaced. However, nursery stock, though more expensive, is hardier and thus stands a 

better chance of surviving. Particularly if the revegetation includes multiple species, especially 

non-woody varieties, a nursery may be the best source. Make sure, though, that the stock is 

delivered and planted promptly, with ample time to get established before the onset of harsh 

weather. Sources for stock can be found through local Natural Resource Conservation officers or 

ads in trade publications. 

The vegetation, whose root mats minimize soil loss, is just as important as the bale barrier in 

arresting the erosion. Generating a stable revegetation zone, however, depends on the inflow of 

sediment. From this perspective, a high amount of sediment in the water will prove advantageous. 

Lake Sharpe has a low amount, so the basin was filled primarily by erosion from the bank. It 

appears the erosion will slow as the slope of the bank and the basin reach equilibrium. The 

vegetation maintains the slope. 

The Technique in Action

As is the case with all stabilization techniques (Figure 6), no one approach is appropriate for 

every setting. This technique was not suited to the entire shoreline; in some places the bank was 

too high, in others the water too deep. Normally, the harsh environment may have disqualified 

this approach. In this case, however, it provided an excellent testing ground for developing and 

refining the technique. Winter temperatures are well below freezing, and the lake freezes to a 

depth of over three feet. This is not particularly destructive in and of itself, but during spring 

strong winds drive broken pieces of ice into the bales. At the least they could be pushed out of 

alignment; at the worst destroyed. 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Figure 7. A south-by-southwest view of the farm. Lake Sharpe, South Dakota, June, 1994. 

In areas protected from ice, the bales remained stable and a beach zone developed behind the 

barriers as predicted. No bales were shifted by wind or waves generated by either boats or the 

weather (although most sites were too shallow for large vessels). In one place, the bales were in 

disarray because they had been dumped at random over the top of the bank; even so, they still 

trapped sediment. 

There have been no complaints that the barriers are unsightly, nor have any been vandalized. Less 

than a year later, fish were spawning in the basins; a mallard and her hatchlings were using one as 

a refuge (Figure 7). Even though some slumping continued, grass was growing in large patches. 

The benefit to the environment cannot be overemphasized. 

Acknowledgments 

The U. S. Army Corps of Engineers field office at Lake Sharpe, South Dakota, developed the 

information in this brief. The staff of the field office was most gracious in sharing their 

experiences in developing the approach. Without their efforts in describing both its positive and 

negative aspects, this brief would not have been possible. I am especially indebted to A. K. 

(Konnie) Olsen, Lake Sharpe Park manager, for his courtesy and cooperation. It has been largely 

through his efforts that the approach was developed. 

Endnote

1. Among these are the Antiquities Act (P.L. 59-209), the National Historic Preservation Act 

(P.L. 89-665, as amended), the National Environmental Policy Act (P.L. 90-190), the 

Archeological and Historic Preservation Act (P.L. 93-291), and the Archaeological Resources 

Protection Act (P.L. 96-95, as amended). Regulations include "Protection of Historic Properties" 

(36 CFR Part 800, especially Section 14), "Secretary of the Interior's Standards for Historic 

Preservation Projects" (36 CFR Part 68), "Secretary of the Interior's Standards for Archeology 

and Historic Preservation" (48 FR 44716-44742, especially 44737-44738), "Protection of 

Archaeological Resources: Uniform Regulations" (18 CFR Part 1312, 32 CFR Part 229, 36 CFR 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

http://www.nps.gov/archeology/pubs/techBr/TCH18.htm 

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Part 296, and 43 CFR Part 7), and U.S. Army Corps of Engineers Regulation ER1130-2-438, 

"Project Construction and Operation, Historic Preservation Program." 

References

Allen, Hollis and Charles V. Klimas 

1986 Reservoir Shoreline Revegetation Guidelines. Technical Report E-86-13. Vicksburg, MS: 

U.S. Army Corps of Engineers Waterways Experiment Station. 

Gray, Donald H. and Andrew T. Leiser 

1989 Biotechnical Slope Protection and Erosion Control. Malabar, FL: Robert E. Krieger 

Publishing Company. 

Jones, Kevin L. 

2000 Native grasslands and the stabilization of earthwork archaeological sites in North Dakota. 

Conservation and Management of Archaeological Sites 4(3):139–150. 

Schiechtl, Hugo 

1980 Bioengineering for Land Reclamation and Conservation. Alberta, Canada: University of 

Alberta Press, Edmonton. 

Thorne, Robert M., Patricia M. Faye, and James J. Hester 

1987 Archaeological Site Preservation Techniques: A Preliminary Review. Technical Report 

EL-87-3. Vicksburg, MS: U.S. Army Corps of Engineers Waterways Experiment Station. 

Thorne, Robert M. 

1988a Filter Fabric: A Technique for Short-Term Site Stabilization. Technical Brief 1. 

Washington, D.C.: U. S. Department of the Interior, National Park Service Archeology Program. 

1988b Guidelines for the Organization of Archaeological Site Stabilization Projects–A Modeled 

Approach. Technical Report No. EL-88-8, Vicksburg, MS: U.S. Army Corps of Engineers 

Waterways Experiment Station. 

1989 Intentional Site Burial: A Technique to Protect Against Natural and Mechanical Loss. 

Technical Brief 5. Washington, D.C.: U. S. Department of the Interior, National Park Service 

Archeology Program. 

1990 Revegetation: The Soft Approach to Archeological Site Stabilization. Technical Brief 8. 

Washington, D.C.: U. S. Department of the Interior, National Park Service Archeology Program. 
Technical Brief 18 

Protecting Archeological Sites on Eroding Shorelines: A Hay Bales Approach 

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1991 Site Stabilization Information Sources. Technical Brief 12. Washington, D.C.: U. S. 

Department of the Interior, National Park Service Archeology Program. 

The briefs series is designed and produced by the DOI Departmental Consulting 

Archeologist/NPS Archeology Program. The series editors are Francis P. McManamon and S. 

Terry Childs. Send comments, ideas for briefs, and requests for copies to: 

NPS Archeology Program, NPS 

1849 C St., NW (2275) 

Washington, DC 20240 

Or, send an email to dca@nps.gov.