Beach Erosion on the Lake Superior Coast

by Jason Franti

Introduction:
The problem of beach erosion has plagued property owners since the first people settled along water bodies. Beach erosion is an even greater concern today because of the large numbers of people who make their homes and businesses on waterfronts. The purpose of this report is to show what causes beach erosion, what people can do about it, how and if it can be prevented, and predicting when beach erosion is likely to occur.

Literature Review:
I first reviewed chapter 15 on shorelines in Surface Processes and Landforms, by Donald J. Easterbrook. The book was published by Macmillan Publishing Company, New York, in 1993. I also I also read Flood Plain Information - Ontonagon River, Ontonagon County, Michigan and Lake Superior Shoreline, Ontonagon County, Michigan. This report was prepared by the Department of the Army, St. Paul District, Corps of Engineers, St. Paul, Minnesota in September of 1970.

Methods of Research:
The research that was conducted was done by interviews, reviewing literature, and an Internet Search. I interviewed people who live on the south beach of Lake Superior, near Ontonagon, Michigan: Bruce Johansen a local historian, and Al and Sally Berman who live on the beach. The interviews were conducted over telephones, electronic mail, and meetings. I asked them what they have done to protect their beach and if they knew examples of methods that did and didn't work. Material on precipitation and lake levels for Lake Superior was acquired by an Internet Search, and was found at the sites: http://sparky.nce.usace.army.mil/precipitation/gifs/suppre/.gif for the precipitation data, and http://sparky.nce.usace.army.mil/levels/hlevsup.html for the lake level data. This data is shown in Tables 1 and 2.

Beach Protection:
What is Beach Erosion? Beach erosion is a natural process. Easterbrook states on page 422 of Surface Processes and Landforms that it is the act of "masses of water being hurled against the land by waves breaking on a shoreline exerting considerable energy resulting in mechanical erosion (of the coastline.)"

Factors in Beach erosion: Beach erosion is caused by wave action, but there are other factors that contribute to erosion. The largest contributing factor to beach erosion is the level of the water doing the eroding. A water body with a high water level is conducive to erosion of the shoreline more so that a water body with a low water level.

The level of the water is influenced greatly by two factors, precipitation, and flow of water in and out of the water body by means of dams and rivers. If there is a large amount of precipitation in a year the lake level will rise and vice versa if there is a small amount of precipitation over a long period of time. The level can also be controlled by outlets and dams. Dams will let water out of the water body, and dams can let water into the water body.

Other minor factors that can contribute to beach erosion and the protection of beaches are: vegetation and their roots, type of bluff material, soils, ice, geology of the land, and wind. (Flood Plain... pages 79-86)

Preventing beach erosion:
Since beach erosion is a natural process, it will always occur. The problem is that people own property and erect permanent structures on land that is threatened by erosion. Thus, people create ways to protect beaches and the property they are on.

Methods of preventing beach erosion:
In my research, I found a property that installed a protection device that was also discussed in Flood Plain Information...and Lake Superior Shoreline, Ontonagon County, Michigan. This method is called gabion baskets. These baskets and the dimension of them as prepared by the A.C.E. are shown in Figure 1. On the property that they have been installed upon, they differ slightly from the A.C.E. designs. The baskets on the property are 2m x 1.3m x 1.3m. They are installed by having the bottom row of baskets placed on the corner of the hardpan and the bluff-line. The baskets are filled with mine rock that is bigger than the holes in the mesh. Then they placed baskets along the entire length of the property, about 33 meters, and then built baskets 8 meters towards the lake. Once the bottom layer of baskets was down, two more layers were placed on top. The baskets are tied together and into the bluff. The baskets are made of galvanized chain link fencing, unlike the PVC baskets that were stated in the A.C.E. designs. Even though there are differences, the baskets have done the same thing that the A.C.E. baskets were intended to do. The baskets have held the bluff-line since the baskets were installed nearly 20 years ago.

In the mid 1980's, people along the studied shore began putting cribs of telephone poles with large rocks between them to protect the beach and bluff-line. The procedure of how the cribs were put in was not available, but here is a description. The cribs were rectangles dug into the beach sand lined with telephone poles and mine rock placed between them. Their purpose was to break up the waves as they came to shore. There was no reinforcement of the cribs. The cribs were gone after the first fall storm season. This was one of the most ineffective methods of beach protection.

Home owners in the study area also put rip-rap on their bluff-line. These boulders were approximately 2-3 cubic meters in size. These boulders sunk into the beach after the first year. The next year the same thing was done. This method was done to protect the bluff-line from undercutting. Once the rip-rap didn't sink anymore, the holes and cracks in the large rocks were filled in with smaller rock. The rock was carefully placed, and in some cases, even hand placed! Since the introduction of this method there has effectively been no net bluff loss. The beach comes and goes with the lake levels, but the owner's property is protected. Because of several (approximately 10-15 homes) neighbors who have done this, the bluff-line by these properties is very effectively protected. Rip-rap is now the method of choice in the area. This method and the gabion basket method are equally effective. However, there is one difference in the rip-rap method. The rip-rap method has more beach sand in-between the water and the bluff-line than the gabion basket, because the rip-rap is not protruding into the surrounding beach area as the gabion basket does.

Seawalls have also been tried in the area. Seawalls receive "frequent damage...when lake levels are high." (Flood Plain..., page 89) This method has been implemented in several places, but has in fact received severe damage during storms because there was nothing for the waves to break on previous to hitting the seawall. All of the waves energy is exerted on the seawall. This avenue may be productive if other measures are implemented along with it.

In addition to these major methods of beach protection, people have also tried several minor methods to protect the beach. In this area, before the influx of gabion baskets, organized rip-rap, and cribbing, people would throw anything on the beach to break up the waves. Bed springs were a popular choice! Also used were broken up pieces of sidewalk, driveways, and roads. There was even an instance of a landowner placing a frame of a Model T on the beach to help protect the property! Anything people could get their hands on was used.

Supplemental Methods:
Once effective means of bluff protection have been installed, supplemental methods have also been added. First and foremost is vegetation. People have planted trees, shrubs, and grasses on their bluff-line to help hold the sod together for if and when the water reaches the bluff. This has proven to be effective when the water has reached the bluff-lines. During storms, trees have helped maintain the bluff. People have also placed round hay bales on the beach to help catch sand and break up waves. This method is effective in short term instances, but after long periods of strong waves attacking the bales, they break up. This may be a good method for seasonal protection such as during the fall and winter storms. Another method has been to tie tires together, place them, and let them break up the waves. Although this seems to be effective, there is concern about the breaking up of the rubber and getting into the lake. Heating and cooling may eventually lead to deterioration of the rubber. A surprisingly successful method has been to place a plastic or heavy tarp "fence" in front of the rip-rap. The fence is anywhere from 30 cm to 60 cm high. This holds water away from the rip-rap, and if waves splash over the material, the water can seep back into the lake but the sand is held.

Predicting beach erosion:
I also researched what years were bad erosion years for the land owners near Ontonagon. In information from both private land owners and the A.C.E. report, I found that erosion could be anywhere from a meter to three meters in an unprotected area for one storm season.

The worst erosion years were 1913 (Army Corps of Engineers), May of 1951 through April of 1952 (Army Corps of Engineers) with losses of up to 15 meters in some places during the time period, the fall of 1968 (Army Corps of Engineers), 1977 (Bruce Johansen) wasn't as large as the other years, but was above average, and the falls of 1984, 1985, and 1986 (Al and Sally Berman.) Since then erosion hasn't been extreme until this past fall, when an unprotected bluff had a loss of about 1 meter. This was noted after a storm that was stated by many to be the worst since the storm that sunk the Edmund Fitzgerald in 1975(Al and Sally Berman.)

I have compared the years of the extreme beach erosion, as determined by the above sources, to data from the U.S. Army Corps of Engineers on the levels of Lake Superior at these times. My finding was that the lake was at high levels during all of these times of recorded erosion. I also compared lake levels during the times of intense erosion to precipitation data for Lake Superior during these times. My findings showed amounts of high precipitation for the Lake Superior basin coincided with those times of high erosion and high lake levels. The data is shown in Table 1 for the precipitation and Table 2 for the lake levels. This would lead one to believe that high precipitation could indirectly lead to high erosion rates.

Conclusions:
I have two conclusions: 1) The best form of property protection for a private land owner is the rip-rap method explained earlier. The gabion basket method was also effective, but it does not leave as much beach as the rip-rap method. You are more likely to have a beach with the rip-rap method than the gabion basket method because the gabion baskets protrude over what would be beach. 2) Years of high precipitation and winters with large accumulations of snowfall precede storm seasons where beach erosion will be likely. Previous to the upcoming storm season would be a good time to implement short-term methods of beach protection to the long-term ones already in place.