Coping with Erosion and High Water on Minnesota Point in Duluth
Minnesota Point, also called Park Point, is a well-known Duluth neighborhood that has a population of about 1,500; it is a major year-round recreational area with beaches and an airport. Minnesota Point is located at the western tip of Lake Superior, at the mouth of its largest tributary, the St. Louis River.
Minnesota Point, seven miles long and averaging 500 feet wide, is geologically part of a continuous, sandy, baymouth bar that stretches between Duluth and Superior. The middle of the bar is submerged, creating the natural entry that separates Minnesota Point on the northwest from Wisconsin Point on the southeast. This bar was formed by two processes: primarily by sands carried from the South Shore and deposited by lake currents, and secondarily by sediment deposited by the St. Louis and Nemadji rivers.
Together, Minnesota Point and Wisconsin Point are about 10 miles long. They protect a magnificent natural harbor, but are extremely vulnerable to the erosive forces of the Lake Superior. On the lake side, extensive sand dunes are constantly shifted by wind blowing off the lake. On the bay side, the land is relatively low and is therefore susceptible to flooding and wave-induced erosion.
Lake Superior’s record high water levels during 1985–86 caused flooding on Minnesota Point. This was not the first time that flooding had occurred: the early 1950s and mid-1970s were also periods of abnormally high lake levels. Modest increases in water levels dramatically affect residents on Minnesota Point. This is especially true on the bay side, where homes are just a few feet above the average water level.
A survey was carried out in summer 1987 to assess the effects of the 1985–86 high water levels on Minnesota Point. The project was conducted by the geography departments at both the University of Minnesota Duluth and Lakehead University, and by the Minnesota Sea Grant Extension Program. This survey obtained information on structure setbacks, erosion rates, flooding problems, and shore protection measures. The results are compiled in Table 1.
|Item Side||Bay Side||Lake Side|
|number of completed surveys||81||94|
|average of length of property ownership (years)||17||20|
|average property value ($)||51,000||53,000|
|Building Setbacks (% of properties)|
|less than 30 feet||37||4|
|30 to 100 feet||44||7|
|more than 100 feet||19||90|
|properties affected by erosion problems (%)||70||34|
|estimated long-term erosion rate (feet/year)||0.43||1.7||estimated 1985-86 erosion rate (feet/year)||3.6||10.3|
|basement flooded ruing 1985-86||58||31|
|yard and outbuildings flooded during 1985-86||49||11|
|properties with sump pump||37||33|
|properties with Federal Flood Insurance||4||3|
|sites with shore protection (%)||65||32|
|average cost of shore protection ($)||2,365||1,033|
|cost of shore protection as a percentage of property value (%)||4.5||1.9|
Every other house with a mailbox was sampled. If the respondent agreed to an interview, the questionnaire was filled out immediately. If no one was home, the questionnaire was left in the mailbox with a request that it be returned by mail. Of 250 households visited, 175 people responded. This represented 70% of those sampled and 36% of all homes on Minnesota Point.
The survey revealed significant differences in the nature of the erosion and flood problems on the two sides of Minnesota Point. On the bay side, most structures have a minimal setback from the water, and many are less than three feet above the long-term average lake level. Consequently, if the lake rises even slightly above normal, many of these properties are subjected to flooding. The intensity of erosion on the bay side is considerably lower because the bay has only several miles of open water or fetch, over which waves can build. On the lake side, in contrast, the maximum fetch exceeds 350 miles.
On the lake side, erosion rates are greater, but most structures are on higher ground and have a much deeper setback. More than one-third of the structures on the bay side have setbacks of less than 30 feet, whereas 90% of those on the lake side have setbacks of more than 100 feet. Three areas with different types of erosion and flood problems were identified.
Landowners were asked to estimate the depth of shoreland lost during the 1985–86 high water period, as well as the total depth lost since they purchased the property. The long-term erosion rates were considerable lower than those for 1985–86. This was especially true on the bay side, where almost 50% of the total reported erosion occurred during 1985–86. Accelerated erosion during this period was due to 12 consecutive months of record high water levels.
Despite shorter fetches and lower erosion rates on the bay side, 71 percent of respondents there reported erosion problems, compared to only 34 percent on the lake side. This is probably because smaller setbacks and lower elevations on the bay side make erosion problems more obvious to people living there. In addition, most properties on the bay side extend to the water’s edge, whereas on the lake side a public beach serves as a buffer between private land and the water’s edge.
Residents reported a variety of flooding problems. Many noted that they had water in their basements for several weeks. Others said their yards and outbuildings (storage sheds, garages, etc.) had flooded. Reports of flooded basements were almost twice as high on the bay side as on the lake side. Reports of flooded yards and outbuildings were almost five times as high on the bay side as on the lake side.
Many respondents (about two thirds on the bay side and one-third on the lake side) reported having some type(s) of shore protection, such as retaining walls (most common), rock rip-rap, and sand and gravel fills. The average cost of shore protection was $1,003 on the lake side and $2,365 on the bay side, or about 1.9% and 4.5%, respectively, of reported property values. Some respondents said that their shore protection was damaged by high water during 1985–86.
Property owners had very little protection from flood problems. Very few had federal flood insurance. Many buildings could not qualify for the National Flood Insurance Program without adequate flood-proofing measures. About one-third of the respondents used sump pumps as their only protection against having standing water in their basements.
Protecting Minnesota Point Sand Dunes
Most of the Minnesota’s Lake Superior shore consists of rock and red clay. The vast sandy beach of Minnesota Point is not common. For traditional solutions to coastal erosion caused by wave action, refer to the references. The erosion protection information presented here is for sandy areas that are subject to wind erosion. This is a problem on the lake side of Minnesota Point.
Sand dunes act as buffers to erosion. The dunes are dynamic; they shift and move. When the dunes are intact, they form a physical barrier, a dune line or dune field, which acts like a sea wall by providing protection from wind and waves. Breaks in the dune line expose low-lying back areas to potential damage from strong winds coming off Lake Superior.
Shifts in dunes and breaks in dune line can occur in just a few hours. If a blow hole forms in a dune line, up to 3,000 cubic feet of sand can shift during a single storm.
Vegetation can help prevent dune erosion. Therefore, revegetation of dunes is important in stabilizing windblown sand. As the plants grow, their roots hold the sand in place and their tops decrease the wind velocity at the soil line, thus reducing sand movement.
It is a challenge to establish vegetation in sand. Plants should be mulched, watered, and fertilized for the first year. Plants that grow naturally on dunes will give the best results.
In a 1981 demonstration by Minnesota Sea Grant, dune grass was the number one choice for use in revegetation. Other plants that did well in the sandy environment were red osier dogwood, Siberian peashurb, hedge cotneaster, tartarian honeysuckle, eastern ninebark, common lilac, box elder, jack pine, and other plants already common on Minnesota Point.
Dunes are extremely important in controlling wind erosion on Minnesota Point. To protect the dunes, it is essential to control pedestrian traffic and prohibit the use of vehicles.
If it is necessary to cross dunes, the use of designated trails with boardwalks or bark mulch can minimize damage. To be successful, such efforts will require community involvement and cooperation between citizens, the Parks and Recreation Department, and the Police Department.
Minnesota Point is subject to both erosion and coastal flooding problems. The lake side has more dune loss and shore erosion because its long fetch allows greater wave action. They bay side has more flooding because of its lower elevation and smaller setbacks.
Properly designed shore protection structures may be necessary to prevent wave-induced erosion. Vegetation and community-based conservation practices can help prevent wind erosion.
Lake Superior water levels will continue to go through periodic fluctuations. Residents of Minnesota Point should acknowledge the inevitability of such fluctuations and plan accordingly.
Sump pumps are the only flood-proofing measure commonly used on Minnesota Point. Other flood-proofing techniques are available. Further information can be obtained from the U.S. Army Corps of Engineers. See references.
by Dale Baker and Harun Rasid
Great Lakes Water Level Facts. U.S. Army Corps of Engineers (COE), 1986. Detroit District, U.S. Army Corps of Engineers, P.O Box: 1027, Detroit, MI 48231. 15 pages.
Monthly Bulletin of Lake Levels for the Great Lakes. COE, monthly. Graphically summarizes average, extreme, current, and projected water levels for all five Great Lakes. 4 pages.
Low Cost Shore Protection. COE, 1981. Explains natural coastal processes and tells how shoreline property can be protected with relatively low cost techniques. 36 pages.
Help Yourself : A Discussion of Erosion Problems on the Great Lakes and Alternative Methods of Shore Protection. COE, 1978. Similar to the above publication, but more detailed and technical. It lists the advantages and disadvantages of various protective devices. 24 pages.
Slip Sliding Away: Erosion on Lake Superior’s North Shore. Minnesota Sea Grant Extension Program, 1987. Describes the impact of coastal erosion along Minnesota’s North Shore during the high water period of 1985–86. 4 pages.
History of Minnesota Point
- Important Dates:
- 1679 — the first visit by a European, Greysolon Sieur Du Luth
- 1854 — signing of the treaty of LaPointe, which transferred ownership of Minnesota Point from the Chippewa to the U.S. Government
- 1858 — completion of the first lighthouse on Lake Superior
- 1897 — opening of Minnesota Point’s first Coast Guard station
- 1905 — construction of the original bridge to Minnesota Point
Because of its location, Minnesota Point became a transportation center for shipping by vessel and rail. A trading post and dock were built in 1852. By 1870, there were wharves and docks on both sides of Minnesota Point. The natural channel between the lake and the harbor was in Superior, Wisconsin, but some Duluthians wanted a channel of their own.
- Creation of Duluth Entry:
“The channel was not a good one. Duluth had only one opinion...that we should cut a new channel through Minnesota Point close to our city, but at this suggestion Superior set up a cry that this would ruin the existing channel with mud and slit.
I was engaged by the citizens of Duluth to dig channel.
We began work on a Saturday and by night Superior knew what we were about. At once the people over there began to scurry around to get a Federal injunction restraining us. I hired a gang of several hundred men…and we worked all that day and far into the night…When the Superior people came over Monday morning there was the channel open and they couldn’t do anything.”
R.S. Munger, 1871, from the History of Duluth by Woodbridge and Pardee, as cited in “Park Point,” edited by Mrs. John Soetebier.