Coping with the Effects of High Water Levels on Property Hazards: North Shore of Lake Superior

J. Great Lakes Res. 15(2):205-216 InternaL Assoc. Great Lakes Res., 1989

COPING WITH THE EFFECTS OF HIGH WATER LEVELS ON PROPERTY HAZARDS: NORTH SHORE OF LAKE SUPERIOR

Harun Rasid and Robert S. Dilley

Department of Geography Lakehead University Thunder Bay, Ontario P7B 5E1 Dale Baker

Minnesota Sea Grant Extension Program University of Minnesota Duluth, Minnesota 55812 Peder Otterson

Minnesota Department of Natural Resources Duluth, Minnesota 55804 ABSTRACT. Property hazards associated with the 1985-86 high-water levels on the north shore of Lake Superior between Duluth, Minnesota, and Thunder Bay, Ontario, are examined. Data on composition of bluff/shore materials, recession rates, property setbacks, and existing shore protection structures were obtained from questionnaire surveys. Estimated long-term bluff/shoreline recession rates vary from less than 3 m to more than 15 m over a minimum period of 5 years, with a substantial amount of erosion occurring during the 1985-86 high water period. Approximately 39 percent of the respondents protected their properties with structural devices, but many were ineffective. Many respondents perceived lower water levels as a higher priority than providing shore protection structures. However, human ability to manipulate the levels of Great Lakes is limited, since lake levels are dependent primarily on climatic cycles. Because of the limitations on controlling water levels, master plans for land use regulations should be developed to prevent or minimize future encroachment of properties upon flood- and erosion-prone reaches of the shoreline. ADDITIONAL INDEX WORDS: Recession, coastal zone management.

INTRODUCTION The north shore of Lake Superior is composed predominantly of resistant bedrock and rocky cliffs. However, many of its shore properties have been developed either on erodible clay and till bluffs or along low-lying sand and gravel beaches. As a result, many of these properties are subject to coastal flooding and accelerated erosion during periods of above-normal lake levels. The term property hazards refers here to actual or potential damage to shore properties from erosion and inundation by high water levels. The nature of damage may be in the form of loss of land and destruction of buildings and other structures due to coastal erosion or combination of erosion and flooding. There are no published data on property hazards

or damages for the Ontario shore of Lake Superior. The Canada-Ontario Great Lakes Shore Damage Survey Technical Report (EC/MNR 1975) does not include the Superior shore. Although systematic survey data for the Minnesota shore have been reported by the U.S. Army Corps of Engineers for the 1951-52 and 1972-73 high water periods (COE 1976,1977,1979), no such data have as yet been obtained for the 1985-86 period. Preliminary estimates prepared by the State of Minnesota for the International Joint Commission (IJC) indicate that the total damages on the Minnesota shore (excluding the City of Duluth) amounted to approximately $74 million during the 1985-86 high water period (IJC 1987). Unfortunately, the basis of this estimate has not been documented in detail 205

RASID et al.

206

and, therefore, there is no way to verify it. The present paper provides results of an alternative survey that utilizes a number of criteria for assessing shore property hazards. Based on the estimates of respondents of two questionnaires, data have thus been obtained for the Minnesota and the Thunder Bay shores on property setting, erosion rates, and shore protection measures. ENVIRONMENTAL SETTING

The north shore of Lake Superior between Duluth and Thunder Bay forms the southwestern edge of the Canadian Shield. Its topography is rugged, characterized by steep coastal hills and extensive outcrops of intrusive igneous rocks (Sharp 1953). The dominant bedrock materials are basaltic lavas that are interbedded with Precambrian sedimentary formations and dip gently toward the lake. The surficial materials are relatively thin, mostly of glacial, glaciofluvial, or glaciolacustrine origin. Because of such diverse origins, a variety of materials may be found along a short stretch of the shore. The Minnesota shore between the northern boundary of the City of Duluth and the international border is about 280 km long and consists of relatively straight reaches. For the purpose of the present study it is divided into three reaches by using the administrative boundaries of the counties: St. Louis (30 km), Lake (102 km), and Cook (146 km) (Fig. lc). Most of these reaches are characterized by massive rocky cliffs alternating with occasional gravel beaches and relatively low lacustrine clay bluffs. In contrast, the shorelines of Thunder Bay - a major embayment of the relatively indented Ontario shore - are characterized by sand, gravel, and cobble beaches, outcrops of Precambrian sedimentary rocks and fewer rocky cliffs. Most of the property development has taken place along the 30-km reach on the north shore of the bay. The study reach excludes the City of Thunder Bay. The north shore of Lake Superior has a humid continental cool summer climate with a mean annual temperature ranging between 2.4 and 2.8°C and an ice-free season of about 7 to 8 months (April to November). Lake Superior is under the dominant influence of the prevailing westerly winds throughout the year, but significant seasonal variations are evident on a regional basis. Mean monthly wind speeds at Thunder Bay range between 16.1 km h- I in November and 11.6 km h- I in August. For Duluth these values are 17 km h- I in

November and 10.2 km h- I in August. More significant differences in wave climate result from the variations in exposure of different reaches to any given wind direction. The longest fetch on the Minnesota shore is 500 km from the northeasterly direction, whereas Thunder Bay has a sheltered wave environment with restricted fetches of less than 50 km. Significant wave heights may range between 5 and 6 m on the Minnesota shore (Resio and Vincent 1978). No such estimates are available for the Thunder Bay shore, but computations by the present authors, using wave charts and wind data, indicate wave heights of much lower magnitudes, ranging between 0.8 and 1.7 m. The levels of Lake Superior fluctuate both seasonally and on a long-term basis. The seasonal regimes are reasonably predictable: the lake normally fluctuates about 30 cm annually, being lowest just before the snow melts in the spring and highest in September. More spectacular changes in levels result from short-term (hourly) oscillations of lake surfaces induced primarily by winds and differential atmospheric pressures (Hough 1958). Wind set-up and seiche (Le., surface oscillation due to pressure difference) may raise or lower the lake level along a given shore by up to 1 m within a period of a few hours (Owens 1979). Measurements since 1860 have shown that longterm lake level fluctuations have an irregular cycle. The lowest mean annual level was recorded in 1925-26 at 182.87 m (600 ft) (IGLD). The other extreme occurred in 1985-86, when new monthly record highs were set for 12 consecutive months at levels exceeding 183.5 m (602 ft). Prior to this, high water levels were experienced at least during three other periods: 1972-73, 1950-51, and 1915-16 (Fig. 2). Such high water levels are caused when inputs of precipitation, ground water, surface runoff, and streamflow exceed the outputs of evaporation and outflow from the lake. The lake levels are also determined by human regulation systems: the outflow is regulated through the Sault Ste. Marie locks by the IJC, whereas two diversion structures (the Ogoki River and Long Lac) divert about 140 m 3 S-I of streamflow from the Hudson Bay basin into Lake Superior. Working under an agreement known as Plan 1977, the IJC strives to keep Lake Superior's monthly mean level between 182.38 m and 183.48 m, while balancing water levels between Lake Superior and Lakes Michigan, Huron, and Erie. However, the lake's natural water balance overrides the effects of human regulation systems. For example, the 1985-86 high

EFFECTS OF HIGH WATER LEVELS ON PROPERTY HAZARDS

207

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FIG 1. North shore of Lake Superior, indicating the location of study reaches: (a) Study areas, (b) Thunder Bay shore, (c) Minnesota shore.

RASID et al.

208

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FIG 2. Lake Superior water level and precipitation, 1900-1986.

water levels resulted from a prolonged regime of above-normal precipitation, higher runoff, and lower evaporation (Quinn 1987). QUESTIONNAIRE SURVEYS The first comprehensive damage surveys on the Minnesota shore were carried out for the 1972-73 high water period by the U.S. Army Corps of Engineers (COE 1976 and 1977). The total number of properties on this shore was estimated by using these surveys (Table 1). Approximately 80 percent of these properties are residential; the rest are industrial, commercial, parks, and open space. To assess property hazards associated with the 1985-86 high water levels, a questionnaire survey was administered as a joint project by the Minnesota Department of Natural Resources, the Minnesota Sea Grant Extension Program, and the Lake Superior Conservation Corps (Baker and Otterson 1987). Approximately one quarter of the population was targeted as a sample. The questionnaire was distributed at random by volunteers who either filled it out at the site or left it in the mailbox (with an addressed, stamped envelope) with a request that it be completed and returned. The response rate, expressed as the proportion of the total population, was approximately 13 percent (197 responses with a confidence limit of ± 70/0 at p = 0.05). From a statistical point of view, such a

response rate may be considered low. However, the distribution of responses was fairly representative of the subpopulations (as Table 1 indicates). The geographical distribution of the responses was also representative, that is the number of responses per county was roughly proportional to the sampled populations. A separate questionnaire using a different strategy was administered on the Thunder Bay shore (Shuniah Township). The entire population in Shuniah Township is residential, consisting of approximately 1,300 shore properties (camps, cabins, and cottages) and 600 inland properties, most of which are located between the shoreline and the TransCanada Highway (Fig. 1b). Despite such geographical concentration, most of the shore properties have restricted public access. Consequently, a door-to-door survey was considered unsuitable. Instead, the questionnaire was mailed to each of the taxpayers of Shuniah Township whether they owned shore property or not. Approximately a 10 percent sample was thus obtained (Table 1). Again, the response rate may be considered low (184 responses with a confidence limit of + 7% at p = 0.05), but the distribution of respon-;es was representative of subpopulations as well as of geographical areas (Le., subreaches). It should be stressed here that despite the differences in methodologies, this paper presents the

EFFECTS OF HIGH WATER LEVELS ON PROPERTY HAZARDS TABLE 1.

209

Population sampling for questionnaire surveys.

Population size

Minnesota Shore

Thunder Bay Shore

1,500* (all shore properties)

1,900** (all residential properties)

Sub-populations: Residential shore properties Residential inland properties Non-residential shore properties No. of properties samples Response rates: Residential shore properties Residential inland properties Non-residential shore properties Total

1,200

1,300 600

300 341

1,900 133(10.2%) 51(8.5%)

159(13.3%)*** 38(12.7070) 197(13.1 %)

184(9.7%)

*Estimated by using earlier surveys by COE (1976 and 1977) **According to Reinders (1983) and confirmed by the Shuniah Township Office ***Percentages in parenthesis indicate rates as relative proportions of subpopulations

TABLE 2.

Property ownership and setting. St. Louis County

Average length of property ownership (years) Bluff/shore composition (percent of sample) Average height of edge of bluff above water (m) Average height of base of main structure above water (m) Average building setback from bluff/edge of water

Shoreline reaches Cook Lake County County

Thunder Bay Shore

16 (N = 12) C (75) B (25)

23 (N = 91) C (51) B (44) S&G (5)

23 (N = 94) B (57) S & G (39) C (4)

20 (N = 184) S & G (80) B (20)

11

5.2

3.3

2

12

5.8

4.6

3

17

16.8

16.8

26

(m)

Number of respondents Bedrock C Clay S&G = Sand and Gravel

N

=

B

common themes of two different questionnaires. The results of the surveys are summarized in Tables 2, 3, and 4. PROPERTY OWNERSHIP AND SETTING The longest period of property ownership is 39 years in St. Louis County, 75 years in Lake County, and 70 years in Cook County. At least

25% of the properties on the Thunder Bay shore have been owned for more than 30 years (Reinders 1983). Many properties have been owned for more than 25 years in all four reaches. These balance out with the more recent buildings and ownerships, reflecting the average values in Table 2. However, the long-term ownerships provide more significant data on property hazards because they represent

RASID et a/.

210 TABLE 3.

Estimated erosion rates and structural damage. Shoreline reaches Cook Minnesota County Shore

St. Louis County

Lake County

(N) 0 2

(N) 63 16 12

(N) 53 23 18

N(%)* 126(64070) 39(20%) 32(16%)

N(OJo)* 89(48%) 43(23%) 52(28%)

Estimated Long-Term Erosion rates (m) -Less than 3 m (10 ft) -3 to 15 m (50 ft) -More than 15 m -Erosion rates not specified

(N) 4 5 1 0

(N) 30 29 4 0

(N) 41 12 0 0

N(%)** 75(60%) 46(36%) 5(4%) 0

N(%)** 56(63%) 17(19%) 0 16(18%)

Frequency of 1985-86 Erosion Rates -Erosion -No erosion -No response

(N) 9 0 3

(N) 55 16 20

(N) 48 26 20

N(%)* 112(57%) 42(21 %) 43(22%)

N(%)*

Estimated 1985-86 Erosion rates (m/y) -Less than 1.5 m (5 ft) -1.5 to 3 m (10 ft) -More than 3 m

(N) 6 2 1

(N) 40 6 9

(N) 36 7 5

N(%)** 82(73%) 15(13%) 15(13%)

N(%)**

(N)

(N) 35 56 0

(N) 20 56 18

Frequency of Long-Term Erosion rates -Erosion -No erosion -No response

Frequency of 1985-86 Structural Damage -Structural damage -No structural damage -No response

10

N

Thunder Bay Shore

N

55 112 18

= Number of respondents N (%)* = Percent of total sample (%)** = Percent of respondents who specified erosion rates

continuous observation through cycles of high and low water. The impact of high lake levels on a specific property is governed largely by two basic factors: bluff! shore composition and building setback. Respondents whose properties are situated on relatively resistant bedrock have reported no major erosion problems and property hazards. However, not all bedrock is absolutely stable. Some of it is highly fractured and shows signs of collapse. On the Minnesota shore approximately one-quarter of all bedrock bluffs exhibit this problem. The greatest

amount of fractured bedrock has been reported form Lake County. None of the property owners on the Thunder Bay shore reported this problem. Only 20 percent of the properties on this shore are situated on bedrock. This contrasts with over 50 and 40 percent respectively, in Cook and Lake counties. In St. Louis and Lake counties some of the properties are located on clay overlying bedrock. In Table 2 these are included as clay bluffs. Properties located on these bluffs are particularly affected by high lake levels. While the toe of such bluffs, being composed of resistant

211

EFFECTS OF HIGH WATER LEVELS ON PROPERTY HAZARDS TABLE 4.

Shore protection measures.

Frequency of Shore Protection Measures -Site with shore protection -No shore protection -No response Types of Protection Measures -Retaining walls -Revetments, riprap, fill -Groins -Others Money spent on shore protection measures ($US) -Under $1,000 -Over $1,000 -Average Cost -(% of property value) Willingness to pay for shore protection (N) N (%)* (%)**

= =

Shoreline reaches Cook Minnesota County Shore

Thunder Bay Shore

S1. Louis County

Lake County

(N) 5 7 0 (N) 3 1 0 1

(N)

27 33 31 (N) 8 11 0 8

(N) 35 37 22

N(ll7o)* 67(34%) 77(39%) 53(27%)

N(%)* 84(46%) 49(26%) 51(28%)

(N) 12 16 0 7

N(%)** 23(34%) 28(42%) 0 16(24%)

N(%)** 30(36%) 24(28%) 4 26(31 %)

(N) 3 2 2,530 (1.5%)

(N) 0 13 2,000 (1.5%)

(N) 11 12 1,059 (1%)

(N) 14 27 1,863 (1.33%)

(N) 20 20 1,415 (2%)

6

14

25

45(67%)**

58(69%)**

Number of respondents Percent of total sample Percent of respondents who specified erosion rates

bedrock, provides protection from wave erosion, rising water levels subject the overlying clay to severe wave erosion and slope instability. A large number of the surveyed properties in St. Louis and Lake counties are located on clay bluffs. The term clay bluffis used here loosely to refer to all bluffs composed of relatively unconsolidated glacial till and glaciolacustrine silt and clay deposits. In St. Louis County some of the clay bluffs exceed 10 m in elevation. These are subject to massive slumping and mass wasting with rising lake levels. Similar clay and till bluffs on the north shore of Lake Erie demonstrate certain cyclic instability relationships with fluctuating lake levels (Quigley et al. 1977). According to these relationships, bluff recession is initiated by toe erosion, which results in loss of support for the bluff face. Slumping and mass wasting reduces the bluff until an equilibrium condition is reached between the toe and the bluff face. The equilibrium is main-

tained within a range of water levels. If the normal range is exceeded by rising lake levels, a new cycle of instability is initiated. In Shuniah Township most of the shore properties (80 percent) are located on low bluffs of unconsolidated materials which are protected during normal water levels by gravel and sand beaches (Table 2). A large number of surveyed properties (44 percent) in Cook County are located in a similar setting with extensive gravel and cobble beaches fronting the properties. With rising lake levels, these protective beaches may be submerged, exposing the bluff and beach materials to new wave erosion. Besides bluff/shore composition, the relative location of a building is a critical factor in property hazard. The term building setback refers to the distance from the corner of the buildings to the edge of water/bluff. On the Minnesota shore, building setback ranges between 1 and 100 m; on the Thunder Bay shore it varies from 3 to 30 m.

RASID et al.

212

While the average setback is wider on the Thunder Bay shore than on the Minnesota shore, the average height of the bluffs is much lower on the former (Table 2). The potential for flooding during high water levels is thus greater on the Thunder Bay shore. The erosion rates, on the other hand, may increase along higher clay bluffs (such as in S1. Louis County) due to potential large-scale slope instability. ESTIMATED EROSION RATES There are no published data on erosion rates for any of the study reaches. The Natural Resources Research Institute of the University of MinnesotaDuluth has recently initiated a coastal erosion measurement program by using historical aerial photographs and ground reconnaissance survey (C. Johnston, pers. commun. 1988). Adequate sequential photographs are not available for the Thunder Bay shore to produce a similar study. In the absence of measured data, property owners were asked to estimate erosion rates. Their responses, summarized in Table 3, might have been influenced by their perception of the erosion problem, though some estimates might have been based on actual property setback records. Since it would be difficult to verify such data, erosion rates are expressed as ranges rather than as absolute values. The magnitude of the erosion problem is reflected in the fact that approximately two-thirds and one-half, respectively, of the respondents of the Minnesota and the Thunder Bay shores reported long-term erosion. The remaining onethird and one-half of the respondents either did not experience the erosion problem or did not respond to this question. Thus, the sample population appears to be fairly representative of the subpopulations (Le., erosion vs. no erosion groups). Long-term erosion rates were estimated over a minimum period of 5 years. The maximum erosion rates (3 m to more than 15 m) were reported from Lake County. This can be attributed not only to the erodibility of clay bluffs in this county but also to the effect of the exposure of its shoreline to long fetches. The effect of restricted fetches is reflected in lower erosion rates on the Thunder Bay shore, where 63010 of the respondents (who reported erosion rates) estimated erosion rates of less than 3 m and 18010 did not specify erosion rates. Lower erosion rates in Cook County probably reflect the effect of its more resistant rocky shoreline (Table 2).

The property owners on the Minnesota shore were also asked to estimate the 1985-86 erosion rates. Approximately three-quarters (73%) of the respondents who specified erosion problems reported only limited amounts of erosion, Le., less than 1.5 m/y. However, if this rate is extrapolated over 5 years or more, it appears to be significantly higher than the long-term estimates. There are at least two probable explanations for this. Firstly, people's perception of a hazard tends to be magnified with the proximity in time of the event (White 1974). Secondly, the 1985-86 erosion rates were probably higher than previous rates due to the above-average duration of high lake levels. In addition, heavy rainfall in early 1986 saturated many clay bluffs, inducing accelerated slumping. Besides shoreline erosion, structural damage was another major impact of high water levels. The most common damage in all four reaches included partial or total destruction of different types of coastal structures, such as retaining walls, jetties and docks. In addition, a substantial number of respondents of Lake and Cook counties (38% and 21 % respectively) reported damage to such other structures as houses, cabins, boat houses, and fish houses (Table 3). No such data have been reported for either S1. Louis County or for Thunder Bay. COPING WITH THE HAZARD Shore Protection Measures Since most of the properties surveyed are privately owned, coastal property owners have had to fend for themselves. The result has been a piecemeal effort to minimize coastal erosion. Confronted with property hazards due to high lake levels and erosion, typical responses of property owners ranged from "doing nothing" to installing a variety of structural devices for combating erosion. On the Minnesota shore only about one-third of the respondents reported some type of shore protection measure; the remaining two-thirds either did not have any shore protection measures or did not respond to this question (Table 4). On the Thunder Bay shore slightly less than one-half (46%) of the respondents reported shore protection measures. Retaining walls (seawalls), revetments, riprap, and fill materials were the most favored measures. Groins were not popular on any of the reaches, while other measures mentioned included planting vegetation and building fences. Only three individuals - two in Cook County and one in

EFFECTS OF HIGH WATER LEVELS ON PROPERTY HAZARDS Thunder Bay - moved buildings and considered relocation. The larger number of shore protection structures on the Thunder Bay shore indicates not only the higher density of shore properties, but also a longer life of structures in the low-energy wave climate of Thunder Bay. Owing to the severity of the wave climate in St. Louis and Lake counties, many of the coastal structures are destroyed within a relatively short time, unless they are constantly maintained and occasionally replaced. Maintenance cost is particularly high for clay bluffs. Rapid erosion and landslides along the bluff face tend to undermine the foundations of protective structures, accelerating the pace of their destruction by waves. One of the principal reasons why more permanent and effective coastal structures have not been built is the cost of construction. The amount spent per property, averaging only 1-1.5% of the property value, is relatively low, compared to the seriousness of the problem. Even this average is raised by a few reporting very large amounts of expenditure. For example, on the Thunder Bay shore one person spent more than $10,000 to build a groin in 1985-86 and four other spent between $3,000 and $4,000 (1985-86 dollars) to construct concrete retaining walls and revetments. Similarly, two persons in St. Louis County spent more than $12,000 each. Most of the remaining respondents spent between $100 and $2,000, indicating the low level of protection provided. If the average costs for shore protection, reported in Table 4, are extended even to the entire shore properties, the total costs of protection according to this survey appear to be relatively low: $2.8 million for the Minnesota shore and $1.8 million for the Thunder Bay shore. In the light of this projection, the 1985-86 damage estimates for the Minnesota shore ($74 million estimated by the State of Minnesota for the BC) appear to be exaggerated. However, it is recognized that the BC estimate includes public infrastructure, whereas the present study is limited to private properties only. Responsibility for Shore Protection Measures If human ability to affect Great Lakes water levels is limited, then damage to shoreline and shore properties should be considered as an inherent operating cost of living on the shoreline. Living in a hazardous environment can be justified only if that environment is considered as a resource out-

213

weighing the risk (White 1974). Coastal property owners who have chosen to live on the edge of water have largely been attracted by the amenities of the shoreline. Despite this, they are divided in their opinion on the responsibility for shore protection. On the Minnesota shore two in every three respondents with shore protection measures indicated willingness to pay for shore protection measures. The remaining one-third refused to bear this responsibility, but did not identify any authority who should do so (Table 4). The residents of Shuniah Township were asked a more specific question: "Who do you think should be responsible for paying for any measures taken to reduce or prevent shoreline damage?" Again, nearly two-thirds of the respondents with shore protection measures agreed to share some responsibility for protection measures, but almost an equal number (60-70) were inclined to look to the federal or provincial levels for financial assistance. In contrast, nearly three-quarters of the inland respondents (38 out of 51) were more inclined to put the onus on the shore property owners, as they suggested that property owners should pay for their own protection measures. Thus the perceived responsibility for paying for shore protection is significantly related to the location of ownership (chi-sq = 8.71; one degree of freedom, significant at 0.05 level). Manipulating Lake Levels The technical limitations to regulating lake levels were poorly understood by most of the respondents. Many believed it was primarily a management decision, exercised by the BC. Only a few appreciated the constraints imposed by meteorological variables. The concern for high lake levels is apparent from the response to the question: "Do you think lowering the level of Lake Superior would help prevent shoreline erosion?" An overwhelming 93070 of Shuniah residents who responded to this question (74 out of 80) favored lowering the lake. Confronted with a more technical but related question: "How many centimeters (originally asked in feet) do you think Superior should be lowered?", a few insisted that it should be decided by experts. Among those who suggested the amount (63 out of 80), approximately twothirds favored lowering the lake by not more than 30 cm (i.e., maintaining the normal level), 29 percent by up to 1 m, and 5 percent by up to 2 m. It is technically possible to further reduce fluctuations in Great Lake levels by controlling the

RASID et al.

214

release of water from outlet rivers. However, benefit-cost analyses of regulatory structures by the IJC do not justify this measure. Regulatory works generally require expensive excavation of the outlet channels to increase their capacities when supplies are high, and the construction of control structures to reduce outflows when supplies are low (EC/MNR 1975). The feasibility of further lowering lake levels by excavation works was investigated by the IJC through its International Great Lake Levels Board (IGGLB 1973). The problem is compounded by divergent interests. While low stable levels would reduce erosion and flooding damages, they would be undesirable to navigation and power interests (EC/MNR 1975). Lowering the lake below its normal levels would also expose many beaches, causing difficulties for boat launching and water intake facilities. The IJC has also recently investigated the potential of using existing diversions to regulate water levels in the Great Lakes. By manipulating the existing diversion structures, such as a permanent shutdown of the Ogoki-Long Lac diversion's inflow and a permanent increase in Lake Michigan's outflow at the Chicago diversion, it is possible to lower the level of Lake Superior by up to 10 cm over a period of 10 years (Yee and Cuthbert 1985). These lowered lake levels would not, however, prevent shore property damage, because these reductions are not significant compared to the short-term extremes that accompany the storms that cause most of the shoreline damage. MANAGEMENT IMPLICATIONS It appears from the foregoing discussions that the

lake levels cannot be regulated effectively and that effective structural protection is expensive. The most valuable lesson that can be learned from these observations is that modern societies cannot expect to cope effectively with an environmental hazard by relying solely upon technological solutions (White 1974). Instead, a broader range of adjustments, that include both structural and nonstructural measures, would provide more flexible and realistic solutions to the problem. The current practices on the north shore of Lake Superior have emphasized either piecemeal protection of individual properties or a "do nothing" approach in which private property owners bear the entire loss. This is an indication that property development on this shore has taken place in a planning vacuum, without sufficient consideration for the effects of fluc-

tuating water levels. Most of the properties on the edge of water were developed during low water periods when shore users were lulled into false security by the relatively stable appearance of the shoreline. As the lake level rises, the stability of the shoreline is threatened and property hazards increase, drawing attention from property owners, government agencies, and news media. The false sense of security returns with falling lake levels, when interest in the problem fades. For an effective solution to the problem, planning processes should be based on a long-term framework beyond this "issue-attention cycle" (Kreutzwiser 1987). Shoreline management represents such a plan for coping with the hazard of fluctuating lake levels. The central philosophy of a comprehensive shoreline management plan (SMP) is to protect existing developments, and to prevent future encroachment of high-risk reaches of the shoreline. For protecting existing developments at least three different procedures may be followed. Firstly, an understanding of the local shoreline's characteristics and its physical processes is a basic requirement for any planning exercise. Specific projects in this context should include an inventory of erosion sites with their annual recession rates. This will provide a basis for monitoring property hazards and for taking appropriate actions for protecting properties. Secondly, another objective of shoreline management is to provide sound technical advice for structural protection measures. If structural protection is required, an SMP can guide decisions concerning effective and environmentally compatible engineering works. Thirdly, an SMP can help decision-makers determine whether alternative responses, such as relocation of buildings or public land acquisition, would be more appropriate (Kreutzwiser 1987). The plan could provide incentives in the form of loans for relocating or removing structures. The main thrust of the SMP lies in its prevention component. Of all the preventive measures, perhaps the greatest potential for reducing shoreline damage lies in the implementation of land use regulations. Such implementation must be carried out within the framework of existing laws. Even though the formulation of local land use zoning is a municipal responsibility in Canada, the provinces are becoming more involved in the development of master plans for land use. In Ontario the Ministry of Natural Resources has recently assumed a leadership role by releasing a muchawaited document, Guidelines for Developing

EFFECTS OF HIGH WATER LEVELS ON PROPERTY HAZARDS

Great Lakes Shoreline Management Plans (MNR 1987). One of the main recommendations of these guidelines is the preparation of coastal zoning maps, indicating the areal extent and intensity of flooding and erosion from certain designated lake levels. The responsibility for preparing such maps has been vested in the conservation authorities, which are experienced in riverine floodplain mapping. Besides the preparation of such maps, other recommended preventive measures include setback regulations, building elevations, and floodproofing measures. If it is not practical to prohibit development entirely on a given reach, construction can be permitted provided certain floodproofing and building codes are incorporated or setbacks based on some standards, such as the 100-year level, are allowed in the construction plan. Prior to the release of these guidelines shoreline management policies in Ontario had been administered on an ad hoc basis in response to fluctuating lake levels. For example, following the 1972-73 high lake levels at least seven shore property assistance programs were administered by the senior governments (Le., Ontario and Canada). One of these programs allowed municipalities to borrow funds from Ontario to make loans to residents for constructing protection works and repairing waterdamaged buildings (Day et al. 1977). The municipality of Shuniah Township did not participate in this program mainly due to its reluctance to get involved in a large number of loans that would be amalgamated with its tax roll. Other measures such as relocation and buyouts were not considered seriously due to the constraints imposed by the limited financial resources of this municipality and the scarcity of land for relocation. Besides, relocation is probably warranted when buildings are directly threatened by erosion. Despite substantial loss of land, none of the properties on the Thunder Bay shore has as yet faced this problem. Minnesota's comprehensive shoreline management program was initiated in the early 1970s. At that time, all three of the north shore counties were required to adopt minimum statewide standards for the protection of inland lakes and Lake Superior. Although setbacks are required, they do not take into account coastal erosion. In the mid-1970s an attempt to establish more extensive shoreline management controls failed when Minnesota decided against opting for the U.S. Coastal Zone Management (CZM) Program. In 1987 the three coastal counties, their townships and municipalities formed the North Shore Management Board.

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Funded by the State of Minnesota for 2 years, their goal is to establish shoreline management standards appropriate to the north shore, of which coastal erosion is a dominant concern. CONCLUSIONS

Many properties along the north shore of Lake Superior are subject to inundation and erosion hazards with rising lake levels. Property hazards are related to a number of site characteristics, such as exposure to wave action, composition and erodibility of bluff and shore materials, and setbacks of individual buildings. Estimated long-term erosion rates range from less than 3 m to more than 15 m over a minimum period of 5 years, with a substantial amount of erosion occurring during the 1985-86 high water period. If erosion continues at the 1985-86 rates during the next few episodes of high lake levels, many properties with limited setback will be undermined within a short period of time. To cope with the erosion hazards, some private property owners have made use of a wide range of shore protection structures. However, effective shore protection is expensive and very few property owners can afford it. No federal or provincial!state agency provides financial assistance for shoreline erosion control projects. Consequently, property owners have invested very little money in these projects, many of which are superficial in nature. Besides this, initiatives of selected property owners have resulted in piecemeal protection of shoreline reaches. Faced with an increased hazard associated with the 1985-86 record-high water levels, a large number of property owners responded with a demand to lower the water levels by regulating the lake's outflow. Unfortunately, human ability to regulate the levels of Lake Superior and of other Great Lakes is limited, as these levels are dependent primarily on climatic cycles. Because effective shore protection is expensive and human ability to regulate lake levels is limited, greater attention should be given to nonstructural measures such as land use regulations, which may be designed to prevent or minimize the encroachment of flood- and erosion-prone reaches of the shoreline. To develop effective land use zoning regulations, coastal municipalities and counties should prepare their own master plans. A recent document, released by the Ontario Ministry of Natural Resources, provides guidelines for preparing such shoreline management plans. According

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to these guidelines, the real power for land use regulations will be exercised jointly by coastal municipalities (in Ontario) and the regional conservation authorities, who have been vested with the new responsibility for preparing coastal zoning regulation maps. Using these guidelines, the Township of Shuniah is in the process of developing a master plan for shoreline management. Similar grass-root level management plans will be required for individual counties on the Minnesota shore for coping effectively with the shore property hazards. ACKNOWLEDGMENTS

This work is the result of research sponsored by the Minnesota Sea Grant College Program supported by the NOAA office of Sea Grant, Department of Commerce, under Grant No. NOAA-86AA-DSGl12 (Journal Reprint Number 214). Financial assistance for field work was also provided by a Lakehead University/University of MinnesotaDuluth collaborative research project. We are grateful to Dr. Brian Greenwood (University of Toronto), Dr. Reid Kreutzwiser (University of Guelph), and an anonymous referee for their many useful comments on an earlier draft of this paper. All final diagrams were drafted by Mr. Greg Pitkanen (Lakehead University). REFERENCES Baker, D., and Otterson, P. 1987. Slip sliding away: erosion on Lake Superior's north shore. University of Minnesota: Minnesota Sea Grant Superior Advisory Note No. 25. COE (Corps of Engineers). 1976. Great Lakes Shoreline Damage Survey: Saint Louis County, Minnesota. Chicago: U.S. Army Corps of Engineers North Central Division Report. _ _ _ _ . 1977. Lake Superior Shoreline Damage Survey: Lake and Cook Counties. Chicago: U.S. Army Corps of Engineers North Central Division Report. _ _ _ _ . 1979. Summary Report Great Lakes Shoreland Damage Study. Chicago: U.S. Army Corps of Engineers North Central Division Report. Day, J. c., Fraser, J. A., and Kreutzwiser, R. D. 1977. Assessment of flood and erosion assistance programs: Rondeau coastal zone experience, Lake Erie. J. Great Lakes Res. 3:38-45.

EC/MNR (Environment Canada and Ontario Ministry of Natural Resources). 1975. Canada/Ontario Great Lakes Shore Damage Survey. Technical Report. Hough, J. L. 1958. Geology of the Great Lakes. Urbana: University of Illinois Press. IGLLB (International Great Lakes Level Board). 1973. Regulation of Great Lakes Water Levels. Appendix C. Shore Property. Report to the International Joint Commission. IJC (International Joint Commission). 1987. Task Group 7, Great Lakes Basin - St. Lawrence River Coastal Zone Inventory of Emergency Measures and Shoreline Management Activities. Report submitted to the International Joint Commission. Kreutzwiser, R. D. 1987. Managing the Great Lakes shoreline hazard. Journal of Soil and Water Conservation 42(3): 150-154. MNR (Ontario Ministry of Natural Resources). 1987. Guidelines for Developing Great Lakes Shoreline Management Plans. Toronto: Ontario Ministry of Natural Resources Conservation Authorities and Water Management Branch. Owens, E. H. 1979. The Canadian Great Lakes: Coastal Environments and the Cleanup of Oil Spills. The Environment Canada: Environmental Protection Service Economic and Technical Review Report EPS-3-EC-79-2. Quigley, R. M., Gelinas, P. 1., Bou, W. T., and Packer, R. W. 1977. Cyclic erosion-instability relationships: Lake Erie north shore bluffs. Canadian Geotechnical Journal 14:310-323. Quinn, F. H. 1987. Testimony of Frank H. Quinn, Head, Lake Hydrology Group, Great Lakes Environmental Research Laboratory, before the Subcommittee of Water Resources Committee on Public Works and Transportation, House of Representatives. Reinders, F. J., and Associates. 1983. Conversion Study: Township of Shuniah. Consulting engineers report. Resio, D. T., and Vincent, C. L. 1978. Design Wave Information for the Great Lakes; Report 5, Lake Superior. Vicksburg: U.S. Army Engineers Waterways Experiment Station Technical Report H-76-1. Sharp, R. P. 1953. Glacial features of Cook County, Minnesota. American Journal of Science 251 (Dec):855-883. White, G. F. 1974 ed. Natural Hazards: Local, National and Global. Toronto: Oxford University Press. Yee, P., and Cuthbert, D. 1985. A Report on the 1985 Record High Water Levels of the Great Lakes. Environment Canada: Inland Waters DirectorateOntario Region, Water Planning and Management Branch.