Minnesota Department of Transportation
Jump to main content.
Minnesota Department of Transportation Go to 511
MnDOT A to Z | General Contacts | Search |
Minnesota River Prairie Model
 

Mn/Model

Final Report Phases 1-3 (2002)

Contact Us   Mn/Model Home | Archaeology | Geomorphology | Geographic Information Systems (GIS) | Implementation

 

Quick Links

Chapters

Appendices

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8.20 MINNESOTA RIVER PRAIRIE SUBSECTION OF NORTH CENTRAL GLACIATED PLAINS SECTION

Location of Minnesota River Prairie

 

8.20.1 Environmental Context
8.20.2 Site Probability Model
8.20.3 Survey Probability Model
8.20.4 Survey Implementation Model
8.20.5 Other Models

 

This regional model report is organized as described in Sections 8.2.1 through 8.4.1. Refer to these sections of the report for explanations of the tables, variables, and statistics.

 

8.20.1 Environmental Context

Minnesota River Prairie is a subsection of the North Central Glaciated Plains Section of the Prairie Parkland Province. It is the largest subsection of all ECS units modeled (Figure 8.1) (Minnesota DNR 1998).

 

Boundaries of this subsection are defined primarily by geomorphology. The northeastern border with the Red River Prairie is based on the interface between the southern extent of the Agassiz Lake Plain and Des Moines moraines on the south. The eastern boundary that adjoins the Hardwood Hills and the Big Woods subsections is based on the interface between Alexandria stagnation moraines, to the north and east, and the Des Moines ground moraines to the south. Further east, the border with the Big Woods follows an ecotone between Big Woods to the east and prairie to the west, as interpreted by Marschner (1974) (Figure 8.20.1.b). The southeast border with the Oak Savanna subsection is based on the ecotone between prairie to the west and oak savanna / prairie complex to the east. The western border from Iowa follows the Des Moines River north to where the river heads west and the border then becomes the interface between the till plain within the subsection and the Coteau to the west to the South Dakota state border (Dan Hanson, personal communication 1997).

 

The subsection is predominantly on ground moraine (Figure 8.20.2a). Topography is gently rolling. The Minnesota River, with associated alluvium and river terraces splits this region in half from northwest to southeast. There are two significant areas of glacial lake sediment located at the north end and the south end of the subsection. The Minnesota and Blue Earth rivers are the most prominent hydrologic features (Figure 8.20.1a). Several outwash channels cut through the region, but only some are occupied by present-day streams. Many of the wetlands in this subsection have been drained for agriculture. Poorly drained soils are quite extensive (Figure 8.20.2b).

 

Historic vegetation was predominantly prairie, with wet prairie, marshes and sloughs distributed throughout the subsection (Figure 8.20.1b). River bottom forest, consisting of silver maple, elm, cottonwood, and willow, populated the river valleys. Small stands of the Big Woods forest community occurred along the eastern border.

 

Return to Top

 

8.20.2 Site Probability Model

8.20.2.1 Description

The distribution of medium and high site potential in the site probability model for the Minnesota River Prairie (Figure 8.20.3) are primarily along major rivers and around larger lakes. The main channel of the Minnesota River Valley contains the longest (300-km) continuous high and medium site potential zone, extending from the western border of the state to the southeastern subsection border. This zone begins along the reservoir-lakes Big Stone and Traverse at the extreme northwest of the subsection and continues uninterrupted to the Minnesota's confluence with the Mississippi River. Major tributaries of the Minnesota are also lined by zones of high and medium site potential. Probability values tend to be high adjacent to water and decline to medium with greater distance from water. Concentrated zones of high and medium site potential also occur around Swan Lake near the Minnesota River bend and around a group of small lakes in Kandiyohi, Meeker and McLeod counties at the north of the subsection.

 

The traces of vertical striping from banded digital elevation data are prevalent in the eastern part of the subsection from Renville County to the eastern border. These artifacts should not be considered predictive features.

 

8.20.2.2 Evaluation

The site probability model for the Minnesota River Prairie performed very well. It is based on 17 variables (Table 8.20.1) representing topography, vegetation, soils and hydrology.

 

Table 8.20.1. Site Probability Model, Minnesota River Prairie Subsection.

Intercept

-0.445

 

ln(nonsites/sites)

1.398092395

 

Variable

Regression Coefficient

Probability

Distance to brushlands

0.02416896

100

Distance to edge of nearest perennial river or stream

-0.009067593

98

Distance to edge of nearest swamp

-0.02100625

100

Distance to hardwoods

-0.009038448

100

Distance to nearest confluence between perennial or intermittent streams and large rivers

-0.007934209

94.6

Distance to nearest intermittent stream

0.01182407

98.6

Distance to nearest lake, wetland, organic soils, or stream

-0.04553736

100

Distance to nearest major ridge or divide

-0.008993313

100

Distance to oak woodland

-0.02461310

100

Distance to prairie

0.01604437

100

Distance to sugar maple

0.003923996

94.6

Height above surroundings

0.05816495

100

On alluvium

0.6502604

98.3

On river terraces

0.6446472

75.6

Size of nearest lake

0.0006067873

70.8

Vegetation diversity within 1 km

0.3166257

100

Vertical distance to water

0.006682293

91.4

 

 

In this model, 82.98 percent of all modeled sites are in high/medium site potential areas, which make up only 19.84 percent of the landscape (Table 8.20.2). This produces a strong gain statistic of 0.76091 (Table 8.6.11). The model tested nearly as well, predicting 80.7 percent of the test sites. The test gain statistic was 0.75421.

 

Table 8.20.2. Evaluation of the Site Probability Model, Minnesota River Prairie Subsection.

 

Region

(30 meter cells)

Random Points

Negative Survey Points

Modeled Sites

Test Sites
                 

Low

27673666

79.34

3079

78.51

812

49.75

156

16.10

10
17.54

Medium

5189284

14.88

606

15.45

454

27.82

258

26.63

15
26.32

High

1729036

4.96

209

5.33

365

22.37

546

56.35

31
54.39
                 

Water

270840

0.78

25

0.64

1

0.06

4

0.41

0
0

Steep Slopes

14821

0.04

3

0.08

0

0

5

0.52

1
1.75

Mines

0

0

0

0

0

0

0

0

0
0
                 

Total

34877647

100

3922

100

1632

100

969

100

57
100

 

 

The database included 969 sites that were not single artifacts. This is the largest number of sites within any subsection. Two preliminary models using different halves of the known sites had 83 percent agreement (83 percent of the cells in the subsection were classified the same in both models). However, the Kappa statistic, which is adjusted for the amount of agreement expected by chance alone, for this model is 0.58827 (Table 8.6.10), only somewhat higher than average. The conditional Kappa statistics (Table 8.20.3) are lowest for the medium and high site potential zones. This indicates that the model's primary instability is in distinguishing between these two zones.

 

Table 8.20.3. Conditional Kappa Values for Site Probability Model, Minnesota River Prairie.

Class

Ki

Proportion Correct

Low

0.6716

0.9179

Medium

0.3817

0.4744

High

0.7074

0.7367

 

 

8.20.2.3 Interpretation

Seventeen variables are used to build the site probability model for the Minnesota River Prairie (Table 8.20.1). Of these variables, two are topographic, seven are hydrologic, six are vegetative, and two relate to soils or landforms. Ten of these variables have correlation coefficients with modeled sites greater than 0.3 (Table 8.20.4).

 

8.20.2.3.1 Differences between Modeled Sites and Random Points for Individual Model Variables

The proximity of high and medium probability to water features is reflected in these statistical relationships. Sites also tend to be nearer perennial rivers or streams (1079 vs. 3,600 meters, Figure 8.20.10c), intermittent streams (993 vs. 1,535 meters, Figure 8.20.11a), swamps (532 vs. 1,379 meters, Figure 8.20.10d), confluences between perennial or intermittent streams and large rivers (4,128 vs. 10,588 meters, Figure 8.20.11c), and lakes, wetlands organic soils, or streams (114 vs. 324 meters, Figure 8.20.10b) compared to random points. Sites are also associated with somewhat larger lakes than would be expected by chance (Figure 8.20.11d).

 

Sites are more likely than random points to be on either alluvium (Figure 8.20.15a) or river terraces (Figure 8.20.15b). They are higher than their surroundings by an average of 9.8 feet (Figure 8.20.4.a and Figure 8.20.9c) and are at greater vertical distances from water (26 vs. 10 feet, Figure 8.20.12b) compared to random points. This also puts them closer to major ridges or divides (Figure 8.20.9a).

 

Sites are strongly associated with areas of high vegetation diversity (Figures 8.20.4.b and 8.20.14d). In this subsection, that implies they are further from the dominant prairie community (Figure 8.20.14b) and closer to hardwoods (Figures 8.20.13c and 8.20.14c), sugar maples (Figures 8.20.5.a and 8.20.14c), oak woodland (Figure 8.20.13d), and brushlands (Figure 8.20.13a).

 

The Mann-Whitney U tests indicate that all 17 site model variables are significant at the 0.05 level (Table 8.20.4). This means that the sites and random points differ enough to be considered drawn from different populations and that this model is able to discriminate between the two.

 

Table 8.20.4.  Model Variable Statistics.

Minnesota River Prairie

Modeled Sites

Surveyed Areas

Modeled Sites

Sites in Low Prob.

Neg. Survey Points

Random Points

                         

Distance to nearest major ridge or divide

-0.176

0

-0.261

0

61.06

32.55

67.62

32.28

62.13

31.03

70.17

32.6

Elevation

-

-

-0.536

0

1038.43

110.18

1111.64

95.3

1050.25

95.77

1098.4

98.74

Height above surroundings

0.609

0

0.525

0

14.77

15.88

5.54

4.57

7.29

8.57

5.03

6.14

Size of major watershed

-

-

0.077

0

1687.25

381.09

1661.64

407.08

1664.33

382.12

1652.4

392.37

Distance to edge of nearest large lake

-

-

0.184

0

82.39

46.07

86.94

38.01

87.01

40.23

92.23

38.69

Distance to nearest lake, wetland, organic soil, or stream

-0.2

0

-0.336

0

10.69

7.11

15.42

9.95

14.19

9.42

18

10.87

Distance to edge of nearest perennial river or stream

-0.487

0

-0.625

0

32.85

27.14

59.64

30.57

47.34

29.86

60.01

29.92

Distance to edge of nearest swamp

-0.37

0

-0.404

0

23.07

13.21

34.65

16.62

30.64

15.3

37.14

16.56

Distance to nearest intermittent stream

-0.118

0

-0.296

0

31.51

16.82

37.46

20.64

36.18

21.63

39.18

22.22

Distance to nearest permanent lake inlet/outlet

-

-

-0.262

0

82.85

45.55

106.61

33.72

100.32

47.77

104.89

35.65

Distance to nearest confluence between perennial or intermittent streams and large rivers

-0.517

0

-

-

64.25

46.75

106.72

40.14

83.48

46.2

102.88

43.06

Size of nearest lake

0.104

0

-

-

464.17

800.78

208.55

327.61

318.34

611.34

270.18

478.5

Size of nearest permanent lake

-

-

0.014

0

464.75

802.09

208.61

327.65

324.27

618.07

271.83

481.43

Vertical distance to water

0.387

0

-

-

25.79

37.9

7.93

15.38

13.34

25.38

10.47

18.71

Vertical distance to permanent water

-

-

0.344

0

37.35

46.21

20.86

31.72

36.11

50.5

23.29

33.95

Distance to aspen-birch

-

-

0.091

0

364.85

83.14

358.4

95.1

363.09

81.12

352.94

93.5

Distance to brushlands

-0.242

0

-

-

88.17

50.36

107.54

46.66

89.59

52.38

108.17

50.26

Distance to Big Woods

-

-

-0.339

0

94.76

84.45

123.83

70.35

97.46

78.33

131.81

77.95

Distance to hardwoods

-0.509

0

-

-

41.96

41.53

76.2

37.09

58.9

42.51

80.21

39.69

Distance to oak woodland

-0.265

0

-

-

89.92

49.2

111.88

42.39

95.71

49.88

111.18

47.77

Distance to paper birch

-

-

-0.127

0

249.66

109.64

271.47

80.77

247.68

110

271.34

92.19

Distance to prairie

0.33

0

-

-

12.16

15.45

7.6

14.56

8.94

15.01

5.67

13.03

Distance to sugar maple

-0.327

0

-

-

120.5

76.63

141.68

48.39

129.29

72.4

142.21

58.43

Vegetation diversity within 1 km

0.357

0

0.431

0

2.38

0.85

1.86

0.76

2.1

0.83

1.76

0.72

On alluvium

0.3

0

-

-

0.2

0.4

0

0

0.07

0.26

0.03

0.16

On river terraces

0.204

0

0.429

0

0.1

0.3

0.01

0.08

0.12

0.32

0.02

0.13

                         

Frequency counts

969

 

2667

 

969

 

156

 

1632

 

3922

 

See Interpretation section for discussion of the statistics:
Coeff.      = correlation coefficient
Sign.         = significance of the Mann-Whitney U test
S.D.          = standard deviation
Distances and areas are expressed in square roots of meters. Square the values in the table to get actual values.

 

 

8.20.2.3.2 Relationships between Variable Pairs

There is very little overlap or redundancy between the site model variables, as indicated by the correlation matrix (Table 8.20.5). Only four variables have correlation coefficients greater than 0.5; a majority are less than 0.1.

 

Since oak woodland and brushlands are often adjacent, as distance to oak woodland declines, distance to brushlands also tends to decline. Likewise, sugar maple is a component of hardwood forests in the Minnesota River Valley and on the margins of the study area (Figure 8.20.1), so distance to sugar maple and distance to hardwoods are positively correlated. Further, as sites increase in relation to height above their surroundings, vertical distance to water also rises. Finally, distance to nearest perennial river or stream generally decreases as distance to nearest confluence between perennial or intermittent streams and large rivers also declines.

 

Table 8.20.5.  Variable Correlation Matrix.

Minnesota River Prairie

Distance to nearest major ridge or divide

Height above surroundings

Distance to nearest lake, wetland, organic soil, or stream

Distance to edge of nearest perennial river or stream

Distance to edge of nearest swamp

Distance to nearest intermittent stream

Distance to nearest confluence between perennial or intermittent streams and large rivers

Size of nearest lake

Vertical distance to water

                   

Distance to nearest major ridge or divide

1

               

Height above surroundings

0.02

1

             

Distance to nearest lake, wetland, organic soil, or stream

0.02

0.06

1

           

Distance to edge of nearest perennial river or stream

0.07

-0.28

0.19

1

         

Distance to edge of nearest swamp

-0.05

-0.05

0.29

0.31

1

       

Distance to nearest intermittent stream

0.05

-0.19

0.15

0.32

-0.01

1

     

Distance to nearest confluence between perennial or intermittent streams and large rivers

0.09

-0.28

-0.01

0.65

0.17

0.4

1

   

Size of nearest lake

-0.08

-0.12

-0.17

0.4

-0.06

0.22

0.33

1

 

Vertical distance to water

0.05

0.59

0.37

-0.13

0.01

0.02

-0.21

-0.12

1

Distance to brushlands

0.05

-0.14

-0.04

0.04

-0.07

0.12

0.18

-0.16

-0.08

Distance to hardwoods

-0.05

-0.28

-0.05

0.33

0.26

0.04

0.43

0.12

-0.3

Distance to oak woodland

0.02

-0.16

-0.05

0.06

-0.06

0.15

0.21

-0.15

-0.08

Distance to prairie

-0.21

0.02

-0.06

-0.03

-0.04

0.08

-0.08

0.18

-0.03

Distance to sugar maple

0.03

-0.24

-0.09

0.3

0.22

-0.02

0.47

0.16

-0.24

Vegetation diversity within 1 km

-0.05

0.09

-0.01

-0.02

-0.1

0.11

-0.17

0.19

0.1

On alluvium

-0.01

0.08

-0.05

-0.35

-0.23

-0.12

-0.37

-0.22

-0.01

On river terraces

-0.11

0.12

0.03

-0.13

0.08

-0.14

-0.17

0.02

0.02

Minnesota River Prairie

Distance to brushlands

Distance to hardwoods

Distance to oak woodland

Distance to prairie

Distance to sugar maple

Vegetation diversity within 1 km

On alluvium

On river terraces

 
                   

Distance to nearest major ridge or divide

                 

Height above surroundings

                 

Distance to nearest lake, wetland, organic soil, or stream

                 

Distance to edge of nearest perennial river or stream

                 

Distance to edge of nearest swamp

                 

Distance to nearest intermittent stream

                 

Distance to nearest confluence between perennial or intermittent streams and large rivers

                 

Size of nearest lake

                 

Vertical distance to water

                 

Distance to brushlands

1

               

Distance to hardwoods

0.22

1

             

Distance to oak woodland

0.98

0.2

1

           

Distance to prairie

-0.33

-0.27

-0.29

1

         

Distance to sugar maple

0.31

0.64

0.3

-0.14

1

       

Vegetation diversity within 1 km

-0.31

-0.41

-0.28

0.32

-0.32

1

     

On alluvium

-0.06

-0.26

-0.07

-0.01

-0.29

0.13

1

   

On river terraces

-0.13

0.1

-0.14

0.1

0.14

-0.03

-0.17

1

 

Refer to "Relationships between variable pairs" for interpretation of the table values.

 

 

8.20.2.3.3 Sites in Low Probability Areas

Sites in low potential areas (Table 8.20.4) have means on 15 variables that are near the values for random points, and two variables have values between modeled sites and random points. There are nine variables where the values for sites in low potential areas are even more different from modeled sites than are random points. Compared to modeled sites and random points, sites in low probability areas are at higher elevations, have less height above their surroundings, are farther from confluences between perennial or intermittent streams and large rivers, are closer to smaller lakes and smaller permanent lakes, are closer to water and permanent water in the vertical dimension, and are less likely to be on alluvium or river terraces.

 

Of the 156 sites not predicted by the model, two are base camps, two are kill or butchering sites, two are mortuary/cemeteries, 21 are mounds or earthworks, 11 are rock art, 39 are artifact scatters, and 79 are lithic scatters. If all site types were predicted equally well by the model, 16 percent of each site type should be in the low probability areas. Base camps come closest to this expectation, with 14.3 percent of all base camps in low probability areas. Mortuary/cemetery sites (8.3 percent), mounds/earthworks (11 percent), and artifact scatters (12.8 percent) are underrepresented in the low probability areas, implying that the model does a relatively good job predicting these types of sites. On the other hand, kill/butcher sites (50 percent), rock art (61 percent), and lithic scatters (19.9 percent) are not well-predicted by this model.

 

8.20.2.3.4 Relationships between Cultural Context, Descriptive, or Settlement Variables and Site Potential

The relatively large number of sites in the Minnesota River Prairie provides a unique opportunity to examine the distribution of sites according to site potential and archaeological context. Table 8.20.6 is a composite of nine separate tables, each listing the number and percent of sites classified according to dichotomous variables and the three areas of site potential. The significance of each relationship is given by the chi-square statistic. Two of the nine relationships are significant at the 0.05 level. Sites containing Plains Village components are relatively more common in the high potential areas than are sites lacking this component (76.6 percent vs. 57.2 percent). Conversely, they are under represented in the low and medium potential areas. Aceramic sites tend to occur in higher percentages in the low potential areas compared to ceramic-bearing ones (18.4 percent vs. 12.0 percent). Archaic sites mirror this pattern with a higher percent of site in the low potential areas compared to sites lacking Archaic components (19.6 percent vs. 12.1 percent). Oneota and Mississippian sites, on the other hand, tend to occur in lower relative frequencies in these areas than sites lacking these components (6.4 percent and 4.8 percent vs. 14.2 percent and 13.7 percent).

 

Table 8.20.6.  Summary of Bivariate Relationships between Nine Dichotomous Archaeological Variables and Three Areas of Site Potential, Minnesota River Prairie (Site Probability Model).

 

Low Potential

Medium Potential

High Potential

Total

Chi-square Test

All Sites

156

16.2

258

26.9

546

56.9

960

100.0

-

-

-

                       

Paleoindian

2

10.0

4

20.0

14

70.0

20

100.0

0.95

2

0.62

Not Paleoindian

49

13.4

101

27.6

216

59.0

366

100.0

     
                       

Archaic

11

19.6

16

28.6

29

51.8

56

100.0

2.76

2

0.25

Not Archaic

40

12.1

89

27.0

201

60.9

330

100.0

     
                       

Woodland

42

13.4

88

28.0

184

58.6

314

100.0

0.73

2

0.69

Not Woodland

9

12.5

17

23.6

46

63.9

72

100.0

     
                       

Plains Village

4

8.5

7

14.9

36

76.6

47

100.0

6.47

2

0.04

Not Plains Village

47

13.9

98

28.9

194

57.2

339

100.0

     
                       

Oneota

3

6.4

16

34.0

28

59.6

47

100.0

2.81

2

0.25

Not Oneota

48

14.2

89

26.3

202

59.6

339

100.0

     
                       

Mississippian

1

4.8

7

33.3

13

61.9

21

100.0

1.53

2

0.47

Not Mississippian

50

13.7

98

26.8

217

59.5

365

100.0

     
                       

Aceramic

117

18.4

170

26.7

349

54.9

636

100.0

6.68

2

0.04

Not Aceramic

39

12.0

88

27.2

197

60.8

324

100.0

     
                       

Single Component

43

14.7

77

26.3

173

59.0

293

100.0

2.41

2

0.30

Not Single Component

8

8.6

28

30.1

57

61.3

93

100.0

     
                       

Mounds

5

12.2

10

24.4

26

63.4

41

100.0

0.85

2

0.65

Not Mounds

151

16.4

248

27.0

520

56.6

919

100.0

     

 

 

Return to Top

 

8.20.3 Survey Probability Model

8.20.3.1 Description

The survey probability model (Figure 8.20.7) for the Minnesota River Prairie subsection indicates that environmental settings away from stream valleys and clusters of lakes have not been adequately surveyed. However, the distribution of the high and medium survey potential zones is greater than twice the amount of corresponding site potential zones.

 

As in the site probability model, the Minnesota River and its major tributaries comprise contiguous high and medium potential zones that are connected and expanded at river confluences. High survey potential zones are wider than those in the site probability model and have approximately 10-15 km average width along valleys and up to 40-60 km width near major confluences. Most tributaries of the Minnesota River, including minor creeks, are lined by zones of high and medium survey potential. These zones frequently extend further upstream than those in the site model.

 

Most surveys have been conducted on riverbanks, terraces or in close proximity to streams. There have been several linear surveys away from stream valleys, but with seemingly little effect on the survey potential level on these types of landscapes. Surveys conducted across landscapes in Chippewa, Stevens, Renville, McLeod, and Sibley Counties have a linear pattern but have little or no high or medium potential in their vicinities. The exception to this is in McLeod County.

 

Linear artifacts from the original elevation maps, known as "banding" because of their characteristic striped pattern, are very noticeable in the survey model. The affected area extends from Renville County to the eastern border of the subsection. These artifacts should not be considered as predictive features.

 

8.20.3.2 Evaluation

The survey probability model predicted surveyed places better than by chance, suggesting that surveys are not located randomly with the subsection. The model is based on 17 variables (Table 8.20.7), representing topography, vegetation, soils and hydrology.

 

Table 8.20.7. Survey Probability Model, Minnesota River Prairie Subsection.

Intercept

1.283

 

ln(nonsites/sites)

0.385647482

 

Variable

Regression Coefficient

Probability

Distance to aspen-birch

0.003135484

100

Distance to Big Woods

-0.005971312

100

Distance to edge of nearest intermittent stream

0.005286273

69.9

Distance to edge of nearest large lake

0.003842949

96.1

Distance to edge of nearest perennial river or stream

-0.008625312

100

Distance to edge of nearest swamp

-0.01768766

100

Distance to major ridge or divide

-0.007550767

100

Distance to nearest lake, wetland, organic soils, or stream

-0.02533337

100

Distance to nearest permanent lake inlet/outlet

0.004031382

98.5

Distance to paper birch

0.004821792

100

Elevation

-0.003494511

100

Height above surroundings

0.04144106

100

On river terraces

1.118862

100

Size of major watershed

0.0006115077

100

Size of nearest permanent lake

0.000187538

62.7

Vegetation diversity within 1 km

0.2414957

100

Vertical distance to permanent water

0 0.004734572

100

 

 

The model predicts 83.24 percent of all sites in high/medium survey potential areas, which make up 44.63 percent of the landscape (Table 8.20.8). This produces a weak gain statistic of 0.46384 (Table 8.6.14), which is slightly below average for a survey probability model. As lower gain statistics are considered desirable for these models, this indicates that surveys in this subsection are perhaps somewhat less biased than in other parts of the state.

 

In Minnesota River Prairie subsection, surveyed places were predicted with less precision than were sites. This indicates that sites are confined to only a portion of the total area surveyed. However, the number of sites (1035) and negative survey points (1632) in the region (Table 8.20.8) indicate a frequency of 0.085 surveys per square km. This is below average for the state.

 

Table 8.20.8. Evaluation of Survey Probability Model, Minnesota River Prairie Subsection.

 

Region (30 meter cells)

All random points

All negative survey points

All sites

All sites and negative survey points

                     

Low

19026549

54.56

2129

54.28

350

21.45

87

8.41

437

16.39

Medium

6918529

19.84

787

20.07

268

16.42

99

9.57

367

13.76

High

8643774

24.79

978

24.94

1013

62.07

840

81.16

1853

69.48

                     

Water

270840

0.78

25

0.64

1

0.06

4

0.39

4

0.15

Steep Slopes

14821

0.04

3

0.08

0

0

5

0.48

6

0.22

Mines

0

0

0

0

0

0

0

0

0

0

                     

Total

34874513

100

3922

100

1632

100

1035

100

2667

100

T

 

he database included 2667 surveyed places (Table 8.20.8). Two preliminary survey probability models had 79 percent agreement. The Kappa statistic for these models was 0.65697 (Table 8.16.14), which is higher than average. The conditional Kappa statistics (Table 8.20.9) are lowest for the medium potential zone, indicating that most instability in the model is distinguishing between this zone and the high and low site potential areas. Distributing more surveys throughout the undersurveyed areas should improve both model performance and model stability.

 

Table 8.20.9. Conditional Kappa Values for Survey Probability Model, Minnesota River Prairie.

Class

Ki

Proportion Correct

Low

0.8197

0.9189

Medium

0.3615

0.4892

High

0.7769

0.8327

 

 

8.20.3.3 Interpretation

Like the site model, the survey model (Figure 8.20.7) also consists of 17 variables. It has only eight variables in common with the site model. About half of the survey probability model variables are hydrologic in nature; the remaining are equally divided between topography and vegetation with one landform variable (on river terraces). Nine of the survey model variables have correlation coefficients above 0.3 (Table 8.20.4).

 

Places that have been surveyed are lower in elevation (Figure 8.20.9b), but higher above water (Figures 8.20.6.a and 8.20.6.b), higher than their surroundings (Figures 8.20.4.a and 8.20.9c), closer to perennial rivers or streams (Figure 8.20.10c), swamps (Figure 8.20.10d), and Big Woods (Figure 8.20.13b) compared to random points. Surveyed areas also tend to be on river terraces (Figure 8.20.15b) and in environments with greater vegetation diversity within one kilometer (Figure 8.20.4.b) than random points. Negative survey points are similar to modeled sites in their proximity to major ridges and divides (Figure 8.20.9a) and to paper birch (Figure 8.20.14a) and their greater distance from aspen-birch (Figure 8.20.12d) compared to random points. Negative survey points are more similar to random points with respect to distance to nearest permanent lake inlet/outlet (Figure 8.20.11b) and size of nearest permanent lake (Figure 8.20.12a). Their mean values are between modeled sites and random points for size of major watershed (Figure 8.20.9d), distance to edge of nearest large lake (Figure 8.20.10a), distance to nearest lake, wetland, organic soil, or stream (Figure 8.20.10b), and distance to nearest intermittent stream (Figure 8.20.11a).

 

According to the Mann-Whitney U tests (Table 8.20.4), all variables are significant at the 0.05 level, which means that surveyed areas are different enough from random points to consider the two as drawn from different populations. This provides additional evidence that surveys have been conducted in a non-random fashion in this subsection.

 

Return to Top

 

8.20.4 Survey Implementation Model

The survey implementation model for the Minnesota River Prairie indicates that 52.63 percent of the subsection is classified as unknown because of inadequate survey (Table 8.20.10 and Figure 8.20.8). These areas are found throughout the subsection away from the Minnesota River, its major tributaries, and several small clusters of lakes. Only three test sites (5.26 percent) are from the unknown area.

 

Water and wetlands occupy only about 11 percent of the unknown area. The low and possibly low site potential zones account for 26.72 percent of the subsection. More surveys away from water are needed to improve model performance and reduce the extent of the unknown area.

 

Table 8.20.10. Evaluation of Survey Implementation Model, Minnesota River Prairie Subsection.

 

Region (30 meter cells)

Random Points

Negative Survey Points

Single Artifacts

Sites

Unknown

18354730

52.63

2061

52.55

332

20.34

9

13.64

59

6.09

Possibly Low

5847799

16.77

658

16.78

227

13.91

4

6.06

51

5.26

Low

3469851

9.95

360

9.18

253

15.5

10

15.15

46

4.75

                     

Suspected Medium

659351

1.89

65

1.66

15

0.92

0

0

16

1.65

Possibly Medium

1030131

2.95

125

3.19

35

2.14

1

1.52

32

3.3

Medium

3498269

10.03

416

10.61

404

24.75

18

27.27

210

21.67

                     

Suspected High

12468

0.04

3

0.08

3

0.18

0

0

3

0.31

Possibly High

40599

0.12

4

0.1

6

0.37

1

1.52

10

1.03

High

1675654

4.8

202

5.15

356

21.81

23

34.85

533

55.01

                     

Water

270840

0.78

25

0.64

0

0

0

0

4

0.41

Steep Slopes

14821

0.04

3

0.08

1

0.06

0

0

5

0.52

Mines

0

0

0

0

0

0

0

0

0

0

                     

Total

34874513

100

3922

100

1632

100

66

100

969

100

 

 

Return to Top

 

8.20.5 Other Models

Landscape suitability models for the Minnesota River (Section 12.3), Mountain Lake Uplands (Section 12.15) and Nicollet Uplands (Section 12.16) are all within the Minnesota River Prairie Subsection. Areas of high buried site potential are found at all depths within the Minnesota River Valley. Buried site potential is present on the uplands, but is not as significant or as extensive. The landscape suitability models should be consulted for projects in the areas mapped. They are relevant for both surface and subsurface sites.


8.21 Oak Savanna
8.22 Pine Moraines & Outwash Plains
8.23 Red River Prairie
8.24 Rochester Plateau
8.25 St. Croix Moraines and Outwash Plains (Twin Cities Highlands)
8.26 St. Louis Moraines/ Tamarack Lowlands
8.27 Conclusion
        References

 

 

The Mn/Model Final Report (Phases 1-3) is available on CD-ROM. Copies may be requested by e-mail: mnmodel@state.mn.us

 

MnModel Orange Bar Logo

Acknowledgements

Mn/Model was financed by the Minnesota Department of Transportation using funds set aside by the Federal Highway Administration's Intermodal Surface Transportation Efficiency Act.

 

Copyright Notice

The Mn/Model process and the predictive models it produced are copyrighted by the Minnesota Department of Transportation (MnDOT), 2000. They may not be used without MnDOT's Consent.