U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5044

In Cooperation With the International Upper Great Lakes Study Board 

and U.S. Army Corps of Engineers

Statistical and Spatial Analysis of Bathymetric Data 

for the St. Clair River, 1971–2007
Cover Image. View of St. Clair River shoreline. (Photo by Greg Kennedy, U.S. Geological Survey).
Statistical and Spatial Analysis of 

Bathymetric Data for the St. Clair River, 

1971–2007

By David Bennion

In Cooperation With the International Upper Great Lakes Study Board 

and U.S. Army Corps of Engineers

Scientific Investigations Report 2009–5044

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Bennion, David, 2009, Statistical and spatial analysis of bathymetric data for the St. Clair River, 1971–2007: U.S. 

Geological Survey Scientific Investigations Report 2009–5044, 58 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Dataset Properties.........................................................................................................................................1

Full-River Datasets................................................................................................................................3

Upper-River Datasets...........................................................................................................................4

Data Properties Summary ...................................................................................................................4

Interpolation....................................................................................................................................................4

Interpolation Uncertainty ....................................................................................................................5

Uncertainty Summary....................................................................................................................................6

Comparative Analysis....................................................................................................................................6

Results .............................................................................................................................................................8

Changes in Volume ...............................................................................................................................8

Changes in Elevation ...........................................................................................................................8

Conclusions...................................................................................................................................................11

Acknowledgments.......................................................................................................................................11

References....................................................................................................................................................13

Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses ............14

Figures

1. Location map .................................................................................................................................2

2. Prediction standard error maps .................................................................................................7

3–5. Maps showing—

3. Regions where the sign of elevation change switches from the 2005–6 

comparison to the 2006–7 comparison ..........................................................................10

4. The “sediment tongue” elevation-gain feature in the upper St. Clair River............11

5. Areas of geomorphic change in the upper St. Clair River and associated 

river features ......................................................................................................................12

Tables

1. Statistical properties of full-river datasets...............................................................................3

2. Statistical properties of upper-river datasets..........................................................................4

3. Results of cell-size estimation according to Hu (2003)...........................................................5

4. Interpolation error statements for 1-meter DEM surfaces....................................................5

5. Statistics for 1-meter DEMs........................................................................................................6

6. Statistics summary for 1-meter DEM error...............................................................................8

7. Results of selected upper-river-area Cut/Fill analysis ...........................................................9

8. Results of selected upper-river-area Cut/Fill with analysis mask ........................................9
iv

Conversion Factors

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square meter (m2

) 0.0002471 acre 

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

cubic meter (m3

) 35.31 cubic foot (ft3)

cubic meter (m3

) 1.308 cubic yard (yd3) 

Flow rate

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

Vertical coordinate information is referenced to the International Great Lakes Datum of 1985 

(IGLD 85).
Statistical and Spatial Analysis of Bathymetric Data 

for the St. Clair River, 1971–2007

By David Bennion

Abstract

To address questions concerning ongoing geomorphic 

processes in the St. Clair River, selected bathymetric datasets spanning 36 years were analyzed. Comparisons of recent 

high-resolution datasets covering the upper river indicate a 

highly variable, active environment. Although statistical and 

spatial comparisons of the datasets show that some changes to 

the channel size and shape have taken place during the study 

period, uncertainty associated with various survey methods 

and interpolation processes limit the statistical certainty of the 

results. The methods used to spatially compare the datasets 

are sensitive to small variations in position and depth that are 

within the range of measurement and interpolation uncertainty 

associated with the datasets. Characteristics of the data, such 

as the density of measured points and the range of values 

surveyed, can also influence the results of spatial comparison. 

With due consideration of these limitations, apparently active 

and ongoing areas of elevation change in the river are mapped 

and discussed.

Introduction

The St. Clair River, Lake St. Clair, and the Detroit River 

form a waterway within the Great Lakes Basin that is part 

of the international boundary between the United States and 

Canada (fig. 1). This waterway connecting Lake Huron and 

Lake Erie is commonly referred to as the “Huron-Erie Corridor” (HEC) and is part of the St. Lawrence Seaway. The HEC 

is a major navigational and recreational resource of the Great 

Lakes Basin over which more than $80 billion in trade takes 

place each year. The St. Clair River constitutes approximately 

the northern third of the HEC; it extends about 68 km from its 

headwaters at the outlet of Lake Huron near Port Huron, Mich., 

to an extensive delta area at the northern end of Lake St. Clair. 

Throughout its length, water-surface elevations decrease 

about 1.5 m as it discharges an average of 5,154 m3

/s from a 

drainage area of about 576,013 km2. Local tributaries to the 

St. Clair River include the Black River at Port Huron, the Pine 

River at St. Clair, and the Belle River at Marine City. The St. 

Clair River channel has undergone extensive modifications 

starting in the mid-1800s. Removal of bottom sediments from 

the river for commercial gravel production and dredging for 

the construction and maintenance of the deep-draft shipping 

channels has changed the system and affected the water levels 

of Lakes Michigan and Huron (Derecki, 1985).

Past studies have quantified changes in water levels in 

Lakes Michigan-Huron on the basis of manmade changes in 

riverbed size and shape (Baird, 2005; Derecki, 1985; International Great Lakes Levels Board, 1973; Brunk, 1968; Horton 

and Grunsky, 1927). The results of these studies were based on 

examination of changes in measured water levels and modeled 

changes in water flow. The study described in this report does 

not consider these hydraulic characteristics, examining only 

changes in riverbed elevation. As presented in the framework 

of the St. Clair River Task Team, part of the International 

Upper Great Lakes Study, this study addresses primary science question 2, “Has the morphology of the St. Clair River 

changed?” and secondary science questions 9 and 12, “Can the 

project establish zones of active erosion and deposition?” and 

“Can the project explain the impact of large object sinking?” 

This study utilized six datasets spanning the years 1971 

to 2007. Because past studies have focused on the historic 

changes in the river, this study focused primarily on the recent 

datasets of riverbed elevation from 1971, 2000, 2002, 2005, 

2006, and 2007. Data for the entire river are available from 

the 1971, 2000, and 2007 datasets. The data from 2002, 2005, 

2006, and 2007 provide high-density depth measurements for 

the upper 4 km of the river, from the head to just below the 

mouth of the Black River. The statistical characteristics of 

these datasets are discussed and comparative analyses performed on the data. Further, uncertainty associated with the 

survey methods used to collect the data and uncertainty associated with the process of creating digital elevation models 

(DEMs) are examined.

Dataset Properties

It is important to consider the statistical properties of the 

datasets before engaging in comparative analysis. The range 

of surveyed values varies greatly among some of the datasets. 

Not all surveys are done with the same aim in mind, and this 
2 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Figure 1. Location map.

Figure 1. Location map. 
 3

difference in aims can influence the area surveyed, the range 

of values surveyed, and the density of measured points. Methods used to process the surveyed values to reduce them to a 

common low water datum can also affect the final water-depth 

values. In this section, the statistical properties of the datasets 

are highlighted and discussed.

In order to allow direct comparison of the water-depth 

data, all measurements have been converted to the International Great Lakes Datum 1985 (IGLD 85) vertical datum, and 

computed river-bottom elevations are based on the step-down 

planes for the river. This process is relatively simple for surveys that reference the IGLD 85. The methods used to convert 

values in the surveys that were referenced to other datums are 

explained in the discussions of the properties of the datasets. 

Full-River Datasets

Data covering the entire St. Clair River approximately 

from the head to near Algonac are available from the 1971, 

2000, and 2007 datasets. The range of surveyed values and the 

density of surveyed points vary greatly among these datasets. 

A summary of the statistical properties of the full-river datasets is given in table 1.

The original 1971 single-beam survey was provided by 

the Corps of Engineers Detroit office and obtained from the 

National Oceanic and Atmospheric Administration (NOAA) 

Geophysical Data Management System (GEODAS) Web site 

(http://www.ngdc.noaa.gov/mgg/geodas/geodas.html). These 

data were referenced to the North American Datum 1983 

(NAD 83) horizontal datum, and depths were adjusted to reference low water surface elevations on the International Great 

Lakes Datum 1955 (IGLD 55) vertical datum. The dataset 

was converted to the Michigan State Plane South (meters) 

projection. The depth values were converted to IGLD 85 by 

computing the changes in the differences of elevations of 

gaging stations between IGLD 55 and IGLD 85 for each set 

of stations. Comparison of the two datums showed an overall 

0.03048-m increase in fall, but this difference was not evenly 

distributed along the course of the river. Analysis showed a 

0.06096-m increase in fall between the Ft. Gratiot gage and 

the Dunn Paper gage. Between the mouth of the Black River 

gage and the Dry Dock gage, there was a 0.03048-m increase 

in fall. Between the St. Clair State Police gage and Algonac, there was a 0.03048-m increase in fall. Below Algonac 

through the delta, a 0.09144-m decrease in fall was calculated. 

The computed change in fall between gages was then divided 

by the number of step planes between the gages and applied 

incrementally to the measurements within each step plane. 

The 1971 dataset consists of 11,736 measurements, mostly 

along regularly spaced transects with the remaining points in 

various locations, resulting in a point density of 0.0003/m2

using an area of 38,556,363 m2 to represent the total area of 

the St. Clair River. The depth values in this dataset appear to 

have been rounded and binned together through an unknown 

process. For example, all values under 2 m are reported as 0.3 

m, 0.6 m, 0.9 m, 1.2 m, 1.5 m and 1.8 m. This trend continues 

throughout the dataset and is in stark contrast to the variability 

in values seen in more recent datasets.

The single-beam data acquired in 2000 were obtained 

directly from the National Oceanic and Atmospheric Administration (NOAA) Geophysical Data Management System 

(GEODAS) Web site (http://www.ngdc.noaa.gov/mgg/geodas/

geodas.html). The 2000 survey was referenced to NAD 83 and 

IGLD 85, and then was converted to the Michigan State Plane 

South (meters) projection. The survey is a series of transects 

with a line of data down the approximate river channel centerline. This dataset consists of 128,227 points, and, as noted 

in Baird (2005), required the removal of approximately 400 

anomalous values. A subset of the data was extracted limiting 

the coverage from the head of the river to just below Algonac, 

resulting in 52,247 points. This yields an average point density 

of 0.0014/m2

. As with the 1971 dataset, the values appear to 

have been rounded and binned. Unlike the 1971 dataset, the 

year 2000 depth values are reported to two decimal places and 

use different values for the bins: all values below 2 m are either 

0.3 m, 0 .61 m, 0.91 m, 1.22 m, 1.52 m, or 1.83 m, except 

for a single measurement at 1.93 m. The number of bins used 

between whole numbers also differs from the 1971 dataset. For 

example, between 10 m and 11 m in the 1971 dataset, values 

are 10.1 m, 10.4 m, and 10.7 m, whereas in the 2000 dataset, 

the values are 10.06 m, 10.36 m, 10.67 m, and 10.97 m.

Table 1. Statistical properties of full-river datasets.

Year Number 

of points

Depth, in meters Bottom elevation, in meters IGLD 85 Point 

density 

per square 

meter (full 

river)

Minimum Maximum Mean Standard 

deviation Skew Minimum Maximum Mean Standard 

deviation Skew

1971 11,736 0.30 22.90 8.13 3.77 -0.43 152.90 175.58 166.98 3.76 0.41 0.0003

2000 52,247 0.30 21.34 8.92 3.40 -0.44 154.33 175.03 166.17 3.40 0.40 0.0014

2007 12,999,986 1.61 24.15 9.51 2.54 0.10 151.58 173.92 165.56 2.56 -0.16 0.3372
4 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

The year 2007 multibeam dataset is the result of a 

survey by the USACE Detroit survey department. Coverage 

is from the head of the river to Algonac. The dataset contains 

12,999,986 measurements, resulting in an average point density of 0.3372/m2

. The depth values are supplied on a 1.524-m 

grid. Depth values were not rounded or binned and exhibit 

greater variability within the range of values than in the two 

previously discussed datasets.

Vertical uncertainty associated with the survey process 

for the 1971 and 2000 datasets is assumed to be ± 0.3 m 

(National Oceanic and Atmospheric Administration, 2003; 

Umbach, 1976). Minimum survey uncertainty for the 2007 

dataset is reported as ± 0.1524 m (N. Noorbakhsh, U.S. Army 

Corps of Engineers, oral commun., 2007).

Upper-River Datasets

Multibeam data collected in 2002, 2005, and 2006 are 

limited to the upper 4 km of the river. All three datasets are 

the result of surveys by the USACE Detroit survey department 

and have a reported minimum survey uncertainty of ± 0.1524 

m. All data in these sets are arranged on a 1.524-m grid. A 

summary of the statistical properties is shown in table 2. 

Subsets of the full-river datasets were extracted from the 

1971, 2000, and 2007 datasets to facilitate comparison in the 

upper-river area. The statistical properties of these subsets are 

very similar to those for the full-river versions.

Data Properties Summary

Inferences can be made about the outcome of comparative analysis based on comparison of the dataset’s statistical 

properties. It would be expected that comparison of the 1971 

data to the 2000 data would indicate overall elevation loss 

based on the mean elevation values, wider distribution of the 

1971 data (as indicated by the standard deviation), and the 

difference in minimum elevations. In addition to the uncertainty associated with the survey methods, the methods used 

to round and bin the measurement values in these two datasets 

are unknown. The effect of these uncertainties and unknowns 

cannot be quantified, but the outcome of comparative analysis 

is undoubtedly affected.

Assumptions about comparison with the 2007 dataset are 

more difficult to make. The vast difference in number of surveyed points, range of depth and elevation values, and smaller 

standard deviation make comparison of the dataset statistical 

properties difficult. The gridded distribution of the measured 

points in the 2007 dataset is significantly different from the 

transect arrangement of the 1971 and 2000 datasets. This difference is considered further in the discussion about creation 

of a DEM.

Interpolation

To allow direct comparison of the survey data, the riverbottom elevation values were used as input for an interpolation process to create a DEM surface. This process creates a 

gridded continuous surface, with each grid cell containing a 

bottom elevation value. Surveyed values are used as input, and 

various methods are applied to make educated guesses about 

elevation values where none were measured. All datasets 

except the 2007 set were interpolated by means of the ordinary 

kriging method as applied through the Geostatistical Analyst 

extension of ESRI’s ArcGIS desktop software. Selection of 

this method was based on error comparison of test interpolation areas. The Inverse Distance Weighting (IDW) method 

of interpolation within Geostatistical Analyst was selected 

for the 2007 data to reduce the increased processing time 

that otherwise would have resulted due to the size and extent 

of this dataset. In all cases, the datasets were sectioned into 

smaller reach sections and interpolated, error tested, compiled 

into a final DEM surface, and error tested again. The sectioning of data and the use of the Geostatistical Analyst extension 

allowed the size, shape, and orientation of the interpolation 

search neighborhood to be adjusted to consider the directional 

nature of a particular river reach. Through error testing, this 

method was found to yield superior results when compared 

to attempting a full-dataset interpolation. In addition, the size 

of some of the datasets precluded a full-dataset interpolation, 

owing to computer processing limitations.

All interpolated surfaces were created with a 1-m cell 

size to mirror past studies (Baird, 2005) and to include as 

much detail as possible. An important consideration when 

choosing an interpolation resolution is the density of the 

Table 2. Statistical properties of upper-river datasets.

Year Number of 

points

Depth, in meters Bottom elevation, in meters IGLD 85 Point 

density 

per square 

meter

Minimum Maximum Mean Standard 

deviation Skew Minmum Maximum Mean Standard 

deviation Skew

2002 773,021 2.49 24.08 11.46 2.74 0.82 151.65 173.24 164.21 2.70 -0.80 0.1571

2005 992,730 1.65 24.12 10.57 2.86 0.68 151.61 173.93 165.07 2.84 -0.65 0.2018

2006 989,502 1.30 24.16 10.59 2.87 0.65 151.57 174.28 165.06 2.85 -0.62 0.2011
 5

original dataset. For an ideal resolution, the number of grid 

cells should equal the number of measured points (McCullagh, 

1988). As stated in Liu and others (2007), “It is inappropriate 

to generate a high-resolution Digital Elevation Model (DEM) 

with very sparse terrain data: any surface so generated is more 

likely to represent the shape of the specific interpolator used 

than that of the target terrain because interpolation artifacts 

will abound.” Further, to thin a high-density dataset to a larger 

cell size will devalue the accuracy of the data and negatively 

influence comparison results. A DEM grid size estimator proposed by Hu (2003) uses the equation 

DEM cell size = square root (area / # of points). 

The results of the application of this equation (using the standardized areas used to compute point density) to each of the datasets 

used in this study are shown in table 3. From these calculations, it 

is evident that the 1971 and 2000 datasets do not have the needed 

point density to be reliably interpolated to a 1-m cell size. 

Interpolation Uncertainty

Assessment of the error associated with the interpolation 

process is essential to maintain an understanding of the uncertainty in the comparative analysis. To facilitate error analysis 

in this study, the bottom-elevation datasets for each section 

of river were subset into training and test sets through the 

use of the “Create Subsets” tool in the ArcGIS Geostatistical 

Analyst extension. The test sets consisted of a random sample 

of 10 percent of the original dataset that were withheld from 

the interpolation process. A measure of accuracy was attached 

to each DEM by means of the 95th-percentile method. This 

Table 3. Results of cell-size estimation according to Hu (2003).

Year Cell size, in square meters

Full-river area Upper-river area

1971 57.32 54.37

2000 27.14 29.19

2002 n/a 2.52

2005 n/a 2.23

2006 n/a 2.23

2007 1.72 1.98

methodology adheres to current National Standard for Spatial 

Data Accuracy (NSSDA), U.S. Geological Survey (USGS), 

and Federal Emergency Management Agency (FEMA) 

standards for DEM creation. The method provides a means 

of examining the error datasets for statistical outliers, allowing the best 95-percent of the points in the error dataset to be 

used for quantifying the vertical accuracy of the interpolated 

surface. The standard deviation of the error datasets is computed and then multiplied by 3 to obtain a 3 sigma value. The 

absolute values of the errors are ranked in descending order, 

and if none of the errors are outliers larger than the 3 sigma 

value, accuracy at the 95th percentile may be stated as 1.96 * 

Root-Mean-Square error (RMSE ) because the data are close 

to normal distribution. If data meet this requirement, accuracy 

is stated as “Tested xx (units) vertical accuracy at 95-percent 

confidence level using RMSE procedures with no outliers.” 

If the error datasets do not meet the requirement of normal 

distribution, a further step of percentile ranking the errors and 

excluding all errors above the 95th percentile is employed. 

The standard deviation is then recomputed and a new 3 sigma 

value obtained. The ranked errors are then examined to see 

whether they exceed the new 3 sigma value. If no error values 

exceed this threshold, accuracy is reported by completing the 

statement “Tested xx (units) vertical accuracy at 95-percent 

confidence level, determined by the 95th-percentile method.” 

The phrase “compiled to meet” is used in place of “tested” 

when an independent source of quality control data of higher 

accuracy is not available for error analysis, as is the case with 

the data in this study. The accuracy value is determined by the 

error value at the 95th-percent ranking. If points in the dataset exceed the recomputed 3 sigma value, the process may be 

repeated for the 90th percentile (Daniel and Tennant, 2001). 

For this study, outputs that did not meet the 95-percent requirements were not tested further but were discarded, and the data 

were reinterpolated until the 95-percent standard was met. 

The skew coefficient is used as an indicator of deviation from 

a normal distribution in the error dataset. FEMA guidelines 

advise that the absolute value of the skewness should not be 

larger than 0.5 to ensure a near-normal distribution of the errors 

at 95 percent (Maune and others, 2001). The interpolation error 

statements for the data used in this study appear in table 4. It is 

important to consider that the test points were withheld from the 

original data, precluding any error analysis outside the extent of 

the original dataset or in areas between measured points. 

Table 4. Interpolation error statements for 1-meter DEM surfaces.

Year Interpolation error statement

1971 Compiled to meet 1.7-meter vertical accuracy at 95-percent confidence level

2000 Compiled to meet 0.7-meter vertical accuracy at 95-percent confidence level

2002 Compiled to meet 0.2-meter vertical accuracy at 95-percent confidence level

2005 Compiled to meet 0.2-meter vertical accuracy at 95-percent confidence level

2006 Compiled to meet 0.3-meter vertical accuracy at 95-percent confidence level

2007 Compiled to meet 0.3-meter vertical accuracy at 95-percent confidence level
6 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

In addition to the 95th-percentile method outlined, 

several other statistics were considered when assessing DEM 

accuracy. The root-mean-square error was examined as a comparative tool. Attempts were made to keep the mean prediction 

error and mean standardized prediction error close to zero. A 

close relation of the mean standard error value to the rootmean-square error value indicates that bias is low. This assessment of prediction variability can be confirmed by inspecting 

the root-mean-squared standardized error for its closeness to 

1. Mean error, mean absolute error, minimum and maximum 

error, and the standard deviation of the error set also are used 

to assess the fitness of the interpolation procedure. A summary 

of select DEM statistics is given in table 5.

As an additional assessment of interpolator fitness, maps 

of the kriging prediction standard errors were created when 

possible. This indicator of error is generated as part of the 

kriging interpolation process. It is a unitless value with an 

ideal of zero that represents how good an estimation the interpolation process is likely to make at a given location. This tool 

is useful when assessing potential interpolation error outside 

of or in between the measured points. The images in figure 2 

are representative excerpts from the 1971, 2000, 2002, 2005, 

and 2006 prediction standard error maps. They clearly show 

that interpolator accuracy diminishes quickly as distance away 

from a measured point increases. Also indicated is the relation 

of point density to interpolator accuracy. In comparing the 

images of the 1971 and 2000 prediction standard errors with 

the 2002–6 images, a much greater distance from the ideal 

value of zero is evident among the measured data points in the 

less dense datasets. 

Uncertainty Summary

The total statistical uncertainty associated with a dataset is plus and minus the sum of the survey and interpolation 

error. Which value to choose to represent interpolator error 

is flexible, but the choice must be applied consistently to all 

datasets. As expected, the high-density datasets are associated 

with significantly lower interpolation uncertainty. The survey 

uncertainty values for the NOAA and USACE survey represent minimum estimated values. A summary of error statistics 

is shown in table 6. 

Comparative Analysis

Two main types of comparisons were done among the 

various datasets. Change in elevation of the river bottom and 

change in volume of the river channel were both examined. 

Comparisons were done between all available datasets rather 

than restricting the output to a time-series analysis. Uncertainty was then assessed and accounted for in presenting the 

results of the comparison. 

Volumetric-change analysis was examined through the 

use of the Cut/Fill tool as part of ESRI’s Spatial Analyst extension. This type of analysis is very sensitive to small changes in 

elevation values and extent. It is imperative that the comparison area be limited to the smallest combined spatial extent of 

the employed datasets to ensure the most statistically certain 

results. An upper-river standard extent and full-river standard 

extent that fit this requirement were used for all comparisons. 

Uncertainty can have a significant influence on the overall 

results of the analysis. The equation that is used to calculate 

the volumetric change at each set of grid cells is 

Cell Volume = Cell Area * (Zbefore – Zafter). 

Total potential Cut/Fill error is represented by the equation

 Cell Count * Cell Area * (Ebefore – Eafter), 

where Ebefore and Eafter are the total error values of each 

dataset. Cell Count is the number of cells in the analysis extent 

and therefore the number of times the potential error could 

be repeated. A very optimistic example is comparison of the 

high-density datasets from 2005 and 2006, assuming that 

combined survey error results are zero. If the mean absolute 

error of the interpolation errors is selected as an estimation of 

interpolation error, then total error is reported as ± 0.08 m for 

each dataset. The standardized upper-river comparison extent 

has an area of 1,578,716 m2

, and the DEM files use a 1-m grid 

size. Potential error is then represented by 1,578,716 * 1 * 

(0.08 – –0.08) or 252,595 m3

. This value represents maximum 

error in the respect that the error values are assumed to be 

oppositely signed throughout both datasets. In order to minimize this rather large impact on results, the Cut/Fill DEM was 

Table 5. Statistics for 1-meter DEMs.

Year

Bottom elevation, in meters IGLD 85 Error, in meters

Minimum Maximum Mean Mean Minimum Maximum Mean 

absolute

Standard 

deviation 

1971 152.86 178.44 167.26 -0.01 -4.83 7.89 0.53 0.85

2000 154.34 176.75 166.85 -0.0069 -4.1 2.69 0.21 0.33

2002 151.65 173.49 164.92 -0.0034 -1.98 1.99 0.05 0.08

2005 151.62 173.78 166.40 -0.0082 -2.04 2.68 0.08 0.13

2006 151.59 174.27 165.59 -0.0062 -3.04 2.44 0.08 0.15

2007 151.61 175.66 166.74 -0.0076 -3.29 3.22 0.08 0.14
 7

Figure 2. Prediction standard error maps for the Upper St. Clair River. The same classification is used on each image. Lower values 

indicate less predicted interpolation error.

1971 2000 2002

2005 2006
8 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

compared to an elevation-change DEM, and the Cut/Fill areas 

that coincided with areas where elevation change was statistically indicated were extracted. This method effectively limited 

volumetric comparison to areas where bathymetric change 

was statistically certain. The elevation comparison was a less 

complicated process. Three types of comparisons were used 

where appropriate. In comparing the high-density upper-river 

datasets, the interpolated DEM surfaces were used. In comparing the full-river datasets, elevation values were extracted 

from the 2007 DEM to the measured points in the 1971 and 

2000 datasets. This was done to exclude the high interpolation 

error associated with the lower density datasets, which must 

be considered in DEM or cross-sectional comparisons. The 

third comparison method was a direct point-to-point comparison of the 0.0696-m gridded 2005, 2006, and 2007 data. These 

three datasets contain an area of approximately 1,900,000 

points that directly coincide in xy location. No interpolation is 

needed, and therefore, no interpolation error was considered 

in analyzing uncertainty. These comparisons yield the smallest 

range of uncertainty and the most statistically accurate indication of geomorphic change in a limited area of the upper river. 

Results

Changes in Volume

None of the results of overall volumetric analysis 

exceeded the error threshold and therefore are statistically 

uncertain. This threshold was calculated using potential 

survey error and the mean absolute interpolation error. The 

1,578,716-m2 upper-river analysis area limits the extent to 

areas of data overlap. Table 7 shows the results of analysis of 

this area. An analysis mask was created and applied, limiting 

comparison areas. This process resulted in comparison areas 

of varying sizes based on excluding regions where elevation 

change between the two datasets was statistically uncertain. 

The results of these analyses are shown in table 8. It should 

be noted that the overall magnitude of volumetric change 

indicated by the masked analyses is still subject to variation 

within the error range. The mean change per year without the 

analysis mask is 1,955 m3

 of volume loss; with the analysis 

masks applied, the mean becomes 2,759 m3 of volume gain. 

If the results are limited to the high-density datasets of 2002, 

2005, 2006 and 2007, the mean is 14,820 m3 of volume gain; 

with the analysis masks applied, the mean is 2,610 m3 of volume loss. No clear pattern emerges from the data. Identifying 

trends is further complicated by the large variations in average 

per year cut, average per year fill, and average overall per year 

change. The large amounts of volume gain indicated in the 

comparisons to the 1971 data can be partially explained by 

the difference in range of surveyed values. This large gain is 

expected also in comparisons with the 2000 dataset but is not 

reflected in the results. The significant difference in minimum 

elevation of the 2000 dataset when compared to other datasets influences the prediction of large-scale volume loss. Even 

in the high-density datasets, areas of volume gain were seen 

to switch to areas of volume loss within a year, highlighting 

the very small tolerances for error in this type of analysis. 

When the map images of these results are visually inspected, 

certain areas do consistently indicate ongoing processes. These 

images are shown in Appendix 1, figures 1–15.

Changes in Elevation 

Comparison of elevation changes does not allow a 

quantification of overall change in volume, but it can indicate 

location, magnitude, and trends of elevation differences. The 

analysis extent was slightly limited along the nearshore areas 

for this method to allow inspection of areas where overlap 

may exist among some, but not all, datasets and to account for 

the exclusion of nearshore data in the high-resolution datasets. 

Where available, data were analyzed along the entire river 

from the head to Algonac. The results were examined with 

prior knowledge of dataset extents and statistical properties to 

yield meaningful results. Results of three types of comparison 

Table 6. Statistics summary for 1-meter DEM error. 

Year

Bottom elevation, in meters 

IGLD 85 Error, in meters

Minmum MaximumMean

At 

95 

pecent

Mean Minmum Maximum

Mean 

absolute

Standard 

deviation

Root 

mean 

square 

Survey 

1971 152.86 178.44 167.26 1.70 -0.0100 -4.83 7.89 0.53 0.8500 0.854 0.3000

2000 154.34 176.75 166.85 0.70 -0.0069 -4.10 2.69 0.21 0.3300 0.334 0.3000

2002 151.65 173.49 164.92 0.20 -0.0034 -1.98 1.99 0.05 0.0790 0.079 0.1524

2005 151.62 173.78 166.40 0.20 -0.0082 -2.04 2.68 0.08 0.1300 0.141 0.1524

2006 151.59 174.27 165.59 0.30 -0.0062 -3.04 2.44 0.08 0.1500 0.148 0.1524

2007 151.61 175.66 166.74 0.30 -0.0076 -3.29 3.22 0.08 0.1400 0.189 0.1524
 9

Table 7. Results of select upper-river-area Cut/Fill analysis.

[m3, cubic meters]

Before 

year After year Amount fill (m3

)

Amount cut 

(m3)

Overall change 

(m3

) (negative = 

volume loss)

Average 

change per 

year (m3

)

Average per 

year fill 

(m3)

Average per 

year cut (m3

)

Error threshold

1971 2000 514,496 1,495,656 981,160 33,833 17,741 51,574 2,115,479

2000 2002 490,472 227,950 -262,522 -131,261 245,236 113,975 1,120,888

2002 2005 94,044 130,436 36,392 12,131 31,348 43,479 678,848

2005 2006 112,869 112,178 -691 -691 112,869 112,178 726,209

2006 2007 65,002 94,256 29,254 29,254 65,002 94,256 726,209

1971 2002 649,740 1,346,630 696,890 22,480 20,959 43,440 1,626,077

1971 2005 671,423 1,359,164 687,741 20,228 19,748 39,975 1,673,439

1971 2006 690,092 1,383,217 693,125 19,804 19,717 39,520 1,673,439

1971 2007 685,407 1,413,303 727,896 20,219 19,039 39,258 1,673,439

2000 2005 472,890 246,762 -226,128 -45,226 94,578 49,352 1,168,250

2000 2006 471,647 253,592 -218,055 -36,343 78,608 42,265 1,168,250

2000 2007 452,252 263,454 -188,798 -26,971 64,607 37,636 1,168,250

2002 2006 110,542 146,242 35,700 8,925 27,636 36,561 678,848

2002 2007 84,080 157,802 73,722 14,744 16,816 31,560 678,848

2005 2007 96,330 133,658 37,328 18,664 48,165 66,829 726,209

Table 8. Results of select upper-river-area Cut/Fill with analysis mask.

[m3, cubic meters]

Before year After 

year

Total area 

(m2

)

Amount fill 

(m3)

Amount cut 

(m3)

Overall 

change (m3

) 

(negative = 

volume loss )

Average 

change 

per year 

(m3

)

Per year fill 

(m3

)

Per year cut 

(m3)

1971 2000 505,477 365,470 955,394 589,924 20,342 12,602 32,945

2000 2002 246,617 199,020 163,226 -35,794 -17,897 99,510 81,613

2002 2005 62,313 24,658 34,659 10,001 3,334 8,219 11,553

2005 2006 53,680 32,454 20,763 -11,691 -11,691 32,454 20,763

2006 2007 23,961 14,306 14,037 -269 -269 14,306 14,037

1971 2002 609,864 512,066 1,013,481 501,415 16,175 16,518 32,693

1971 2005 600,842 525,428 1,019,141 493,713 14,521 15,454 29,975

1971 2006 618,988 552,162 1,038,407 486,245 13,893 15,776 29,669

1971 2007 630,345 548,970 1,067,581 518,611 14,406 15,249 29,655

2000 2005 230,072 184,227 164,003 -20,224 -4,045 36,845 32,801

2000 2006 235,879 200,010 160,306 -39,704 -6,617 33,335 26,718

2000 2007 232,087 197,356 156,319 -41,037 -5,862 28,194 22,331

2002 2006 65,722 33,863 31,444 -2,419 -605 8,466 7,861

2002 2007 89,925 32,602 43,156 10,554 2,111 6,520 8,631

2005 2007 55,996 34,604 17,520 -17,084 -8,542 17,302 8,760
10 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

are offered here. DEM-to-DEM, point-to-DEM, and direct 

point-to-point comparisons were made where appropriate, and 

resulting location and magnitude patterns were examined. 

DEM-to-DEM comparisons were made by subtracting 

the coincident values of the later DEM from the values of the 

earlier DEM. From this equation, positive values indicate elevation gain, and negative values indicate elevation loss. These 

comparisons were made for the upper river from approximately the Ft. Gratiot gage to the Black River. The amount of 

uncertainty associated with the interpolation of the 1971 and 

2000 datasets precludes these datasets from producing statistically meaningful results from this type of analysis along the 

full river course. In place of DEM-to-DEM and cross-section 

comparison, the 1971 and 2000 dataset points were compared 

with the 2007 DEM data. This eliminated the need to consider 

interpolation uncertainty associated with the 1971 and 2000 

DEM datasets and minimized overall uncertainty. The pointto-point comparisons of the 0.0696-m-spaced 2005, 2006, and 

2007 datasets yielded the smallest range of uncertainty and the 

most statistically accurate indication of geomorphic change in 

a limited area of the upper river. 

 The DEM-to-DEM comparison images are shown in 

Appendix 1, figures 16–30. A generally consistent pattern of 

limited elevation loss and elevation gain areas can be seen in 

the high-density data for the upper river. Although the areas 

of change seem rather constant, certain areas switch from 

elevation gain to elevation loss within the analysis timeframes. 

In examining the 2002 to 2005 analysis (Appendix 1, fig. 

25) and the 2005 to 2007 analysis (Appendix 1, fig. 29), an 

example of this switching is apparent. In the upper northeast 

corner of the analysis area (outlined in white) on the 2002 to 

2005 image, one can see a large swath of elevation gain area 

with an elevation-loss area below. When these same areas are 

inspected on the 2005 to 2007 image, this pattern is reversed, 

indicating a large elevation loss area with an elevation-gain 

area below. These changes indicate that a highly variable 

process is at work in the upper river, that an unknown bias 

exists in the survey data, or that uncertainty in the survey data 

was underestimated. All comparisons with the 1971 dataset 

indicated large areas of elevation gain and elevation loss. 

These areas became much more limited in comparisons with 

the 2000 dataset. This pattern would indicate that the ongoing process in these areas changed around 2000 from mainly 

elevation loss to a mainly elevation gain. This is supported 

by comparison of the volumetric analysis per-year-change 

amounts (tables 7 and 8) and the comparisons of the 1971 and 

2000 point data to the 2007 DEM. 

The point-to-DEM comparison shows widespread elevation loss from 1971 to 2007 (Appendix 1, figs. 31, 32, 33). 

This trend is largely reversed in the 2000 to 2007 comparison 

(Appendix 1 fig. 34, 35, 36). It is expected to some extent to 

see indications of elevation loss close to the nearshore areas 

Figure 3. Region (highlighted with the red line) where the sign of elevation change switches 

from the 2005–2006 comparison to the 2006–2007 comparison. Blues and black indicate elevation loss, and yellows, 

orange and red indicate elevation gain. 

Figure 3. Region (highlighted with the red line) where the sign of elevation change switches from the 2005–6 

comparison to the 2006–7 comparison. Blues and black indicate elevation loss, and yellows, orange and red 

indicate elevation gain.
 11

 Figure 4. The “sediment tongue” elevation-gain feature in the upper St. Clair River.

in both comparisons due to the differences in the range of 

surveyed values. Areas that were consistently indicated as 

elevation loss such as the head of Fawn Island, the shoals at 

St. Clair, and the head and tail of Stag Island were areas of no 

data coverage in the 2007 dataset. An area of consistent elevation gain was indicated in the upper river along the east shore 

between the Blue Water Bridge and Point Edward. 

The very high density point-to-point comparisons indicated that dynamic processes were at work in the upper river. 

Again, areas were found that changed from elevation loss to 

elevation gain from year to year. These areas tended to be 

associated with high change values, indicating close to 1 m of 

elevation loss one year and close to 1 m of elevation gain the 

next (Appendix 1, figs. 37 and 39) These areas are highlighted 

in figure 3 (on preceding page). Within these comparisons, 

and supported by most other comparisons made for this study, 

a “sediment tongue” (fig. 4) can be seen progressing through 

the system with a trailing area of variable elevation loss and 

elevation gain. Also consistently indicated in these analyses 

and supported by other comparisons is the general pattern of 

elevation loss and elevation gain within the flow-recirculation 

zone along the eastern shore of the upper river. 

Conclusions

The accuracy of available data was not great enough to 

reliably detect widespread geomorphic change throughout 

the St. Clair River at the scale required. The issue of how 

data values were rounded and binned in the 1971 and 2000 

datasets and the differences in the density, location, and range 

of surveyed values contribute to the uncertainty. Even among 

the high-density datasets, the processes that are indicated 

are unusual or are a result of an unknown error in one of the 

employed datasets. Because minimum estimations of error 

were used, refining the error values could be expected to further restrict the amount of area available for analysis, leaving 

fewer areas of statistical certainty. None of the results from 

volumetric analysis exceeded the error threshold associated 

with the dataset comparisons. Because of this, volumetricanalysis results should be used only qualitatively and not as 

firm measurement of change. To continue to monitor geomorphic change in the river, high-resolution survey datasets, like 

the 2007 dataset, will be required in the future. 

Comparisons of the datasets did provide indication of 

geomorphic processes at work. The analyses of the comparison results discussed herein indicated highly variable areas of 

elevation loss and elevation gain. Figure 5 highlights areas of 

the upper river where change was consistently indicated and 

illustrates the proximity of these areas to other river features. 

Visual inspection confirms a spatial relationship between areas 

of change and sunken large objects. Bottom materials appear 

to be moving in the system, although whether this is due to 

direct action of the river or other forces such as propeller wash 

from passing freighters or gouging from ice jams is unknown. 

The analyses of the area of the “sediment tongue” showed an 

advancing elevation gain feature. 

Acknowledgments

This study was supported by the International Upper 

Great Lakes Study Board and U.S. Army Corps of Engineers. 

The author wishes to acknowledge the assistance of Bruce 

Manny, Sandy Morrison, Christine Schmuckal, Greg Kennedy and Kurt Kowalski from the USGS Great Lakes Science 

Center; Jim Nicholas from the USGS Michigan Water Science 

Center; Mike Eberle from the USGS Columbus Publishing 

Service Center; Nanette Noorbakhsh, Eric Tauriaine, and Tony 

Eberhardt from the U.S. Army Corps of Engineers; Jacob 

Bruxer and Aaron Thompson from Environment Canada; 

Christine Geddes from Great Lakes GIS; and Syed Moin from 

the International Joint Commission. This report is Contribution 1515 of the USGS Great Lakes Science Center.

Figure 4. The “sediment tongue” elevation-gain feature in the 

upper St. Clair River.
12 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Figure 5. Areas of geomorphic change in the upper St. Clair River and associated 

 river features. 

Figure 5. Areas of geomorphic change in the upper St. Clair River and associated river features. 
 13

References

Baird, W.F., & Associates Coastal Engineers Ltd., 2005, 

Regime change (man made intervention) and ongoing erosion in the St. Clair River and impacts on Lake MichiganHuron lake levels: Oakville, Ontario, prepared for the 

Georgian Bay Association Foundation [variously paged].

Brunk, I.W., 1968, Evaluation of channel changes in St. Clair 

and Detroit Rivers: Water Resources Research, v. 4, no. 6, 

p. 1335–1346.

Daniel, C., and Tennant, K., 2001, DEM quality assessment, 

in Maune, D.F., ed., Digital elevation model technologies 

and applications—The DEM users manual: Bethesda, Md., 

American Society for Photogrammetry and Remote 

Sensing, chap. 12, p. 395–440.

Derecki, J.A., 1985, Effect of channel changes in the St. Clair 

River during the present century: Journal of Great lakes 

Research, v. 11, no. 3, p. 201–207.

Horton, R., and Grunsky, C., 1927, Hydrology of the Great 

Lakes: Report of the Engineering Board of Review of the 

Sanitary District of Chicago on the lowering controversy 

and a program of remedial measures, part III, Appendix II.

Hu, Yong, 2003, Automated extraction of digital terrain 

models, roads and buildings using airborne LiDAR data: 

University of Calgary, Canada, Department of Geomatics 

Engineering, UCGE report 20187 (Ph.D. thesis), 206 p.

International Great Lakes Levels Board, 1973, Regulation of 

Great Lakes water levels: Report to the International Joint 

Commission, International Levels Board, p. 43–49.

Liu, X., Zhang, Z., Peterson, J., and Chandra, S., 2007, The 

effect of LiDAR data density on DEM accuracy, in

MODSIM07 International Congress on Modelling and 

Simulation, December 10–13, 2007, Christchurch, New 

Zealand: [Proceedings] p. 1363–1369.

Maune, D., Maitra, J., and McKay, E., 2001, Accuracy standards, in Maune, D.F., ed., Digital elevation model technologies and applications—The DEM users manual: American 

Society for Photogrammetry and Remote Sensing, chap. 3, 

p. 61–82.

McCullagh, M.J., 1988, Terrain and surface modelling systems—Theory and practice: Photogrammetric Record, v. 12, 

no. 72, p. 747–779.

National Oceanic and Atmospheric Administration, 2003, 

National Ocean Service, hydrographic surveys specifications and deliverables: Silver Spring, Md.

Umbach, M.J., 1976, Hydrographic manual (4th ed.): U.S. 

Department of Commerce, National Oceanic and Atmospheric Administration [variously paged].
14 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Appendix 1. Images Showing Results From Volumetricand Elevation-Change Analyses

Figures 

1–1 through 1–15. Volumetric-change analysis of the upper St. Clair River, with uncertainty 

removed:

1–1. 1971–2000.........................................................................................................................................16

1–2. 1971–2002.........................................................................................................................................17

1–3. 1971–2005.........................................................................................................................................18

1–4. 1971–2006.........................................................................................................................................19

1–5. 1971–2007.........................................................................................................................................20

1–6. 2000–2002.........................................................................................................................................21

1–7. 2000–2005.........................................................................................................................................22

1–8. 2000–2006.........................................................................................................................................23

1–9. 2000–2007.........................................................................................................................................24

1–10. 2002–5...............................................................................................................................................25

1–11. 2002–6...............................................................................................................................................26

1–12. 2002–7...............................................................................................................................................27

1–13. 2005–6...............................................................................................................................................28

1–14. 2005–7...............................................................................................................................................29

1–15. 2006–7...............................................................................................................................................30

1–16. through 1–30. DEM file comparison indicating change in riverbed elevation in the 

upper St. Clair River, with uncertainty removed:

1-16. 1971–2000.........................................................................................................................................31

1–17. 1971–2002.........................................................................................................................................32

1–18. 1971–2005.........................................................................................................................................33

1–19. 1971–2006.........................................................................................................................................34

1–20. 1971–2007.........................................................................................................................................35

1–21. 2000–2002.........................................................................................................................................36

1–22. 2000–2005.........................................................................................................................................37

1–23. 2000–2006.........................................................................................................................................38

1–24. 2000–2007.........................................................................................................................................39

1–25. 2002–5...............................................................................................................................................40
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 15

1–26. 2002–6...............................................................................................................................................41

1–27. 2002–7...............................................................................................................................................42

1–28. 2005–6...............................................................................................................................................43

1–29. 2005–7...............................................................................................................................................44

1–30. 2006–7...............................................................................................................................................45

1–31. 1971 point bathymetry compared to 2007 DEM data in the upper St. Clair River, 

with uncertainty removed .........................................................................................................46

1–32. 1971 point bathymetry compared to 2007 DEM data in the middle St. Clair River, 

with uncertainty removed .........................................................................................................47

1–33. 1971 point bathymetry compared to 2007 DEM data in the lower St. Clair River, 

with uncertainty removed .........................................................................................................48

1–34. 2000 point bathymetry compared to 2007 DEM data in the upper St. Clair River, 

with uncertainty removed .........................................................................................................49

1–35. 2000 point bathymetry compared to 2007 DEM data in the middle St. Clair River, 

with uncertainty removed .........................................................................................................50

1–36. 2000 point bathymetry compared to 2007 DEM data in the lower St. Clair River, 

with uncertainty removed .........................................................................................................51

1–37. 2005–6 high-density point-to-point comparison of elevation change in the 

upper St. Clair River, with uncertainty removed....................................................................52

1–38. 2005–7 high-density point-to-point comparison of elevation change in the 

upper St. Clair River, with uncertainty removed....................................................................53

1–39. 2006–7 high-density point-to-point comparison of elevation change in the 

upper St. Clair River, with uncertainty removed....................................................................54

1–40. Area (outlined in red) where elevation changes dramatically in the 2006–7 

comparison (fig. 1–41)................................................................................................................55

1–41. Area (outlined in red) where elevation changes dramatically from the 2005–6 

comparison (fig. 1–40)................................................................................................................56

1–42. Area highlight of the “sediment tongue” elevation-gain feature in the 

upper St. Clair River....................................................................................................................57

1–43. Areas of high geomorphic activity in the upper St. Clair River and spatial relation

to selected river features ..........................................................................................................58
16 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Explanation

Elevation Loss

Elevation Gain

Figure 1–1. Volumetric change analysis of the upper St. Clair River 1971–2000, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 17

Explanation

Elevation Loss

Elevation Gain

Figure 1–2. Volumetric change analysis of the upper St. Clair River 1971–2002, with uncertainty removed.
18 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Explanation

Elevation Loss

Elevation Gain

Figure 1–3. Volumetric change analysis of the upper St. Clair River 1971–2005, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 19

Explanation

Elevation Loss

Elevation Gain

Figure 1–4. Volumetric change analysis of the upper St. Clair River 1971–2006, with uncertainty removed.
20 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Explanation

Elevation Loss

Elevation Gain

Figure 1–5. Volumetric change analysis of the upper St. Clair River 1971–2007, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 21

6

 Figure 1–6. Volumetric-change analysis of the upper St. Clair River, 2000–2002, with uncertainty removed.
22 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

7

 Figure 1–7. Volumetric-change analysis of the upper St. Clair River, 2000–2005, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 23

8

Figure 1–8. Volumetric-change analysis of the upper St. Clair River, 2000–2006, with uncertainty removed.
24 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

9

Figure 1–9. Volumetric-change analysis of the upper St. Clair River, 2000–2007, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 25

10

Figure 1–10. Volumetric-change analysis of the upper St. Clair River, 2002–5, with uncertainty removed.
26 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

11

Figure 1–11. Volumetric-change analysis of the upper St. Clair River, 2002–6, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 27

12

Figure 1–12. Volumetric-change analysis of the upper St. Clair River, 2002–7, with uncertainty removed.
28 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

13

Figure 1–13. Volumetric-change analysis of the upper St. Clair River, 2005–6, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 29

14

Figure 1-14. Volumetric-change analysis of the upper St. Clair River, 2005–7, with uncertainty removed.
30 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

15

Figure 1-15. Volumetric change analysis of the upper St. Clair River, 2006–7, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 31

Figure 1−16. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

1971–2000, with uncertainty removed.
32 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Figure 1−17. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

1971–2002, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 33

Figure 1−18. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

1971–2005, with uncertainty removed.
34 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

Figure 1−19. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

1971–2006, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 35

Figure 1−20. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

1971–2007, with uncertainty removed.
36 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

21

Figure 1–21. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2000–2002, with uncertainty removed. 
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 37

22

Figure 1–22. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2000–2005, with uncertainty removed. 
38 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

23

Figure 1–23. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2000–2006, with uncertainty removed. 
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 39

24

Figure 1–24. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2000–2007, with uncertainty removed. 
40 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

25

Figure 1-25. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2002–5, with uncertainty removed. 
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 41

26

Figure 1-26. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2002–6, with uncertainty removed. 
42 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

27

Figure 1-27. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2002–7, with uncertainty removed. 
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 43

28

Figure 1-28. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2005–6, with uncertainty removed. 
44 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

29

Figure 1-29. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2005–7, with uncertainty removed. 
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 45

30

Figure 1–30. DEM file comparison indicating change in riverbed elevation in the upper St. Clair River, 

2006–7, with uncertainty removed. 
46 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

31

Figure 1-31. 1971 point bathymetry compared to 2007 DEM data in the upper St. Clair River, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 47

32

Figure 1–32. 1971 point bathymetry compared to 2007 DEM data in the middle St. Clair River, with uncertainty removed.
48 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

33

Figure 1–33. 1971 point bathymetry compared to 2007 DEM data in the lower St. Clair River, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 49

34

Figure 1–34. 2000 point bathymetry compared to 2007 DEM data in the upper St. Clair River, with uncertainty removed.
50 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

35

Figure 1–35. 2000 point bathymetry compared to 2007 DEM data in the middle St. Clair River, with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 51

36

Figure 1–36. 2000 point bathymetry compared to 2007 DEM data in the lower St. Clair River, with uncertainty removed.
52 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

37

Figure 1–37. 2005–6 high-density point-to-point comparison of elevation change in the upper St. Clair River, 

with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 53

38

Figure 1–38. 2005–7 high-density point-to-point comparison of elevation change in the upper St. Clair River, 

with uncertainty removed. 
54 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

39

Figure 1–39. 2006–7 high-density point-to-point comparison of elevation change in the upper St. Clair River, 

with uncertainty removed.
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 55

40

Figure 1–40. Area (outlined in red) where elevation changes dramatically from the 2006–7 comparison (fig. 1–41). 
56 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

41

Figure 1–41. Area (outlined in red) where elevation changes dramatically from the 2005–6 comparison (fig. 1–40).
Appendix 1. Images Showing Results From Volumetric- and Elevation-Change Analyses 57

42

Figure 1–42. Area highlight of the “sediment tongue” elevation-gain feature in the upper St. Clair River.
58 Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007

43

Figure 1–43. Areas of high geomorphic activity in the upper St. Clair River and spatial relation to selected river 

features. 
Bennion—Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971–2007—Scientific Investigations Report 2009–5044