Measuring Knickpoint Migration in Z, Seven

Mile Creek Park, Nicollet County, MN

By

Michael Dickens

A thesis submitted in partial fulfillment of the requirements of the

degree of Bachelor of Arts

(Geology)

at

Gustavus Adolphus College

2015 Measuring Knickpoint Migration in Ravine Z, Seven

Mile Creek Park, Nicollet County, MN

By Michael Dickens Under the supervision of Laura Triplett

Abstract

The Minnesota is facing increasing loads, which are a result of sediment in the watershed. Likely sources for that sediment include upland topsoil, incising and head-cutting , bluffs and streambanks. The focus of this study is ravines, which are poorly understood in terms of erosional processes. One main way that ravines erode is through knickpoint migration, which happens as water flows over a tougher material, and falls onto a softer material, creating a back-cutting and over-steepening effect at the toe of the knickpoint. Material from the bottom of the ravine is thus mobilized, and can be transported down the ravine into the Minnesota River.

To help decipher the role of knickpoint migration in sediment loading on the Minnesota River, we examined a single ravine and its knickpoints over a span of several years. Seven Mile Creek, a to the Minnesota River in Nicollet County, is an ideal location to study the factors that contribute to knickpoint migration. Ravine Z, a prominent ravine in Seven Mile Creek Park, Nicollet County, MN, is a very active eroding that is largely fed by farm drainage tiles. A and surveying tools were used to make a series of slope profiles spanning the period 2007-2014. Rates of knickpoint migration could then be determined and compared to the precipitation record over each time interval. Results of this study indicated knickpoint migration in Ravine Z is rapid, with rates between 10.47-34.27 feet per year on average. These data suggest that both the amount and intensity of rainfall influence knickpoint migration rate in Ravine Z.

2

Acknowledgements

For a project so large, I have plenty of people to thank. First, I would like to thank Dr. Laura Triplett for being my advisor, and keeping me on track though the year. I would also like to thank Dr. Julie Bartley for her help during J-term and semester, as I had many questions to ask during that section of time. I would like to thank Dr. Jim Welsh for providing me with many materials for the use of better understanding my site. I want to thank my friends, Jeff Halvorson and Dom

Delmont, for going into the field with me to collect data, and Scott Hauer and Lance

Erickson for providing me with their 2013 data profile. Lastly, I want to thank my parents and family for all of their support.

3

Table of Contents

Introduction 5

Geologic Setting 8

Methods 11

Results 13

Discussion 19

Conclusion 23

References 24

Figures

Map 1- Map of Minnesota 8

Figure 1- Slope profile correction 14

Figure2- Slope profile 2007-2013 15

Figure 3- Slope profile 2013-2014 16

Figure 4- Slope profile 2007-2014 17

Table 1- Precipitation data 17

Table 2- Migration rate 18

4

Introduction

The Minnesota River is a large river that drains the southern half of Minnesota before it flows into the Mississippi River. The Minnesota River is considered to be impaired due to high suspended sediment and turbidity under the US Clean Water Act

(Wilcock et al., 2009). This can cause many problems, such as the infilling of different bodies of water that receive water from the river (MPCA 2007). Water clarity also decreases, causing people to not want to be around the river. Also, it can negatively affect the ecological health of the river. Suspended sediment decreases the amounts of photosynthesis that plants can do, and clog the feeding apparatuses for filter feeders such as mussels (Best et al., 2001; Wilber and Clark, 2001). Sediment erosion in the Minnesota

River watershed is a serious concern for people living both inside and outside of

Minnesota. The amount of sediment erosion has increased in the Minnesota River watershed are causing different and rivers that are fed by the Minnesota River, such as Pepin, to be infilled with sediment (MPCA 2007). Increased sediment loads in the river can cause problems with drinking water. Many people in and out of Minnesota use the Mississippi River, downstream of its with the Minnesota River, as a source of drinking water. When there is a higher amount of sediment, they must have their municipal water supplier use a stronger filter system. The Minnesota and Mississippi

Rivers are well known for fishing, but if the rivers have too much sediment, fish can struggle (Wilber and Clark, 2001).

5 Much of the Minnesota River’s sediment load comes one sub-watershed, that of the

Le Sueur River in south-central Minnesota. In 2011, the Minnesota Pollution Control

Agency created a sediment budget for the Le Sueur River, in order to better understand how much sediment has been added by anthropogenic processes on a yearly basis compared to natural amounts (Gran et al., 2011). This analysis determined that sediment in the river comes from a variety of sources in the landscape, such as bluffs, ravines, or topsoil. Like the Le Sueur River, The Minnesota River gets much of its sediment from bluffs and ravines, and though the amounts of sediment that the river receives from bluffs has been well calculated, the sediment contribution by ravines is still uncertain as ravines can either store or erode sediment (Wilcock et al., 2009).

Ravines are relatively short and steep tributary that feed water into larger bodies of water, such as creeks or rivers. Ravines incise through the glacial till of the

Minnesota River , allowing water to drain from the uplands down to the river.

Ravines connect the uplands of the watershed, which is a glacial till plain, to the river.

When water flows through a ravine, some amount of erosion occurs in the bed of the ravine. Ravines can also store sediment for periods of time when sediment is deposited in the middle of the ravine when there is a decrease in water (Wilcock et al., 2009).

Ravines erode in a combination of hillslope and river processes (Wilcock et al.,

2009). If there is a more resistant portion in the ravine, like a tree root or bedrock outcrop, that portion will resist erosion, while the softer part will erode. This causes knickpoints, which are areas in the ravine that have a much steeper slope, and they are of interest because they are the points in ravines that produce a lot of sediment. The knickpoints will then migrate towards the head of the ravine when water is flowing through the system

6 because as water falls over the knickpoint, the vertical face of the knickpoint is eroded more quickly than the rest of the knickpoint.

Understanding how knickpoints erode and migrate is very important when looking at an area dominated by agricultural land use like southern Minnesota. Because erosion in ravines only happens during times of water flow, the rates that knickpoints move can change from year to year as precipitation and runoff vary. Knickpoint migration rate depends on the type of geologic material the knickpoint is eroding through, the amount of water that enters the ravine, and the time that the knickpoint has to erode. Although this part of the state has been “primed” for increased amounts of sediment erosion because of the soft unconsolidated till unit that forms the valley, modern agricultural methods have increased the rate of erosion of sediment into the Minnesota River even more (Belmont et al, 2011).

Approximately 65% of the Minnesota River watershed is used for farming annual row crops (Wilcock et al., 2009). That cropland is often drained by a system of drain tiles, which are used to decrease the amount of standing water has on cropland. Ravines are important to study when looking at sediment erosion into the Minnesota River because many drain tile outlet pipes flow into ravines. Drain tile systems often have an outlet at the top of a ravine, and contribute a large amount of water to ravines. That water increases the amount of erosion in the ravine, which in turn may lead to higher suspended sediment in the Minnesota River.

7 River processes are mainly controlled by knickpoint migration in the ravine. As a knickpoint migrates, hillslope erosion happens as the ravine walls oversteepen and slump, which widens the ravine (Gran et al., 2011).

Here, I used a combination of field observations, digital elevation model (DEM) analyses, and precipitation data to explore knickpoint migration rates, as well as to determine what seems to play the biggest factor in determining the rates of knickpoint migration.

8 Geologic Setting

Southern Minnesota is largely covered by Wisconsin age till, though there are outcroppings of other geologic units in some of these areas. The Minnesota River drains this section of the state, and it flows into the Mississippi River on the southeastern portion of the state. The Minnesota River is fed by a series of ravines and creeks that drain water from the uplands into the river. My field area is Seven Mile Creek Park in southeastern

Minnesota, near Mankato, MN in Nicollet County.

Map 1- This shows the regional and study area. Seven Mile Creek Park is highlighted in green on the study area map, and the creek is highlighted in red. Map taken from Jeremy Bock, 2010. The geology of Seven Mile Creek Park consists of Jordan , Oneota

Dolostone, and glacial till. The oldest unit in the park, the Jordan Sandstone, is a weakly cemented quartz arenite deposited during the Cambrian (Geologic Atlas, 2012). This unit is only exposed near the entrance of the park and in the channel of Seven Mile Creek in the upstream areas of the park. The Oneota Dolomite is a well-lithified dolomite that was

9 deposited during the Ordovician in a shallow epicontinental sea; however, it occurs only in the subsurface in the park and is not observed in outcrop. Glacial till is the youngest unit, and makes up nearly all of the exposed geologic material in the park. It was deposited by the retreat of the Glacial Des Moines lobe of the Wisconsin ice sheet. The Des Moines lobe was a large lobe of an ice sheet that dominated the Minnesotan landscape until around

12,000 years ago when it finished retreating. There are several till units exposed within the park, but all are dominantly fine-grained, unlithified, unconsolidated sediment that is very easily eroded. However, the glacial till is very heterogeneous because there are many different types of till that is within the study area. Some units are more resistant to erosion, as they may have more sand particles or be overconsolidated (Jennings 2010).

The heterogeneity of the till units could potentially cause different rates of erosion between two knickpoints in the same ravine. The ravines are mostly contained in this till unit.

At the last glacial period, a large called Glacial Lake Agassiz was dammed by ice, but as the glacial period was ending the dam broke. The outlet for melt water from the glacial lake was in the present day Minnesota River Valley, which began the erosion of the valley. During and after the draining of Lake Agassiz, Glacial River Warren flowed through the same outlet channel, creating the large terraces and steep valley slopes that are common along the Minnesota River (Gran et al. 2009). The Minnesota River now flows through a portion of Glacial River Warren’s old river channel.

The amount of water that fed into Glacial River Warren began to slowly decrease

11,500 years ago, and the level of the river began to lower (Day et al. 2012). The for the Glacial River Warren began to drop because of the decrease of water, which caused the incision of the Minnesota River into the old valley of Glacial River Warren. As the

10 Minnesota River incised into the old river valley, two different zones were created where sediment erosion can occur: the uplands, and the developing drainage network.

The uplands are at a higher elevation, and the drainage ditches and streams transports sediment from this zone. The uplands are relatively flat, with rolling hills and kame-kettle topography. Streams are relatively low-gradient, and most are used to drain excess water from cropland. The lower zone is found closer to the Minnesota River, and on the sides of the uplands. This zone produces sediment from bluffs and ravines, and is thought to contribute more sediment to the Minnesota River than the uplands (Wilcock et al., 2009). The tributary streams and ravines are actively to reach the new base level for water in this area, which was established when the Minnesota River incised into the channel of the old Glacial River Warren (Wilcock et al., 2009). The incising of the

Minnesota River into the bed of River Warren caused ravines and knickpoints to develop in the valley walls, and is part of the reason why the watershed is geologically primed for increased amounts of sediment erosion. The other reason is that the glacial till that forms the majority of the watershed is very easy to erode because it is unlithified.

The increase in sediment loading in the incised portions of the Minnesota River watershed has been found to be very large in smaller watersheds that enter the Minnesota

River from its left bank, such as Seven Mile Creek Park (Wilcock et al., 2009). Though the entirety of the Minnesota River watershed has been naturally primed for increased sediment erosion, anthropogenic changes have further increased the amounts of erosion

(Belmont et al. 2011). Many of the ravines in Seven Mile Creek Park contain pipes that lead from drain tiles from farms that are used to increase the speed that water leaves farm fields. The drain tile array moves water rapidly from the upper zone to the lower zone,

11 increasing water discharge into many of the ravines in the watershed, which potentially further increases sediment erosion in the ravine.

12 Methods

Manual Slope Profiles

Slope measurements of Ravine Z were made using a surveyor’s sight level, staff, and a tape measure (Erickson and Hauer 2013) to produce a slope profile of the base of the ravine. By using these methods, two slope profiles of the same ravine were made at two different times, the first on 9/25/13, and the second on 9/22/14. Measurements were started at the drain tile outlet pipe at the top of the ravine, and were taken until the ravine intersected Seven Mile Creek at the mouth. After leveling the sight, the initial elevation of the sight was determined at the front of the sight by using the staff; the staff was then moved down ravine for a distance, which was measured by using a tape measure. Staff elevation was then determined again, and then the sight was moved downstream to the staff. There is a large amount of potential error. It is very difficult to get the horizontal tape measure to be perfectly flat, so there typically a curve in the tape, decreasing accuracy.

When measuring the vertical drop between the starting and ending points, if the staff is tilted, the measurements can be incorrect as well. Due to some error, the 2013 survey was incorrect, so a series of corrections were done to attempt to fix the data.

The manual slope profiles were constructed by entering all of the elevation and horizontal distance data into Excel. Then, those were manipulated by subtracting the end elevation of the staff from the initial elevation. The elevations were converted to feet from meters. By plotting the horizontal distance from the drain tile outlet on the x-axis, and the horizontal drop from the drain tile outlet on the y-axis, two sets of graphs for each of the slope profiles were made, the first with vertical exaggeration, and the second without vertical exaggeration.

13

Digital Slope Profiles

ArcMap 10.0 was used to create a slope profile from a2007 DEM (digital dlevation model) that was accessed on the 1/18/15, which was downloaded from the Minnesota

Geospatial Information Office

(http://www.mngeo.state.mn.us/chouse/elevation/lidar.html). The DEM has a horizontal accuracy of .75 meters, and a vertical accuracy of .18 meters. The DEM was used to make a slope shapefile in ArcMap. By using the 3D analysis tools, a slope profile was drawn from the top of the ravine to the edge of Seven Mile Creek.

Precipitation Data

Monthly summaries of precipitation data were downloaded from the National

Climatic Data Center (http://www.ncdc.noaa.gov/).

Identifying Knickpoints

Each slope profile is a two-dimensional representation of the slope in the middle of the ravine. Knickpoints can be seen in the areas where the slope increases over short period of time. Some knickpoints can be vertical or near vertical. It is important to note that the ravine has many more knickpoints (around 10) than can be seen from the data resolution shown on the graphs, and the number of knickpoints can change from year to year.

The slope profiles were compared by identifying the knickpoints on the profile, and then finding the distance that the top of each knickpoint migrated headward between each

14 of the different measurement periods. The following two equations were used to see how different factors affected the migration of the knickpoints.

Equation 1.

!"#$%& !" !"#$%&"'( � = ( ) ! !"#$ !"#$""% !!"#$ !"#$%&'

This determines the migration rate in feet/day, and is determined by dividing the amount of headward movement by the number of days between measurements

Equation 2.

!! ��� = !"#$%& !" !"#$%!%&'&%() !"#$ !" !"#$%!%&'&%() !.!!"

This determines the rate of movement for the daily precipitation during the study period that the study period had over .1 in of precipitation. I named this the Precipitation

Migration Index (PMI) and it is a measure of how the intensity of precipitation affects the migration, and is in the units of feet of migration/inch of precipitation. Higher values for

PMI indicate a larger amount of migration per unit of precipitation.

15

Results The three slope profiles were laid on top of each other in order to determine the distance that a knickpoint migrated. The vertical axis of the profiles shows the vertical distance that the ravine drops from the drain tile outlet pipe to the edge of the creek. The horizontal axis shows the horizontal distance from the drain tile outlet to the creek. The steep areas are spots with knickpoints, and the largest ones (Figures 2-4)were used to calculate the distance that was migrated between the study periods.

Due to measuring errors in the field, there was a problem with the 2013 slope profile. In order to continue to use that data, the 2013 profile was visually corrected. The first two graphs show the need for vertically and horizontally correcting the 2013 data

(Figure 1). Though it is possible for the 2013 survey to have a higher elevation than the

2007 survey in some areas due to sediment build up, it is not sensible that the whole survey would have a higher elevation. It is also unlikely that any given knickpoint would be located closer to the creek in 2013 than it was in 2007 (Figure 1). The 2013 survey was corrected by finding “anchor points”, where the profile would have not been affected.

Three spots were chosen: the location of the creek, the drain tile, and a series of small knickpoints that could be seen on both the 2013 and 2007 surveys. The vertical and horizontal heights from these three spots on the 2007 survey were then entered into the

Excel spreadsheet for 2013. The vertical and horizontal change between each point was calculated, then that distance was spread out using the equation

�������� = �������� �������� − �������� �������� ∗ !!!"#$ !" !"#$%&"' . !"#$%&'( !" !!!"#$

16 250 225 1A 200

175

150

125 10/24/07

100 9/25/13

75 9/22/14

50

25 Vertical distance from drain tile outlet (ft) 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Lateral distance from drain tile outlet (ft)

250

225 1B 200

175

150

125 10/25/07 9/25/13 100 9/22/14 75

50 Vertical drop from drain tile outlet (ft) 25

0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Lateral distance from drain tile oultet (ft)

Figure 1- Figure 1A shows the need for horizontally and vertically correcting the 2013 survey. The line from the 2013 survey has a higher elevation than either of the two other surveys, and has the knickpoints moving down ravine (further from the drain outlet) compared to the 2007 survey. Figure 1B is post-correction, and it better fits what is expected in knickpoint migration. 250 Ravine Proile Survey, Seven Mile Creek Park, Mn 225 2007-2013 (corrected)

200

175

150

125 KP1 10/24/07 9/25/13 100

75 Vertical drop from drain tile outlet (ft) 50

25

0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Lateral distance from drain tile outlet (ft)

Figure 2- This graph shows the change in knickpoint position, marked KP1 from the 2007 survey and the corrected version of the 2013 survey. This graph has a vertical exaggeration of 8. 250 Ravine Proile Survey, Seven Mile Creek Park, Mn 225 2013 (corrected)-2014

200

175

150

125 9/25/13 KP1 9/22/14 100

75 Vertical drop from drain tile outlet (ft) 50

25

0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Lateral distance from drain tile outlet (ft)

Figure 3- This graph shows the change in knickpoint position, marked KP1 from the corrected version of the 2013 survey and the 2014 survey. This graph has a vertical exaggeration of 8. At 1300 feet from the drain tile outlet, it appears that there is a knickpoint developing, however, that is due to measurement errors in 2013 that were not fully fixed in the correcting of that profile. 250 Ravine Proile Survey, Seven Mile Creek Park, Mn 225 2007-2014

200

175

150 KP2

125 10/24/07 KP1 9/22/14 100

75 Vertical drop from drain tile outlet (ft) 50

25

0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Lateral distance from drain tile oultet (ft)

Figure 4-This graph shows the change in knickpoint positions, marked KP1, and KP2, from the 2007 survey and the 2014 survey. This graph has a vertical exaggeration of 8. At the location 1500 feet horizontally from the drain tile outlet, I observed a large slump from the sidewalls (Figure 4). That slump created a 25-foot long section of a gradual decrease, then increase in the slope at that location. These slope profile show that there is a general trend that the profiles have, but that the knickpoints move headward up the ravine as time goes on. That headward movement up the ravine is also called knickpoint migration.

Date%range Total%precipitation%(in) Precip%days Total%days 10/24/2007;9/25/2013 162.03 336 2164 9/25/2013;9/22/14 22.91 44 362 Totals 184.94 380 2526 Precip/precip%days% precip/precip%days/total%days 10/24/2007;9/25/2013 0.4822 0.0002 9/25/2013;9/22/14 0.5207 0.0014 Totals 0.4867 0.0002

Table 1-This table shows the amount of precipitation (snow water equivalent and rain) that occurred between each study period, as well as the days that had more than .1 inches of precipitation, and the total number of days in each study period. It also shows the amount of precipitation happened in however many days that had more than .1 in of precipitation, and lastly that number divided by how many days were between each study period.

Date%range Migration%(ft) Migration/Day PMI Knickpoint%1 2007;2013 62 0.0287 0.0595 2013;2014 34 0.0939 0.1803 2007;2014 96 0.038 0.0781

Knickpoint%2 2007;2014 27 0.0107 0.0220

Table 2- The total knickpoint migration, average migration/day, and the PMI score for each knickpoint over each of the study periods are shown. The 2013-2014 profile has a much higher migration per day and PMI than the 2007-

2013 profile (Table 2). There was also more precipitation per day during that study period than there was during the other study period (Table 1). Precipitation should increase the rate of knickpoint migration, as with more precipitation there should be more erosion in the ravine.

These data have a large amount of uncertainty. The methods used to create the

2013 and 2014 manual slope profiles are imprecise due to human error. For every measurement, an amount of uncertainty is created, as the meter-tape could potentially not be stretched as tautly as it should be, or the meter-stick could be at some non- perpendicular angle, changing the lateral or vertical distance over that area. The 2013 slope profile, which was horizontally and vertically corrected, still has a large source of possible unknown error. The 2013 profile has an unknown amount of error that caused me to have to correct it. Though it may not be fully corrected, this 2013 profile is very important, because during the summer of 2013, there were very intense rainfalls over short periods of time. This profile contains the potential for having large amounts of uncertainty, much information can be gathered from this data set, and if there is too much uncertainty, some amount of information can still be gathered from the 2007 and 2014 graphs.

22 Discussion

The rate that a knickpoint migrates is largely controlled by the intensity of precipitation and the type of geologic unit that the ravine cuts through. Precipitation is a controlling factor because without some kind of flow, there would not be any kind of erosion in the ravine. Precipitation intensity is how much rain comes down in a period of time. In the summer of 2013, there was a large increase in precipitation in the study area, which was exacerbated by the farm tile outlet pipe that is located at the top of the ravine.

Much of water that fell on the cropland would have been collected in the tile system before being forced to exit into the ravine. This deluge of water from the drainage system seems to be a large controlling factor on knickpoint migration.

The PMI score should be large when there was a lot of precipitation for how many days of rain there were if the intensity of precipitation was the biggest factor in knickpoint migration. This is because the PMI equation measures how much migration there was by how much precipitation there was (feet of migration/in of precipitation). What is important to remember is that even though only a small amount of precipitation may happen, the surrounding drain tiles accumulate the water, which leads to large amounts of water entering the ravine. There does seem to be an increase of PMI for the 2013-2014 profiles, which supports that the intensity of precipitation is a driving factor in knickpoint migration. The PMI in this study period is an order of magnitude larger than the other

!"#$%&%'('%)* study periods, and the amount of !"#$ !"#! !"#$%!%&'&%() , or the amount of precipitation, is 1-2 !"!#$ !"#$ orders of magnitude larger (table 1). However, this correlation could be due to the very large amount of migration that happened during this study period.

23 Knickpoint 1 to migrated close to 34 feet between 2013-2014 (one year), and there was 62 feet of migration between 2007-2013 (six years). Though there was more migration during the six-year period, the one-year time period had much more migration per day. This means that time is not a very important direct factor on knickpoint migration, but that as more time goes by, it is more likely that a site will have a big precipitation event, causing lots of erosion. The increase of rain between 2013 and 2014 was mainly due to a large rainstorm during the summer of 2014.

The material the knickpoints cut through is also likely a very important factor for knickpoint erosion (Gran et al. 2013). However, sediment data was not collected for this research. Much of the increased amounts of sediment erosion from 2013-2014 likely happened because of how easy the till is to erode due to it being very unconsolidated. The till is also heterogeneous, which cause variation in the rate of knickpoint migration because different materials have different properties that change how easy or hard it is for the material to be eroded. Even though the till is very easy to erode, without having precipitation running through the ravine, there would not be anything to erode the knickpoints.

Ravines erode and evolve in a sporadic and dynamic manner. Between 2007 and

2014, a new knickpoint appears to have developed. At location A3 (Figure 4), a new knickpoint appears to be evolving, or becoming more vertical. Though there is no hard data that support my hypothesis of how this formed, I believe this happened because there is a more resistant layer in the till that is resisting erosion, causing a steepening at this area.

Between the summer of 2014 to the fall of 2014, slumping was observed. Slumping happens because after the middle of the ravine erodes downward the sidewalls of the

24 ravine oversteepen and eventually collapse into the center of the ravine. The sediment that collapsed into the ravine will eventually be eroded away, but until then, a positive increase in the slope profile can be seen. Between 2007 and 2014, a knickpoint broke up into two different knickpoints. This is likely due to the heterogeneous nature of the till. Knickpoints have been thought of as being a large geologic feature that moves as a single unit that does not break up, however, most knickpoints that have been previously studied are not in unconsolidated, heterogeneous sediment like glacial till.

With further research into the affects of increased amounts of water into ravines, this could help to define the amounts of sediment that are entering into rivers in the

Mississippi River watershed, allowing for a more accurate sediment budget.

25 Conclusion

Knickpoints in Ravine Z, a tributary to Seven Mile Creek, are migrating in very quick bursts. The intensity of precipitation has a large effect on these systems, but the geologic material seems to also play an important role. Knickpoints are very dynamic, and in order to better understand how they erode, much more work needs to be done. Since knickpoints and ravines change in quick episodes, an annual or bi-annual survey should be done to be able to better plot how different factors change the rate that a knickpoint changes. Research could also be conducted into the effects of knickpoint erosion through unconsolidated, heterogeneous material. The standard idea of how knickpoints retreat is that they move as a single unit. KP1 shows that the tops and toes of knickpoints may change as water flows and falls onto materials with different properties (Figure 5). This data can begin to show how much sediment has been added into the Minnesota River; however, it would be much more beneficial to be able to calculate the volume of sediment that was added into the river. Much of the sediment produced as knickpoints migrated have entered the Minnesota River, further decreasing water clarity and health.

26 References

Belmont, P., Gran, K. B., Schottler, S. P., Wilcock, P. R., Day, S. S., Jennings, C., Lauer, J. W., Viparelli, E., Willenbring, J. K., and Engstrom, D. R., 2011, Large shift in source of fine sediment in the Upper Mississippi River: Environmental science & technology, v. 45, no. 20, p. 8804-8810. Best, E.P.H.,C.P. Buzzelli, S.M. Bartell, R.L. Wetzel,W.A. Boyd, R.D. Doyle, and K.R. Campbell. 2001. Modeling submersed macrophyte growth in relation to underwater light climate: modeling approaches and application potential: Hydrobiologia. V.444, p. 43-70 Bock, J., 2010, Geology and of Seven Mile Creek Park. Gustavus Adolphus College senior thesis. Day, S. S., Gran, K. B., Belmont, P., and Wawrzyniec, T., 2013, Measuring bluff erosion part 2: pairing aerial photographs and terrestrial laser scanning to create a watershed scale sediment budget: Earth Surface Processes and Landforms, v. 38, no. 10, p. 1068-1082. Erickson, L., Hauer, S., 2013, Independent Study: Gustavus Adolphus College Geology Department. Gran, K., Belmont, P., Day, S., Jennings, C., Lauer, J. W., Viparelli, E., Wilcock, P., and Parker, G., 2011a, An integrated sediment budget for the Le Sueur River basin: MPCA Report wq-iw7-29o. Gran, K. B., Belmont, P., Day, S. S., Finnegan, N., Jennings, C., Lauer, J. W., and Wilcock, P. R., 2011b, Landscape evolution in south-central Minnesota and the role of geomorphic history on modern erosional processes: GSA Today, v. 21, no. 9, p. 7-9. Gran, K. B., Belmont, P., Day, S. S., Jennings, C., Johnson, A., Perg, L., and Wilcock, P. R., 2009, Geomorphic evolution of the Le Sueur River, Minnesota, USA, and implications for current sediment loading: Geological Society of America Special Papers, v. 451, p. 119- 130. Jennings, C.E., 2010, OFR10-07, Glacial Geology of Seven Mile Creek Watershed. Minnesota Geological Survey. Retrieved from the University of Minnesota Digital Conservancy, http://purl.umn.edu/98107. Matsch, C. L., 1972, Quaternary geology of southwestern Minnesota, in Sims, P. K., and Morey, G. B., eds., Geology of Minnesota: a centennial volume: St. Paul, Minnesota, Minnesota Geological Survey, p. 548-560 Meyer, G.N.; Runkel, A.C.; Lusardi, B.A.. 2011. C-25 Geologic Atlas of Nicollet County, Minnesota [Part A]. Minnesota Geological Survey. Retrieved from the University of Minnesota Digital Conservancy, http://purl.umn.edu/116090. Minnesota Geospatial Information Office, 2007. LiDAR data for Seven Mile Creek in Nicollet County, retrieved from the Minnesota Geospatial Information Office, http://www.mngeo.state.mn.us/chouse/elevation/lidar.html. Minnesota Pollution Control Agency, 2007, Lake Pepin Watershed TMDL-Eutrophication and Turbidity Impairments Project Overview. Project Overview. National Oceanic and Atmospheric Administration, 2015. Precipitation data for Nicollet County, retrieved from the National Centers for Environmental Information, http://www.ncdc.noaa.gov/.

27 Wilber, D.H. and D.G. Clarke. 2001. Biological effects of suspended : a review of suspended sediment impacts on fish and shellfish with relation to dredging activities in . North American Journal of Fisheries Management. l21:855-875. Wilcock, P., Belmont, P., Baskfield, P., Birr, A., Cooper, P., Engstrom, D., Jennings, C., Kiesling, R., Matteson, S., Mulla, D., Nieber, J., Regan, C., and Schottler, S., 2009, Identifying sediment sources in the Minnesota River Basin: Minnesota River Sediment Colloquium Report.

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