Mont Ripley Ski Hill As a Result of an Extreme Rainfall Event Occurring in Michigan’S Keweenaw Peninsula in June 2018, Locally Known As the “Father’S Day Flood”

Fall-Spring 2018-19

Powderstash Run Failure: Analysis and Stability Report

Submitted in partial fulfillment of the requirements for the degree of Allison Green, Maisy Snyder, B.S. GEOLOGICAL ENGINEERING Michele Reaume, Paige Courtney, MICHIGAN TECHNOLOGICAL UNIVERSITY Virginia Cistaro Department of Geological & Mining Engineering & Superior Geotech Solutions Sciences Fall-Spring 2018-19

May 6, 2019 Under the advisement of: Dr. Rudiger Escobar Wolf & Dr. John Gierke

ABSTRACT

Slopes failed across two ski runs at Mont Ripley Ski Hill as a result of an extreme rainfall event occurring in Michigan’s Keweenaw Peninsula in June 2018, locally known as the “Father’s Day Flood”. Hydrological and slope analyses were performed to understand the likely failure mechanisms/events and to consider mitigation methods to restore the ski runs and protect infrastructure downslope of the failures. The failure area was examined by comparing digital elevation models (DEMs) derived from aerial imagery obtained prior to and after the flood and included field observations. The DEMs were used to evaluate the slope stability using two geotechnical models. Slope hydrology was considered in the analysis. The TR-55 Method, Rational Method, and Manning’s equation were utilized in order to find time of concentration, rainfall intensity, and flood-stage height. These hydrological inputs were used in an excel-based Bank Stability and Toe Erosion Model Static Version 5.4 from the USDA, a two-dimensional profile model using Rocscience Slide Version 8.015, and an aerial surface stability analysis using Scoops3D. The propensity for erosion was analyzed using the Hjulstrom Erosion Model approach. The volume of material moved by the flood event was calculated using the before and after DEMs in ArcGIS. It is hypothesized that the heavy overland flow of water, associated with the flooding event, travelling down the ski hill was the primary cause of failure and the failure area was minimally impacted by toe erosion at the base. Currently, the failure area is unstable and continues to erode with snowmelt and spring rain events. It is proposed that inserting a steel culvert, larger than the one existing pre-flood, will redirect overland flow to Ripley Creek, located below the failure, and allow for the continued use as ski runs. Debris deflectors and rip-rap will also be utilized to minimize erosive potential along the open channel ditch running down the ski hill that would empty into the proposed culvert.

TABLE OF CONTENTS

Abstract ...... 1 1. Project Background ...... 7 1.1 Purpose ...... 7 Rain Event Description ...... 7 1.2 Location and Site Characterization ...... 8 Geology from Published Sources ...... 10 Groundwater Conditions ...... 10 1.3 Objectives & Scope ...... 11 2. Approach ...... 12 2.1 Data Acquisition ...... 12 2.2 Drone Survey ...... 12 2.3 DEM Generation ...... 18 2.4 GIS Analysis ...... 18 3. Geohydrology Study ...... 22 3.1 TR-55 Method ...... 22 3.2 Rational Method ...... 25 3.3 Manning’s Equation ...... 29 Parameter Disscusion ...... 29 Derivation of Stage Height ...... 30 Derivation of Velocity from Equation ...... 30 4. Geotechnical Study ...... 32 4.1 Toe Erosion Model ...... 32 4.2 Scoops 3D Model ...... 33 4.3 Rocsience Slide Model ...... 34 4.4 Volume of Material Moved ...... 37 4.5 Erosion Model ...... 38 5. Results ...... 40 5.1 From Geohydrology...... 40 Storm Event Results ...... 40 Future Snowmelt Results ...... 40

Stage Height Results ...... 41 Velocity over Powderstash Results ...... 45 5.2 From Geotechnical ...... 45 Toe Erosion Eesults ...... 45 Scoops3D Results ...... 47 Rocscience Slide Results ...... 48 Hjulstrom Diagram Results ...... 55 5.3 Discussion of Method of Failure ...... 56 6. Recommendations ...... 58 6.1 Solutions ...... 58 6.1.1 Culverts ...... 58 6.1.2 Slope Stability ...... 59 6.2 Recommended Future Work ...... 63 7. Conclusions ...... 64 Acknowledgements ...... 65 References ...... 66 Appendices ...... 68

List of Figures

Figure 1. Annotated Map of Failure Locations on the Mont Ripley Ski Hill ...... 7 Figure 2: Location of Ripley, Michigan and Mont Ripley Ski Hill ...... 8 Figure 3: Location of slope failure on Mont Ripley Ski Hill ...... 9 Figure 4: Slope Failure Measurements...... 9 Figure 5. Topography of Ripley, Michigan ...... 10 Figure 6: eMotion Flight Path for SenseFly eBee Classic Drone ...... 13 Figure 7: Drone Working Area Parameters ...... 14 Figure 8: Drone Take-off Parameters ...... 14 Figure 9: Drone Landing Parameters ...... 15 Figure 10: Drone Safety Settings ...... 16 Figure 11: Drone Flight Path Settings...... 17 Figure 12: May 2018 Hillshade ...... 19 Figure 13: December 2018 Hillshade ...... 20 Figure 14: May 2018 Watersheds ...... 21 Figure 15: Watershed Delineation of Ripley Creek and Powderstash Run ...... 22 Figure 16: Segments on Powderstash Watershed ...... 23 Figure 17: Time of Concentration Path ...... 24 Figure 18. KRC versus NWS rainfall data on June 17th, 2018 ...... 28 Figure 19: Rocscience Slide Cross Sections May 2018 ...... 35 Figure 20: Rocscience Slide Cross Sections December 2018 ...... 36 Figure 21: Elevation Difference for Before and After Flood DEMs ...... 37 Figure 22. Hjulstrom Diagram...... 39 Figure 23: Cross Section of Ripley Creek Channel ...... 41 Figure 24: Cross-Section Points of Ripley Creek ...... 42 Figure 25: Cross-Sections of Powderstash Creek Channel ...... 43 Figure 26: Cross-Section 1 of Powderstash Creek ...... 44 Figure 27: Cross Section 2 of Powderstash Creek ...... 44 Figure 28: Before and After Toe Erosion Cross-Section 4 ...... 46 Figure 29: Before and After Toe Erosion Cross-Section 4 ...... 46 Figure 30: Scoops3D Factor of Safety Test 1 ...... 47 Figure 31: Rocscience Slide Minimum FS Cross Section 1 May 2018 ...... 48 Figure 32: Rocscience Slide Minimum FS Cross Section 2 May 2018 ...... 49 Figure 33: Rocscience Slide Minimum FS Cross Section 3 May 2018 ...... 49 Figure 34: Rocscience Slide Minimum FS Cross Section 4 May 2018 ...... 50 Figure 35: Rocscience Slide Minimum FS Cross Section 5 May 2018 ...... 50 Figure 36: Rocscience Slide Minimum FS Cross Section 6 May 2018 ...... 51 Figure 37: Rocscience Slide Minimum FS Cross Section 1 December 2018 ...... 51 Figure 38: Rocscience Slide Minimum FS Cross Section 2 December 2018 ...... 52

Figure 39: Rocscience Slide Minimum FS Cross Section 3 December 2018 ...... 52 Figure 40: Rocscience Slide Minimum FS Cross Section 4 December 2018 ...... 53 Figure 41: Rocscience Slide Minimum FS Cross Section 5 December 2018 ...... 53 Figure 42: Rocscience Slide Minimum FS Cross Section 6 December 2018 ...... 54 Figure 43: Powderstash Creek Flow Velocities on Hjulstrom Diagram ...... 55 Figure 44. Basic cost of culverts for Houghton County ...... 59 Figure 45. Design of geotextile reinforcement layers for over-steep slopes ...... 60 Figure 46. Illustration of Wrap-Faced geotextile reinforcement used for slopes 1:1 or greater ...... 61 Figure 47.Detailed illustration of Wrap-faced supports with soil and vegetation placement ...... 61 Figure 48.Cross section view containing ...... 62 Figure 49.Placement of GeoWeb panels secured with soil nails ...... 62 Figure 50.Rip Rap Sizing Chart ...... 63

List of Tables

Table 1: Table of Runoff Coefficients for Land Use ...... 26 Table 2: Table of Runoff Coefficients for Topography and Vegetation ...... 27 Table 3. Hydrology Results for the Powderstash Watershed ...... 28 Table 4. Hydrology Results for the Ripley Creek Watershed ...... 29 Table 5. Friction and Ru-Value Inputs for Scoops3D ...... 33 Table 6. Spring Discharges for the past 5 years in the Houghton County area ...... 40 Table 7.Common Stable Slope Ratios for Varying Soil/Rock Conditions ...... 60

List of Equations

Equation 1: Simplified Manning’s Equation ...... 24 Equation 2: Travel Time Equation ...... 24 Equation 3: Rational Method Equation ...... 25 Equation 4: Manning’s Equation ...... 29 Equation 5: Manning's Equation for Triangular Channel ...... 30 Equation 6: Volumetric Flow Rate ...... 30 Equation 7: Flow Velocity for Triangular Channel ...... 31 Equation 8: Average Boundary Shear Stress ...... 32

List of Appendices

Appendix 1. BARR Soil Properties ...... 68 Appendix 2. TR-55: Relationship between velocity and watershed slope ...... 69 Appendix 3.Daily Discharge at Trap Rock River by Lake Linden, MI 2018-19 ...... 70 Appendix 4. Daily Discharge at Trap Rock River by Lake Linden, MI 2017-18 ...... 71 Appendix 5. Daily Discharge at Trap Rock River by Lake Linden, MI 2016-17 ...... 72 Appendix 6. Daily Discharge at Trap Rock River by Lake Linden, MI 2015-16 ...... 73 Appendix 7. Daily Discharge at Trap Rock River by Lake Linden, MI 2014-15 ...... 74 Appendix 8. Scoops3D Simulation 1 ...... 75 Appendix 9. Scoops3D Simulation 2 ...... 76 Appendix 10. Scoops3D Simulation 3 ...... 77 Appendix 11. Scoops3D Simulation 4 ...... 78 Appendix 12. Scoops3D Simulation 5 ...... 79 Appendix 13. Scoops3D Simulation 6 ...... 80 Appendix 14. Before and After Erosion at Toe of Line 5 ...... 81 Appendix 15. Before and After Erosion of Line 5 ...... 82 Appendix 16. Before and After Erosion at Toe Cross Section of Line 3 ...... 83 Appendix 17. Before and After Erosion Cross-Sections for Line 3 ...... 84 Appendix 18. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 1 ...... 85 Appendix 19. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 2 ...... 85 Appendix 20. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 3 ...... 86 Appendix 21. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 4 ...... 86 Appendix 22. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 5 ...... 87 Appendix 23. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 6 ...... 88 Appendix 24. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 1...... 89 Appendix 25. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 2...... 89 Appendix 26. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 3...... 90 Appendix 27. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 4...... 90 Appendix 28. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 5...... 91 Appendix 29. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 6...... 91 Appendix 30. Rocscience Slide Project Settings - General ...... 92 Appendix 31. Rocscience Slide Project Settings - Methods ...... 93 Appendix 32. Rocscience Slide Surface Options ...... 94

1. PROJECT BACKGROUND

1.1 Purpose

RAIN EVENT DESCRIPTION A 1000-year flooding event occurred in Houghton, MI on June 17th, 2018, known locally as the “Father’s Day Flood”. The storm duration was approximately 6 hours. During the flood, significant damage occurred throughout Houghton County due to 2-7 inches of rainfall, including the Mont Ripley Ski Hill. The focus of this report is to assess the amount of damage that occurred on damage location 5, shown in Figure 1 below.

Figure 1. Annotated Map of Failure Locations on the Mont Ripley Ski Hill Location of Interest is here noted as Damage Location 5 [1]

1.2 Location and Site Characterization Mont Ripley is located in Franklin Township, Houghton County, Michigan at coordinates 47.13*N, 88.55*W (Figure 2). The area of interest is at the intersection of Powderstash and Deer Track trails immediately west of Ripley Creek (Figure 3).

Powderstash ravine is an ephemeral stream that crosses Deer Track through a culvert. The culvert, which was designed for a 100 year flood event, was damaged during the flood and removed after the flood. A rip-rap channel is currently in place to divert water flow away from the slope failure area into Ripley Creek. The ravine had been scoured, exposing rocks and boulders. The upper portion of the post-event slope, which faces east, is about 21 meters in height (Figure 4). The lower portion shallows out before dropping 2 meters to join Ripley Creek.

Figure 2: Location of Ripley, Michigan and Mont Ripley Ski Hill The town of Ripley and Mont Ripley Ski Hill are boxed in red.

Figure 3: Location of slope failure on Mont Ripley Ski Hill Deer Track Trail and Powderstash boxed in red [2].

Figure 4: Slope Failure Measurements The upper portion of the failure is approximately 21 m in height with a slope less than 1:1

GEOLOGY FROM PUBLISHED SOURCES The Keweenaw Peninsula is part of the Mid-Continental Rift that formed during the Mesoproterozoic era. The bedrock is Portage Lake Volcanics, a series of over 200 lava flows, is over 4500 meters in depth at its greatest known thickness. Glacial till covers the basalt and is what remains of the Keweenaw Moraine deposited during the Pleistocene Epoch [3]. The glacial till exposed by the failure presents laminated layered sand, clay, silt and gravel, which suggests a lacustrine deposition. The topography is characteristic of an escarpment (Figure 5), which are generally areas known for landslides.

Figure 5. Topography of Ripley, Michigan This hillshade depicting the escarpment area was created in ArcGIS

GROUNDWATER CONDITIONS Ground water conditions change with precipitation and it is assumed that pore pressure was maximized during the storm event. Water seepage was present, as well as minor overland runoff. The water table was not observed in the failure area [1].

1.3 Objectives & Scope The objective for this project was to suggest potential stabilization solutions for the failed Mont Ripley Slope and prevent further damage from a similar flash flood in the future. In order to propose the most effective stabilization solutions, the method of failure was to be determined. The failure method would be analyzed using hydrologic and geotechnical approaches. A digital elevation model (DEM) was to be created of the post-Father’s Day Flood slope to further visualize the damage. The water flow over the pre-flood slope was to be analyzed and the volumetric flow rate for Ripley and Powderstash Creeks determined using a combination of the TR-55 and the rational method. The pre-flood slope stability was to be analyzed using Scoops3D and Slide 8.0. Finally, erosion at due to Ripley Creek and Powderstash Creek would be considered. Toe erosion was to be analyzed due to Ripley Creek using the Bank Stability Toe Erosion Model and the overland erosion due to Powderstash Creek using the Hjulstrom Diagram. The results from all of the analysis were to be considered in the final design plan. This final design plan would take cost and ski slope remediation into consideration.

2. APPROACH

2.1 Data Acquisition Topographic data were acquired from several sources. The Michigan Statewide Authoritative Imagery & LiDAR Program [4] provided a 5-foot DEM of the Mont Ripley Ski Area as well as high resolution orthophotos from May 2018. UP Engineers and Architects provided a contour map of the failure area. Barr Engineering provided their report about the site, which included borehole data, soil properties, and maps [1]

2.2 Drone Survey Aerial imagery was captured using SenseFly’s eBee Classic drone with SenseFly camera model WRX RBG. A Trimble Geo 7X was used to obtain eight control points for image processing, however the control points were not used. SenseFly’s software program eMotion was used to program the drone flight (see Figure 6). The parameters and settings used for the flight can be found in Figures 7-11.

The first drone flight was on November 15, 2018. 115 images were captured, however 57 of the images were unable to be georeferenced for unknown reasons. This data set was put aside and a second flight was conducted on December 19, 2018. 125 images were captured, however all images were blurry due to bubbling of the plastic film covering the camera lens. This data set was discarded. A third flight was conducted on the same day, capturing 74 images. Less images were captured because the drone battery was not at full charge and died just over halfway through the flight. These images were not ideal for photogrammetry because they did not have good overlap between them, however they were sufficient for creating a DEM.

Weather conditions on December 19th were not favorable for a drone survey. The sky was overcast with wind speeds less than 10 knots. The temperature was 36°F. Snow covered approximately 90-100% of the ground with an average depth of seven inches.

Figure 6: eMotion Flight Path for SenseFly eBee Classic Drone

Figure 7: Drone Working Area Parameters

Figure 8: Drone Take-off Parameters

Figure 9: Drone Landing Parameters

Figure 10: Drone Safety Settings

Figure 11: Drone Flight Path Settings

2.3 DEM Generation From the aerial imagery, a DEM was created using photogrammetry software. Initially, Pix4DMapper was to be used, however an acceptable DEM was unable to be produced due to lack of knowledge about the software. Agisoft Photoscan was used instead and produced a high-resolution DEM.

To create the DEM, first Agisoft Photoscan completed the image matching and sparse point cloud generation (bundle adjustment, etc.) of the set of 74 aerial images. For this step, a high accuracy with generic preselection setting was chosen. Points were cleared and edited based on visual inspection of alignment quality and noise levels. No control points were used for the processing. Then, the camera parameters were optimized, and a second round of point editing and clearing was done. After that, the point densification was done using a high-quality setting. Editing and cleaning of the dense point cloud was done again at this point based on visual inspection. Mesh and texture were generated from the cleaned and edited dense point cloud. Finally, the DEM and Orthomosaic were generated from the high-density mesh in a geographic latitude and longitude coordinate system (WGS84 Datum).

2.4 GIS Analysis Using the DEM from May 2018 and the new DEM from December 2018, two hillshades were created in ArcGIS to better visualize the data (Figures 12 and 13). The hydromorphological analysis of the May 2018 DEM included two components: delineating the streams and the watersheds from surface morphology. The "Spatial Analyst Tools" toolbox in ArcMap 10.6 was used to do the analysis. First the "sinkholes" (areas of pixels with the lowest elevation values surrounded on all sides by pixels with higher elevations) in the DEM were filled and stored in a raster, using the "Fill" tool, to make sure that the DEM was hydrologically consistent. Then, the directions of steepest descent for each pixel in the "filled DEM" were calculated (from the eight adjacent pixels) using the “Flow Direction” tool. Using the "Flow Direction raster", the number of pixels that would contribute their flow (if flow was only controlled by steepest descent paths) to any given pixel in the "filled DEM" were calculated using the "Flow Accumulation" tool. The resulting “Flow Accumulation raster” was divided into two categories (stream and no stream) using a threshold of 1000 for the number of contributing pixels. This raster was then reclassified to a raster with values only for pixels above the threshold, and that raster was converted to a vector line shapefile using the "Stream to Feature" tool.

For the watershed delineation analysis, a series of points at which the watershed flow would converge were chosen; the points were defined in a vector point shapefile (“Pour Points”) in the same coordinate system as the DEM. Using the "Flow Direction raster" and the "Pour Points" vector shapefile with the "Watershed" tool, the watersheds corresponding to the selected "Pour Points" were generated. See Figure 14 for the results of this analysis, as well as the “Stream to Feature” tool.

Figure 12: May 2018 Hillshade

Figure 13: December 2018 Hillshade

Figure 14: May 2018 Watersheds

3. GEOHYDROLOGY STUDY

3.1 TR-55 Method TR-55 Method from the National Resources and Conservation Service (NRCS) was followed to obtain the time of concentration, an input for calculating peak discharge using the Rational Method [5]. The TR-55 Method is used by the NRCS to approximate urban hydrology for small watersheds. The first step in following the TR-55 Method is done by dividing each watershed with an outlet at the failure site in ArcGIS into areas due to significant changes in slope in the watershed. These watersheds are outlined in Figure 15. The green dots on the map symbolize culverts, which were integral to determining the total water runoff into those watersheds, which would also change the overall area of each watershed.

Figure 15: Watershed Delineation of Ripley Creek and Powderstash Run

Then, the slope (in percent) and the shortest length (in feet) for each of the areas in ArcGIS. These were used as inputs for calculating the velocity using a simplified Manning’s Equation which is an equation used to approximate channel flow. Figure 16 illustrates how the segments

22 for each watershed were made in ArcGIS. The lengths and slopes were found using these segments.

Figure 16: Segments on Powderstash Watershed A more detailed explanation of the Manning’s Equation is found under Section 3.3. The simplified Manning’s equation used the assumptions that this was shallow, concentrated flow, that the roughness coefficient, n, equals 0.05, and that the hydraulic radius, r, was 0.4 in feet. This simplified equation was also obtained from NRCS in the TR-55 Method. See Equation 1 below, with the inputs being the watershed slope (s) in its decimal form [5]. The graph provided by the TR-55 Method that illustrates this relationship can be found in Appendix 2.

Then, the time of concentration was calculated for each area using the TR-55 Method. See Equation 2, where L is the total length of the watershed in feet, as found in ArcGIS, and V is the average velocity in feett/sec [5] The time of concentration is the time it takes for water to travel from the most distal point of the watershed to the outlet point. See below Figure 17 for an example of the path traveled during the duration of a time of concentration for each watershed. The total time of concentration for the watershed was the sum of each area’s time of concentration, which was calculated to be 23.4 minutes for Powderstash’s watershed, and 31.7

23 minutes for Ripley Creek’s watershed. The time of concentration was used to determine rainfall intensity. Equation 1: Simplified Manning’s Equation [5]

Equation 2: Travel Time Equation [5]

Figure 17: Time of Concentration Path Illustration path (in cyan) of the most distal point to the outlet on each watershed

3.2 Rational Method The calculated rainfall intensities from the previous section was used as inputs for the Rational Method. The Rational Method from the NRCS was used to approximate a peak discharge for the two watersheds. The equation uses the following inputs: rain intensity in inches per hour (i), the watershed area in acres (A), and the runoff coefficient (C), which is unitless, to obtain a peak discharge in cubic feet per second [6]. This method is used to approximate peak flow rates for small, urban watersheds. It is important to note that this method is less accurate when the watersheds analyzed are larger than 50 acres. See Equation 3 for the Rational Method equation.

Equation 3: Rational Method Equation

The watershed areas of the failure site were approximated using ArcGIS tools. The Powderstash watershed has an area of 82.5 acres, while the Ripley Creek watershed has an area of 513.4 acres. See Figure 15 under section 3.1 to visualize how the watershed was delineated.

The runoff coefficient, C was determined by looking at the land use, soil type, and slope of each watershed area. For the Powderstash watershed, the runoff coefficient was determined to be 0.35, whereas the runoff coefficient for Ripley Creek is 0.31, both of which are very close. Tables 1 and 2 from NRCS [6] depict runoff coefficients for different conditions The watershed areas were weighted accordingly to the different coefficient descriptions to obtain the overall runoff coefficients for each watershed.

Table 1: Table of Runoff Coefficients for Land Use

Table 2: Table of Runoff Coefficients for Topography and Vegetation

The rainfall intensity was determined summing rainfall depths, during peak discharge, using the total time of concentration. For Powderstash, the rainfall intensity was determined to be 3.26 inches/hour, and for Ripley Creek, 2.99 inches/hour.

The intensity was derived from local data from the Keweenaw Research Center (KRC) [7]. It was used to characterize the storm because the data was more reliable for accuracy and higher frequency of data collection than the National Weather Service (NWS). The KRC data was collected every minute, in comparison to the NWS collecting data about every sixty minutes [8], though both collection locations were right next to each other [7]. A likely error was found in the KRC data at 2:30 a.m. in the morning of June 17th, 2018 [7]. However, the KRC found that removing this error, plotted as the blue line in Figure 18, plots the new adjusted data as generally following the trend of the data obtained from NWS.

Figure 18. KRC versus NWS rainfall data on June 17th, 2018 The green line is the adjusted KRC data that was created after removing the error of 1.75” of rain in 1 minute from the blue line [7]

Note the green and red lines on Figure 18. The general trends of both data collections should be closely aligned, since the locations of each are next to each other, thus both sites should have received a similar amount of rainfall. The adjusted KRC data set is considered more accurate than the non-adjusted one.

See the Hydrology results compiled in Tables 3 and 4.

Table 3. Hydrology Results for the Powderstash Watershed

Table 4. Hydrology Results for the Ripley Creek Watershed

3.3 Manning’s Equation

PARAMETER DISSCUSION Manning’s equation describes the calculation of volumetric flow rate of an open channel or pipe. Cross-sectional area, hydraulic radius, channel slope, and surface roughness are variables that determine the flow rate for this method; the relationship is described in the following equation:

Equation 4: Manning’s Equation

ퟐ ퟏ 푲×푨×푹ퟑ ×푺ퟐ 푸= 풏

where Q is volumetric flow rate, K is a unit conversion constant, A is cross-sectional area, R is hydraulic radius, S is the slope of the channel, and n is channel roughness. Hydraulic radius can be defined as the cross-sectional area of the flow divided by the wetted-perimeter of the channel. The parameter for channel roughness, n, is based on various conditions of the channel or pipe such as roughness, vegetation, scouring, and obstructions. The value for channel roughness can be determined from standard reference roughness charts.

Ideally, the Manning’s equation has a 10 to 20% accuracy for flow determination. However, Manning’s equation has some assumptions that are not achievable in most natural situations. The conditions for Manning’s equation include a straight channel for 200 feet with a uniform cross-section, roughness, and slope, no rapids or sudden changes in slope or width, no

29 tributaries, and no flow backup. Realistically, the Manning’s equation method for flow calculation is 25% to 30% accurate [9]

DERIVATION OF STAGE HEIGHT For the purposes of our report, a method was derived to solve for the stage height of the river from the Manning’s equation. Rearranging Equation 4 provides the following relationship for a triangular channel:

Equation 5: Manning's Equation for Triangular Channel

2 3 퐾 푏2 1 푏2 푄 = × × 푆2 × 푛 푚 푏 2 푏2 + 2푚√( ) ( 푚 ) where Q is volumetric flow rate, K is a unit conversion constant, n is channel roughness, b is stage height, m is the slope of banks, and S is the slope of the channel. Since the flow rate of the river would be known after completion of the rational method, the only unknown is stage height, b. This equation can be solved iteratively when given the flow rate to find the stage height of the river.

DERIVATION OF VELOCITY FROM EQUATION The volumetric flow rate equation was used in for derivation of water velocity in each channel. The equation states:

Equation 6: Volumetric Flow Rate

푄 = 푣 × 퐴 where Q is the volumetric flow rate, v is velocity, and A is the cross-sectional area. This equation was rearranged to solve for velocity given the stage height, width, and flow rate for each channel. The new equation places velocity as the unknown for a triangular channel:

Equation 7: Flow Velocity for Triangular Channel 2푄 푣 = 푏 × 푎 where v is velocity, Q is volumetric flow rate, b is stage height, and a is width of flow. Although width of flow, a, is not distinctly given in cross-sections or Equations 4 and 5, it can be solved for by using the newly found values of stage height into Manning’s equation.

4. GEOTECHNICAL STUDY

4.1 Toe Erosion Model In order to characterize the erosion at the toe of the failed slope due to the flooding of Ripley Creek, the Bank Stability and Toe Erosion Model, Static Version 5.4, was utilized. This model was used to determine whether the toe erosion from Ripley Creek was a main factor in the destabilization of the slope. This is an excel-based, public access model created by Eddy Langendoen and Michael Ursic at the USDA’s National Sedimentation Laboratory. Its intended purpose is to estimate the amount of erosion to occur on river banks due to hydraulic shear stress where the removal of material threatens bank stability

BSTEM 5.4 allows for the input of different bank geometry and material parameters in order to create an accurate depiction of slope conditions. The exact slope geometry can be inputted as coordinates. Up to 5 different horizontal soil layers can be created within this slope. For each layer, the friction angle, cohesion, saturated unit weight, (Phi b), critical shear stress, and erodibility coefficient must be specified. Different channel and flow parameters such as length, slope, stage height, and duration are required. The depth of the water table is also an input parameter. Bank vegetation and toe protection methods are optional inputs for the model.

The shear stress for each node in the slope that is affected by the river is calculated using the equation following equation:

Equation 8: Average Boundary Shear Stress

푡0 = 훾푤 × 푅 × 푆

3 where t0 is the average boundary shear stress (Pa), γw is the unit weight of water (9.81 kN/m ), R is the local hydraulic radius (meters), and S is the channel slope (meters/meters). Shear stress that is exerted from the flow on the cross-section is calculated for individual points along the bank. Further explanation of the erosion calculation process can be viewed on the technical background sheet of the BSTEM-5.4 excel sheet.

4.2 Scoops 3D Model The software Scoops3D was utilized to calculate the factor of safety at the site of the failure, as well as across the entire ski hill. To predict and analyze typically thousands or even millions of potential landslides, this program uses a three-dimensional method of columns limit-equilibrium analysis [10]. Scoops3D assesses slope stability across a given DEM, input by the user, along with inputs for the cohesion (C) and internal angle of friction (φ) for the soil layers, and an input representing the ratio of pore pressure to geostatic pressure (Ru).

In order to assume one homogeneous soil properties layer six simulations were run, varying the friction angle and the Ru-value. Varying these parameters to assume one homogeneous soil layer is appropriate due to the non-uniform tendencies of glacial till in the area. The friction angle was varied between 30 and 36 degrees because the five layers of soil, determined by Barr Engineering in one borehole test, had friction angle values between 30 and 36 degrees (See Appendix 1). According to the user’s manual for Scoops3D, it is recommended that an Ru- value of less than 0.5 is to be used [11] However, Ru-values are an unrefined way of representing how pore pressure affects groundwater conditions, especially related to slope stability [12]. Since the DEM doesn’t have a Ru-value associated with it, an approximation was used for the six Scoops3D simulations. The values of Ru were chosen to be between 0 and 0.25 because these values indicated low factor of safety levels in areas with noticeable failure due to the storm event, coinciding with the Mont Ripley failure and other failures in the vicinity. A unit weight of 120 pounds per cubic feet (pcf) and cohesion of 0 pounds per square feet (psf), also obtained from Barr’s soil properties (Appendix 1), were used for all six simulations. The combinations of the Friction Angle and Ru-Value are listed in Table 5.

Table 5. Friction and Ru-Value Inputs for Scoops3D

Test # Friction Angle (degrees) Ru-Value

1 36 0 2 30 0 3 30 0.25 4 30 0.1 5 36 0.25 6 36 0.1

4.3 Rocsience Slide Model A slope stability model was created using Rocscience Slide version 8.015. Six cross sections of the slope failure area were analyzed using the 5-foot DEM from May 2018 and the new DEM from December 2018 (see Figures 19 and 20). The Slide model was used to further investigate results from the Scoops3D model.

Each cross section was imported into Slide and the soil layers were inputted using borehole data from the Barr Engineering report [1]. Dimensions for the material layers can be found in Appendices 18-29. The soil layers were assumed to be horizontal due to having limited borehole data, and the strength type was calculated using Mohr-Coulomb. The project settings and surface options are listed in Appendices 30-32. Under surface options, Path Search was used because the soil was not homogenous. Global Minimum factor of safety was evaluated for each cross section.

Figure 19: Rocscience Slide Cross Sections May 2018

Figure 20: Rocscience Slide Cross Sections December 2018

4.4 Volume of Material Moved It visually apparent that a significant amount of material from the failure area was carried downstream. To determine the amount of material affected by the flood waters, the difference in elevations, for each cell in the DEM, between the before and after DEMs was calculated using a raster calculation function in ArcMap 10.6, shown in Figure 21.

Figure 21: Elevation Difference for Before and After Flood DEMsThe difference in elevation for each cell between the before and after flood DEMs shown in meters.

After the difference in elevations was calculated, the volume was approximated by multiplying the dimensions of each of the cells with their respective elevation change. It was calculated that about 4,255 cubic meters of material were moved by the flood waters. That is equivalent to nearly 2,870 full-sized pickup truck bed loads [13] or 560 commercial-sized dump truck loads [14].

4.5 Erosion Model The Hjulstrom Diagram empirically plots the relationship between particle erosion, transport, and deposition with flow velocity. The x-axis shows the particle diameter in millimeters, while the y-axis is the flow velocity in centimeters per second. It is used to determine the velocity needed to erode, suspend, and deposit particles of different sizes. The Hjulstrom curves can be seen in Figure 22. In this diagram, the upper line indicates the critical erosion velocity, or minimum velocity needed to erode a material. It can be observed that fine particles require more energy for erosion to occur than sands. This is due to the clay and fine particles’ cohesive properties. The energy then increases for larger particles due to their increasing weights. The bottom line is the critical settling velocity. This is the maximum velocity at which particles will settle out of the flow. The settling velocity is higher for larger grains; they require more energy to be carried in the load so they will fall out of the water with a smaller velocity [15].

Figure 22. Hjulstrom Diagram. This diagram shows the critical settling and critical erosion velocities for varying grain sizes. The upper section of the graph shows the erosion zone, where particles will be eroded and suspended in the flow of water. The middle section, transport, has a range of velocities for which the grains will be carried by the flow. The bottom section, deposition, displays the velocities at which particles will settle [16].

5. RESULTS

5.1 From Geohydrology

STORM EVENT RESULTS The peak discharge, calculated using the Rational Method, was determined to be 94.1 cubic feet per second (cfs) for Powderstash, and 479.7 cfs for Ripley Creek. Finally, the peak discharges were converted to SI units: 2.7 cubic meters per second (cms) for Powderstash, and 13.6 cms for Ripley Creek.

FUTURE SNOWMELT RESULTS The spring discharges for the past 5 years through Trap Rock River were used as an approximation of snowmelt for the Hancock area. It was assumed that Lake Linden has the most accurate data for snowmelt volume since its data is gauged daily by the United States Geological Survey meters (USGS). The total discharges were calculated by subtracting the average baseflow from the data, which was obtained from USGS as well. Then the data was visually inspected to determine when the spring snowmelt began, and the total discharge over a month to a couple of months were summed together. See Table 6 for the results of this analysis.

Table 6. Spring Discharges for the past 5 years in the Houghton County area Year 2018 2017 2016 2015 2014 Avg. Daily 4080 6060 2950 4600 9090 Discharge (cubic feet per second, cfs) Total Spring 185 141 69 94 211 Discharge (cubic feet per second, cfs)

See Appendices 3-7 for graphs of the daily discharges in Trap Rock River by Lake Linden, MI. This past data can be extrapolated to future years, showing that there should not be a concern for future snowmelt causing further damage. The average daily discharges of 185 cubic feet per second will be managed by the solution proposed at the end of the report.

STAGE HEIGHT RESULTS The stage height for Ripley Creek was calculated using data from the MiSail 5 foot DEM [4] and Equation 5. A cross-section was created for the Ripley Creek channel at the base of the pre- flood slope. It runs from 25,859,447 ft E 859,427 ft N to 25,859,516 ft E to 859,419 ft N on the MiSail DEM. The location of the cross-section can be viewed in Figure 23. The slope of the banks, m in Equation 5, were obtained from the cross-section; the left and right slope were averaged for our final value of 0.17 ft/ft. Figure 24 shows a plot of the cross-section and the calculation of bank slope. A cross-section line was drawn perpendicular to the established Ripley Creek cross-section in order to obtain the slope, S, of the channel: 0.35 ft/ft. Channel roughness was assumed to be 0.035. According to Corvallis Forestry Research Community, this is the normal n value for a straight, clean, full stage river with some stones and weeds. [17]. The unit conversion value, K, is 1.49 due to usage of imperial units. These values were used with the flow value calculated from the rational method, 479 cfs, to iteratively solve for stage height. The stage height for Ripley Creek at location of the cross-section was calculated to be about 1.81 ft.

Figure 23: Cross Section of Ripley Creek Channel Location of the cross-section of the Ripley Creek channel below the slope failure. The cross-section is indicated by the red line. It runs from 25,859,447 ft E 859,427 ft N to 25,859,516 ft E to 859,419 ft N. (Adapted from [4])

The same steps were used in the calculation of the stage height of Powderstash creek. For Powderstash creek, two cross-sections were taken. Cross Section 1 is located in the Powderstash channel above the slope failure. This cross-section line runs from 25859318 ft E 852518 ft N to 25859423 ft E 859495 ft N. Cross Section 2 runs across the pre-failure area from 25849424 ft E 859488 ft N to 25859355 ft E 859377 ft N. The location of these two cross- sections can be viewed in Figure 25. The two cross-sections and the calculation of the bank slope can be viewed in Figures 26 and 27. The slope of the channel for Cross Section 1 was 0.16 and the slope for Cross Section 2 is 0.6, which was determined from a cross-section line running parallel to the channel. The same n and K values were used from the stage height calculation of Ripley Creek, 0.035 and 1.49, respectively. These values were used with the calculated flow for Powderstash Creek from the rational method, 94 cfs, to determine the stage height for the two cross-sections. For Cross Section 1, the stage height was calculated to be about 1.3 ft. For Cross Section 2, the stage height was calculated to be about 0.89 ft.

Figure 24: Cross-Section Points of Ripley Creek The two trend lines show the equations and slopes for the left and right bank. The averaged bank slope is about 0.17 ft/ft.

Figure 25: Cross-Sections of Powderstash Creek ChannelThe yellow line is Cross Section 1, which runs above the slope failure from 25859318 ft E 852518 ft N to 25859423 ft E 859495 ft N. Cross Section 2 is in blue, running across the pre-failure slope from 25849424 ft E 859488 ft N to 25859355 ft E 859377 ft N (Adapted from [4]).

Figure 26: Cross-Section 1 of Powderstash Creek The trend lines show the slope of the right and left banks. The average bank slope was calculated to be 0.24 ft/ft.

Figure 27: Cross Section 2 of Powderstash Creek The trend lines show the slopes of the right and left banks. The average bank slope was computed to be 0.19 ft/ft.

VELOCITY OVER POWDERSTASH RESULTS Using Equation 4, the flow width for the two cross sections was computed. For Cross Section 1, the width is 11.09 feet. For Cross Section 2, the flow width is 11.11 feet. Then, Equation 7 was used to calculate the velocity for the specified flow, width, and height. The velocity at Cross Section 1 is about 12.7 ft/s, or 3.9 m/s. The calculated velocity at Cross Section 2 is about 19.04 ft/s, or 5.8 m/s.

5.2 From Geotechnical

TOE EROSION EESULTS Cross-section lines 3, 4, and 5 were used in the toe erosion analysis of Ripley Creek below the slope failure. Their locations are previously mentioned in the Rocscience Slide section and can be viewed in Figure 19. The soil property and layer data was interpreted from the Barr Report (Appendix 1), assuming horizontal soil layers. The D50 value for each soil layer was used in the bank material input sheet to calculate the critical shear stress of each layer. The erodibility coefficient for each layer was assumed to be 0.1 cubic centimeters per Newton second (cm3/Ns). According to Michigan State University, sandy soils usually have an erodibility factor of 0.05 to 0.2 cm3/Ns [18] The channel was set to a depth of 1.8 feet, or 0.55 meters, which was obtained from Manning’s Equation, for a total time of 2.5 hours.

Cross-Line 4 experienced the most erosion out of the three trials. It experienced 2.465 m2 of erosion with a maximum lateral retreat of 73 cm. The before and after erosion cross-sections for Line 4 can be seen in Figures 28 and 29. The erosion experienced on this slope is minimal and would not have an effect on the overall stability. The erosion experienced on the cross-sections for lines 3 and 5 is even less. Cross-line 3 experienced a total of 0.468 m2 of erosion with a maximum lateral retreat of 92.6cm. For cross-line 5, there was a total of 1.514 m2 of eroded material from the slope, with a maximum lateral retreat of 27 cm. The before and after cross- sections for lines 3 and 5 can be viewed in Appendices 14-17.

Figure 28: Before and After Toe Erosion Cross-Section 4 The erosion at the base of the slope due to Ripley Creek is barely noticeable. It should not have a large impact on the overall stability of the slope.

Figure 29: Before and After Toe Erosion Cross-Section 4 The cross-section is zoomed in on the toe. The bottom of this slope only experienced a total of 2.464 m2 of erosion.

SCOOPS3D RESULTS The raster outputs from the six Scoops3D simulations were classified to show four classes of factor of safety, as seen in Figure 30 below (all simulations can be found in Appendices 8 through 13). The outputs are shown on top of the pre-flood DEM and the failure area is outlined in white. Areas that are red on the output indicate a factor of safety of less than or equal to one in those cells and are deemed “high risk” or likely to fail given the current input parameters.

Figure 30: Scoops3D Factor of Safety Test 1Scoops3D simulation 1 has a friction angle of 36 degrees and an Ru-value of 0. There are two small “high risk” areas within the bounds of the Mont Ripley slope failure.

Small patches of “high risk” areas exist within the bounds of the failure area for each of the six simulations. However, size and relative location of the high risk areas within the bounds of the failure area vary between the simulations, due to the changes in the input variables: friction angle and Ru-value. The factor of safety values are reasonable across all six simulations of Mont Ripley. However, there is a bit of uncertainty in the input variables due to assuming a homogeneous soil layer and approximating Ru-values and therefore, these simulations should be considered as a risk assessment model rather than a complete slope stability model.

ROCSCIENCE SLIDE RESULTS Global Minimum factor of safety was calculated for each cross section of the May 2018 and December 2018 DEM. All cross sections from the May 2018 DEM showed minimum FS less than 1 which is consistent with the findings from the Scoops3D model (see Figures 31-36). Similarly, the cross sections from the December 2018 DEM all showed minimum FS less than 1 (see Figures 37-42).

Figure 31: Rocscience Slide Minimum FS Cross Section 1 May 2018

Figure 32: Rocscience Slide Minimum FS Cross Section 2 May 2018

Figure 33: Rocscience Slide Minimum FS Cross Section 3 May 2018

Figure 34: Rocscience Slide Minimum FS Cross Section 4 May 2018

Figure 35: Rocscience Slide Minimum FS Cross Section 5 May 2018

Figure 36: Rocscience Slide Minimum FS Cross Section 6 May 2018

Figure 37: Rocscience Slide Minimum FS Cross Section 1 December 2018

Figure 38: Rocscience Slide Minimum FS Cross Section 2 December 2018

Figure 39: Rocscience Slide Minimum FS Cross Section 3 December 2018

Figure 40: Rocscience Slide Minimum FS Cross Section 4 December 2018

Figure 41: Rocscience Slide Minimum FS Cross Section 5 December 2018

Figure 42: Rocscience Slide Minimum FS Cross Section 6 December 2018

HJULSTROM DIAGRAM RESULTS Using the velocity results from the Manning’s equation analysis for Powderstash Creek, the erodible particle size on Mont Ripley over the failed slope was determined. The two velocities, 3.8 m/s and 5.8 m/s, can be plotted on the Hjulstrom curve in order to determine the range of erodible particle sizes. Figure 43 shows the two velocities from the Powderstash analysis on the Hjulstrom diagram.

Figure 43: Powderstash Creek Flow Velocities on Hjulstrom Diagram Velocities from analysis on two points of Powderstash Creek plotted on Hjulstrom diagram (adapted from [16]).

From Figure 43, the particle sizes that would have been eroded during the Father’s Day Flood can be determined. According to our results, all fines would have been eroded and suspended in the flow. The upper limit of particle size erodibility is not as definite. For the velocity of 3.9 m/s, grain sizes of about 100 mm would have eroded. Using the velocity of 5.8 m/s, erosion would have occurred for grain sizes up to 300 mm. Transport would be likely for all grain sizes on the Hjulstrom diagram: 0.001 mm to 1000 mm. Deposition would not occur for any grain sizes included on the chart.

From the grain size distribution curves obtained from Barr Engineering’s Phase 1 report [1], it can be determined that there was a 100% passing rate for all soil samples obtained from the field for the 2 in sieve opening. All soil particles are smaller than 2 in, or 5.08 cm. From the results of the Hjulstrom Diagram analysis, it can be speculated that all of the soil that was exposed to the flow on the slope would have experienced erosion. Since the soil is glacial till, its composition is variable. Therefore, there may have been larger boulders that would not have eroded in the field.

5.3 Discussion of Method of Failure Based on the findings from the Scoops3D simulations, it was determined that at least small portions of the failure area were “high risk” and likely to fail under conditions similar to the storm event, prior to the event via aerial analysis.

This likelihood of failure was also confirmed by the results from the Slide models. These models also indicated slope conditions prior to the storm event were considered unstable via cross section analysis. Also, it is determined from Slide that the current state of the failure area is still unstable, providing clear reason to determine a strategy for slope stabilization and mitigation.

From the two erosion analyses, it was determined that overland erosion likely played a primary role in the slope failure. The results from the Hjulstrom Diagram show that all of the soil types would experience erosion from the flow of Powderstash Creek. However, the toe erosion due to Ripley Creek seemed to have minimal impact on the stability of the slope. The toe erosion model showed little difference in the cross-sections for pre- and post-flood conditions. Overall, the results from our analyses indicate a combination of factors that contributed to the resulting Mont Ripley slope factor. According to the Scoops3D and Slides simulations, small

56 portions of the slope were unstable before the flood and failure. The instability was assisted by overland erosion from Powderstash Creek to cause the resulting slope failure.

The results from Scoops3D and Slide point to overland erosion as the primary factor in the Mont Ripley slope failure scenario. (Initial instability in combination with the overland erosion seems to be the cause of failure) This is backed by the findings from the excel-based Toe Erosion Model. Toe erosion at the time of failure was determined to have minimal impact on the entire slope, effectively eliminating toe erosion as a major contributor to the overall slope failure.

6. RECOMMENDATIONS

6.1 Solutions

6.1.1 CULVERTS Culvert remediation should be a priority as overtopping and surface flow appears to be the largest factor in the slope failure. In the design of any culvert, grading of the ravine to a more stable slope angle is recommended.

The Powderstash ravine culvert should be designed using a 36 inch steel pipe culvert that is 150 feet long, according to MDOT standards for flow rates greater than 335 cfs. The addition of debris deflectors may afford protection from clogging due to washout material.

If the new culvert were to be placed in the same position as the old culvert, the flow velocity would be much too high due to the steep change in elevation between Powderstash Creek and Ripley Creek. High flow velocities may damage the culvert and surrounding soil at the exit. To prevent this, the new culvert would need to be connected to Ripley Creek at a lesser angle. This can be achieved if the new culvert directs water flow from Powderstash to the east, instead of the southern direction of the old culvert. However, this design poses new challenges at the culvert entrance; redirecting the flow nearly 90 degrees will allow water to impact the side of the culvert which may damage it in a short period of time. Further research will be needed to assess the feasibility of this design.

To protect the culvert exit at Ripley Creek and the sides of Powderstash Creek from erosion, rip- rap sized between 0.508-1.524 meters may be placed. Cost analysis for a basic culvert installation can be found in Figure 44. It should be noted however that the cost analysis in Figure 44 is for driveway culverts, which require less earthwork to install. The culvert replacement at Powderstash would require much more earthwork, driving up the cost of installation.

Figure 44. Basic cost of culverts for Houghton County [19]

6.1.2 SLOPE STABILITY The slope is currently unstable and continues to degrade at the ridge due to the angle and weight of the soil. This is compounded by snowmelt and precipitation. The slope will be reshaped to allow for the securement of geotextile, placement of GeoWeb and soil nails on the upper two-thirds of the face.

Reconstruction of Deer Track Trail will require the addition of fill and stabilization supports. The slope will be graded and benched to a stable slope ratio for the given soil type (see Table 7 from the US Forestry Service [20]).

Table 7.Common Stable Slope Ratios for Varying Soil/Rock Conditions [20]

Reinforcement with a geotextile, either flat or wrap-faced, will be used to support the on-site or imported fill (see Figure 45-49 for examples).

Figure 45. Design of geotextile reinforcement layers for over-steep slopes [20]

Figure 46. Illustration of Wrap-Faced geotextile reinforcement used for slopes 1:1 or greater [21]

Figure 47.Detailed illustration of Wrap-faced supports with soil and vegetation placement [21]

Topsoil and biodegradable erosion control mats will be placed on the slope surface and seeded with local vegetation. The toe of the slope, which borders Ripley Creek, will be reinforced with appropriately sized rip-rap (Figure 50) [22].

Figure 48.Cross section view containing a fully developed reinforced slope with supports, soil, and vegetation [21]

Figure 49.Placement of GeoWeb panels secured with soil nails [23]

Figure 50.Rip Rap Sizing Chart [22]

6.2 Recommended Future Work The results from the three geotechnical models—Scoops3D, Slide, and B-STEM—provided a conclusive and straightforward analysis. However, for a more refined analysis, the team recommends the following strategies: • Analyze the post-flood stability of the area using Scoops3D to determine new factor of safety data on current conditions. This would add value to developing a solution strategy in slope stability and mitigation. • Conduct testing on groundwater conditions to eliminate uncertainty in groundwater levels and infiltration rates for modeling. Knowing this information would provide better insight on groundwater conditions during the storm event and more accurate modeling. • Collect more information on soil layers. The team would advise more than one borehole to better understand the fluctuating and varying layers of glacial till. This information would help to increase the accuracy of the three models. • Conduct another drone flight to encompass a larger area. This would provide a more detailed topography surface for modeling and increase the accuracy of modeling. • Complete a costs analysis/feasibility study comparing the replacement of the north culvert at Powderstash Creek to the replacement of the south culvert at Powderstash Creek.

7. CONCLUSIONS

Mont Ripley’s Deer Track Trail experienced a slope failure due to the June 17, 2018 flood event. An on-site evaluation was performed to identify areas that needed to be rectified. It was noted that the slope to the south of the intersection of Powderstash and Deer Track Trail had failed as well as the culvert connecting Powderstash ravine to Ripley Creek. Data were collected from drone surveillance, soil analysis, field measurements, and derive topographic maps of post- event areas. This information was used to calculate watershed characteristics and flow rates to use as inputs for models. Modelling programs were used to define how the slope likely failed and provide information to develop options to stabilize and/or repair the damage to Mont Ripley. Overland erosion from Powderstash Creek played a crucial role in the slope failure. Ripley Creek did not have a significant impact in the erosion of the toe of the slope. Culvert and slope reconstruction options were formulated along with preliminary costs estimates.

ACKNOWLEDGEMENTS

Rudiger Escobar Wolf John Gierke Ripley Township Residents Ryan Williams, GISP James Degraff and Daniel Lizzadro-McPherson Chris Nelms Kate Thayer Curtis Edson Alex Mayer Michigan Tech Facilities & Mont Ripley Staff UP Engineers & Architects Barr Engineering Dave Watkins and Civil Senior Capstone group: Leah DeSimpelare, Charles Miller, Ashley Lingle Sarah Washko

REFERENCES

[1] Barr Engineering Co., "Geotechnical Evaluation and Feasibility Report: Mt Ripley Father's Day Flood Repairs," Duluth, MN, 2018.

[2] Michigan Technological University, "Mont Ripley Ski Area," 2019. [Online]. Available: https://www.mtu.edu/mont-ripley/.

[3] C. J. Doonan, "Water Investigation 10 Ground Water and Geology of Keweenaw Peninsula, Michigan," Lansing, MI, 1970.

[4] Michigan.gov, "SOM - Michigan Statewide Authoritative Imagery and LiDAR Program," 2019. [Online]. Available: https://www.michigan.gov/som/0,4669,7-192- 78943_78944_78949_78952_63834---,00.html..

[5] National Resources Conservation Service, "Urban Hydrology for Small Watersheds: TR-55," USDA, 1986.

[6] NRCS, "Hydrology Training Series," 2019. [Online]. Available: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/nedc/training/resources/?cid=stelprdb 1083083 .

[7] KRC, "Index of /~weather," 2019. [Online]. Available: http://blizzard.mtukrc.org/~weather/.

[8] National Weather Service, "2018 Fathers Day Weekend: Upper Michigan Flooding.," 2018. [Online]. Available: https://www.weather.gov/mqt/fathersday2018weekendflooding.

[9] Open Channel Flow, "Manning's Formula For Determining Open Channel Flow," 2019. [Online]. Available: https://www.openchannelflow.com/blog/manning-formula-for- determining-open- channel-flows .

[10 USGS, "Scoops3D," 2015. [Online]. Available: https://www.usgs.gov/software/scoops3d . ]

[11 Reid, M.E., Christian, S.B., Brien,, D.L. and Henderson, S.T., Scoops3D—Software to analyze ] 3D slope stability throughout a digital landscape: US Geological Survey Techniques and Methods, USGS, 2015.

[12 GEO-SLOPE International Ltd., "Pore-Water Pressures Defined Using Ru," 2019. [Online]. ] Available: http://www.geo-slope.com.

[13 Cedar Grove, "Average Pickup Truck Capacities in Cubic Yards.," [Online]. Available: ] http://www.cedar-grove.com.

[14 Coopersburg & Liberty Kenworth, "LEARN HOW MUCH DIRT YOU CAN CARRY WITH ] KENWORTH DUMP TRUCKS," 2018. [Online]. Available: https://www.coopskw.com/learn- much-dirt-can-carry-kenworth-dump-trucks/.

[15 WikiVisually, "Hjulstrom Curve," 2019. [Online]. Available: ] https://wikivisually.com/wiki/Hjulstr%C3%B6m_curve.

[16 Kokkinos, P., "Revision questions for AS Rivers, Floods and management," Geography is easy, ] [Online]. Available: https://geographyiseasy.wordpress.com/2015/02/15/revision-questions-for- as-rivers-floods-and-management/.

[17 Fsl.orst.edu, "Manning's n Values," 2019. [Online]. Available: ] http://www.fsl.orst.edu/geowater/FX3/help/FX3_Help.html#8_Hydraulic_Reference/Mannings_n _Tables.htm.

[18 RUSLE - Online Soil Erosion Assessment Tool, "K Factor," 2019. [Online]. Available: ] http://www.iwr.msu.edu/rusle/kfactor.htm.

[19 Houghton County Road Commisssion, "Minutes of Regular Monthly Meeting," Houghton, MI, ] 2018.

[20 G. Keller, "Chapter 11," in Slope Stabilization and Stability of Cuts and Fills, US Forestry ] Service.

[21 Geogrid, StrataGrid, https://www.geogrid.com/en-us/products/stratagrid. ]

[22 USDA, National Engineering Handbook, 2009. ]

[23 Steven C Devin PE GE, https://devingeo.com/. ]

[24 USGS, 2019. [Online]. Available: waterdata.usgs.gov. ]

APPENDICES

Appendix 1. BARR Soil Properties [1]

Appendix 2. TR-55: Relationship between velocity and watershed slope [5]

Appendix 3.Daily Discharge at Trap Rock River by Lake Linden, MI 2018-19 [24]

Appendix 4. Daily Discharge at Trap Rock River by Lake Linden, MI 2017-18 [24]

Appendix 5. Daily Discharge at Trap Rock River by Lake Linden, MI 2016-17 [24]

Appendix 6. Daily Discharge at Trap Rock River by Lake Linden, MI 2015-16 [24]

Appendix 7. Daily Discharge at Trap Rock River by Lake Linden, MI 2014-15 [24]

Appendix 8. Scoops3D Simulation 1

Appendix 9. Scoops3D Simulation 2

Appendix 10. Scoops3D Simulation 3

Appendix 11. Scoops3D Simulation 4

Appendix 12. Scoops3D Simulation 5

Appendix 13. Scoops3D Simulation 6

Appendix 14. Before and After Erosion at Toe of Line 5

Appendix 15. Before and After Erosion of Line 5

Appendix 16. Before and After Erosion at Toe Cross Section of Line 3

Appendix 17. Before and After Erosion Cross-Sections for Line 3

Rocscience Slide Material Layers Dimensions Before Cross-Sections

Appendix 18. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 1

Appendix 19. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 2

Appendix 20. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 3

Appendix 21. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 4

Appendix 22. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 5

Appendix 23. Rocscience Slide Material Layers Dimensions May 2018 Cross Section 6

Rocscience Slide Material Layers Dimensions After Cross-Sections

Appendix 24. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 1

Appendix 25. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 2

Appendix 26. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 3

Appendix 27. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 4

Appendix 28. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 5

Appendix 29. Rocscience Slide Material Layers Dimensions December 2018 Cross Section 6

Appendix 30. Rocscience Slide Project Settings - General

Appendix 31. Rocscience Slide Project Settings - Methods

Appendix 32. Rocscience Slide Surface Options