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Home My WebLink AboutI-49_NHC_Task 9.1 Technical Memo Year SixTo Sandi Wilbur, PE City of Durham Public Works Department, Stormwater and GIS Services Division 101 City Hall Plaza Durham, NC 27701 Page 1 Subject Summary of 6-Year Stream Bank Erosion Monitoring Results and Development of Bank Erosion Rate Curves Originally Prepared by Wildlands Engineering, Inc. 312 West Millbrook Road, Suite 225 Raleigh, NC27609 WiLDLANDs Date October 28, 2015 Revised by Kimley-Horn and Associates, Inc. 421 Fayetteville Street, Suite 600 Klr ley)))Horn Raleigh, NC 27601 AECOM 1600 Perimeter Park Drive, Suite 400 /�i�w ECOM Morrisville, NC 27560 Revised Date March 9, 2021 Contents 1.0 Introduction............................................................................................................................ 3 2.0 Initial Site Selection and Field Data Collection........................................................................3 3.0 Monitoring Data Analysis.......................................................................................................8 4.0 Results and Conclusions...................................................................................................... 16 5.0 Root Dendrogeomorphology................................................................................................17 6.0 Future Monitoring................................................................................................................. 19 7.0 References.......................................................................................................................... 21 2 1.0 Introduction The City of Durham Stormwater and GIS Services Division (City) is collecting stream erosion data to develop local empirical relationships between erosion estimation methods and stream bank erosion rates. These types of empirical relationships were originally developed in North Carolina by researchers at N.C. State University using data collected in western North Carolina from the Mitchell River watershed (Harman, unpublished data). However, the City recognizes that the alluvial soil types in the Triassic Basin found within the City of Durham are generally sandier and more erosive than the western Piedmont soils. To increase confidence in the estimates of erosion estimation methods and measured stream bank erosion rates in Durham, the City's goal is to develop local empirical relationships using near -bank stress (NBS) and Bank Erosion Hazard Index (BEHI) observations compared to measured stream bed and bank erosion in local streams. Wildlands Engineering (Wildlands) and the City selected and installed 16 bank monitoring sites in 2014. These sites were monitored in March and August 2015 producing results for Year 1. Kimley- Horn and AECOM continued the bank monitoring for two additional years (Year 2 and 3). In addition to monitoring the original sites chosen by the City and Wildlands in 2014, an additional site, Site 17, was established to replace Site 16 which was discontinued after the first year of monitoring. Kimley- Horn and AECOM completed another 20 months of bank monitoring (one monitoring event every 5 months for 4 monitoring events) from September 2019 through December 2020. During this time, Site 1, Site 8, and Site 14 were damaged and not re-established. Site 10 was damaged between the March 2018 and October 2019 monitoring events and was reestablished on October 2, 2019. Wildlands, under a separate contract with the City, provided design, permitting, and construction services for the Third Fork Creek Stream Restoration project. As part of this work, four additional sites were monitored by Wildlands for approximately 1.5 years to estimate bank stability and erosion rates within the project limits at Third Fork Creek. The purpose of this Technical Memorandum is to provide a summary of the field data collected and results from a five-year assessment of stream bank erosion sites from 2015 through 2020, develop localized erosion rate curves, and provide a comparison to the root dendrogeomorphology erosion study data. 2.0 Initial Site Selection and Field Data Collection In 2014, sixteen (16) study sites were identified across six of the City's local watersheds, including two in the Third Fork Creek watershed and five in the Northeast Creek watershed (Figure 1). Both watersheds were prioritized by the City during a meeting in June 2014. In addition, two sites in the Ellerbe Creek watershed, three sites in the Little Lick Creek watershed, two sites in the Sandy Creek watershed, and two sites in the Southwest (Crooked) Creek watershed were also selected for monitoring. A full analysis of the initial site selection can be found in the previous memorandum titled "Summary of Bank Pin Installation Sites and Monitoring" (Wildlands, 2014b). 3 13 4 ,,- Tihird Fork I . 10 2 8 1 R1 Creek 15 0 Brier Creek T .! 1. % Southwest 'Creek' Iron 54 Crooked Creek Creek 5 ' �3 4 Legend Monitoring Sites Roads N Little Creek — Streams �J g Durham City Limits 0 3,500 7,000 0 7 G Watersheds Feet Jordan_L-ake Carolina Slate Belt (Non -Triassic Basin Soils) City of Durham Figure 1 aCom Public Works Department Bank Erosion Monitoring Sites 101 City Hall Plaza Durham, NC 27701 Kimley CITY OF DURHAM ENO RIVER >) Horn CITY OF WATERSHED IMPROVEMENT PLAN March 2021 DURHAM Monitoring at Site 16, located in the Third Fork Creek watershed, was discontinued after Year 1 of monitoring. After observing the site for the first year, it was determined that the location was likely recently disturbed when selected, as it had aggraded and revegetated during the first year of monitoring. In 2016, an additional site (Site 17) was chosen to replace Site 16 for monitoring Years 2 and 3. Site 17 also had a BEHI rating of Extreme and NBS rating of High (similar to that of Site 16) and was located in the Third Fork Creek watershed. Monitoring stations at each of the identified sites consists of a minimum of one toe pin and three bank pins installed in one bank. Full -height stream bank profiles and the end of each pin were surveyed at each location along with a measurement of the length of the exposed portion of each pin. BEHI and NBS assessments were performed during the initial site installation to categorize the sites ranging from Moderate to Extreme BEHI and NBS adjective ratings. The BEHI assessment tool determines the susceptibility of a stream bank to erosion based on the scoring of seven visual and quantitative field measurements. The near bank stress (NBS) assessment tool estimates the energy distribution against the stream bank using one or more field estimation methods. A detailed description of the BEHI and NBS assessment methods can be found in a previous memorandum titled "Guidance for Selection of Sites for Bank Pin Installation" (Wildlands, 2014a). Table 1 summarizes the 21 study sites identified, including stream and watershed name, GPS coordinate locations, and BEHI and NBS categorizations. Figure 1 shows the location of each site and includes watershed and Triassic Basin boundaries. Initial conditions photos for each of the 17 sites are included in Appendix A. 5 Table 1: City of Durham Bank Erosion Monitoring Sites Long-TermBank Site No. . Sites Bank Site #1 UT to Ellerbe Creek Watershed Ellerbe Creek Comment Camden Ave. Latitude 36.0246 Longitude '-BEHI -78.8604 Rating Extreme NBS Rating Extreme Bank Site #2 UT to Ellerbe Creek Ellerbe Creek Museum of Life and Science 36.0307 -78.9032 High Very High Bank Site #3 UT to Northeast Creek Northeast Creek McAdams Upstream (approx. 100' D/S of road) 35.9103 -78.8953 Very High Very High Bank Site #4 UT to Northeast Creek Northeast Creek McAdams Middle 35.9099 -78.8954 High Extreme Bank Site #5 UT to Northeast Creek Northeast Creek McAdams Downstream 35.9093 -78.8959 Moderate Very High Bank Site #6 Crooked Creek Southwest (Crooked) Creek Scott King Rd. Upstream 35.8758 -78.9436 Moderate Extreme Bank Site #7 Crooked Creek Southwest (Crooked) Creek Scott King Rd. Downstream 35.8750 -78.9433 Moderate High Bank Site #8 Northeast Creek Northeast Creek So Hi Dr. Downstream 35.9367 -78.8777 Very High Moderate Bank Site #9 Northeast Creek Northeast Creek So Hi Dr. Upstream 35.9381 -78.8768 Very High High Bank Site #10 Third Fork Creek Third Fork Creek Weaver St. 35.9664 -78.9130 Extreme Very High Bank Site #11 UT to Little Lick Creek Little Lick Creek West of S. Woodcrest St. Upstream 35.9835 -78.8522 High Moderate Bank Site #12 UT to Little Lick Creek Little Lick Creek West of S. Woodcrest St. Downstream 35.9836 -78.8521 High High Bank Site #13 UT to Sandy Creek Sandy Creek West of Wade Rd. Upstream 35.9770 -78.9521 Moderate Moderate Bank Site #14 UT to Sandy Creek Sandy Creek West of Wade Rd. Downstream 35.9772 -78.9521 Extreme Moderate Bank Site #15 Chunky Pipe Creek Little Lick Creek Southern School of Energy and Sustainability Fitzgerald Ave. Chalmers St. 36.0032 -78. 8261 Very High Extreme Bank Site #16 (discontinued) UT to Third Fork Creek Third Fork Creek 35.9687 -78.9059 Extreme High Bank Site #17 Third Fork Creek Third Fork Creek 35.9663 -78.8963 Extreme High Table 1 Continued: City of Durham Bank Erosion Monitoring Sites Bank Site No. Stream Watershed Comments Latitude Longitude BEHI Rating NBS Rating rShort-term Monitoring Sites TFC — BP#1 UT to Third Fork Creek Third Fork Creek stream N/A N/A High High Third Fork Creek restoration pre -construction monitoring of UT2A TFC — BP#2 UT to Third Fork Creek Third Fork Creek Third Fork Creek stream N/A N/A Moderate Moderate restoration pre -construction monitoring of UT3 TFC — BP#3 Third Fork Creek Third Fork Creek Third Fork Creek stream N/A N/A High Low restoration pre -construction monitoring of Third Fork Creek TFC — BP#4 Third Fork Creek Third Fork Creek Third Fork Creek stream N/A N/A High High restoration pre -construction monitoring of Third Fork Creek In March 2015, the length of exposure at each pin was measured at each site to estimate bank recession rates. In August 2015, one year following the initial bank pin installations, field data was again collected at each of the 16 original study bank sites, completing Year 1 monitoring. Data collection consisted of surveys of full -height bank profiles and a measurement of the length of the exposed portion of each bank pin. In August 2016, Kimley-Horn initiated Year 2 of the bank pin monitoring. Monitoring continued at Sites 1-15 and the new Site 17. Site 16 and the short-term monitoring sites at Third Fork Creek were not revisited after August 2015. Approximately every 6 months from August 2016 until March 2018, the 16 sites were monitored, and bank profiles were collected along with photos. The Kimley-Horn team began site monitoring again in September 2019 and every 5 months until the fourth and final monitoring event in December 2020. Full bank profiles along with photos were collected at the sites. Photos collected at each location in August 2014, August 2015, August 2016, March 2017, August 2017, March 2018, September 2019, February 2020, July 2020, and December 2020 are included in Appendices B - J. 3.0 Monitoring Data Analysis The semi-annual surveyed bank profiles were plotted against the initial surveyed profile data collected in 2014. Annualized bank erosion rates were calculated by comparing the surveyed bank profiles following methodology provided by Will Harman (NCSU) (Wildlands 2014b) in development of the North Carolina erosion rate curves. Following similar methodology, the erosion rates calculated for these study sites were used to develop localized erosion rate curves. Annualized erosion rates (feet/year) were calculated as follows: Area of Bank Loss (sf) 365 days/year X Bank Height (ft) Days of Record Additionally, two methods were used to calculate the average bank recession during the six -year study period. A quick method, the average bank recession in inches from pin exposure (Table 2), was determined by averaging the maximum increase of bank pin exposure at a given monitoring site. The second method (Table 2) was calculated as the area of bank loss between surveys divided by the overall bank height (see Figure 2). Figure 2 Area of Bank Loss Between Surveys Table 2: Annualized Bank Erosion Rates for Streams Found in City of Durham with Triassic Basin Soils Site No. TFC - BP#2 (UT3) * BEHI Rating Moderate NBS Rating Moderate NBS Plot Value 3 PeriodBank Time ..Exposure' 512 Average 2.13 2.96 0.18 Bank Site #13 Moderate Moderate 3 2309 6.35 7.49 0.10 Bank Site #7* Moderate High 4 2337 9.72 20.71 0.27 Bank Site #5 Moderate Very High 5 2337 3.14 4.68 0.06 Bank Site #6 Moderate Extreme 6 2337 0.52 0.49 0.01 TFC - BP#3 (TFC)* High Low 2 512 24.11 26.00 1.54 Bank Site #11 * High Moderate 3 2309 4.35 0.69 0.01 TFC - BP#1 (UT2A)* High High 4 512 32.08 30.90 1.84 TFC - BP#4 (TFC) * High High 4 512 3.25 4.85 0.29 Bank Site #12 High High 4 2309 3.63 10.60 0.14 Bank Site #2 High Very High 5 2337 7.31 9.56 0.12 Bank Site #4 High Extreme 6 2337 7.90 5.54 0.07 Bank Site #8 Very High Moderate 3 1324 5.49 20.48 0.47 Bank Site #9 Very High High 4 2331 16.9 12.90 0.17 Bank Site #3 Very High Very High 5 2337 12.40 12.24 0.16 Bank Site #15 Very High Extreme 6 2302 11.60 9.90 0.13 Bank Site #14 Extreme Moderate 3 1302 11.30 4.95 0.12 Bank Site #16* Extreme High 4 352 3.46 -0.71 N/A3 Bank Site #17 Extreme High 4 1573 7.24 7.84 0.15 Bank Site #10* Extreme Very High 5 2331 12.49 67.93 0.89 Bank Site #1 Extreme Extreme 6 1330 11.59 10.94 0.25 'Average recession from pin exposure calculated from maximum exposure values recorded over monitoring period. 2Average length of recession calculated as area of bank loss over monitoring period divided by bank height. 'Negative annualized bank erosion rates removed from plot and calculated curves. *Sites that are in italicized text indicate sites that were considered outliers as described in the technical memorandum. They have not been included in the best fit curves in Figure 3. This includes Bank Sites 7, 8, 10, 11, 16, and the Third Fork Creek sites. Both calculated values, average recession based on pin exposure and average recession based on area of bank loss, were similar in most cases; however, the average length of recession is a more accurate representation of the bank loss incurred during the monitoring period as it accounts for bank loss across the entire bank profile rather than the erosion experienced at each bank pin. Bank Site 11 yielded negative bank loss values at the end of the three-year monitoring in 2018 (average length of recession); however, continued monitoring has shown a positive bank loss (from an average of 0.1 feet/year aggradation at the end of Year 3 Monitoring to 0.01 ft/yr of erosion at the end of Year 6 Monitoring). Negative bank loss indicates that a bank is aggrading rather than eroding. Streams are dynamic with a regular process of erosional and depositional points within the system. Calculated negative bank loss could also have been due to overall stream bank stability, lack of rainfall to create bank erosion, or bank stabilization/aggradation over the monitoring period. When negative bank loss values were calculated, these sites should be eliminated from the data pool. The data collected from Site 11 appears that the site is still an outlier based on the other High BEHI sites, so the data point for Site 11 is not included in the calculation of erosion rates for that reason. The purpose of this monitoring effort is to determine bank erosion rates based on BEHI and NBS ratings, therefore, if a bank experiences overall aggradation, it no longer falls within the initially determined BEHI/NBS rating. If the City decides to continue monitoring the sites established for this data analysis, the data should be reevaluated to determine if any sites experience aggradation. Significant bank loss was calculated at two bank pin sites (TFC- BP#3 (TFC) and TFC-BP#1 (UT2A)) that are part of the Third Fork Creek stream restoration project. These two bank pin sites were initially installed in highly erosive areas of the project for validation of the proposed restoration approach. TFC- BP#1 (UT2A) is located along a tributary that is actively cutting through unconsolidated soil. There are some indications that this is likely not the natural location of this stream and it is experiencing overflow from Third Fork Creek that has created high stresses in this channel resulting in significant bank loss. TFC-BP#3 (TFC) is located immediately downstream of a pedestrian bridge crossing and riprapped channel experiencing consecutive 90-degree turns. This area experiences uncharacteristically high stream velocities and shear stress and field observations have noted the collapse of a tree on the opposite bank immediately upstream of the bank pin location. The resulting erosion rates were magnitudes larger than the two similarly rated sites from the pool of study sites skewing the calculated average bank erosion rates and plotted curves. The Third Fork Creek sites represented stream sections uncharacteristic of the rest of the stream. For this reason, and because the Third Fork Creek bank pin sites will not be available for long-term monitoring, these sites were eliminated from the plots. From the remaining 13 bank pin sites (excludes Bank Sites 7, 8, 10, 11, 16, and the Third Fork Creek bank pin sites), annualized bank erosion rates were plotted against NBS ratings determined during the field reconnaissance. Values were grouped by BEHI ratings to calculate plotted trends in sediment loss for the range of NBS ratings. Sites that were eliminated from the data pool are shown on Figure 1 for visual purposes but were not used to determine calculated trend lines (Figure 3) or average erosion rates (Table 2). As additional data is gathered, different trends may be evident; therefore, after additional data collection from bank monitoring, all the sites should be reevaluated to determine which data points should or shouldn't be eliminated from the average erosion rate equations. Figure 3: Prediction of Annual Streambank Erosion Rates 10 for streams found in City of Durham with Triassic Basin soils y = 0.054eo.256lx R2 = 0.9996 y = 0.2854e-0.126X RZ = 0.9039 TFC - BP#3 (TFC) —TFC - BP#1 (UT2A) y = 0.5628e-0.33X 1 R2 = 0.8767 � Bank Site #10 L y = 1.5257e-01.817X Bank Site #8 R2 = 0.7284 TFC - BP#4 (TFC) WBank Site #7 Bank Site #1 m TFC - BP#2 (UT3) — Bank Site #8 Bank Site #17 Bank Site #9 0.1 Bank Site #14 Bank Site #2 Bank Site #12 Bank Site #3 Bank Site #13 p Bank Site #5 Bank Site #4 .N O W Y C m 0.01 Bank Site #11 Bank Site #6 0.001 2 3 4 5 6 7 Near -Bank Stress (NBS) ■Extreme BEHI ♦Very High BEHI 0High BEHI •Moderate BEHI *Points Excluded from Curves —Third Fork Creek Sites Four sites (Bank Sites 7, 8, 10, and 11) yielded results that were inconsistent with other sites within their respective BEHI rating categories. While they were not helpful in the development of the preliminary erosion rate curves and average bank erosion rates, these sites are recommended for continued monitoring to validate whether additional data will yield more consistent results when compared to other sites within the same rating categories. All sites should be reevaluated as data collection continues (for new sites and/or additional monitoring of existing sites) to determine which sites should be included in the bank erosion rate calculations. During Years 2 and 3 of the monitoring, three sites experienced issues with the bank pins that had to be rectified. The horizontal bank pins and toe pin at Site 1 were displaced between the monitoring by Wildlands in August of 2015 and the monitoring by Kimley-Horn in August 2016. The toe pins and horizontal bank pins were reestablished as close to the original pin location as possible based on photos. Two bank profile graphs are provided in Appendix K for this site for the pin set-ups, and the bank loss was calculated as a weighted average based on length of time the pin set-up was in place. Sites 8 and 10 had the horizontal pins displaced, while the toe pin stayed intact. The new horizontal pin locations are shown with a different symbol on the same bank profile graph. Between Years 4 and 5 of monitoring, Sites 1, 8, 10, and 14 were disturbed. The pins had fallen out of the bank and the toe pins were lost or disturbed. It was decided to re-establish only Site 10. Two bank profile graphs are provided for site 10 in Appendix K. The first graph includes observations from July 2014 through March 2018 and the second graph includes the re-established Site 10 pins from October 2019 through December 2020. Before the July 2020 monitoring event, Site 10's toe pin had been lost. The profile data for this site was adjusted by assuming the low pin was in the same location during the July and December 2020 monitoring events as the initial installation in October 2019. Based on photos, this appeared to be the case. This adjusted bank profile is included on the second graph for Site 10 in this report. The toe pin at Site 2 was disturbed when a large rock rolled over the pin between the observation periods of March 2018 and September 2019. For the remaining observation periods, Site 2 data was adjusted similarly to Site 10, assuming that the low pin was in the same location as the initial installation in July 2014 and adjusting the profile data based on the location of the low pin. Before the final monitoring event in December 2020, the toe pin at Site 9 had been washed away. Additionally, the low pin was still in the bank but had fallen due to erosion below the pin. The low pin exposed length was still able to be recorded. Site 9 data was adjusted assuming the location of the low pin was the same as the initial installation in July 2014. Based on photos, this appeared to be the case. It was observed during the monitoring event in August 2017 that the toe pin at Site 11 was disturbed and no longer aligned with the bank pins. Site 11 data was collected and was adjusted based on the location of the low pin during the initial installation in August 2014 through the remaining observation periods. The toe pin at Site 15 was lost, likely a result of a headcut that formed near this location, before the final monitoring event in December 2020. Data was adjusted assuming the location of the low pin was the same as the initial installation in August 2014. Based on photos, this appeared to be the case. Reviewing the photos and bank profile data at Sites 3 and 4, it appeared that the stream bed had moved, moving the toe pin with it. For example, see the following photos of Site 4 in August 2016 (Figure 4) and again in December 2020 (Figure 5). Figure 4 Site 4 in August 2016, red arrow marks Figure 5 Site 4 in December 2020, red arrow marks the location of the toe pin the location of the toe pin Based on the photos, the horizontal pins appear to be relatively in the same location in the bank; however, the toe pin (under the red arrow) is significantly farther away from the end of the pins. To rectify this data, the bank profile surveys were adjusted assuming that the end of the low pin was in the same location during each monitoring event for Sites 3 and 4. Initially, all the measured pin recession lengths were plotted assuming that the horizontal pins were at the same relative height above the toe pin. It became apparent during this analysis that this was not accurate for some bank sites. At Site 2 and Site 12, the bank profile data appeared correct; however, the horizontal pins were not located at the same height above the toe pin between surveys. For Site 2, the stream bank near the top horizontal pin has fallen over the years of monitoring. See Figure 6 for the changing location of the top pin circled on the profile plot. The location where the pin is exposed from the bank is represented by an 'Y'. See Appendix K for the full bank profile. 13 7.0 6-O 10 4.0 � as 2-4 i_Q 0-4 -t_4 O.dd 1.00 2.00 3.00 4.00 5_d0 Horgan al O istan ce (ft) • Surveyed End of Bank Pin * Measured Pin Recession - 07117r2O14 through 12l0912020 --*--Bank Prof le - 7117114 Bank Profile - 8114M 5 MBank Profile - 8116M 6 MBank Profile - 3r2t2017 W Bank grofie - 812512017 Bank Profile - 3114J2018 MBank Profile - 912 YI9 Bank Profile - 214t2O MBank Profile - ZW2020 tBank Profile - 121912020 Figure 6 Site 2 profile plot with a circle highlighting the location of the top horizontal pin which changed over the monitoring period, see Appendix K for the full plot. For Site 12, it appeared that the entire bank has been slumping over the monitoring period and the height of all the horizontal pins have changed with respect to the toe pin. Because all pins have changed and it is not easy to distinguish which symbols represent the top, middle, and low horizontal pins, two plots are provided with different color schemes in Appendix K. Figure 7 shows the bank profiles in different colors to distinguish which profile represents each monitoring period and Figure 8 shows all the profiles in black. The horizontal pins are shown in three different colors for the high, middle, and low pin. See Appendix K for the full plots. A brief summary by site is included in Appendix L to be used as reference for changes and issues experienced at the bank monitoring sites. 14 6_fl 5_6 a 7 2.0 IA a.0 0.00 1.0D 2.00 3.00 4.00 5.00 6.00 Horiaontai Distance (ft) Surveyed End of Bank Pin x Measured Pin Recession-08M02014 through 121d9r2020 +Bank Profile - 8114114 MBank Profile - 8114M 5 —E-- Bank Profile - 8M &16 —y--Bank Profile - 3017 MBank Profile - 8f25M7 Bank Profile - 3114118 —Bank Profile - 9r2&19 MBank Profile - 214120 6 Bank Profile - 7ffr2D20 --&- Ba nk Profile- 12MO020 Figure 7 Site 12 bank profile with profiles differentiated, see Appendix K for the full plot. 9- 6.0 6A O1 4_D 2.0 1.0 o_a -�_ 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Horrxontal Distance (ft) • Surveyed End of Bank Pin (Low) % Measured Pin Recession {Law}- 0811412014 th roug h UM912020 • Surveyed End of Benk Pin (Middle) x Measured Pin Recession (Middle)-08l1412014 through 12ftj9f2020 • Surveyed End of Benk Pin (high) x Measured Pin Recession (high)-0811412014 through 1M912020 Bank Profile-4Y14114 T, Bank Profile - W4115 Bank Profile - 8116116 Bank Profile - 3r1117 Bank Profile - 825117 Bank Profile - 3114118 Bank Profile - 9125119 Bank Profile - 214r20 Bank Profile - 7f712021) —Bank Profile - 12f9r2020 Figure 8 Site 12 bank profile with pin markers differentiated, see Appendix K for the full plot. 4.0 Results and Conclusions Table 2 summarizes the recorded data and calculated bank erosion rates for each site. Figure 3 illustrates the relationship between bank erosion rates, Near Bank Stress (NBS) assessment categories and BEHI categories. Microsoft Excel was used to calculate power function equations, sorted by BEHI category, for the measured bank erosion rates. Curves were developed for each of the four BEHI category ratings, which include Extreme, Very High, High, and Moderate. It should be noted that these results are based on six years of monitoring and a limited sample population, so the curves are subject to change over time. This is further illustrated by the wide data point scatter around the curves. These log normal distribution curves are consistent with the methodology used by NCSU to develop similar plots for North Carolina. As additional data is collected, the power function curves should be reevaluated to determine trends. Based on preliminary data, a curve can be developed from the calculated bank erosion rates for all four different BEHI conditions (Figure 3), evidenced by the R2 values. Ongoing monitoring and additional data points for all BEHI sites will help validate and improve the curve and prediction potential of the erosion rate curves for streams found with Triassic Basin soils. Average bank erosion rates were developed based on the six years of monitoring data to be used until additional data is collected. Average bank erosion rates, median, and standard deviations were determined from the values in Table 2 for BEHI categories Extreme, Very High, High, and Moderate and are summarized in Table 3. Table 3: Average Bank Erosion Rates for Extreme, Very High, High, and Moderate BEHI Categories. BEHI Category Average Bank Erosion Rate (ft/yr) Median (ft/yr) Standard Deviation 0.0 04 Moderate. 0.05 • - 0. Refer to Table 2 for specific erosion rates calculated for each bank site. Average bank erosion rates for each BEHI category was calculated using the non -italicized rows (i.e., sites determined to be usable, see Section 3.0 for explanation of eliminated sites). Table 4 shows the average bank erosion rates after 3 years of monitoring (Kimley-Horn, 2018) compared to the full 6 years of monitoring data available at this time. Table 4: Percent Change in Average Bank Erosion Rates Between Data Analysis Periods CategoryBEHI After 3 years of monitoring After 6 years of monitoring Extreme 0.20 0.17 -15% Very High 0.24 0.15 -37.5% High 0.16 0.11 -31.3% Moderate 0.06 0.06 0% Although the percent change in the average bank erosion between data analysis periods is not a primary indicator of accuracy of the data, this information illustrates that the data collected is relatively consistent thus far. 5.0 Root Dendrogeomorphology Root dendrogeomorphology is another method of estimating erosion rates by analyzing a sample of a tree root that is protruding from the stream bank. By analyzing the rings of the tree root, the total time the root has been exposed from the stream bank can be estimated. Since the root is likely exposed due to bank erosion, an estimate for the amount of erosion in feet per year can be produced based on field measurements. See the Root Dendrogeomorphology Analysis and Results report (AECOM and Freese and Nichols, Inc., 2021) for details. Root dendrogeomorphology analysis was completed at four of the existing bank pin monitoring sites; Site 2, 10, 12, and 13. Table 5 compares the average calculated erosion rate based on root dendrogeomorphology and the bank profile erosion monitoring data. Because a small sample size is available, data is compared separately for each site (instead of compared to the average rate based on BEHI scores). Based on the information in Table 4 and as also noted in the Root Dendrogeomorphology report, additional data will need to be collected using this method to determine if it can be substituted for bank profile monitoring. Limited data suggests that erosion rates vary by site; in all but one instance the erosion rate estimated using the root dendrogeomorphology data is lower than the erosion rate estimated from the bank profile data. It should also be noted that the data from Site 10 has been determined to be an outlier based on the bank profile monitoring data (see Section 3.0 of this report). With the current data and based on the percent difference between the two data sets, it does not appear that root dendrogeomorphology can be substituted for bank profile monitoring. See the Root Dendrogeomorphology report, Table 4-1 Results of Root Analysis for Estimated Years of Exposure and the Calculated Erosion Rate for more details on the data. Root Dendrogeomorphology analysis can only be completed in sections of bank where roots are exposed/available for analysis. Bank profile monitoring takes significantly more time and effort, but can evaluate any section of bank, with or without tree roots. It is also more accurate because it gives a full picture of the entire bank height over time. It is recommended that bank profile monitoring is used to develop local empirical relationships between erosion estimation methods and stream bank erosion rates until more data is available on root dendrogeomorphology analysis at sites in the City of Durham. 17 Table 5: Root Dendroaeomoroholoav Erosion Rate Compared to Averaae Bank Erosion Rate based on Bank Pin Moni 2 0.16 High 10.7 0.12 High 0.04 29% 10 0.21 High 7 0.89 Very High 0.68 124% 12 0.03 Moderate 7 0.14 High 0.11 129% 13 0.02 Moderate 10.5 0.12 Moderate 0.1 143% Average Difference 0.23 `Percent difference = (difference between erosion rates) / (average of erosion rates). i.e. for Site 2, percent difference = 0.04 / [ (0.16+0.12) 12 ] 6.0 Future Monitoring Based upon the results of the six -year monitoring, it is recommended that the City consider closing out these bank monitoring sites and establish additional sites, including additional watersheds within the City that have not been included in the previous monitoring. Because stream banks are constantly changing, the BEHI and NBS rating of the current sites are also likely to change over time. The BEHI and NBS scores could be reevaluated for the existing sites, and if any sites have changed to another category, future monitoring data should be included in that category. Additional data will help to validate the sediment rating curves that have been developed in this memorandum. A total of 40-50 sites is recommended based on the number of sites monitored by David Rosgen to develop sediment rating curves for Colorado and Yellowstone National Park (Rosgen, 2001). It is also recommended that the City follow the same assessment and survey methods advised in this and previous technical memorandums. The following data should be collected for each annual monitoring assessment: • A full bank profile should be performed aligning to the previous year's toe/bank pin measurements to the greatest extent possible; • The length of exposed portion of each bank pin; • A photo of each bank profile, and photos looking upstream and downstream from the bank profile location; • Notes regarding any significant change in vegetation, recent disturbance, logging, etc. Understanding that the City has limited time and resources, there is a balance between collecting additional data and other projects and priorities. There are also a limited number of eligible sites since the sites must fall within specific BEHI/NBS ratings and be on accessible properties, considering both property owner (City, County, easement, or other public property) and logistical site access (distance from available parking, safety, terrain, etc.). Further root dendrogeomorphology monitoring will need to be completed to verify the results. After monitoring bank pin sites and analyzing the monitoring data, the following modifications to data collection and site installation are recommended: Two top of bank pins could be installed in addition to the toe pin. The top of bank pins should be installed far enough from the edge of the top of bank to prevent the pin from interfering with any potential bank loss. A tape measure reel can be pulled across the top of bank pins during data collection to align the bank profile more accurately. This would provide an additional guide for the exact location to collect the bank profile data and the ability to continue to collect bank profiles if the toe pin (or even horizontal pins) is lost or disturbed. See Figure 9 for a cross-section illustrating the location of the top of bank pins. Top of bank pins Toe pin Horizontal bank pins Figure 9 Cross section illustrating the use of top of bank pins • Horizontal bank pins should be hammered into the banks at the end of each monitoring site visit after data is collected. This prevents the pins from falling from the bank. • Horizontal bank pins should also be monitored after large storm events and/or more frequently than the bank profiles are collected. This provides additional data that can be collected quickly. • If the horizontal bank pins will not be monitored more frequently than the bank profile data is collected (1 — 2 times a year), then the horizontal pins are not necessary. The data analyzed in this memorandum shows that the erosion rates calculated from bank profile data is more accurate than rates calculated from the bank pin data. • Instead of using Microsoft Excel to record the data, the computer program RIVERMorph can record and generate bank profiles and horizontal bank pins measurements. Multiple profiles can be overlaid which provides profile plots similar to those created in Microsoft Excel for this memorandum. RIVERMorph can calculate the change in bank profile and bank erosion rates and this program can also store photos. Monitoring profile plots are provided in Appendix K. Guidance documents for the stream bank profile survey is provided in Appendix M. Information on the initial site selection, assessment methods, and bank profile setup can be found in the previous memorandums titled "Guidance for Selection of Sites for Bank Pin Installation" (Wildlands, 2014a) and "Summary of Bank Pin Installation Sites and Monitoring" (Wildlands, 2014b). The original Wildlands report following year one of monitoring can be found in the previous memorandum titled "Summary of 1-Year Stream Bank Erosion Monitoring Results and Development of Bank Erosion Rate Curves" (Macaluso, Nicole, 2015). 20 7.0 References AECOM and Freese and Nichols, Inc. January 2021. Root Dendrogeomorphology Analysis and Results. Freese and Nichols, Inc. Raleigh, North Carolina. Harman, W. 2015. (Unpublished data). Personal correspondence. Kimley-Horn and Associates, Inc. July 2018. Summary of 3-Year Stream Bank Erosion Monitoring Results and Development of Bank Erosion Rate Curves. Kimley-Horn and Associates, In. Raleigh, North Carolina. Macaluso, Nicole, P.E., CFM. October 28, 2015. Summary of 1-Year Stream Bank Erosion Monitoring Results and Development of Bank Erosion Rate Curves. Wildlands Engineering, Raleigh, North Carolina. Rosgen, D. 2001. A Practical Method of Computing Streambank Erosion Rate. Proceedings of the Seventh Federal Interagency Sedimentation Conference, Vol. 2, pp. II — 18-26, March 25-29, 2001, Reno, NV. Wildlands Engineering. 2014a. Guidance for Selection of Sites for Bank Pin Installation. Wildlands Engineering. Raleigh, North Carolina. Wildlands Engineering. 2014b. Summary of Bank Pin Installation Sites and Monitoring. Wildlands Engineering. Raleigh, North Carolina. 21 Appendix A: Site Photos —Initial Installations, 2014 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 23 BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 24 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream k BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 — UT to UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 25 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #16 — UT to Third Fork Creek BEHI: Extreme I NBS: High Location: Fitzgerald Ave. 26 Appendix B: Site Photos — Year 1 Monitoring, August 2015 27 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 0. BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 29 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. ,� AL 6 3i•,�n �y `� y � —tea � •, _.,i. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 30 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability 4 i BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #16 — UT to Third Fork Creek BEHI: Extreme I NBS: High Location: Fitzgerald Ave. 31 Appendix C: Site Photos — Year 2 Monitoring, August 2016 32 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 33 BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 34 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 35 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 — Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 36 Appendix D: Site Photos — Year 3 Monitoring, March 2017 37 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 0. BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream r,f BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 39 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 — UT to UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 — UT to UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 40 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 —Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 41 Appendix E: Site Photos — Year 3 Monitoring, August 2017 42 : BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 43 BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream POO 1 f: Y J ' 4 "- BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 44 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 — UT to UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 — UT to UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 45 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 — Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 46 Appendix F: Site Photos — Year 4 Monitoring, March 2018 47 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 49 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 50 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 — Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 51 Appendix G: Site Photos — Year 5 Monitoring, September 2019 52 7N F7 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 53 BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 54 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 55 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 —Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 56 Appendix H: Site Photos — Year 6 Monitoring, February 2020 57 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 0:3 BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 59 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream .E BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream y BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 — Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 61 Appendix I: Site Photos — Year 6 Monitoring, July 2020 62 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. n �y\ r e, r.. L BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle 63 BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream 64 BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 65 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream t// BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 — Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 0 Appendix J: Site Photos — Year 6 Monitoring, December 2020 67 BP #1 — UT to Ellerbe Creek BEHI: Extreme I NBS: Extreme Location: Camden Ave. f BP #3 — UT to Northeast Creek BEHI: Very High I NBS: Very High Location: McAdams Upstream (approx. 100' D/S of road) BP #2 — UT to Ellerbe Creek BEHI: High I NBS: Very High Location: Museum of Life and Science BP #4 — UT to Northeast Creek BEHI: High I NBS: Extreme Location: McAdams Middle .: BP #5 — UT to Northeast Creek BEHI: Moderate I NBS: Very High Location: McAdams Downstream BP #7 — Crooked Creek BEHI: Moderate I NBS: High Location: Scott King Rd. Downstream BP #6 — Crooked Creek BEHI: Moderate I NBS: Extreme Location: Scott King Rd. Upstream BP #8 — Northeast Creek BEHI: Very High I NBS: Moderate Location: So Hi Dr. Downstream • • BP #9 — Northeast Creek BEHI: Very High I NBS: High Location: So Hi Dr. Upstream BP #11 —UT to Little Lick Creek BEHI: High I NBS: Moderate Location: West of S. Woodcrest St. Upstream BP #10 — UT to Third Fork Creek BEHI: Extreme I NBS: Very High Location: Weaver St. BP #12 —UT to Little Lick Creek BEHI: High I NBS: High Location: West of S. Woodcrest St. Downstream 70 BP #13 — UT to Sandy Creek BEHI: Moderate I NBS: Moderate Location: West of Wade Rd. Upstream BP #15 — Chunky Pipe Creek BEHI: Very High I NBS: Extreme Location: Southern School of Energy and Sustainability BP #14 — UT to Sandy Creek BEHI: Extreme I NBS: Moderate Location: West of Wade Rd. Downstream BP #17 — Third Fork Creek BEHI: Extreme I NBS: High Location: Chalmers St. 71 Appendix K: Bank Profile Plots 72 10.0 M 7.0 6.0 > 4.0 3.0 2.0 1.0 Bank Site #1 07/17/2014 - 08/14/2015 1.0 2.0 3.0 4.0 5.0 6.0 Horizontal Distance (ft) 7.0 8.0 9.0 Surveyed End of Bank Pin Measured Pin Recession - 07/17/2014 through 08/14/2015 Bank Profile - 7/17/14 Bank Profile - 8/14/15 73 10.0 M +, 6.0 > 4.0 2.0 1.0 0.0 4- 3.0 Bank Site #1 09/26/2016 - 03/08/2018 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 Horizontal Distance (ft) Surveyed End of Bank Pin Measured Pin Recession - 09/26/2016 through 03/08/2018 —*--Bank Profile - 9/26/16 --O—Bank Profile - 3/2/17 --)I-Bank Profile - 8/25/17 +Bank Profile - 3/14/18 74 Bank Site #2 7.0 5.0 4.0 1.0 m -1.0 0.00 1.00 2.00 3.00 4.00 5.00 Horizontal Distance (ft) • Surveyed End of Bank Pin Measured Pin Recession - 07/17/2014 through 12/09/2020 Bank Profile - 7/17/14 Bank Profile - 8/14/15 tBank Profile - 8/16/16 --X—Bank Profile - 3/2/2017 —I--Bank Profile - 8/25/2017 +Bank Profile - 3/14/2018 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 --*--Bank Profile - 7/7/2020 Bank Profile - 12/9/2020 75 4.5 4.0 3.5 3.0 8 2.5 c .2 2.0 L 1.5 1.0 0.5 0.0 Bank Site #3 Ali sl�� 111■II■I�� III►r .III■II■ , fl ,41 111■Il��air� IIII■II■ 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 Horizontal Distance (ft) • Surveyed End of Bank Pin Measured Pin Recession - 07/17/2014 through 12/09/2020 Bank Profile - 7/17/14 Bank Profile - 8/28/15 --*—Bank Profile - 8/15/16 --X—Bank Profile - 3/2/2017 --*—Bank Profile - 8/28/2017 Bank Profile - 3/08/2018 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 --*—Bank Profile - 7/7/2020 tBank Profile - 12/09/2020 76 Bank Site #4 Surveyed End of Bank Pin Measured Pin Recession - 07/17/2014 through 12/09/2020 MBank Profile - 7/17/14 tBank Profile - 8/28/15 tBank Profile - 8/15/16 Bank Profile - 3/2/17 Bank Profile - 8/28/17 Bank Profile - 3/08/18 (Bank Profile - 9/25/2019 Bank Profile - 2/4/20 tBank Profile - 7/7/2020 Bank Profile - 12/09/2020 1 177 m E41] 4.0 0 3.0 Bank Site #5 1.50 2.00 2.50 3.00 3.50 4.00 Horizontal Distance (ft) • Surveyed End of Bank Pin Measured Pin Recession - 07/17/2014 through 12/09/2020 Bank Profile - 7/17/14 Bank Profile - 8/28/15 --*—Bank Profile - 8/15/16 MBank Profile - 3/2/17 MBank Profile - 8/28/17 Bank Profile - 3/08/18 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 --*—Bank Profile - 7/7/2020 —a--Bank Profile - 12/9/2020 7.0 5.0 2.0 1.0 -1.0 L 0.00 Bank Site #6 2.00 4.00 6.00 8.00 10.00 Horizontal Distance (ft) • Surveyed End of Bank Pin * Measured Pin Recession - 07/17/2014 through 12/09/2020 ♦Bank Profile - 7/17/14 ♦Bank Profile - 8/28/15 --*—Bank Profile - 8/15/16 --O—Bank Profile - 3/2/17 Bank Profile - 8/28/17 Bank Profile - 3/08/18 (Bank Profile - 10/2/19 Bank Profile - 2/4/20 ♦Bank Profile - 7/7/2020 Bank Profile - 12/9/2020 79 10.0 m :e 7.0 3.0 2.0 1.0 Bank Site #7 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 Horizontal Distance (ft) • Surveyed End of Bank Pin Measured Pin Recession - 07/17/2014 through 12/09/2020 Bank Profile - 7/17/14 Bank Profile - 8/28/15 ♦Bank Profile - 8/15/16 MBank Profile - 3/2/17 Bank Profile - 8/28/17 Bank Profile - 3/08/18 (Bank Profile - 10/2/19 Bank Profile - 2/4/20 —*--Bank Profile - 7/7/2020 —a--Bank Profile - 12/9/2020 :E 0.0 1.0 2.0 3.0 4.0 Horizontal Distance (ft) Surveyed End of Bank Pin (installed 7/23/14) Measured Pin Recession (7/23/14 through 8/15/16) Bank Profile - 7/23/14 Bank Profile - 8/14/15 tBank Profile - 8/15/16 ♦ Surveyed End of Bank Pin (installed 9/26/16) * Measured Pin Recession (9/26/16 through 3/8/18) —0—Bank Profile 3/2/17 Bank Profile - 8/25/17 + Bank Profile - 3/8/18 5.0 6.0 81 Bank Site #9 7.0 6.0 5.0 m 4.0 �a 0 R 3.0 m 2.0 xy • 1.0 �v .7 _/001 0.. 0.0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Horizontal Distance (ft) • Surveyed End of Bank Pin x Measured Pin Recession - 07/23/2014 through 12/09/2020 MBank Profile - 7/23/14 —a—Bank Profile - 8/14/15 —*--Bank Profile - 8/15/16 MBank Profile - 3/2/17 MBank Profile - 8/25/17 +Bank Profile - 3/08/18 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 tBank Profile - 7/7/2020 —a—Bank Profile - 12/9/2020 82 M 7.0 M 5.0 1.0 mis FAIII -2.0 ' 0.00 Bank Site #10 7/23/2014 - 3/08/2018 2.00 4.00 6.00 8.00 10.00 12.00 14.00 Horizontal Distance (ft) • Surveyed End of Bank Pin * Measured Pin Recession - 07/23/2014 through 08/14/2015 ♦ Surveyed End of Reestablished Bank Pin (9/26/16) * Measured Pin Recession - 09/26/2016 through 03/02/2017 —*--Bank Profile - 7/23/14 --*--Bank Profile - 8/14/15 ♦Bank Profile - 8/16/16 MBank Profile - 3/2/17 MBank Profile - 8/25/17 MBank Profile - 10/18/17 Bank Profile - 3/08/18 83 7.0 Me 5.0 4.0 2.0 1.0 m -1.0 1 0.00 Bank Site #10 10/02/2019 - 12/09/2020 2.00 4.00 6.00 8.00 10.00 Horizontal Distance (ft) Surveyed End of Reestablished Bank Pin (10/02/2019) Measured Pin Recession - 10/02/2019 through 12/09/2020 (Bank Profile - 10/2/19 Bank Profile - 2/4/20 tBank Profile - 7/7/2020 Bank Profile - 12/9/2020 84 M 5.0 4.0 0 3.0 m m > 2.0 1.0 MOM Bank Site #11 1.00 2.00 3.00 4.00 5.00 6.00 7.00 Horizontal Distance (ft) Surveyed End of Bank Pin Measured Pin Recession - 08/14/2014 through 12/09/2020 Bank Profile - 8/14/14 Bank Profile - 8/14/15 tBank Profile - 8/16/16 ---�(—Bank Profile - 3/2/17 Bank Profile - 8/25/17 Bank Profile - 3/14/18 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 --*--Bank Profile - 7/7/2020 Bank Profile L - 12/9/2020 185 II 411 .�. 0 3.0 Quo 1.0 Bank Site #12 III�111!�riii� IIII'1'��I�11111� dig I of 1.00 2.00 3.00 4.00 Horizontal Distance (ft) Surveyed End of Bank Pin Measured Pin Recession - 08/14/2014 through 12/09/2020 Bank Profile - 8/14/14 Bank Profile - 8/14/15 tBank Profile - 8/16/16 --O—Bank Profile - 3/2/17 Bank Profile - 8/25/17 Bank Profile - 3/14/18 Bank Profile - 9/25/19 MBank Profile - 2/4/20 tBank Profile - 7/7/2020 (Bank Profile - 12/9/2020 5.00 6.00 G1 5.0 4.0 m c R 0 3.0 2.0 1.0 le Bank Site #12 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Horizontal Distance (ft) t Surveyed End of Bank Pin (Low) * Measured Pin Recession (Low) - 08/14/2014 through 12/09/2020 • Surveyed End of Bank Pin (Middle) * Measured Pin Recession (Middle) - 08/14/2014 through 12/09/2020 • Surveyed End of Bank Pin (High) * Measured Pin Recession (High) - 08/14/2014 through 12/09/2020 Bank Profile - 8/14/14 Bank Profile - 8/14/15 Bank Profile - 8/16/16 Bank Profile - 3/2/17 Bank Profile - 8/25/17 Bank Profile - 3/14/18 Bank Profile - 9/25/19 Bank Profile - 2/4/20 Bank Profile - 7/7/2020 Bank Profile - 12/9/2020 I= Bank Site #13 Surveyed End of Bank Pin Measured Pin Recession - 08/14/2014 through 12/09/2020 Bank Profile - 8/14/14 Bank Profile - 8/14/15 tBank Profile - 8/16/16 --O—Bank Profile - 3/2/17 Bank Profile - 8/25/17 Bank Profile - 3/08/18 (Bank Profile - 10/2/19 Bank Profile - 2/4/20 tBank Profile - 7/7/2020 Bank Profile - 12/9/2020 4.0 3.0 a m c R 0 2.0 1.0 M Bank Site #14 0 NI X 0.0 1.0 2.0 Horizontal Distance (ft) Surveyed End of Bank Pin Measured Pin Recession - 08/14/2014 through 03/08/2018 Bank Profile - 8/14/14 Bank Profile - 8/14/15 tBank Profile - 8/16/16 --O—Bank Profile - 3/2/17 Bank Profile - 8/25/17 Bank Profile - 3/08/18 0 9.0 8.0 7.0 6.0 Of as 4.0 0 R 3.0 m 2.0 1.0 0.0 -1.0 -2.0 0.00 Bank Site #15 • 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 Horizontal Distance (ft) • Surveyed End of Bank Pin * Measured Pin Recession - 08/21/2014 through 12/09/2020 --*—Bank Profile - 8/21/14 --*--Bank Profile - 8/14/15 —*--Bank Profile - 8/16/16 --OE—Bank Profile - 3/2/17 —I--Bank Profile - 8/25/17 +Bank Profile - 3/14/18 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 ♦Bank Profile - 7/7/2020 Bank Profile - 12/9/2020 .m Bank Site #17 9.0 8.0 7.0 6.0 m 5.0 R T) 0 c2i 4.0 m 3.0 • 2.0 1.0 0.0 4A- 0.00 2.00 4.00 6.00 8.00 10.00 Horizontal Distance (ft) Surveyed End of Bank Pin Measured Pin Recession - 08/19/2016 through 12/09/2020 ♦Bank Profile - 8/19/16 --O—Bank Profile - 3/2/17 — Bank Profile - 8/25/17 --m-- Bank Profile - 3/08/18 (Bank Profile - 9/25/19 Bank Profile - 2/4/20 ♦Bank Profile - 7/7/2020 Bank Profile - 12/9/2020 91 Appendix L: Summary of Events at Bank Pin Sites through December 2020 92 Third Fork Creek Bank Sites (TFC-BP#1, TFC-BP#2, TFC-BP#3, and TFC-BP#4) • Sites monitored only 512 days. • Not available for long term monitoring. Bank Site #1 • Toe pin and horizontal pins fell out of the bank between the August 2015 and August 2016 monitoring events. • Toe pins and horizontal pins were reestablished in September 2016. • Toe pin and horizontal pins disturbed again between the March 2018 and September 2019 monitoring events and was not reestablished. Bank Site #2 • Toe pin disturbed between the March 2018 and September 2019 monitoring events. • The top horizontal pin remained in the bank but it appears the soil around this pin has slumped down over the monitoring period. Bank Site #3 • Pins remained in place for all monitoring events, however stream bed appears to have shifted away from the bank based on photo evidence. Bank Site #4 • Pins remained in place for all monitoring events, however stream bed appears to have shifted away from the bank based on photo evidence. Bank Site #5 • Pins remained in place for all monitoring events. Bank Site #6 • Pins remained in place for all monitoring events. Bank Site #7 • Pins remained in place for all monitoring events. Bank Site #8 • Horizontal pins were disturbed between the August 2015 and August 2016 monitoring events but the toe pin remained intact. The horizontal pins were reestablished in August 2016. • Toe pin and horizontal pins disturbed again between the March 2018 and September 2019 monitoring events and was not reestablished. Bank Site #9 • Toe pin washed away between the July 2020 and December 2020 monitoring events and was not reestablished. The horizontal pins were intact at that time. Bank Site #10 • Horizontal pins were disturbed between the August 2015 and August 2016 monitoring events but the toe pin remained intact. The horizontal pins were reestablished in August 2016. • All pins were disturbed between the March 2018 and October 2019 monitoring events and reestablished in October 2019. • Between the February 2020 and July 2020 monitoring events, the toe pin was disturbed and was not reestablished. The horizontal pins were intact. 93 Bank Site #11 The toe pin was disturbed and no longer aligned with the horizontal pins prior to the August 2017 monitoring event. Bank Site #12 • All pins remained intact, however it appeared that the entire bank has been slumping into the stream over the monitoring period and the height of the horizontal pins with respect to the toe pin has changed significantly during monitoring. Bank Site #13 • Pins remained in place for all monitoring events. Bank Site #14 • Toe pin and horizontal pins disturbed between the March 2018 and September 2019 monitoring events and was not reestablished. Bank Site #15 Toe pin was disturbed prior to the December 2020 monitoring event but horizontal pins remained in place. Bank Site #16 • Monitoring at this site was discontinued after the first year. Bank Site #17 • Established March 2017 to replace Site #16. 94 Appendix M: Stream Bank Profile Survey Guide (Rosgen 2009) 95 WATERSHED ASSESSMENT OF RIVER STABILITY AND SEDIMENT SUPPLY Streambank Erosion Measurement Procedure: Bank Profiles The most detailed measure of bank erosion rate is obtained by implementing a bank profile. The bank profile is surveyed at least once per year to obtain annual erosion and contribution to the sediment supply. The profile is accomplished in conjunction with a permanent cross-section and is composed of bank pins and a toe pin. The toe pin is installed off -set from the bank. An elevation rod (plumb) is set on the toe pin with corresponding horizontal measurements taken to intercept the bank (Figure 6-9). A resurvey at the toe pin location allows for a detailed computation of a change in bank profile yielding lateral erosion rate. Bank pins are smooth steel rods, four feet long or longer if needed, which are driven horizontally at various positions in the strearbank. The amount of exposed pin upon resurvey following runoff events or annually is measured as the amount of lateral erosion at that site. Bank pins are not used if sod mats "overhang" the bank as the erosion pins help stabilize or hold the sod mats in place. Bank pins are also generally not used in cobble / gravel / sand matrix banks due to the physical disturbance during their installation. In these cases, only a bank profile is obtained. The advantage, however, of bank pins is to rapidly observe erosion rates throughout the runoff season. Various processes of seasonal ramping flows, ice -off, snowmelt, stormflow or other events may help explain the nature of erosion rate by process or season. The procedure to monitor bank erosion using bank pins and bank profiling methods is depicted in Figure 6-10. Bank profile data is documented in the bank profile Worksheet 6-2. RIVERMorphT`1 also has a bank profiling tool that computes the lateral erosion rate and sediment yield from the study streambank and for additional reaches. Figure 6-9. Surveying a bank profile at a toe pin. Chapter 6 W RIVER ASSESSMENT and MONITORING iM6.- PROCOTOL. for BANK PROFILE MEASUREMENT Survey Rod "Bank -Side" Edge of Survey Rod J - o Of m - o— Line Level ------------------- Horizontal Distance Bank Pins Survey -rod Edge to Bank Surface m U ' O .c Bank Surface U jEL a C_ �F OS r: Toe Pin Plan View Bank Surface Survey Rod Toe Pin Line Level ------------- Horizontal Distance Survey -rod Edge to Bank Surface Bank Pin Pocket Rod Monitoring 1. Place survey rod on toe pin with numbers facing either upstream or downstream. 2. Position rod so that the bank -side edge or side of the rod is aligned with bank -side edge of the toe pin cap. 3. Using an extended pocket rod (with a line -level in place, as shown), position pocket -rod edge at selected or noted vertical distance stations. Measure the horizontal distance from the bank surface to bank -side edge of the survey rod. 4. Adjunct Data: Measure distance from top of toe pin to channel bottom. Note: Best done with three persons: Survey -rod holder, pocket -rod profiler and data recorder. Figure 6-10. Procedure to monitor bank erosion using erosion pins and bank profiling methods. WATERSHED ASSESSMENT OF RIVER STABILITY AND SEDIMENT SUPPLY Worksheet 6-2. Bank profile and bank erosion summary data form Bank Profile Form Stream: Observers: Location: Date: Cross -Section: BEHI Adjective Ratin : Bank: NBS Adiective Rating: Toe -Pin Station (ft): Predicted Erosion ft : Toe -Pin Elevation (ft): Measured Erosion ft : Date: Date: Horizontal I Vertical Notes I I Hnriynn#al Ve%rtlr,%l Vertical Bank Profile T s •-� 7 =-- — --- --- --- v6 --- --- --- rn p 4-- --- --- --- -- ----- ia v-- 3 --- --- -- — — 7 2 — -- ^—� Q 0 2 3 4 5 6 Horizontal Distance (ft)