Monitoring the Effects of Knickpoint Erosion on Bridge Pier and Abutment Structural Damage Due to Scour Thanos Papanicolaou University of Iowa, [email protected]

University of Nebraska - Lincoln <a href="/goto?url=http://digitalcommons.unl.edu?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">DigitalCommons@University of Nebraska - Lincoln </a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">Final Reports & </a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">T</a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">e</a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">chnical Briefs from Mid-America </a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">Transportation Center </a> <a href="/goto?url=http://digitalcommons.unl.edu/matc?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">Mid-America </a><a href="/goto?url=http://digitalcommons.unl.edu/matc?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">T</a><a href="/goto?url=http://digitalcommons.unl.edu/matc?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">ransportation Center </a>2012 Monitoring the Effects of Knickpoint Erosion on Bridge Pier and Abutment Structural Damage Due to Scour anos Papanicolaou University of Iowa, [email protected] David M. Admiraal University of Nebraska-Lincoln, [email protected] Christopher Wilson University of Nebraska-Lincoln Clark W. Kephart University of Nebraska-Lincoln, [email protected] Follow this and additional works at: <a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">h</a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">t</a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">p://digitalcommons.unl.edu/matcreports </a> Part of the <a href="/goto?url=http://network.bepress.com/hgg/discipline/252?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">Civil Engineering Commons </a>Papanicolaou, anos; Admiraal, David M.; Wilson, Christopher; and Kephart, Clark W., "Monitoring the Effects of Knickpoint Erosion on Bridge Pier and Abutment Structural Damage Due to Scour" (2012). Final Reports & T echnical Briefs f om Mid-America Transportation Center. 3. <a href="/goto?url=http://digitalcommons.unl.edu/matcreports/3?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">h</a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports/3?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">t</a><a href="/goto?url=http://digitalcommons.unl.edu/matcreports/3?utm_source=digitalcommons.unl.edu%2Fmatcreports%2F3&utm_medium=PDF&utm_campaign=PDFCoverPages" target="_blank">p://digitalcommons.unl.edu/matcreports/3 </a>is Article is brought to you for free and open access by the Mid-America Transportation Center at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Final Reports & Technical Briefs from Mid-America Transportation Center by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. <ul style="display: flex;"><li style="flex:1">Report # MATC-UI-UNL: 471/424 </li><li style="flex:1">Final Report </li></ul>25-1121-0001-471, 25-1121-0001-424 Monitoring the Effects of Knickpoint Erosion on Bridge Pier and Abutment Structural Damage Due to Scour ®A.N. Thanos Papanicolaou, Ph.D. Professor Department of Civil and Environmental Engineering IIHR—Hydroscience & Engineering University of Iowa David M. Admiraal, Ph.D. Associate Professor Christopher Wilson, Ph.D. Assistant Research Scientist Clark Kephart Graduate Research Assistant 2012 A Cooperative Research Project sponsored by the U.S. Department of Transportation Research and Innovative Technology Administration The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein. This document is disseminated under the sponsorship of the Department of Transportation University Transportation Centers Program, in the interest of information exchange. The U.S. Government assumes no liability for the contents or use thereof. Monitoring the Effects of Knickpoint Erosion on Bridge Pier and Abutment Structural Damage Due to Scour A.N. Thanos Papanicolaou, Ph.D. Professor Department of Civil and Environmental Engineering IIHR—Hydroscience & Engineering University of Iowa David M. Admiraal, Ph.D. Associate Professor Department of Civil Engineering University of Nebraska–Lincoln Christopher Wilson, Ph.D. Assistant Research Scientist IIHR—Hydroscience & Engineering University of Iowa Clark Kephart Graduate Research Assistant Department of Civil Engineering University of Nebraska–Lincoln A Report on Research Sponsored by Mid-America Transportation Center University of Nebraska-Lincoln April 2012 Technical Report Documentation Page <ul style="display: flex;"><li style="flex:1">1. Report No. </li><li style="flex:1">2. Government Accession No. </li><li style="flex:1">3. Recipient's Catalog No. </li></ul>25-1121-0001-471 (also reporting for 25-1121-0001-424) 4. Title and Subtitle Monitoring the effects of knickpoint erosion on bridge pier and abutment structural damage due to scour 5. Report Date April 2012 6. Performing Organization Code <ul style="display: flex;"><li style="flex:1">7. Author(s) </li><li style="flex:1">8. Performing Organization Report No. </li></ul>25-1121-0001-471 (also reporting for 25-1121-0001-424) A. N. Thanos Papanicolaou, David Admiraal, Christopher Wilson, and Clark Kephart 9. Performing Organization Name and Address Mid-America Transportation Center 2200 Vine St. 10. Work Unit No. (TRAIS) 11. Contract or Grant No. PO Box 830851 Lincoln, NE 68583-0851 12. Sponsoring Agency Name and Address Research and Innovative Technology Administration 1200 New Jersey Ave., SE 13. Type of Report and Period Covered Final Report July 2010-April 2012 Washington, D.C. 20590 14. Sponsoring Agency Code MATC TRB RiP No. 28504 15. Supplementary Notes 16. Abstract The goal of this study was to conduct a field-oriented evaluation, coupled with advanced laboratory techniques, of channel degradation in a stream of the Deep Loess Region of western Iowa, namely Mud Creek. The Midwestern United States is an ideal place for such a study considering that ~$1 Billion of infrastructure and farmland has been lost recently to channel degradation. A common form of channel degradation in this region is associated with the formation of knickpoints, which naturally manifest as short waterfalls within the channel that migrate upstream. As flow plunges over a knickpoint face, scouring of the downstream bed creates a plunge pool. This downcutting increases bank height, facilitating bank failure, stream widening, and damage to critical bridge infrastructure. We conducted a state-of-the-art geotechnical analysis of the sediments from the knickpoint face, plunge pool, and adjacent stream banks to determine the areas of the streambed near the bridge infrastructure that favor knickpoint propagation. Soil characterization using particle size distributions and Gamma Spectroscopy identified a stratigraphic discontinuity at the elevation where the knickpoint forms. An automated surveillance camera was established to monitor the location of the knickpoint face relative to a fixed datum and provide a first-order approximation of its migration rate, which was approximately 0.9 m over a 248-day study period. Surveys conducted of the stream reach also facilitated information about knickpoint migration. Flow measurements using Largescale Particle Image Velocimetry were conducted during the study to understand the hydrodynamic conditions at the site. The results of this research will assist local and federal transportation agencies in better understanding the following: (1) principal geotechnical and hydrodynamic factors that control knickpoint propagation, (2) identify necessary data for extraction and analysis to predict knickpoint formation, (3) provide mitigation measures such as grade control structures (e.g., sheet-pile weirs, bank stabilization measures) near bridge crossings to control the propagation of knickpoints and prevent further damage to downstream infrastructure. <ul style="display: flex;"><li style="flex:1">17. Key Words </li><li style="flex:1">18. Distribution Statement </li></ul>Knickpoint, Scour, Bridge Infrastructure Safety 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 51 22. Price ii Table of Contents Acknowledgements <a href="#11_0">Disclaimer </a>viii <a href="#11_0">ix </a> <a href="#12_0">Executive Summary </a><a href="#14_0">Chapter 1 Introduction </a> <a href="#14_1">1.1 Problem Statement </a><a href="#17_0">1.2 Definitions </a><a href="#12_0">x</a><a href="#14_0">1</a><a href="#14_1">1</a><a href="#17_0">4</a> <a href="#19_0">1.3 Previous Research </a> <a href="#0_0">Chapter 3 Methodology </a> <a href="#0_1">3.1 Study Site </a> <a href="#19_0">6</a><a href="#0_0">10 </a><a href="#0_1">10 </a><a href="#0_2">11 </a><a href="#0_3">14 </a><a href="#0_0">18 </a><a href="#0_4">21 </a><a href="#0_5">21 </a><a href="#0_0">26 </a><a href="#0_1">26 </a><a href="#0_6">35 </a><a href="#0_0">40 </a>43 <a href="#0_7">49 </a> <a href="#0_2">3.2 Core Extraction </a><a href="#0_3">3.3 Core Parameterization </a><a href="#0_0">3.4 Knickpoint Propagation Using a Time-Lapse Camera </a><a href="#0_4">3.5 Knickpoint Propagation Using Survey Data </a><a href="#0_5">3.6 Flow Velocity Distributions Using LPIV </a> <a href="#0_0">Chapter 4 Results </a> <a href="#0_1">4.1 Geotechnical Analysis </a><a href="#0_6">4.2 Knickpoint Propagation </a><a href="#0_0">4.3 Flow Velocity Observations </a><a href="#0_0">– </a><a href="#0_0">LPIV </a> Chapter 5 Summary and Conclusions <a href="#0_7">References </a>iii List of Figures <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727389" target="_blank">Figure 1.1 (a) Channel straightening of Mud Creek, IA in the 1950s. The </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727389" target="_blank">white line is the original channel. The blue line is the creek after straightening; </a><ul style="display: flex;"><li style="flex:1">(b) Channel incision at Mud Creek. </li><li style="flex:1">1</li></ul><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727391" target="_blank">Figure 1.2 Knickpoint formation. The circled area is a knickpoint in </a><ul style="display: flex;"><li style="flex:1"><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727391" target="_blank">Mud Creek, IA. </a></li><li style="flex:1">4</li></ul><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727392" target="_blank">Figure 1.3 Knickpoint processes. A sketch of the steps involved in knickpoint </a><ul style="display: flex;"><li style="flex:1"><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727392" target="_blank">migration. </a></li><li style="flex:1">5</li></ul><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727393" target="_blank">Figure 3.1 Mud Creek, IA. The red dot on the aerial photo is the monitored </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727393" target="_blank">knickpoint. The circle in the site photo highlights the knickpoint. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727394" target="_blank">Figure 3.2 Core Collection. Cores from the stream banks near the knickpoint </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727394" target="_blank">face were collected using a Giddings probe and Shelby tube system. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727395" target="_blank">Figure 3.3 Stratigraphic Interpretation. A close-up of the surface section for the </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727395" target="_blank">stream bank core used in the stratigraphy analysis. The ruler in </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727395" target="_blank">the image is in inches. </a> 12 13 15 16 <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727396" target="_blank">Figure 3.4 Gamma Scanner. The gamma scanner system at IIHR. Typical </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727396" target="_blank">results of a core’s density. </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727397" target="_blank">Figure 3.5 Measuring Core Bulk Density. A section of the stream bank core </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727397" target="_blank">was placed in a vertical frame. A </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727397" target="_blank">241</a>Am sealed source was moved up <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727397" target="_blank">and down the core length in conjunction with a gamma energy </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727397" target="_blank">detector on the other side of the core. The attenuation of the received </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727397" target="_blank">radioactivity was indication of the core density. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727398" target="_blank">Figure 3.6 Time-lapse images collected on (a) September 15, 2011 </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727398" target="_blank">(b) December 3, 2011, and (c) February 12, 2012. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727399" target="_blank">Figure 3.7 Corrected Time-lapse images from (a) September 15, 2011 </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727399" target="_blank">(b) December 3, 2011, and (c) February 12, 2012. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727401" target="_blank">Figure 3.8 LPIV image samples: (a) original image sampled from LPIV video </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727401" target="_blank">and (b) rectified LPIV image. </a> <a href="#0_8">Figure 3.9 Depiction of subareas associated with interrogation points used for </a><a href="#0_8">discharge calculations. </a> 17 20 19 23 24 <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727403" target="_blank">Figure 4.1 Stratigraphic Discontinuity. There appears to be a stratigraphic </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727403" target="_blank">discontinuity close to the knickpoint with a darker sediment </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727403" target="_blank">(in the black circle) overlaying a lighter-colored sediment </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727403" target="_blank">(in the red circle). </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">Figure 4.2 Particle Size Distribution. These graphs show key particle size </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">diameters of the sampled depth intervals in a stream bank core </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">from the study site. The d16, d50, and d84 for each interval are </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">plotted relative to depth. The red circle highlighting the 600-650 cm </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">depth interval corresponds to a coarsening of the overall particle size distribution, </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">as there are increases in the d50 and d84. This elevation corresponds to the top </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727404" target="_blank">elevation of the knickpoint face. </a> 26 28 iv <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">Figure 4.3 Soil Texture. The percentages of clay, silt, and sand for each depth interval </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">of a stream bank core from the study site. The red</a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank"> </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">circle highlighting the </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">600-650 cm depth interval corresponds to a</a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank"> </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">discontinuity in bank stratigraphy. </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">This discontinuity corresponds</a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank"> </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727405" target="_blank">to the top elevation of the knickpoint face. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">Figure 4.4 Soil Ternary Diagram. The soil texture of depth intervals in a stream </a> 29 <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">bank core based on USDA soil classifications and particle size measurements. Red </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">circles represent samples above 600 cm, and blue circles represent samples </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">below 600 cm. The 600-650 cm</a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank"> </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">elevation corresponds to the top elevation </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">of the knickpoint face. There is a coarsening of sediment below this elevation, as </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727406" target="_blank">seen through a shift in the texture as the material becomes sandier. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727407" target="_blank">Figure 4.5 Atterberg Limits. The Atterberg limits of select depth intervals were </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727407" target="_blank">measured using a fall cone. The samples were chosen because they had a </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727407" target="_blank">majority of fine particle sizes. Red circles represent samples above 600 cm, </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727407" target="_blank">and blue circles represent samples below 600 cm. The 600-650 cm elevation </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727407" target="_blank">corresponds to the top elevation of the knickpoint face. The samples are mostly </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727407" target="_blank">characterized as clay with low plasticity. </a> 31 32 <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">Figure 4.6 Surrogate Bulk Density. The density of a stream bank core was measured </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">using the attenuation of a gamma radiation source. These graphs show the depth </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">profile of attenuation count rates for a stream</a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank"> </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">bank core. A high count rate </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">translates to high transmission of the</a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank"> </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">gamma source through the core, so that </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">depth interval will have a lower bulk density. The red circles highlight shifts in the </a><ul style="display: flex;"><li style="flex:1"><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727408" target="_blank">depth profile. </a></li><li style="flex:1">33 </li></ul>Figure 4.7 Stream bed cores. The depth profile of the percent sand of cores collected along a transect of the stream bed reach near the knickpoint. The zero level represents the top of the knickpoint face. Old KP represents the core furthest downstream where the knickpoint was in 2009. The transect moves upstream as follows: Chute -> Sensors -> Current KP. There appears to be no difference in the depth profiles; however, there is a coarsening four feet <ul style="display: flex;"><li style="flex:1">below the surface. </li><li style="flex:1">35 </li></ul><ul style="display: flex;"><li style="flex:1">36 </li><li style="flex:1"><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727409" target="_blank">Figure 4.8 Knickpoint migration between July 14, 2011 and March 16, 2012. </a></li></ul><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727410" target="_blank">Figure 4.9 50 cm contours for surveyed data for (a) September 27, 2011, and </a><ul style="display: flex;"><li style="flex:1"><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727410" target="_blank">(b) March 21, 2012. </a></li><li style="flex:1">38 </li></ul><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727411" target="_blank">Figure 4.10 (a) Image of the knickpoint on March 18, 2011, prior to installation </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727411" target="_blank">of knickpoint monitoring equipment. Note the previous trench in the foreground </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727411" target="_blank">and the previous and new scour holes. (b) Plan view of the current knickpoint </a><a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727411" target="_blank">location depicting the approximate location of the current trench. </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727412" target="_blank">Figure 4.11 Surface velocity distribution measured with LPIV on </a> <a href="file:///C:/Users/ntc-amack/Documents/Reports%20in-progress%20September%2017-21/Papanicolaou-Admiraal_471_Monitoring_the_Effects_Knickpoint_Edited%20Version.docx%23_Toc335727412" target="_blank">(a) September 27, 2011, and (b) March 21, 2012. </a> 39 41

Monitoring the Effects of Knickpoint Erosion on Bridge Pier and Abutment Structural Damage Due to Scour Thanos Papanicolaou University of Iowa, [email protected]

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