State of Oregon Oregon Department of Geology and Mineral Industries Brad Avy, State Geologist OPEN FILE REPORT O-16-07 MONITORING THE RESPONSE AND EFFICACY OF A DYNAMIC REVETMENT CONSTRUCTED ADJACENT TO THE COLUMBIA RIVER SOUTH JETTY, CLATSOP COUNTY, OREGON by Jonathan C. Allan and Laura L. Gabel Oregon Department of Geology and Mineral Industries, Coastal Field Office, P.O. Box 1033, Newport, OR 97365 2016 Monitoring the Response and Efficacy of a Dynamic Revetment, Columbia River South Jetty, Clatsop County, Oregon DISCLAIMER This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, or sur- veying purposes. Users of this information should review or consult the primary data and information sources to ascertain the usability of the information. This publication cannot substitute for site-specific investigations by qualified practitioners. Site-specific data may give results that differ from the results shown in the publication. Cover photograph: Oblique aerial photo looking south over the Columbia River south jetty dynamic revetment project study area, Clatsop County, Oregon. The structure is located at the apex of the embayment that separates the sand beach from the vegetation line. Photograph taken by D. Best, March 09, 2015. Oregon Department of Geology and Mineral Industries Open-File Report O-16-07 Published in conformance with ORS 516.030 For additional information: Administrative Offices 800 NE Oregon Street, Suite 965 Portland, OR 97232 Telephone (971) 673-1555 Fax (971) 673-1562 http://www.oregongeology.org http://www.oregon.gov/dogami Oregon Department of Geology and Mineral Industries Open-File Report O-16-07 ii Monitoring the Response and Efficacy of a Dynamic Revetment, Columbia River South Jetty, Clatsop County, Oregon TABLE OF CONTENTS 1.0 INTRODUCTION .......................................................................................................................................... 1 2.0 STUDY OBJECTIVES ..................................................................................................................................... 3 3.0 METHODOLOGY .......................................................................................................................................... 4 3.1 Topographic Beach Mapping ...................................................................................................................... 4 3.1.1 Background ...................................................................................................................................... 4 3.1.2 Columbia River Dynamic Revetment Survey Control ....................................................................... 6 3.1.3 Profile Surveys ................................................................................................................................. 8 3.1.4 Topographic Mapping ...................................................................................................................... 9 4.0 BEACH PROCESSES ON THE OREGON COAST ............................................................................................. 10 4.1 Background............................................................................................................................................... 10 4.1.1 Coastal Change on the Clatsop Plains ............................................................................................ 10 4.2 The Concept of a Dynamic Revetment ..................................................................................................... 13 4.2.1 Examples of Dynamic Revetment Construction ............................................................................. 14 4.2.2 The Columbia River Dynamic Revetment ...................................................................................... 15 5.0 RESULTS .................................................................................................................................................... 20 5.1 Beach Profile Morphological Changes ...................................................................................................... 20 5.2 Topographic 3D Changes .......................................................................................................................... 26 5.3 Physical Processes .................................................................................................................................... 29 6.0 CONCLUSION ............................................................................................................................................ 33 7.0 ACKNOWLEDGMENTS ............................................................................................................................... 34 8.0 REFERENCES.............................................................................................................................................. 34 9.0 APPENDIX: COLUMBIA RIVER SOUTH JETTY DYNAMIC REVETMENT PROFILES .......................................... 37 Oregon Department of Geology and Mineral Industries Open-File Report O-16-07 iii Monitoring the Response and Efficacy of a Dynamic Revetment, Columbia River South Jetty, Clatsop County, Oregon LIST OF FIGURES Figure 1. Location map of (A) the lower Columbia River estuary, Clatsop Plains, and jetties, (B) the much larger Columbia River littoral cell and (C) the dynamic revetment study area ....................... 1 Figure 2. The jetty root (left side of photo) and the impending breach of the remaining foredune ............... 2 Figure 3. The Trimble R7 base station antenna in operation on the Clatsop Plains......................................... 5 Figure 4. A 180-epoch calibration check is performed on a survey monument (Mag_nail_3) ........................ 6 Figure 5. The Columbia River dynamic revetment beach profile monitoring network established adjacent to the south jetty ................................................................................................................ 7 Figure 6. A topographic 3D survey undertaken on September 1, 2015, showing the spatial distribution of the measurements ........................................................................................................................ 9 Figure 7. Shoreline changes adjacent to the Columbia River south jetty from the 1920s to 2009 ................ 11 Figure 8. Historical 1928 breaching of the south jetty and adjacent dune system. Top view faces the southeast ......................................................................................................................................... 12 Figure 9. Looking south along the completed dynamic revetment structure ................................................ 16 Figure 10. Schematic map showing the spatial characteristics of the completed structure, including the locations of various key morphological features. ........................................................................... 17 Figure 11. The Columbia River south jetty dynamic revetment conceptual design (after USACE, 2013). ....... 19 Figure 12. Morphological changes observed at four of the Columbia River south jetty dynamic revetment beach cross-section sites ............................................................................................... 21 Figure 13. Time stack of changes at the 6 m (19.7 ft) contour elevation for transects than span the dynamic revetment ......................................................................................................................... 22 Figure 14. An overtopping event on the Columbia River south jetty revetment January 12, 2014 ................. 23 Figure 15. Erosion of gravels at the distal north end of the structure (bottom of photo) are currently being transported south along the beach ....................................................................................... 24 Figure 16. Morphological changes observed at two representative beach profile sites located within the study control area ..................................................................................................................... 25 Figure 17. Topographic 3D measurements of beach changes measured for select intersurvey periods ........ 27 Figure 18. Net 3D topographic beach changes at the Columbia River south jetty dynamic revetment .......... 28 Figure 19. Wave height and total water level measurements during the study period .................................. 31 Figure 20. Wave height anomalies calculated for the Oregon (#46002) wave buoy operated by the National Data Buoy Center (NBDC) ................................................................................................. 32 LIST OF TABLES Table 1. Survey benchmarks used to calibrate GPS surveys of the Columbia River dynamic revetment. BASE identifies the location where the GPS base station was established during each respective survey .............................................................................................................................. 7 Table 2. Horizontal and vertical coordinates (expressed as a standard deviation) at each of the benchmark locations, compared to the final coordinates referenced in Table 1 ............................. 8 Table 3. Dates when beach surveys and mapping efforts were undertaken .................................................. 8 Oregon Department of Geology and Mineral Industries Open-File Report O-16-07 iv Monitoring the Response and Efficacy of a Dynamic