AN ABSTRACT OF THE THESIS OF SUING SHIRLY TANG for the degree of MASTER OF OCEAN (Name of Student) (Degree) ENGINEERING in CIVIL ENGINEERING presented on (Major Department. JUNE, 1977 Title: CHETCO RIVER TIDAL HYDRODYNAMICS AND ASSOCIATED MARINA FLUSHING Redacted for privacy Abstract Approve 5aotta, Major Pl'otessor The purpose of this study was to provide an understanding of the interrelationships between fresh and salt water Circulation, tidal trans- port and flushing patterns in the Chetco River estuary and its boat basins. Field work and water quality measurements were conducted at the entrance of the Chetco River during 1975 and 1976. These results were used for classifying the estuary and for developing and verifying both numerical and physical models. A one-dimensional numerical model was successfully used to simulate the tide and currents cf the Chevso River. The model was calibrated Prior to the recent (1976) port expansion and was used to predict the expected. changez in tidal response due to the enlargement of the tidal basin. Subsequently, analytical and physical models were applied to predict the flushing ability of the new boat basin. Attempts were made to use a two-dimensional finite element numerical model for calculating currents and simulating the circulation in the boat basins. Results were compared with those taken during seasonal field studies. Analytical models were found to be economical and effective for estimating the flushing rate in small marinas, when applied with caution. Application of numerical models to small basins seems somewhat imprac- tical because of grid size detail and computational costs. When study- ing the flushing characteristics of proposed marinas, a reduced-scale physical model is considered to be a most effective tool. For proto- type considerations, field studies can be most instructive in providing information for decisions regarding the flushing characteristics of marinas. The study results show that the Port of Brookings marina flushing ranges from four to eight tidal cycles (two to four days). The new marina flushing rate depends on the range of tide and the strength of the ambient river currents. Water quality studies indicated that the Chetco River area has satisfactory water quality throughout all seasons; the only possible exception being when continuous dry summer months might occur along with high recreational use of the marina. Chetco River Tidal Hydrodynamics and Associated Marina Flushing by Shing Shirly Tang A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Ocean Engineering June 1977 APPROVED: Redacted for privacy orciiriFKaireerni incharge of major (Redactedfor privacy Head ofVV LL11111-UT U1V11tngineering / Redacted for privacy Dean of Graduate Scllool Date thesis is presented Le224._ Typed by Kris Thomsen for Shing Shirly Tang TABLE OF CONTENTS I. INTRODUCTION 1 II. TIDAL HYDRODYNAMICS OF THE CHETCO RIVER General Description 6 Hydrology and Climatology 10 Bathymetry 15 Tidal Dynamics 17 One-Dimensional Numerical Model Application 22 Numerical Model Calibration 25 Estuarine Classification 40 III. FLUSHING PREDICTIONS FOR THE BROOKING'S MARINA-- ANALYTICAL MODEL APPLICATION 49 Tidal Prism Method 49 Mixed Tank Approach SO Richey's Prediction 54 Yearsley's Diffusion Time Prediction 57 IV. FLUSHING CHARACTERISTICS OF THE BROOKING'S MARINA- - PHYSICAL MODEL APPLICATION 60 Principles of Hydraulic Similitude 60 Model Design 69 Selection of Test Conditions 73 Description of Model and Appurtenances 74 Model Calibration 76 Tests and Results 78 Model Verification 96 V. SUMMARY AND RECOMMENDATIONS 104 BIBLIOGRAPHY 108 APPENDICES: Appendix A: Bathymetric information of the Chetco 110 River and side-scan sonar recordings of the Chetco River mouth and boat basin entrance--June,'1975. Appendix B: Chetco River schemmtization input for 115 one-dimensional numerical model simu- lation. Appendix C: Water quality data obtained from the 116 Chetco River and boat basin area. Appendix D: Computer output of a finite-element 121 numerical model applied to the new boat basin, Port of Brookings. LIST OF FIGURES Figure Page 1. Location map of the Chetco River, Oregon. 2 2. Chetco River project site. 8 3. Proposed boat basin, Chetco River project area. 9 4. Representative precipitation and temperature data: Brookings, Oregon. 12 5. Representative wind direction data: Chetco Cove area. 13 6. Mean monthly hydrograph for the Chetco River at its mouth. 14 7. Cross-sectional areas of the Chetco River under low water levels and high water levels during high and low river flow conditions and a 1.8 meter tide. 16 8. Volume of water accumulated upstream under LWL and HWL during high and low river flow conditions and a 1.8 meter tide. 18 9. High and low water levels in the Chetco River under high and low river flow conditions. 19 10. Typical mixed semi-diurnal tide. 20 11. Input tide for the computer model at station 1, Chetco River, February 8 and 9, and June 18 and 19, 1975. 24 12. Schematization of the Chetco River for computer model and location of tidal and current stations. 27 13. Comparison of computer simulated and field measured tidal elevation at stations 3 and 5, Chetco River, February 8 and 9, 1975. 29 14. Comparison of computer simulated and field measured tidal elevation at station 3, Chetco River, June 18 and 19, 1975. 30 15. Comparison of computer simulated and field measured values of flow rate and average velocity for the Chetco River, February 8 and 9 with water inflow 397 m3/sec. 32 LIST OF FIGURES (continued) Figure Page 16. Computer simulated average velocity and discharge at station 2 and tidal elevation at station 1 at the Chetco River, June 18 and 19, 1975 with 85 m3/sec. river runoff. 33 17. Predicted tidal elevations for the Chetco River with a 2.0 meter tide and 255 m3/sec: river inflow. 35 18. Predicted tidal elevations for the Chetco River with a 1.5 meter tide and 5.7 m3/sec. river inflow. 36 19. Predicted discharge and the corresponding average velocity for stations 2 and 4 at the Chetco River. The river inflow was 255 m3/sec. and the tide had a 2.0 meter range. 37 20. Comparison of computer predicted discharge at stations 2 and 4, Chetco River with and without port expansion sited at station 3. 38 21. Comparison of computer predicted average velocities at station 2, Chetco River with and without a port expansion added at station 3. 39 22. Four types of estuarine circulation and their velocity and salinity distribution. 42 23. Estuary classifications according to the stratifi- cation--circulation diagram by Hansen and Rattray (1966). 45 24. Tidal, flow and mass curves--Mixed Tank Approach. 53 25. Definition sketch--Richey's Prediction method. 55 26. Comparison of velocity contours in prototype and distorted model. 68 27. Chetco River hydraulic model layout. 71 28. Photograph of the Chetco River hydraulic model. Scales of 1:300 horizontal and 1:30 vertical. 72 29. Comparisons of the water surface elevations between numerical and physical model predictions at stations 3 and 5 for a 1.5 meter tide with a 5.8 m3/sec. river flow and at station 3 for a 2.1 meter tide with a 255 m3/sec. river inflow. 77 LIST OF FIGURES (continued) Figure Page 30. Comparisons of average velocities at stations 2 and 4 between numerical model predicted value and physical model measurements for a 2.1 meter tide with a 255 m3/sec. river flow. 79 31. Comparison of average velocity at station 2 between numerical model predicted value and physi- cal model measurement for a 1.5 meter tide with a 5.8 m3/sec. river inflow. 80 32. Miniature-float pathlines in the new boat basin, Port of Brookings. Simulating a 1.5 meter tide and 5.8 m3/sec. ambient river runoff. 84 33. Miniature-float pathlines in the new boat basin, Port of Brookings. Simulating a 1.5 meter tide and 255 m3/sec. ambient river runoff. 86 34.a-i Surface current pattern photographs at each 1/8 tidal interval for a 1.5 meter tide and 5.8 m3/sec. ambient river runoff. 87-91 35.a-hSurface current pattern photographs at each 1/8 tidal interval for a 1.5 meter tide and 255 m3/sec. ambient river runoff. 92-95 36. Comparison of dye concentrations taken from the field and the hydraulic model. 98 37. Drogue pathlines, observed on January 20, 1976. 99 38. Drogue pathlines, observed on January 20 and 21, 1976. 100 39. Water quality parameter profiles at the mouth of the new boat basin and entrance to the Chetco River. 102 40. Float pathlines observed in the hydraulic model simulating a 1.83 meter tide and 80 m3/sec. ambient river runoff. 103 LIST OF TABLES Table Page I. Man-made Physical Alterations to the Chetco River 7 II. Median Monthly Discharge Near the Mouth of the Chetco River 11 III. Summary of Field Activities on the Chetco River Undertaken by OSU Ocean Engineering Staff During 1975/1976 26 IV. Classification of the Chetco Estuary by the Flow Ratio, Salinity Gradient and Hansen and Rattray's Methods 47 V. Comparison of Diffusion Coefficients of Actual and Required Values in Undistorted and Distorted Models 67 VI. Summary of Physical Model Prediction Flushing Times for Select Test Cases 83 CHETCO RIVER TIDAL HYDRODYNAMICS AND ASSOCIATED MARINA FLUSHING I. INTRODUCTION The objectives of this study were: first to present a general view of physical parameters of the Chetco River, and second to determine the flushing characteristics of a recently expanded marina located 300 meters upstream from its mouth. The River: The Chetco River discharges into the Pacific Ocean approximately 480 kilometers (300 miles) south of the mouth of the Columbia River.