SIMULATION ON THE EFECT OF SUBMERGED BREAKWATER TO THE WAVE TRANSMISSION AND RUN-UP ZAHEDER BIN ABD AZIZ

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1 SIMULATION ON THE EFECT OF SUBMERGED BREAKWATER TO THE WAVE TRANSMISSION AND RUN-UP ZAHEDER BIN ABD AZIZ A project report submitted in partial fulfillment of the requirements for the award of the degree of Master of Engineering (Civil - Hydraulics and Hydrology) Faculty of Civil Engineering Universiti Teknologi Malaysia JANUARY, 2013

2 iii To My Beloved Mother and Father Thanks for all your pray, attention and spiritual support

3 iv ACKNOWLEDGEMENTS In the duration of completing this thesis, first and foremost I would like to give praise to Allah s.w.t on his blessing and gift of life in order for me to continue with my studies. It is with great pleasure I would like to give my heartiest gratitude to my supervisor, Dr. Mohamad Hidayat bin Jamal on his tireless support and guidance. His dedication and willingness to go the extra miles is very much appreciated and will be my motivation for my future undertaking. I would like to give thank also to my parents and family on their pray, guidance and moral supports for me to complete this study. Also I would like to give thanks to my colleague in UEM Builders Sdn Bhd on their friendship and motivation for me to further my studies. Last but not least, I would like to express my gratitude to my fellow classmates of hydraulic and hydrology course session 2011/13 on their co-operation and friendships. It has been a memorable one and half year. It has been great pleasure in knowing every one of you. Thank you

4 v ABSTRACT The construction of submerged breakwater is one of the methods to reduce the effect of wave energy on the beach. Submerged breakwater has many advantages compared to emerge breakwater such lower construction cost, a higher aesthetic values and have a lower environmental impact to the surrounding areas. The aim of this study is to simulate and investigate the effect of submerged breakwater to the value of wave transmission coefficient, K t and also the run-up value on the beach slope. The initial data for wave period, wave height, water depth and beach slope was taken from experimental dataset done by Saville, (1955). Several submerged breakwater height will be tested in the numerical simulation which will follow the experimental setup done by Chiranjeevi Rambabu and Mani (2005). The numerical simulation will be based on the Non-Linear Shallow Water Equation (NLSWE). As a results, the wave transmission coefficient, K t value will decrease in relation to the increase of submerged breakwater height. This will caused the increase energy during breaking and also the velocity speed of the wave induced currents. The increased of the current speed will resulted in a higher run-up value. The effective submerged breakwater height is determined by its wave reduction capabilities which influence the run-up values.

5 vi ABSTRAK Pembinaan tembol pemecah ombak tenggelam permukaan adalah salah satu cara untuk mengurangkan kesan kuasa ombak ke atas permukaan pantai. Terdapat banyak kelebihan tembok pemecah ombak tenggelam permukaan berbanding pembinaan tembok pemecah ombak timbul permukaan diantaranya kos pembinaan yang lebih rendah, nilai estatik yang lebih tinggi malah memberikan kesan semulajadi yang lebih baik ke atas kawasan sekitarnya. Tujuan kajian ini adalah untuk menilai kesan pembinaan pemecah ombak tenggelam permukaan ke atas nilai koeffensi K t dan nilai run-up diatas kecerunan pantai. Data utama seperti nilai masa ombak, ketinggian ombak, kedalaman air dan kecerunan pantai diambil daripada data ekperimen yang dilakukan oleh Saville (1955). Beberapa ketinggian tembok pemecah ombak tenggelam permukaan telah dipilih untuk diujikaji didalam simulasi komputer mengikut keadaan ekperimen yang dilakukan oleh Chiranjeevi Rambabu dan Mani (2005). Simulasi adalah berdasarkan Non-Linear Shallow Water Equation (NLSWE). Keputusan simulasi menunjukkan nilai koeffensi K t akan berkurangan dengan peningkatan ketinggian tembok pemecah ombak tenggelam permukaan. Ini akan mengakibatkan peningkatan tenaga semasa pemecahan ombak dan juga peningkatan kelajuan arus ombak. Peningkatan kelajuan arus ombak ini akan mengakibatkan peningkatan kadar run-up. Ketinggian tembok pemecah ombak tenggelam permukaan yang effektif adalah bergantung kepada kebolehan struktur untuk mengurangkan kuasa ombak yang boleh member kesan kepada nilai run-up.

6 vii TABLE OF CONTENTS CHAPTER TITLE PAGE TITLE PAGE DECLARATION DEDICATION ACKNOWLEGMENT ABSTRACT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF APPENDICES i ii iii iv v vii x xi xiii xiv 1 INTRODUCTION 1.1 General Background problem Importance of study Objective Scope of study 5 2 LITERATURE REVIEW 2.1 General Sea, tides, wave, currents and surges Wave mechanics Wave transformation Wave set down, set up and run-up 18

7 viii 2.6 Wave transmission over breakwater Previous studies on wave transmission 22 coefficient, K t 2.8 Coastal management plan Breakwater structure Shore connected breakwater Detached breakwater Floating breakwater Submerged breakwater 32 3 METODOLOGY 3.1 General Foundation to numerical simulation Data collection Numerical simulation setup Computer program introduction Model calibration 40 4 RESULTS AND DISCUSSIONS 4.1 General Model calibration results Effect of friction factor on the run-up Effect of different wave characteristic 45 on the run-up 4.5 Effect of submerged breakwater has on 47 wave transmission 4.6 Effect of submerged breakwater has on 51 the K t value 4.7 Effect of submerged breakwater has on 53 the run-up 4.8 Discussion 55 5 CONCLUSION AND RECOMMENDATIONS 5.1 Conclusion 59

8 ix 5.2 Recommendation 60 REFERENCES 61 APPENDICES 63

9 x LIST OF TABLES TABLE NO. TITLE PAGE 2.1 Common equation in coastal engineering Tabulated K d value by Weigel (1964) Summary of breaker type Summary of coastal protection structure Converted run-up data from laboratory experiment 36 (Saville, 1955) 4.1 Run-up value of experiment and numerical simulation Person s R-square value for empirical equation 54

10 xi LIST OF FIGURES FIGURE NO. TITLE PAGE 2.1 Representation to the linear wave theory Water particle displacement in deep, intermediate and 11 shallow water 2.3 Diffraction process due to barrier K d value by Weigel (1964) Different form of breaking Sketch definition of run-up, set up and set down Tabulated figure for K t estimation by Saville (1963) Shows connected type breakwater Shows detached type breakwater Shows floating type breakwater Graphical representation of NLSWE Experiment dataset published by (Saville, 1955) Numerical simulation setup Example of variable used in FORTRAN program Example of output file produced by FORTRAN program Example of wave transmission profile using TECHPLOT Percentage difference of run-up value for various friction 43 factors 4.2 Run-up value of different wave characteristic and 44 friction factor 4.3 Simulation run-up value for case with different wave period Simulation run-up value for case with different wave height 45

11 xii 4.5 Simulation for case without submerged breakwater - T=6s, 47 H=2.4384m, d=5.334m, h s /d=0, B/d=0 4.6 Simulation for case without submerged breakwater - T=6s, 48 H=2.4384m, d=5.334m, h s /d=0.625, B/d= Simulation for case without submerged breakwater - T=6s, 48 H=2.4384m, d=5.334m, h s /d=0. 5, B/d= Simulation for case without submerged breakwater - T=6s, 49 H=2.4384m, d=5.334m, h s /d=0. 375, B/d= Simulation for case without submerged breakwater - T=6s, 49 H=2.4384m, d=5.334m, h s /d=0. 25, B/d= Simulation for case without submerged breakwater - T=6s, 50 H=2.4384m, d=5.334m, h s /d= K t obtained from numerical simulation reference to submerged 52 breakwater height 4.12 K t obtained from numerical simulation reference to submerged 52 breakwater crest width 4.13 Comparison of K t value simulated and calculated Comparison of run-up value for different test cases 55

12 xiii LIST OF SYMBOLS K t - Wave transmission coefficient d - Water depth from the toe of submerged breakwater to SWL d s - Water depth from top of the breakwater crest to SWL h s - Submerged breakwater structure height from ocean bed B - Submerged breakwater crest width H - Wave height E - Wave energy T, t - Wave period L - Wave length g - Acceleration of gravity d/gt 2 - Dimensionless water depth H/gT 2 - Dimensionless wave steepness h s /d - Structure height to water depth ratio SWL - Still water level I r - Iribarren parameter f - Friction factor η - Deviation height from the SWL ρ - Water density α - Slope of breakwater structure on the seaward side θ, β - Slope of beach profile F - Freeboard - measured height of breakwater crest from SWL. Negative value if structure is submerged

13 xiv LIST OF APPENDICES APPENDIX TITLE PAGE Table A.1 Run-up, K t simulated, K t calculated value for 63 case 1 (h s /d=0.625) Table A.2 Run-up, K t simulated, K t calculated value for 63 case 1 (h s /d=0.5) Table A.3 Run-up, K t simulated, K t calculated value for 64 case 1 (h s /d=0.375) Table A.4 Run-up, K t simulated, K t calculated value for 64 case 1 (h s /d=0.25) Figure B.1 Simulation for case without submerged breakwater - T=4.5s, 65 H=1.2192m, d=5.334m, h s /d=0, B/d=0 Figure B.2 Simulation for case without submerged breakwater - T=4.5s, 65 H=1.2192m, d=5.334m, h s /d=0.25, B/d=1.25 Figure B.3 Simulation for case without submerged breakwater - T=4.5s, 66 H=1.2192m, d=5.334m, h s /d=0.375, B/d=1.25 Figure B.4 Simulation for case without submerged breakwater - T=4.5s, 66 H=1.2192m, d=5.334m, h s /d=0.5, B/d=1.25 Figure B.5 Simulation for case without submerged breakwater - T=4.5s, 67 H=1.2192m, d=5.334m, h s /d=0.625, B/d=1.25 Figure B.6 Simulation for case without submerged breakwater - T=5.5s, 67 H=1.2192m, d=5.334m, h s /d=0, B/d=0 Figure B.7 Simulation for case without submerged breakwater - T=5.5s, 68 H=1.2192m, d=5.334m, h s /d=0.25, B/d=1.25 Figure B.8 Simulation for case without submerged breakwater - T=5.5s, 68 H=1.2192m, d=5.334m, h s /d=0.375, B/d=1.25

14 xv Figure B.9 Simulation for case without submerged breakwater - T=5.5s, 69 H=1.2192m, d=5.334m, h s /d=0.5, B/d=1.25 Figure B.10 Simulation for case without submerged breakwater - T=4.5s, 69 H=1.2192m, d=5.334m, h s /d=0.625, B/d=1.25

15 CHAPTER 1 INTRODUCTION 1.1 General Coastal area is a country natural treasure trove which is priceless not only due to its diverse marine ecosystems but also crucial for the continuation of the country economic progress. However this area is facing continues threat of destruction due to action of natural forces such as wind and waves and also due to the interference of human activities. The establishment of coastal protection system is an important step in order to minimize the destruction and also to rehabilitate the damaged coastal area. Countries with a large coastline area such as United State of America, Australia and Japan are the pioneer in implementing coastal protection systems. This system can be implemented in the form of soft or hard approached. Soft approached dictates the coastal protection systems that does not require permanent protection structure such as better conservation regulation, stricter law enforcement, giving greater public awareness etc. The hard approached is the opposite where permanent structures need to be constructed in order to protect the shoreline area. These permanent structures such as jetties, sea wall, tide gate, emerged breakwater, submerged breakwater etc.

16 2 1.2 Background problem Wave and current forces is the source of many coastal engineering problems. These natural forces not only cause damage the coastal area but also damage the properties of the communities located along the coastal area. The need to provide protection to the coastline area is crucial in order to avoid further devastation. The construction of shoreline protection structure such as submerged breakwater is one of the methods available in order to reduce this problem. However in order to ensure the submerged breakwater structure effectiveness, the determination of the submerged breakwater dimension need to consider many factors such as the local wave parameters, material to be used for the submerged breakwater, the location of the breakwater etc. All this parameter will influence the submerged breakwater wave transmission coefficient which also can be the basis of measuring the structure effectiveness. The purpose of this study is to investigate the effect of different submerged breakwater geometry have on the wave transmission and run-up values. 1.3 Importance of study The main function of constructing submerged breakwater structure is as a wave reduction structure. The submerged breakwater will act as an artificial barrier which will reduce the energy of the propagating wave and currents. However the effectiveness of the submerged breakwater structure depends very much on the structure geometry such as breakwater height and crest width. This study is done in order to investigate the effect of the structure geometry has on the submerged breakwater wave reduction capabilities or wave transmission coefficient values.

17 3 Without the additional submerged breakwater structure acting as an artificial barrier the coastal area will be subjected to the devastative impact of the high wave and current forces. This energy of this wave will hit the beach surface with great force, which will then dislodge the loose soil particle on the slope surface. The repeating impact of the high wave on the slope of the beach will expedite the coastal erosion problems. Apart from expediting the coastal erosion problems, the high wave impacting the slope of the beach will also caused high run-up value. This high run-up value will cause the excessive water to spill over on land and will caused flesh flooding. The frequent flesh flooding in the coastal area will allow sea water excess in order to infiltrate more easily into the ground water table. Due to the salinity of the sea water, excessive amount of sea water infiltration will contaminate the fresh ground water table in the coastal area. 1.4 Objective The objective of this study will involve two different criteria or case study Case without submerged breakwater A) To investigate the effect of friction factor has on the value of run-up on the slope of the beach B) To investigate the effect of different wave characteristics has on the value of runup on the slope of the beach

18 Case with submerged breakwater A) To simulate and investigate the effect of submerged breakwater with different geometry has on wave transmission coefficient value, Kt B) To evaluate the effect of submerged breakwater with different geometry has on values of run up at the slope of beach 1.5 Scope of work The purpose of this study is to investigate the effect of submerged breakwater with different design geometry has on the wave transmission coefficient value K t and also the value of run-up at the beach slope. This study will be conducted by using computer program in order to simulate and produced numerical calculation on the wave transmission propagating above the submerged breakwater and also the run-up value over the slope of the beach. The computer program will be using the Nonlinear Shallow Water equation NLSWE based model which was first developed by Kobayashi, et al. (1987) and further developed by Pedrozo-Acuna (2005). There are many factors that will influence the wave transmission coefficient value K t,. However for this study, the focus will be on the influence factors due to the different wave characteristic and different submerged breakwater geometry. For the factor involves the different wave characteristic the simulation data will be based on the dataset produced by Saville (1955). A total six different wave characteristic will be used in the numerical simulation. As for the different submerged breakwater geometry focus will be on the submerged breakwater ratio comprises of structure height to depth ratio h s /d and also breakwater crest width to depth ratio B/d which will based on the work done by Chiranjevee Rambabu and Mani (2005). Other

19 5 influence factors for the submerged breakwater structure such as breakwater structure slope, impermeability, structure orientation were not being considered.

20 61 REFERENCES Chiranjeevi Rambabu, A and Mani, J.S. (2005). Numerical prediction of performance of submerged breakwater, Ocean Engineering 32(2005) pp Coastal Engineering Manual (2002). US Army Coastal Engineering Research Centre.,1, U.S Government Printing Office,Washington D.C. D Angremond, K., Van der Meer, J.W., De Jong, R.J., 1996, Wave Transmission at Low-crested Structures, Proceedings of the 25th Int. Conf. Coast.Engineering, pp Friebel, H. C., Harris, L. E., 1999, Re-evaluation of Wave Transmission Coeffcient Formulae from Submerged Breakwater Physical Model, Florida. Fuchs, R.A., Johnson, J.W. and Morison, J.R., "The Damping Action of Submerged Breakwaters," Transactions of the American Geophysical Union, Vol. 32, No. 5, 1951, pp Jeffreys, H., "Note on the Offshore Bar Problems and Reflection from a Bar," Wave Report No. 3, Great Britain Ministry of Supply, Kobayashi, N., Otta, A. K., and Roy, I. (1987). Wave reflection and run-up on rough slopes, Journal of Waterway, Port, Coastal, Ocean Engineering, ASCE 113(3), pp Kobayashi, N and Wurjanto, A (1989), Wave transmission over submerged breakwaters, Journal of Waterway, Port, Coastal and Ocean Engineering, vol.115, ISSN x/89/ , pp Pedrozo Acuna,A. (2011). Concerning swash on steep beaches. Ph.D Thesis. University of Plymouth, United Kingdom Saville, T.,Jr. (1955). Wave Runup on Shore Structures. Journal of the Waterways and Harbor Division, Volume 82.

21 62 Saville, T.,Jr. (1956). Laboratory Data on wave Runup and Overtopping on Shore Structures. Technical Memorandum No. 64. Beach Erosion Board.Corps of Engineers. Saville, T., Jr. (1963) Hydraulic Model Study of Transmission of Wave Energy by Low-Crested Breakwater, Unpublished Memo for Record, U.S. Army,Corps of Engineers, Beach Erosion Board, Washington, D.C. Shore Protection Manual (1975). US Army Coastal Engineering Research Centre.,1, U.S Government Printing Office,Washington D.C Sorensen, R. M. (2006). Basic Coastal Engineering, Springer Science, New York. Svendsen, I.A. (2006). Introduction to Nearshore Hydrodynamics, World Scientific, London Van der Meer, J.W., Janssen, J.P.F.M., 1995.Wave run-up and wave over topping at dikes. Wave Forces on Inclined and Vertical Structures ASCE Task Committee Reports, pp Wiegel, R.L. (1962), Diffraction of Waves by Semi-infinite Breakwater, Journal, Hydraulics Division, American Society of Civil Engineers, January, pp