Impacts of Typhoon on Wave Height at Bangkhuntien Shoreline

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America Joural of Evirometal Scieces 6 (4): 308-315, 2010 ISSN 1553-345X 2010 Sciece Publicatios Impacts of Typhoo o Wave Height at Bagkhutie Shorelie 1 Prasertsak Ekphisutsutor, 1 Prugcha Wogwises,

1 America Joural of Evirometal Scieces 6 (4): , 2010 ISSN X 2010 Sciece Publicatios Impacts of Typhoo o Wave Height at Bagkhutie Shorelie 1 Prasertsak Ekphisutsutor, 1 Prugcha Wogwises, 2 Jiag Zhu ad 3 Suphat Vogvisessomjai 1 The Joit Graduate School of Eergy ad Eviromet, Kig Mogkut s Uiversity of Techology Thoburi, Bagkok, 10140, Thailad 2 Istitue of Atmospheric Physics, Chiese Academic of Scieces, Beijig, PR Chia 3 Team Cosultig Egieerig ad Maagemet Co., Ltd., 151 TEAM Buildig, Nua Cha Road, Bueg Kum, Bagkok 10230, Thailad Abstract: Problem statemet: I this study, the chagig of wave height at Bagkhutie durig a passage of typhoo LINDA was simulated by usig the Simulatig WAves Nearshore Model (SWAN) versio The study domai covered from E logitude ad N i latitude with resolutio of km. The simulatio covered 10 days durig typhoo LINDA eterig ito the Upper Gulf of Thailad. The wave height ad its chagig through the Bagkhutie shorelie were simulated. The simulated sigificat wave height by the SWAN model at Petchburi ad Ko Srichag buoy statios were compared with the observed sigificat wave height at these statios for the model verificatio. Approach: The sigificat wave height at Bagkhutie shorelie durig a passage of typhoo LINDA was simulated. Results: The results idicated that the sigificat wave height simulated by SWAN model were i good agreemet with the observed data. The average simulated sigificat wave height at Bagkhutie shorelie was 0.36 m ad the sigificat wave height was i a rage of m. before typhoo LINDA eterig ito the Upper Gulf of Thailad. The sigificat wave height icreased to 2.16, 2.22 ad 1.66 m at 26, 18 ad 5.7 m sea water depth respectively at the Bagkhutie shorelie durig typhoo LINDA passed. Coclusio: The fidigs of this study could be useful for the risig wave height, erosive calculatio, shorelie protectio ad coastal zoe maagemet whe typhoos passed through the Upper Gulf of Thailad. Key words: Sigificat wave height, LINDA, SWAN, the Upper Gulf of Thailad, Bagkhutie shorelie INTRODUCTION Bagkhutie is a district of the Bagkok Muicipality uder the authority of the Goveror of Bagkok Thailad. Bagkhutie shorelie is the oly muddy shorelie i the Bagkhutie district (Ekphisutsutor et al., 2010). This shorelie is located i the Upper Gulf of Thailad (Ekphisutsutor et al., 2010) which cosists of four river mouths: the Mae Klog, the Tha Chi, the Chao Phraya ad the Bag Pakog (Fig. 1). This shorelie is a part of a muddy coastlie with magrove forests. The legth of this shorelie is about 5 km (Ekphisutsutor et al., 2010; Kamphuis, 2000). I the past, this coastlie was a real iter-tidal area with plety of magrove bushes beig subject to floodig ad allowig the delta to maitai a dyamic equilibrium. Fig. 1: Map of Thailad ad the locatio of Bagkhutie shorelie Correspodig Author: Prasertsak Ekphisutsutor, The Joit Graduate School of Eergy ad Eviromet, Kig Mogkut s Uiversity of Techology Thoburi, Bagkok, 10140, Thailad 308

2 Fig. 2: Based track of typhoo LINDA (Waawog et al., 2010b) Its coastlie could, at times, be eroded but was built up agai, depedig o the sedimet load ad the goverig hydraulic coditios (Horikawa ad Hattori, 1987; Kamphuis, 2000). The Bagkhutie coastal zoe was degraded ad loss of the lad occurred due to the erosive forces of the sea. The sedimet supply decreased from the river ad the attackig of wave ad curret seem to be the major factors causig the shorelie erosio i this area (Kamphuis, 2000; Jackso, 1999). Therefore, the characteristics of wave i this area will be studied whe typhoo LINDA passed ito the Gulf of Thailad from October 31st to November 5th, The track of typhoo LINDA is show i Fig. 2 (Aschariyaphotha et al., 2006; Waawog et al., 2010b). The SWAN cycle III model versio (Booij et al., 2004) was used for this study. METERIALS AND METHODS The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie must be properly uderstood by ivestigatig the wave forces o the shorelie. Kowledge of the waves geerated by wid ad the sedimet trasported by wave height is very useful i shorelie erosio study i this area. The sigificat wave height durig typhoo LINDA passed ito i this area were simulated by the SWAN cycle III model versio (Booij et al., 2004; Ekphisutsutor et al., 2010; Hargreaves ad Aa, 2001; Hasselma et al., 1973; Waawog et al., 2010a; 2010b; Saleh et al., 2010). Am. J. Eviro. Sci., 6 (4): , Model descriptio: The SWAN model was developed by Delft Uiversity of Techology (Booij et al., 2004; Ekphisutsutor et al., 2010; Hargreaves ad Aa, 2001; Hasselma et al., 1973; Waawog et al., 2010a; 2010b) ad is free for the public domai. It is used by may govermet authorities, research istitutes ad cosultat worldwide. The feedback has widely idicated the reliability of the SWAN i several experimets ad field cases. It is widely used for earshore wave forecasts aroud the world. Based o the wave actio balace equatio with sources ad siks, the shallow water wave model acroym for Simulatig WAves Nearshore (SWAN) is a extesio of the deep water third-geeratio wave models. It icorporates the state-of-the-art formulatios for the deep water processes of wave geeratio, dissipatio ad quadruplet wave-wave iteractios from the WAve Model (WAM) model (Hargreaves ad Aa, 2001; Kome et al., 1996). I shallow water, these processes have bee supplemeted with the formulatios for dissipatio due to bottom frictio, triad wave-wave iteractios ad depth-iduced breakig. The SWAN is fully spectral (i all directios ad frequecies) ad computes the evolutio of wid waves i coastal regios with shallow water ad ambiet curret. Wid-geerated waves have irregular wave heights ad periods, caused by the irregular ature of wid. The sea surface elevatio, i oe poit as a fuctio of time, ca be described as: i i i (1) i η (t) = a cos( σ t + α ) Whe: η = The sea surface elevatio α i = The amplitude of the i th wave compoet σ i = The relative radia or circular frequecy of the i th wave compoet i the presece of the ambiet curret (equal to the absolute radia frequecy ω, whe o ambiet curret is preseted) σ i = The radom phase of the i th wave compoet This is called the radom-phase model. The total eergy desity at a frequecy f is distributed over the directios θ i E (f, θ), it follows that: 2π E(f ) = E(f, θ)dθ (2) 0 Based o the eergy desity spectrum, the itegral wave parameters ca be obtaied. These parameters ca

be expressed i terms of th momet of the eergy desity spectrum: m f E(f )df = (3) 0 The total eergy of a wave system is the sum of its kietic eergy ad its potetial eergy.

3 be expressed i terms of th momet of the eergy desity spectrum: m f E(f )df = (3) 0 The total eergy of a wave system is the sum of its kietic eergy ad its potetial eergy. The kietic eergy is the part of total eergy. The kietic eergy per uit legth of wave crest for a liear wave ca be foud from: E k = ρ gh L (4) The potetial eergy per uit legth of wave crest for a liear wave is give by: E p = ρ gh L (5) Accordig to the Airy theory, the total wave eergy i oe wave legth per uit crest width is give by: 2 ρgh L E = EP + Ek = (6) 8 Total average wave eergy per uit surface area, termed the specific eergy or eergy desity, is give by: 2 E ρgh E = = (7) L 8 Where: H = The sigificat wave height ρ = The specific gravity of sea water g = Gravity acceleratio Data collectio: The bathymetry data (1: 240,000) at the Upper Gulf of Thailad were take from the Hydrological Departmet of the Royal Thai Navy, wid data (10 m height) obtaied from the Thai Meteorological Departmet (TMD) was collected i every 3 h at Pilot statio i ad the observed sigificat wave height at Petchburi ad Ko Srichag buoys i 1996 ad 1998 (Fig. 3) were take from the Geo-Iformatics ad Space Techology Developmet Agecy (Public Orgaizatio) (GISTDA). Model performace: The simulated performace is evaluated usig a goodess of fit measures, amely the Correlatio Coefficiet (CC): CC = i= 1 ( Ho ) ( Ho ) ( Hm ) ( Hm i i ) ( Ho ) ( Ho ) ( m ) ( m i H H i ) i= 1 i= (8) Where: H = The sigificat wave height, the subscripts o ad m = Represet the observed ad model simulated values respectively Model verificatio: The SWAN model has bee verified with the buoy observatioal data (the sigificat wave heights) i 1996 ad 1998 at Petchburi ad Ko Srichag statios respectively. Figure 4a shows the correlatio betwee the observed sigificat wave heights ad the simulated sigificat wave heights from the model at Petchburi statio i Figure 4b shows the correlatio betwee the observed sigificat wave heights at Ko Srichag statio ad the simulated sigificat wave heights from the model i I this study, the SWAN cycle III model versio supported by Rijkswaterstaat (as part of the Miistry of Trasport, Public Works ad Water Maagemet, The Netherlads) was used. The SWAN model (Hasselma et al., 1973; 1985; 1988) was applied to solve the wave variace spectrum or eergy desity, wave eergy over frequecies ad propagatio directios. Study domai: The study domai covered the Upper Gulf of Thailad ad the Bagkhutie shorelie from E i logitude ad N i latitude with resolutio of km as show i Fig Fig. 3: The bathymetry map of the Upper Gulf of Thailad

4 Fig. 4: Correlatio betwee the observed sigificat wave heights ad the simulated sigificat wave height i 1996 Petchburi statio ad Ko Srichag statio The Correlatio Coefficiet (CC) at Petchburi ad Ko Srichag statios were 0.72 ad 0.82 respectively. Figure 5a shows the correlatio betwee the observed sigificat wave heights at Petchburi statio ad the simulated sigificat wave heights from the model i Figure 5b shows the correlatio betwee the observed sigificat wave heights ad the simulated sigificat wave heights at Ko Srichag statio from the model i The Correlatio Coefficiet (CC) at Petchburi ad Ko Srichag statios i 1998 showed the same value of The compariso of the observed sigificat wave height at the buoy statios ad the simulated sigificat wave heights preseted that the simulatio correspoded with the observatio. Model simulatio: The SWAN model simulated the sigificat wave height from (the data were ot collected i 1982 ad 1983) at the Upper Gulf of Thailad ad the sigificat wave height from October 31st to November 5th, 1997 (durig typhoo LINDA passed) were simulated. Fig. 5: Correlatio betwee the observed sigificat wave heights ad the simulated sigificat wave height i 1998 Petchburi statio ad Ko Srichag statio RESULTS Sigificat wave height at Bagkhutie shorelie whe typhoo LINDA passed: The applicatio of a two-dimesioal model based o the SWAN model to predict the sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie before ad durig typhoo LINDA passed has bee described. Figure 6 presets the sigificat wave height (m) at the Upper Gulf of Thailad o October 25th 1997 before typhoo LINDA passed. Figure 6a presets the sigificat wave height at 09:00 o October 25th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Figure 6b presets the sigificat wave height at 12:00 o October 25th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. 311

5 (c) (c) Fig. 6: Sigificat wave height (m) at the Upper Gulf of Thailad o October 25th 1997 before typhoo LINDA passed Sigificat wave height (m) at 09:00 UTC Sigificat wave height (m) at 12:00 UTC ad (c) Sigificat wave height (m) at 18:00 UTC Figure 6c presets the sigificat wave height at 18:00 o October 25th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Fig. 7: Sigificat wave height at the Upper Gulf of Thailad o November 4th 1997 durig a passage of typhoo LINDA Sigificat wave height (m) at 09:00 UTC Sigificat wave height (m) at 12:00 UTC ad (c) Sigificat wave height (m) at 18:00 UTC Figure 7 shows the sigificat wave height at the Upper Gulf of Thailad o November 4th 1997 durig a passage of typhoo LINDA. Figure 7a presets the sigificat wave height at 09: 00 o November 4th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Figure 7b shows the sigificat wave height at 12:00 o November 4th

The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about 0.20-0.70 ad 0.20-0.70 m respectively.

60 m respectively. Figure 8 shows the sigificat wave height at the Upper Gulf of Thailad o November 7th 1997 after typhoo LINDA passed.

Figure 8b presets the sigificat wave height at 12:00 o November 7th 1997. The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about 0.40-0.65 ad 0.40-0.55 m respectively.

6 The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Figure 7c presets the sigificat wave height at 18: 00 o November 4th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Figure 8 shows the sigificat wave height at the Upper Gulf of Thailad o November 7th 1997 after typhoo LINDA passed. Figure 8a presets the sigificat wave height at 09:00 o November 7th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Figure 8b presets the sigificat wave height at 12:00 o November 7th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. Figure 8c presets the sigificat wave height at 18:00 o November 7th The sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie were about ad m respectively. DISCUSSION The wave height at the Upper Gulf of Thailad was icreased due to the accumulated wid eergy from the deep sea far away from the shorelie whe typhoo LINDA passed over the Gulf of Thailad. Additioally, the wave height was also icreased o the seashore ad Bagkhutie shorelie. CONCLUSION Bagkhutie shorelie was degraded ad loss of the lad occurred. The attackig wave is oe of the major factors of the shorelie erosio, especially at Bagkhutie shorelie. The SWAN model ca be used to simulate the hourly sigificat wave height at the Upper Gulf of Thailad ad Bagkhutie shorelie. Table 1: The summary of wave characteristics at Bagkhutie shorelie (P.III) from Maximum sigificat Average sigificat wave Year wave height (H S) (m) height (H S) (m) (c) Fig. 8: Sigificat wave height at the Upper Gulf of Thailad o November 7th 1997 after typhoo LINDA passed Sigificat wave height (m) at 09:00 UTC Sigificat wave height (m) at :00 UTC ad (c) Sigificat wave height (m) at 18:00 UTC Average

Fig. 9: Represetative positios (P.I, P.II, P.III) used for wave height compariso Fig. 10: Sigificat wave height (m) at the Upper Gulf of Thailad (28 m depth, 18 m depth ad 5.

7 Fig. 9: Represetative positios (P.I, P.II, P.III) used for wave height compariso Fig. 10: Sigificat wave height (m) at the Upper Gulf of Thailad (28 m depth, 18 m depth ad 5.7 m depth) ACKNOWLEDGMENT Table 2: The chage of sigificat wave height durig the typhoo Lida passed Maximum wave Sigificat wave sigificat height (m) Depth height (m) before durig a passage Statio (m) typhoo LINDA passed of typhoo LINDA Lower poit of the Upper Gulf of Thailad (P.I) Middle poit of the Upper Gulf of Thailad (P.II) Bagkhutie shorelie (P.III) The average sigificat wave height of the 21 year simulated data at Bagkhutie shorelie was 0.36 m as show i Table 1. The sigificat wave height icreased durig typhoo LINDA eterig ito the Gulf of Thailad ad decreased whe the storm passed over. The storm affected the sigificat wave height at the Bagkhutie shorelie. The sigificat wave height at differet depth of the Upper Gulf of Thailad were 2.16, 2.22 ad 1.66 m at 26 (P.I), 18 (P.II) ad 5.7 m (P.III, Bagkhutie shorelie) sea water depth respectively i frot of the Bagkhutie shorelie as show i Fig. 9 ad 10 ad Table 2. It decreased at water depth of 5.7 m due to the bottom frictio (Booij et al., 2004). Recommedatio: The storm wave is the cause of the shorelie erosio ad disaster. The storm wave height ad the storm wave eergy should be studied. The mechaisms of the erosio ad other factors will be cosidered for the Bagkhutie shorelie ad other shorelies which have the storm wave effects. The effects of storm wave ad the shorelie erosio must be simulated uder the storm wave height ad erosio parameters. The suitable solves ad suitable protectios will be cosidered i the future. 314 This study was supported by the Joit Graduate School of Eergy ad Eviromet, Kig Mogkut s Uiversity of Techology, Thoburi. Special thaks are offered to the Hydrological Departmet of the Royal Thai Navy, the Royal Thai Survey Departmet (RTSD), the SWAN team ad Faculty of Civil Egieerig. The authors are grateful to Faculty of Civil Egieerig ad Geoscieces Delft Uiversity of Techology for kigly providig the SWAN model. Fially, the authors are greatly idebted to Mr. Michael Willig for helpful commets o Eglish grammar ad usage. REFERENCES Aschariyaphotha, N., P. Wogwises, S. Wogwises ad U. Humphries, Pheomea i the Gulf of Thailad whe Typhoo Lida 1997 Passed. Proceedig of the 2d Joit Iteratioal Coferece o Sustaiable Eergy ad Eviromet, Nov , Bagkok, Thailad, pp: Booij, N., I.J.G. Haagsma, L.H. Holthuijse, A.T.M.M. Kiefteburg ad R.C. Ris et al., SWAN Cycle III versio user maual. Delft Uiversity of Techology. Ekphisutsutor, P., P. Wogwises, C. Chiarasri, U.W. Humpries ad S. Vogvisessomjai, Numerical modelig of erosio for muddy coast at Bagkhutie shorelie, Thailad. J. Eviro. Sci., Eg., 2: Hargreaves, J.C. ad J.D. Aa, Commets o Improvemet of the short fetch behavior i the Wave Ocea Model (WAM). J. Atmos. Ocea. Tech., 18:

8 Hasselma, H., T.P. Barett, E. Bouws, H. Carlso ad D.E. Cartwright et al., Measuremets of wid-wave growth ad swell decay durig the Joit North Sea Wave Project (JONSWAP). Dtsch. Hydrogr. Z. Suppl., 12: Hasselma, S., K. Hasselma, E. Bauer, P.A.E.M. Jasse ad G.J. Kome et al., The WAM model-a third geeratio ocea wave predictio model. J. Phys. Ocea., 18: Hasselma, S., K. Hasselma, J.H. Alleder ad T.P. Barett, Computatios ad parameterizatios of the oliear eergy trasfer i a gravity-wave spectrum, Part II: Parameterizatios of the oliear eergy trasfer for applicatio i wave models. J. Phys. Ocea., 15: Horikawa, K. ad M. Hattori, The earshore eviromet research ceter project. Proceedigs of a Specialty Coferece o Advaces i Uderstadig of Coastal Sedimet Processes, America Society of Civil Egieers, May 12-13, New Orleas, LA., USA., pp: Jackso, N.L., Evaluatio of criteria for predictig erosio ad accretio o a estuarie sad beach, Delaware Bay, New Jersey. J. Estuar. Coast., 22: Kamphuis, J.W., Itroductio to Coastal Egieerig ad Maagemet. 1st Ed., World Scietific Publishig, Sigapore, ISBN: 10: , pp: 472. Kome, G.J., L. Cavaleri, M. Doela, K. Hasselma ad S. Hasselma et al., Dyamics ad Modelig of Ocea Waves. 1st Ed., Cambridge Uiversity Press, UK., ISBN: 10: , pp: 556. Saleh, E., J. Beliku, T. Aug ad A. Sigh, Wave characteristics i Sabah waters. Am. J. Eviro. Sci., 6: Waawog, W., U.W. Humphries, P. Wogwises, S. Vogvisessomjai ad W. Lueagaram, 2010a. Numerical aalysis of wave ad hydrodyamic models for eergy balace ad primitive equatios. J. Math. Stat. Sci., 6: Waawog, W., U.W. Humphries, P. Wogwises, S. Vogvisessomjai, 2010b. Three steps of oeway ested grid for eergy balace equatios by wave model. J. Compt. Math. Sci., 5:

The Application of Simulating WAves Nearshore Model for Wave Height Simulation at Bangkhuntien Shoreline

The Application of Simulating WAves Nearshore Model for Wave Height Simulation at Bangkhuntien Shoreline America Joural of Evirometal Scieces 6 (3): 299-307, 2010 ISSN 1553-345X 2010 Sciece Publicatios The Applicatio of Simulatig WAves Nearshore Model for Wave Height Simulatio at Bagkhutie Shorelie 1 Prasertsak