K. Ayyappan Research Scholar, Department of Harbor and Ocean Engineering. K. Thiruvenkatasamy Professor, Department of Harbor and Ocean Engineering

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 6, June 218, pp , Article ID: IJCIET_9_6_14 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed ON THE HYDRODYNAMICS OF SHORELINE MORPHOLOGICAL CHANGES AND ITS IMPACT ON TIDAL STABILITY IN THE PRESENCE OF GROINS USING FIELD MEASUREMENTS AT MUTTUKADU ESTUARY K. Ayyappan Research Scholar, Department of Harbor and Ocean Engineering AMET University, Chennai, Tamilnadu, India K. Thiruvenkatasamy Professor, Department of Harbor and Ocean Engineering AMET University, Chennai, Tamilnadu, India ABSTRACT The severe erosion problems in the Coast of Muttukadu (Kovalam) threaten both the population and properties. Most of the locations in the East coast of India, are especially vulnerable. A coastal defense method using groin system was introduced in order to reverse the present erosional trend. In the present study, shoreline changes in the presence of groins using measurements and Satellite Images. The cause behind the work is a prevention of removal of sandbar operation due to considerable erosion and siltation problems which causes the sediment deposition near and inside the backwater entrance which in turn in causes the tidal instability. The scope of this study helps in understanding the dynamics of the beach based on results of the field work, utilizing the field sediment data. The comparison of field investigation and satellite image was performed by Dumpy Level and GPS measurements. Key words: Morphological Changes; Groin system; Field Measurements, Hydrodynamics, Sediment Transport. Cite this Article: K. Ayyappan and K. Thiruvenkatasamy, On the Hydrodynamics of Shoreline Morphological Changes and its Impact on Tidal Stability in the Presence of Groins using Field Measurements at Muttukadu Estuary, International Journal of Civil Engineering and Technology, 9(6), 218, pp INTRODUCTION Coastal structures such as groins, seawalls, breakwaters, jetties, etc. contributes in modification of the Beach Morphology and Shoreline (Elmoustapha et al., 27) and also editor@iaeme.com

2 K. Ayyappan and K. Thiruvenkatasamy their significant impact on dynamics of the coast such as waves, currents, etc. and stabilization of the Shoreline (Elsayed and Mahmoud, 27). The changes in the coastline and coastal processes due to the construction of groins, jetties, breakwaters, and harbors are brought out by Bakker (1968); Komar (1998); and Cuadrado, Gomez, and Ginsberg (25). Physical and numerical models are used to study the effects of shorelines caused by the Groin parameters (Elmoustapha et al., 27; Elsayed and Mahmoud, 27; Kokpinar et al., 27; Ozolcer and Komurcu, 27; Ozolcer et al., 26). The erosion/accretion trend changes accordingly due to the construction of hard structures along the coast, either for development of ports and harbors or for protecting the coast from erosion. The shore protection structures which are designed to trap longshore sediment in order to build a protective beach are called groins, retarding erosion of the existing beach, or preventing down drift point such as a harbor or inlet from longshore drift reaching these points. The accumulation of sand is caused by the modification of the long shore sand transport due to the groins and result in mostly on the up drift side, and erosion of sand on the down drift side. The rate at which sediment is supplied and removed from the shore also causes erosion and accretion along the shoreline. The beach profile is affected significantly due to the cross-shore sediment transportation. The beach profile perpendicular to the shoreline has characteristic features that reflect the action of littoral processes. Three major factors that contribute to the Mean grain size of the sediment are wave energy level, nature of the source sediment and general offshore slope (Komar, 1998). At any given location and time, The mean grain size indicates the erosional/depositional environment of the area and reflects the stability of the beach. Erosion is marked by the increase in mean size while deposition decreases the mean size (Chauhan, et al., 1988). Field measurements on waves, tides, currents and beach geomorphology at spatiotemporal scales are made (Mishra P et al., 211; Mohapatra M and Mohanty; 24). A seasonal minor port Gopalpur along the eastern coast of India is undergoing infrastructural development for making it to a major open-coast port. Shoreline significantly changed in the last two decades due to the construction activity along the shorefront (Mohanty P K, et.al 212; Sundar V and Sarma S; 1992 ). The hard engineering solutions such as concrete protection methods which are designed to trap the sediment in order to build a protective beach, preventing sedimentation of inlet, erosion of beaches invariably fails and causes various irreversible situations by altering the coastal geomorphology in the Indian Coast such as progression of coast on up-drift side whereas erosion, recession of the shoreline on downdrift side and accumulation of sediment (Rao V R, et al., Sarma K and Reddy B, 1988; Mishra P, et al., 21; Sanilkumar V et al., 26). In this present study, an analysis on the hydrodynamic shoreline change due to impact on groins at Muttukadu (Kovalam), along the East Coast of India. 2. STUDY AREA Muttukadu backwater is situated (latitude 12 46'N and longitude 8 18'E) in Kovalam Region, 36 km South of Chennai along the South-East coast of India. Muttukadu backwater is a bar built estuary; between March and September, it is separated from the sea by the Sandbar. The sandbar erodes during the period October to December due to the inundation by water from the upper reaches, and connection with the sea is restored. The backwater is used for fishing and boating activities which covers an area of.87 km 2. The backwater opens into the Bay of Bengal at its Eastern end by a narrow opening varying from a few to 33 m in width and it extends to about 15 km in a North-South direction with ranges in width of 8m to 15m (Fig.1). The Maximum depth at the center of estuary 2 m, while most of the other areas the depth is 1 m or less. The Tamil Nadu Tourism Development Corporation (TTDC) constructed a boathouse at Muttukadu to encourage tourism activities which make Muttukadu backwater as a favorite picnic spot and a center for water sports such as boating and editor@iaeme.com

3 On the Hydrodynamics of Shoreline Morphological Changes and its Impact on Tidal Stability in the Presence of Groins using Field Measurements at Muttukadu Estuary windsurfing. The livelihood of the economically disadvantaged people of the fishing village depends on small-scale fishing in the backwater. Figure 1 Location of Study area 3. METHODOLOGY The Wave field for the East coast regions, a wave rider buoy (Latitude: N and Longitude: E) is used to measure wave data, from October 216 to April 217 (period of seven months) recorded at interval of 3 minutes by Indian National Centre for Ocean Information Services (INCOIS) Hyderabad, was used for analysis the wave characteristics of Muttukadu (Kovalam) along the Chennai Coast. Coastal profiles are usually measured perpendicular to the shoreline and may be near shore profiles, shelf profiles or beach profiles (CERC, 1998). To measure the beach profile different methods are used. The elevation varies with distance is shown by the beach profiles which are two-dimensional vertical sections. In this study, 2 transects along the coastline of the study area were identified Northern and southern groins sides of Muttukadu (Kovalam). Dumpy level and GPS were used to carry out beach profile surveys during October 217 to April 218 in order to compare and identify the changes in the beach profiles. The cross-sections of the beach profiles of the 2 transects which were surveyed for the 7 months are compared, using trapezoidal rule the erosion and accretion quantities were estimated, beach profile survey depicted in Fig.2 & Fig3. Figure 2 Beach profile measurement Muttukadu (Kovalam) editor@iaeme.com

4 K. Ayyappan and K. Thiruvenkatasamy Figure 3 Damages of Road Erosion Muttukadu (Kovalam) Using the Dumpy level and GPS (Global Position System), beach profile data were collected. These profiles extended from the reference line through the top of the berm to a water line around 6m and data measured each 5m interval. Data collected were reduced to chart datum by applying tide correction based on the tide tables for the Chennai coast. Using the polythene bags sediment samples were collected at 2-meter water depth in Northern and Southern groins side for sampling in the nearshore regions. A mechanical sieve shaker was used for the grain size analysis and values were obtained. The water depths were corrected for tidal variation. Further details were measured groins structure (length and width), satellite images along the coastal stretch of Muttukadu (Kovalam) and identified from field survey. The details of structures existing along the Muttukadu (Kovalam) presented in table 1. Table 1 Groins details along the Muttukadu (Kovalam) coast, groins are numbered from Northern and Southern Sides (source: field measurements) Sl. No Structure Details Latitude Longitude Length (m) 1 Groin N E 5 2 Groin N E 7 3 Groin N E 85 4 Groin N E 18 5 Groin N E Groin N E 65 7 Groin N E 85 8 Groin N E RESULTS AND DISCUSSIONS The data collected by Indian National Centre for Ocean Information Services (INCOIS) Hyderabad by the wave rider buoy (Pondicherry), from October 216 to April 217 is used in the present hydrodynamic analysis. Measured wave data during the observation period from October 216 to April 217 in month wise is presented in Table 2. Fig.4 to Fig.8 shows wave parameter variation from October to April (216 to 217) editor@iaeme.com

5 Wave Height in (m) Wave Height in (m) On the Hydrodynamics of Shoreline Morphological Changes and its Impact on Tidal Stability in the Presence of Groins using Field Measurements at Muttukadu Estuary Table 2 October to April (216 to 217) measured wave characteristics of Puducherry wave rider buoy East coast of Muttukadu (Kovalam) Chennai, Tamilnadu (Source: INCOIS) Monthly Significant Wave Height (m) Mean wave Period (s) Peak Direction (Deg) Maximum Minimum Mean Maximum Minimum Mean Maximum Minimum Mean October November December January February March April Significant Wave Height (Hs) Figure 4 Variation of wave height with Date/time (October to December 216) Significant Wave Height(Hs) Figure 5 Variation of wave height with date/ time (January to April 217) editor@iaeme.com

6 Wave mean period (s) Wave mean Period (s) K. Ayyappan and K. Thiruvenkatasamy Wave Mean Period (s) Figure 6 Variation of wave mean period (s) with date/time (October to December 216) Wave Mean Period (s) Figure 7 Variation of wave mean period (s) with date/ time (January to April 217) Figure 8 Variation of Wave Direction (Deg) with date/time (October to April ) editor@iaeme.com

7 Beach Elevation w.r.t.msl (m) Beach Elevation w.r.t MSL (m) On the Hydrodynamics of Shoreline Morphological Changes and its Impact on Tidal Stability in the Presence of Groins using Field Measurements at Muttukadu Estuary Maximum wave height of 2.38m, Maximum means wave period of 1.21(s) and Peak direction was recorded, during the observation period, November and April. From the results, it can be inferred that the characteristics of wave parameter from the month of January to April 217 (fair weather) are found to be normal along Muttukadu (Kovalam) coastline and during the North East monsoon period (October to December) it is abnormal and also frequently hit by cyclone for the past ten years in the East Coast region of Chennai. The predominant breaker wave types are plunging and collapsing at the locations in the study area. Net sediment transport direction is predominately Northwards, however during strong winds and storms, the local sediment transport can change direction towards the south when waves approach from NE-E. The status of beach morphology is analyzed in Muttukadu (Kovalam) Northern and Southern Groins side through beach profile survey. All the levels were adjusted to Mean Sea Level(M.S.L.) and related to the phase of the tide. The place of transect was fixed with GPS and manual paint (yellow color) marking in groins through recognized permanent reference station at groins Muttukadu (Kovalam) Northern and Southern sides. Beach profiles surveyed during these seven months for the two transects are compared and presented in Fig.1 & Fig. 11. Length of shoreline changes and quantities of erosion and accretion from the cross-sections of the beach profiles are calculated using trapezoidal rule have been presented in Table Beach Profile - Northern Groins Side Cross - Shore Distance (m) October November December January february march April Figure 1 Beach Profile at Transect 1 Northern Groins Side (During October to April along the East Coast of Muttukadu, Kovalam) Beach Profile - Southern Groins Side Cross-Shore Distance (m) october November December January february march April Figure 11 Beach Profile at Transect 2 South Groins Side (During Month of October to April along the East Coast of Muttukadu, Kovalam) editor@iaeme.com

8 K. Ayyappan and K. Thiruvenkatasamy The cross-section of the beach profile- transect 1&2 located on the Northern and Southern side of the Muttukadu (Kovalam), are shown in Fig.1 & Fig.11. The coast is accreting and the magnitude of accretion is compared in the two transects are presented in Table 3 for the study period. Table 3 Shoreline Changes and Volume of sediment changes Beach profile Erosion Volume m 3 /m Accretion Net Gross Transect 1(Northern Side) Transect 2 (Southern Side) Sediment size distribution along the coastal region of Muttukadu (Kovalam), using the sediment sample collected from the beach surface/seabed, the sediment characteristics can be determined. Beach samples, collected during field investigation, have been analyzed for different seasons in order to find the mean size for both the locations. The fractions retained in each mesh were weighed. The sediment size distribution along the Muttukadu is given in Table 2. Sediment size distribution analyses show that the median particle sizes vary.93 mm and.138 mm and the beach composed mainly of fine sand and sediment distribution presented in Table 4. Table 4 Sediment Distribution Muttukadu (Kovalam) S.No Season Sample location Median Particle Types of sand size 1 North East monsoon m water depth.96mm Fine sand 2m water depth.83mm Fine sand 2 Fair Weather meter.116mm Fine sand 2m water depth.122mm Fine sand The accretion has to take place naturally; since the Muttukadu Lake is located in the southern side. Similarly; the Tamil Nadu State Government authorities are dredging, the mouth continuously to keep the Muttukadu Lake mouth open to the inlet of freshwater flow due to the frequent closing of mouth taking place. The groins act as an obstacle for the movement and deposition of marine sediments results in coastline accretion in the southern side. This has been confirmed earlier by various studies along the East coast and also worldwide (Vernon Harcoart, 1881; Spring, 1919; Johnson, 1957; Cornick, 1969; Shepard &Wanless, 1971; Komar, 1998; Sahadevan, 1996). The erosion has started on the Northern side due to the construction of groins Muttukadu (Kovalam), and is clearly shown by the beach profile transect 1 and satellite images. In forthcoming years, it is possible that erosion will take place further North. The accretions in the Southern side are clearly demonstrated by beach profile transect 2. If the erosion is to continue at this rate, it would make these villages vulnerable for getting washed away, under these, when this region is hit by a big storm or a cyclone. 5. COMPARISON OF SATELLITE IMAGES The comparison of satellite images of Google earth before and after the construction of the Southern breakwater is shown Fig.12. Considerable accretions in the South side can be seen clearly. There was a minimum depth available at the entrance channel (from the color of the image) indicated by the 216 and 218 image. The sediments were deposited near the editor@iaeme.com

9 On the Hydrodynamics of Shoreline Morphological Changes and its Impact on Tidal Stability in the Presence of Groins using Field Measurements at Muttukadu Estuary southern side and the deposition kept on increasing, it is clear in the 218 satellite images and sediment was eroded in the Northern side of Muttukadu (Kovalam) before and after the construction of the breakwater. The shoreline is drifted towards the South. Hence it is seen that construction of groins without proper study could increase the sediment transport as in the case of Muttukadu(Kovalam). Figure 12 Before and after construction of Groins structure Muttukadu (Kovalam)Source: (Google Earth) 6. CONCLUSIONS Hydrodynamic field measurements and data analysis have been carried out to assess the impact of a groin system on the Muttukadu (Kovalam) coast. Using field measurements for the parameters, viz, beach profiles, laboratory sediment analysis, wave data, sediment transportation and shoreline morphological changes under the action of waves have been performed in the sandy beaches of Muttukadu (Kovalam) coast. The present hydrodynamic analytical results will be useful in calculating shoreline changes due to erosion and sedimentation process. In the present analysis, it is observed that severe erosion occurs in Northern side and accretion is noticed in the Southern side of the Muttukadu (Kovalam) coast. This will affect more in future, and, hence, immediate mitigation measures have to be implemented. Necessary coastal structures such as groins, detached breakwaters may be introduced after proper analysis and design. This study shows that the north side of Muttukadu (Kovalam) coast is getting eroded. Therefore, proper protection measures have to be designed. It is concluded that a long-term monitoring is necessary to plan for an effective coastal defense in this sensitive coastal belt. The alignment of harbor breakwater and groins or other coastal structure and the direction of littoral drift would certainly depend upon the wave direction. The ever-increasing exploration of ocean reserves requires continues observation of ocean wave climate for efficient near shore and offshore operation. This field measurement and analysis will serve as one of the generic analysis for comparison with numerical studies editor@iaeme.com

10 K. Ayyappan and K. Thiruvenkatasamy ACKNOWLEDGEMENTS The authors are thankful to the Department of Harbor and Ocean Engineering, AMET University. Chennai. Authors are also thankful to the Indian National Centre for Ocean Information Service (INCOIS), Hyderabad for provided the wave data. REFERENCES [1] Elmoustapha, A.O.; Levoy, F.; Manfort, O., and Koutitonsky, V.G., 27. A numerical forecast of shoreline evolution after harbor construction in Nouakchott, Mauritania. Journal of Coastal Research, 23(6), [2] Elsayed, M.A.K. and Mahmoud, S.M., 27. Groins system forshoreline stabilization on the east side of the Rosetta Promontory,Nile Delta coast.journal of Coastal Research, 23(2), [3] Bakker, W.T., Mathematical theory about sand waves and itsapplication on the Dutch Wadden Isle of Vlieland.Shore and Beach,36(2), [4] Komar, P.D., 1998.Beach Processes and Sedimentation. Upper SaddleRiver, New Jersey: Prentice Hall Inc., 544p. [5] Cuadrado, D.G.; Gomez, E.A., and Ginsberg, S.S., 25. Tidal andlongshore sediment transport associated to a coastal structure.estuarine, Coastal and Shelf Science, 62, [6] Elsayed, M.A.K. and Mahmoud, S.M., 27. Groins system forshoreline stabilization on the east side of the Rosetta Promontory,Nile Delta coast.journal of Coastal Research, 23(2), [7] Kokpinar, A.M.; Darama, Y., and Guler, I., 27. Physical andnumerical modelling of shoreline evaluation of the Kizihrmak Rivermouth, Turkey.Journal of Coastal Research, 23(2), [8] Ozolcer, I.H. and Komurcu, M.I., 27. Effects of straight groinparameters on accretion.indian Journal of Marine Sciences, 36(3), [9] Ozolcer, I.H.; Komurcu, M.I.; Birben, A.R.; Yuksek, O., and Karasu,S., 26. Effects of T-shape groin parameters on beach accretion.indian Journal of Marine Sciences, 33, [1] Turker, U. and Kabdasli, M.S., 27. Verification of sedimenttransport rate parameter on cross-shore sediment transportanalysis.ocean engineering, 34(8 9), [11] Komar, P.D., 1998.Beach Processes and Sedimentation. Upper SaddleRiver, New Jersey: Prentice Hall Inc., 544p. [12] Chauhan, O.S.; Verma, V.K., and Prasad, C., Variation in meangrain size as indicators of beach sediment movement at Puri andkonark beaches, Orissa, India.Journal of Coastal Research, 4, [13] Sarma K and Reddy B, Longshore sediment transport near Visakhapatnam port, India.Ocean and Shoreline Management, (2): [14] Mishra P, Mohanty P, Murty A, and Sugimoto T, Beach profile studies near an artificial open-coast port along south Orissa, east coast of India.Journal of Coastal Research, 21: [15] Sanilkumar V, Pathak K, Pednekar P, Raju N, and Gowthaman R, Coastal processes along the Indian coastline.current Science, (4):53-536p editor@iaeme.com

11 On the Hydrodynamics of Shoreline Morphological Changes and its Impact on Tidal Stability in the Presence of Groins using Field Measurements at Muttukadu Estuary [16] Rao V R, Murthy M, Bhat M, and Reddy N, Littoral sediment transport and shoreline changes along Ennore on the southeast coast of India: Field observations and numerical modeling.geomorphology, (1): [17] Mohanty P K, Patra S K, Bramha S, Seth B, Pradhan U, BeheraB, Mishra P, and Panda U S, Impact of Groins on Beach Morphology: A Case Study near GopalpurPort, East Coast of India.Journal of Coastal Research, (1): [18] Sundar V and Sarma S, Sediment transport rate and its distribution across surf zone off Gopalpur Port, eastcoast of India.Indian Journal of Marine Sciences, (2): [19] Mishra P, Patra S, Murthy M R, Mohanty P, and Panda U, Interaction of monsoonal wave, current and tide near Gopalpur, east coast of India, and their impact on beach profile: a case study.natural Hazards, (2): [2] Mohapatra M and Mohanty U, Some characteristics of low pressure systems and summer monsoon rainfall over Orissa.Current Science, (9): [21] CERC (1998) Coastal Engineering Manual. Virginia: Coastal Engineering Research Center, U.S. Army Corps of Engineers, Vol.I. [22] Vernon-Harcoart LF (1881) Harbours and Estuaries on Sandy Coasts. Minutes of Proceedings Institute of Civil Engineering. 7,1-32. [23] Spring FJE (1919) Coastal Sand Travel near Madras Harbour. Minutes Proceedings Institute of Civil Engineering. 21, [24] Johnson J.W (1957) The Littoral Drift Problem at Shoreline Harbours. Journal of Waterways and Harbours Division. 83, [25] Cornick HF (1969) Dock and Harbour Engineering. London: Charles Griffin, 2, 352p. [26] Shepard FP and Wanless HR (1971) Our Changing Coastlines. New York: McGraw- Hill, p: 579. [27] Komar PD (1998) Beach processes and sedimentation, Prentice-Hall Inc., New Jersey, 2 nd edition, pp: 429. [28] Sahadevan PV (1996) Royapuram Sea Erosion: Its Varying Magnitude and the Possible Ways to Solve the Century Old Problem Permanently. Proceedings on Workshop to Deliberate the Design to be Adopted for Controlling North Chennai Royapuram Sea Erosion, Madras: Public Works Department, pp: editor@iaeme.com