Indian Journal of Marine Sciences Vol. 43(7), July 2014, pp.

Morpho- dynamic evolution of Ekakula spit of coast, using satellite data

R. Mani Murali* & P. Vethamony

CSIR-National Institute of Oceanography, Dona Paula, Goa – 403004, India.

*[Email: [email protected]]

Received 1 October 2013; revised 13 November 2013

Ekakula spit is t at the northern end of Gahirmatha coast in the state of Odisha, India. This spit is located at the mouth of Maipura River which is falling in the delta region. This spit is a prominent and important for many reasons. This spit triggers interests to the coastal managers and environmentalists because of its nature. Multi-temporal satellite images (1999 – 2009) were used to study the Morpho-dynamic evolution of this spit. Results show that the spit grows towards northeast mainly by the deposition of sand brought by the littoral drift from the south. Spit got fragmented and detached portion moved away towards the offshore in the past. A close inspection of the temporal satellite images of the area reveals the progressive evolution of the spit. Spit appears to have undergone growth and fragmentation over the years and accordingly the Maipura river mouth shifted to and fro. The growth of the spit forces the river to shift its mouth and the river causes fragmentation by breaching the spit during heavy floods and cyclones. Ekakula spit lost about 306m when compared its position in 1973 (SOI toposheet) with that in the satellite image of 1999. The year- wise length of the Ekakula spit was estimated using satellite data for the period 1999-2009 from a base point selected for this purpose. Ekakula spit length increased since 1999 by 2710 m by 2008 and little reduced to 2431 m during 2008-09. Spit appears to be growing steadily by deposition of sediment brought from south by the littoral drift except during 2003 and 2009 when it suffered some erosion. Maximum increase in length was during 2004-2005 followed by 2000-01 and 1999-2000. Minimum was during 2004- 05. Erosion was minimal during 2002-03.

[Keywords: Gahirmatha coast, erosion, Ekakula spit, Odisha, Mahanadi delta.]

Introduction south and the Budhabalanga and Subarnarekha Odisha coast of India is about 476 km long1 rivers in the north have very little or no delta stretching from Icchapuram in the south to the west formation4. The lone Hukitola bay off Jambu has of Subarnarekha river mouth on the western shore been formed as a result of the huge complex spit to of the Bay of . In general, Odisha coastline the north of the Mahanadi estuary5. There are only is oriented in a SW-NE direction. Accretion and three islands off the Orissa coast - Outer Wheeler erosion processes in parts of Orissa coast were Island, Long Wheeler Island, and Coconut Wheeler studied by2.There are several major and minor Island off Dhamara and Maipura River mouths. rivers joining the at several locations The net littoral drift along the coast is northerly6. along the coast. From south up to Dhamara, the This littoral drift together with the river discharged rivers and creeks opening to the sea are Rushikulya, sediments make the river mouths a depositional Chilka lake, Bhargavi, Kushbahdra, Prachi, Devi, environment7. Hence, the river mouths protrude in Jatadharmohan creek, Mahanadi, Jambu, Hansua, to the sea. The littoral drift deposition builds spits Bansgarh, Maipura and Dhamara. North of and bars at the river mouths especially at the Dhamara coast, the Budhabalanga and southern side of the river mouths. Most of the river Subarnarekha rivers enter the sea at the northern mouths have well developed spits. This causes the most part of Odhisa coast. The sediment coastline orientation shifting towards west or contributions from all these rivers spread along the northwest at the immediate vicinity of the northern coast and make the Orissa coast depositional in side of the openings. Again after a stretch, the nature3.The coast bulges out in the central portion, coastline tends to orient itself towards north east. from Chilka Lake to Dhamara, where Mahanadi, The Gahirmatha coast (Fig. 1) lie at its southern Brahmani and systems form a end is about 10 km northwest of the Paradip coast combined delta. The coast is concave in shape on the north side of Mahanadi River. Between these between Dhamara and the Subarnarekha River coasts, there are two rivers, the Dharma and mouth as no major river pushes the shoreline into Maipura which are at the northern side of the Bay of Bengal. The in the Gahirmatha coast discharge into the sea.

INDIAN J. MAR. SCI., VOL. 43, NO. 7, JULY 2014

86°47'25"E 86°52'30"E 86°57'35"E 87°2'40"E 20°49'0"N

20°49'0"N

Nasi II Nasi I 20°43'55"N Maipura river Ekakula 20°43'55"N

Habalihuti Gahirmatha

Kanhupur 20°38'50"N 20°38'50"N 20°33'45"N Pentha 20°33'45"N Fig 2. Field photos showing the deposition at the spit

Ekakula spit (Fig. 2) is an extension of the 20°28'40"N

20°28'40"N Gahirmatha coast at the Maipura river mouth. This elongated spit extending towards north from Ekakula owes its origin mainly to the deposition of 20°23'35"N

20°23'35"N sediments brought by the northerly long shore 86°47'25"E 86°52'30"E 86°57'35"E 87°2'40"E 5,000 Meters sediment transport from south and partly to the Fig 1. Study region sediments deposited by the Maipura -Dhamara river system8. A close inspection of the temporal satellite images of the area (Table 1) reveals the progressive evolution of the spit. Same was observed during the field trip in December,2008 (Fig. 2). Spit appears to have undergone growth and fragmentation over the years and accordingly the Maipura river mouth shifted to and fro.Growth of the spit forces the river to shift its mouth and the river causes fragmentation by breaching the spit during heavy floods and cyclones9.

Materials and Methods Available data and information pertaining to the study area from different sources are collected and used here. Satellite data pertaining to the study area was procured from the National Remote Sensing Centre, Hyderabad, after atmospheric correction. Linear Imaging Self-scanning Sensor (LISS) III sensor data from the Indian Remote Sensing Satellite (IRS) are used in this study. Cloud free data pertaining to January-February months for the years 1999 to 2009 are processed and analysed. Spatial resolution of these data is about 23 m. Geo- referencing was carried out using the reference points from toposheets. Details of data sets, image characteristics and tidal positions are presented in Table 1. Digital image processing of satellite imagery and the spatial mapping was undertaken using commercial digital image processing software. The accuracy was maintained with less than 1.0 RMS error. Then the coastlines were digitized using common data interpretation techniques. They were superimposed on registered toposheet published by Survey of India in 1975

MANI MURAI &VETHAMONY: MORPHO- DYNAMIC EVOLUTION OF EKAKULA SPIT

(Survey period, 1973-73) to study the long term prolongation of the spit may lead to the withdrawal changes occurred on the spit. of material from the proximal end of the spit Apart from these, a field survey of the coastline causing thinning and deposition at the distal end using a DGPS (Accuracy is 2m) was carried out in causing widening. During high episodic floods or December 2008. The positions along the Ekakula extremely high wave conditions and storm surges spit to Maipura River mouth were taken to associated with cyclones, the river tends to breach demarcate the high water line and to compare with the spit in between especially at the thinned the other data sets. location. Ekakula spit lost about 306m when compared its Table 1: Details of satellite images position in 1973 (SOI toposheet) with that in the Tidal Path/ro Satelli Time satellite image of 1999. But a comparison between Year Date height[m w te ID [GMT] ] the images in 1989 (before it was breached and the 28/2/9 05:10: detached part remained separately as Nasi bar) and 1999 107-58 1D 1.781 9 30 1999 showed that the loss was about 6 km. Since 19/1/0 05:13: 1999 the spit has been growing again towards 2000 107-58 1D 1.098 0 44 northeast. The year-wise length of the Ekakula spit 22/2/0 05:11: was estimated using satellite data for the period 2001 107-59 1D 1.338 1 43 1999-2009 from a base point selected for the 13/1/0 05:05: purpose. The details are presented in the Table 2. 2002 107-60 1D 1.865 2 26 The Ekakula spit length increased since 1999 by 17/2/0 04:53: 2710 m by 2008 and 2431 m during 2008-09 2003 107-61 1D 1.740 3 16 towards northeast (Fig. 3). The spit appears to be 13/1/0 04:59: growing steadily by deposition of sediment brought 2004 107-62 P6 1.723 4 09 from south by the littoral drift except during 2003 24/2/0 04:57: and 2009 when it suffered some erosion. The 2005 107-63 P6 1.900 5 30 maximum increase in length was during 2004-2005 09/12/ 04:51: (712 m) followed by 2000-01 (687 m) and 1999- 2005 107-64 P6 1.180 05 53 2000 (597 m). Minimum was during 2004-05. 21/01/ 04:54: Erosion was minimal during 2002-03 by 63m. 2007 107-64 P6 10 07 19 A study by on the spatio- temporal changes of 16/1/0 04:51: the detached Nasi bar for the period 1988-2001 2008 107-64 P6 1.441 8 00 revealed interesting features. The change positions 10/01/ 04:57: of the barrier bar centroid clearly depicted the 2009 107-64 P6 09 36 migration of Nasi barrier along a north-east direction during the period 1989–1996. Within Results & Discussion seven years, the sandbar had migrated about 6.85 This spit grew towards north east and reached km from the point of origin or breaching. The closer to the Outer Wheeler island by 198810. A evolutionary trend of the spit had undergone five comparison of satellite imageries in November predominant cycles of mass erosion and post- 1988 and March 1989 showed that the spit was cyclone rebuilding in a span of 14 years from 1988 breached near the northern end near Wheeler Island to 2001. Each of the major erosion processes was during this period. It appears that the spit was again invariably linked with the incidence of cyclones in breached and fragmented at its Ekakula end in the the region. In the early stage of migration after the south during a cyclone in 1989 and the Maipura separation from the spit, the barrier bar was in the river mouth shifted towards back towards south. shallow water regime of the estuary and hence the The detached portion of the spit remained as a sediment deposition was significant under the barrier offshore bar known as Nasi bar towards influence of littoral current. On the other hand, south of Maipura mouth. This bar extended further during the same period, the region had experienced northeasterly in the later years under the influence three major cyclonic events that resulted in mass of long-shore current. However, the Nasi bar got erosion of the spit successively and the transported further fragmented into two parts in May 1997 sediments were redistributed in the barriers. during a cyclone and since then it is subjected to However, due to the absence of cyclones during further fragmentation. Accelerated long shore 2000-2008, the spit dimension had progressively transport of sands helps building and prolongation increased in spite of minor changes in between. of Barrier Island spit system. The continued

INDIAN J. MAR. SCI., VOL. 43, NO. 7, JULY 2014

Ekakula spit and the Nasi bars are known for providing mass nesting sites for the Olive Ridley turtles. Satellite images of the area revealed that spit underwent marked temporal changes. In general, the spit grows towards north east but get fragmented during the heavy floods and cyclones. Accordingly the Maipura river mouth shifts to and fro. The build up and subsequent fragmentation processes of the spit created different landforms in the offshore. The Ekakula spit grew towards north 1999 east and reached closer to the Outer Wheeler Island by 1988 and hence the Maipura river mouth shifted progressively towards north. It appears that the spit was breached and fragmented during a cyclone in 1989 and the Maipura river mouth shifted back towards south by about 6 km. The detached portion of the spit remained as an offshore sand bar known as Nasi bar. This bar extended further northeasterly in the later years under the influence of littoral drift 2009 from south. The migration rate of Nasi barrier bar 5000 was found to be substantial during the period 1989– 4500 1997.The Ekakula spit lost about 1.8 km when 4000 3500 compared its position in 1973 with that in the 3000 2500 satellite image of 1999. But a comparison between (m) the images in1989 (before it was breached and the 2000 1500 detached part remained separately as Nasi bar) and 1000 1999 showed that the loss was about 6 km. Since 500 1999 it has been growing again towards northeast. 0 1999 2000 2001 2002 2003 2004 2005 Dec- 2007 2008 2009 The year-wise length of the Ekakula spit estimated 05 from satellite data for the period 1999-2009 showed Year that the Ekakula spit length increased from 1999 by Fig 3. Year-wise variation in length of the Ekakula spit from a 2710 m up to 2008 towards northeast. The spit base point appears to be growing steadily by deposition of As described earlier the Ekakula spit grows sediment brought from south by the littoral drift towards northeast mainly by the deposition of sand except during 2002-03 and 2008-09 when it brought by the littoral drift from the south. But over suffered some erosion. This erosion may be due to the years, the spit got fragmented and the detached the severe monsoon, heavy runoff from the rivers, portion moved away towards the offshore etc, but need to be explored in detail. The undergoing further fragmentation. After some time, prolongation of the spit growth could cause erosion some fragmented portions got dispersed in the sea. and narrowing of the proximal end of the spit. This episodical fragmentation of the spit leads to Severe floods and/ or extremely high wave loss of large quantum of sand that was deposited conditions especially during cyclones cause the earlier on the spit. This loss of sand caused breaching of the spit at the narrow and weak spot. reduction in the quantum of the littoral drift The reasons for the erosion may be due to natural towards south which normally happens during the processes and manmade interventions. This coast NE monsoon season. This in turn reduced the sand is prone to cyclones, storm surges and floods which replenishment towards south along the Gahirmatha cause episodical changes in the morphology of the coast adversely affecting the extent of building up coast. of beaches normally taking place on the coast during NE monsoon.

MANI MURAI &VETHAMONY: MORPHO- DYNAMIC EVOLUTION OF EKAKULA SPIT

Table 2: Year-wise variation in length of the Ekakula spit from face is reduced, erosion will dominate on the shore. a base point Due to reduced sediment input from rivers under 0 0 Base point position: 87 2’ 3.12’’ E, 20 42’ natural forcing and manmade interventions in the 15.6’’ E river course from catchment area to the river Year Distance Differenc Difference from mouth, and also factors such as sea level rise due to from e from 1999 (m) global warming and local subsidence / tectonic Base previous causes, and occurrence of more frequent cyclones point year (m) and floods, the significant changes are triggered (m) along the coastal regions and need to be studied in 1973 1776 - - detail for the proper coastal zone management. 1999 1469 307 0 Jan Acknowledgements 2000 2066 597 597 Authors acknowledge The Director, NIO for the Feb support and the interest shown in this study. First 2001 2753 687 1286 author acknowledgesDr.Kesavdas, Jan Dr.M.D.Rajagopal and Dr.Prabhakara Rao for the 2002 2811 058 1342 field data and the constant support for this work. Feb The NIO contribution No is xxxx. 2003 2748 - 63 1279 Jan References 2004 3212 464 1743 1. Kumar V S, Pathak K C, Pednekar P, Raju N S N, Feb and Gowthaman R, Coastal processes aliong the 2005 3924 712 2455 Indian coastline.Current Science, 2006. 91:530-536. Feb 2. Murali R M, Shrivastava D, and Vethamony P, 2005 4070 146 2601 Monitoring shoreline environment of Paradip, east Dec coast of India using remote sensing.Current Science, 2007 4083 13 2614 2009. 97(1):79. Jan 3. Meijerink A, Dynamic geomorphology of the Mahanadi delta.ITC J, 1982. 3:243-250. 2008 4179 96 2710 4. Mohanti M, and Swain, M. R.,, Mahanadi River Jan Delta, East Coast Of India : An overview on Net increase during 1999 – 2008: 2710 m evolution and dynamic processes. 1993. Net increase during 1999 – 2009: 2431 m 5. Mohanti M. Coastal processes and management of the Mahanadi River deltaic complex, east coast of Conclusions India. in Proceedings Coastal Zone 93. 1993: ASCE. However, for a better understanding of the 6. Kumar V S, Pathak K C, Pednekar P, Raju N S N, seasonal and annual cycles of the coastal and Gowthaman R, Coastal processes along the geomorphologic changes, we need regular Indian coastline.Current Science, 2006. 91:530-536. monitoring of the beaches with measurements of 7. Mohanty P, Panda U, Pal S, and Mishra P, beach profiles and littoral parameters for estimation Monitoring and management of environmental of littoral transport at least on a monthly basis. The changes along the Orissa coast.Journal of Coastal inaccessibility of the coast by roads makes the data Research, 2008. 24(sp2):13-27. collection difficult and cumbersome. Remote 8. Bharali B, Rath S, and Sarma R, A brief review of sensing images are used to find out the variations of Mahanadi Delta and the deltaic sediments in spit growth and it is found that for the period 1999- Mahanadi Basin.Quaternary Deltas of India, 1991. 2009, the Ekakula spit length increased from by 22:31. 2710 m up to 2008 towards northeast. It lost about 9. NIO report., Shoreline changes along the Gahirmatha coast. 2009. 306m when compared its position in 1973. The spit 10. Prusty G, Dash S, and Singh M, Spatio‐temporal appears to be growing steadily now by deposition analysis of multi‐date IRS imageries for turtle habitat of sediment brought from south by the littoral drift dynamics characterization at Gahirmatha coast, after facing erosion. The delta advance and retreat India.International Journal of Remote Sensing, 2007. depend on the critical factor of sediment supply to 28(5):871-883. the shore face. When sediment supply to the shore