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l.Introfuction:

The shoreline is an intersection of sea and land surfaces. In the remote sensing context,

a shoreline is dividing line between land and water that is visibly discernible in coastal

imagery (Elizabeth et al, 2005). The shoreline is understood as the dynamic boundary

between land and sea for all practical purposes. Shoreline is fundamental element in

defining the Exclusive Economic Zone (EEZ), Coastal Regulation Zone (CRZ) and

other tenitorial boundaries in the ocean. Its identification involves two stages. Firstly, it

requires selection of a shoreline indicator features such as high-water line IHWLI or

mean high woter, the intersection of a tidal datum with the coastal profile. Secondly,

detection of the chosen shoreline features within the available data source. Shoreline is

not permanent line and it keeps changing continuously and steadily by adding or

removing beach each year. Shoreline changes can be both of long and short terms. The

long-term rise in relative sea level moves the shoreline by simply by shifting waves and

current actions landward and inundating the coast. A shoreline that has retreated over

100 years by erosion of the coast afterwards can advance due to formation of sandy

beaches. Extreme eventllike storm surge also inundates shorelines. The short-term,/)

shoreline changes are more of geomorphologic perspeclive as the foreshore slope

composed of fine sand responds to the variation of incident wave height, resulting in

seasonal changes. The short term changes are also quite variable alongshore. The

changes at one place over short period may be different long-term; ohe portion of the

coast may be experience retreat, while just a few kilometres away,stable or advance.

/l

Episodic events like tropical storms and cyclones can move the shoreline several meters

landward in a day due to high wave erosion (Crowell et al, 1999)

Shoreline maintains equilibrium by restoring the sediment in summer that is eroded by

high waves during winter. A wide, well-maintained sand or gravel beach is good

protection against wave erosion because wave energy is dissipated on the beach before

it reaches the bluffs behind and because the upper part of the beach is subjected to wave

action only during high tidal elevations and storm conditions. When fine grain particles

such as silts and clays are washed and held in suspension by the moving water and

swept away by winds, Sand is transported along the beach in the direction of prevailing

winds, waves, and currents. This helps maintain a sandy beach and builds accretion

deposits such as spits and bars. Pebbles, cobbles, and boulders too large to be moved by

the waves and currents remain on the beach,. forming a lag deposit that is highly

resistant to erosion. Modifuing coastland use and land cover can trigger shoreline

erosion that laterally and gradually alter the coastal morphology. Coastal structures

effect erosion by,continuously mobilizing sediment transport under different tidal and

wave cycles.

As descriptors, study of decadal change in coastal geomorphologfu facilitates

characterisation shoreline to physical changes and assessment of shoreline susceptibility

of the various coastal types. Coastal processes responsible for shoreline changes can be

monitored by l) Satellite data based observations to identifu critical areas of shoreline

change, 2) Hydrographic measurements such as bathymetry, waves, wind, currents and

tides 3) beach profiling, measurement of response of shoreline to sediment transport

over a period of time. By combining all these more definite solutioni can be arrived

(Kairu, K. and Nyandwi, N, 2000).

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Potential data sources for shoreline investigation include historical photographs, coastal

maps and charts, high resolution satellite imagery and aerial photographs, beach surveys

and profiling, in situ geographic positioning system shorelines. Remote sensing studies

not only map temporal and spatial changes but also to retrospect changes. To date, the

most common shoreline detection technique has been subjective visual interpretation of

satellite data with the support of topographic data and digital image-processing

techniques. In addition to the shoreline change, other shoreline features indicator and

their spatial relationship relative to the physical land-water boundary help in improving

the quantitative shoreline changes and understanding their processes (NOAA, 2003).

2,Stub t4rea:

The coast from Bhimunipatnam to Gangavaram (Figure-l) has long and diverse

geomorphology such as residual hills (Inselbergs), coastal plains, pediments, paleo

channels, gully land, alluvial plain and natural levee etc. Other land forms include sea

cave, sea stack, lateric mounts, sandy beach, and marshes (Jagannadha Rao M., 2003).

The residential, agricultural land, coastal plantations, resorts, recreations and waste land

are the major land use patterns. The shoreline with rTOy beaches dispersed with rocky

hills indicate depositional environment. In a depositional environment, the coast is

characterised by coarse sediment along the offshore boundary of the shoal and finer

sediments adjacent to the coastline. This aspect clearly demonstrates that shoals

interacting with large waves reduce the energy of the incoming waves which results in

deposition of coarser sediment along the offshore boundary of the shoals. Finer clay

and slit carried in suspension by relatively low energy waves and deposit adjacent to the

coastline.

r

The study area is a micro tidal, wave dominated semidiurnal coast with mean spring tide

of 1.43m and neap tide of 0.54m,. It has significant wave height (HS) of 4.9 meter and

wind speed is 50m/s. The wave climate of this region varies during June to September

due to change wind direction due to shifting of SW to NE monsoon. The significant

wave height ranges from 1-3 during May to September, 0.5 to 2m during October to

December, remaining period it is less than 1.5 meters. The average wave period varies

from 9 to l2s for greater part of the year. The wave is predominantly from south during

March - September and from east during December to February. The wave direction is

transitional, shifting from south to east during October and November. Seasonal

currents measured up to 30 m depth are northerly during SW monsoon and southerly

during NE monsoon The annual net sediment transport at Visakhapatnam is northerly,

which is estimated as 0.94 xl06 m3/yr. (Sanil Kumar etat,2006).

The waves, wlich approach the coast are dissipated in friction on the beaches or

converted on/offshore and long shore currents to move the sediment. The sediment that

is transported along the coast, move with in a boundary zone called coastal cell.

Variable coastal orientation with in cell (shape between drift and a swash alignment,

swash alignment is the area, where coastal system little or no sediment input is

received) serves as diagnostic tool to the geomorphologist with an indication of the

amount and direction of sediment to cause shoreline change (Lawler. D. M., 2006). The

Gangavaram-Bhimunipatnam coast has four major coastal cells based on the sediment

transport patterns (Jphn Pethic, 2008) studied from OCM data (Figrtre-2). They are 1)

Bhimunipatnam 2) Uppada-Rishigonda, 3) Visakhapatnam 4) Gangavaram (Figure -3).

r1

3, gVletfiofofogy:

Firstly, the satellite data, the hydrographic chart and topographic maps are projected to

UTM under WGS-84 datum. Both low and high-resolution data (IRS-IDJP6,LISS-il,

IV and PAN) are co-registered, merged and resampled to S-meter resolution.

Geometrically rectified satellite data of 1998, 2001 , 20A3,2005 and 2008 are digitized

online for delineating shoreline at 1:10000 as contiguous boundary between land and

water and interpreting at 1:15,000 scales. In satellite data, the shoreline are distinct in

high wave length (REDAIIR) and other interpretation keys such as beach faces, berms,

sand spit, mouth and barrier bars and shoals, tidal flats and wetlands, salt encrustation

and coastal vegetation are used for confirmation.

Satellite-derived shorelineslchanges from two data sets with different tidal conditions,

lowest in one data and highest tides in another data atthe time of pass can force error.

Therefore, a simple trigonometric solution is applied using High Tide Line (HTL) from

topographic map (Figure-a) corresponding highest hide tide level (HHTL) and mean sea

level (MSL) from hydrograph data (Table-l) from topography map (Appendix). This

method enables to fit corresponding inundation of shoreline during satellite pass

(Figure-5) with predicted tide from Xtide table (Figure-6) and compute relative error

percentage. In this method, a small variation with in low tides force unknown errors and

beach losses during monsoon are regained in summe4 therefore, different season data

also force errors. However, care is taken in selecting low tide data to minimise error. A

shoreline change above 25 % is taken as significant change. The result are further field

by taking sunmer beach profiling using Arc-GPS at low tide conditions and net change

over a decade (1998-200S) in each cell are computed and presented in following

sections.

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lishakapatn&ffi,India 17.6933o N, 93.2933o E a4ltUt9981998-l l-04 2:21 AM IST 0.24 meters Low Tide1998-l l-04 5:56 AM IST Sunrise1998-Il-04 8:13 AM IST 1.67 meters Hieh Tide1998-l l-04 10:49 AM IST Full Moon1998-l l-04 2:31 PM IST 0.08 meters Low Tide1998-11-04 5:23 PM IST Sunset1998-l t-04 8:47 PM IST 1.85 meters F{ieh Tide

Vishakhapatn&ffi, India 17.69330 N, 93.2933" E 29.11.lggg1998- ll-29 4:10 AM IST 1.30 meters F{ieh Tide1998-ll-29 6:09 AM IST Sunrise

1998-ll-29 10:54 AM IST 0.3I meters Low Tide1998- lL-29 5:18 PM IST 1.3 I meters High Tide1998-ll-29 5:20 PM IST Sunset

1998-ll-29 11:26 PM IST 0.52 meters Low Tide

Vishakhapatn dn,India 17 .68330 N, 93.29330 E 6-2.20012001-A2-06 1:15 AM IST 0.23 meters Low Tide2001-02-A6 6:27 AM IST Sunrise

2001-A2-06 6:57 AM IST I.A2 meters Hieh Tide2A0I-02-06 l:11 PM IST 0.01 meters Low Tide2001-02-A6 5:54 PM IST Sunset

2001-02-06 7:43 PM IST 1.37 meters High Tide

240\-02-07 2:06 AM IST 0.10 meters Low Tide

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2003-09-14 4:17 AM IST 0.44 meters Low Tide

2003-09-14 5:44 AM IST Sunrise

2003-09-14 10:28 AM IST 1.60 meters Hieh Tide

2003-09-14 4:32 PM IST 0.3 8 meters Low Tide

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2003-09-14 10:52 PM IST 1.58 meters Hieh Tide

2003-09-15 4:46 AM IST 0.50 meters Low Tide

Vishakpatnam, India 17 .68330 N, 83.28330 E 05/1212003

2003-12-05 12:41 AM IST 0.59 meters tr,ow Tide

2A03-12-05 6:13 AM IST' Sunrise

2003-12-05 6:20 AM IST 1.23 meters Hieh Tide

2003-12-05 12:40 PM IST 0.36 meters I-ow Tide

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2005-03-17 6:18 AM IST 0.18 meters Low Tide2005-03-17 1:15 PM IST 0.93 meters Flieh Tide2005-03-17 6:07 PM IST Sunset

2005-03-17 7:A4 PM IST 0.45 meters Low Tide2005-03-18 12:46 AM IST 0.73 meters Hieh Tide

2005-03-18 12:49 AM ISTF irst

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Vishakhapatn dn,India 17.69330 N, 93.29330 E 01/0112008

2008-01-01 2:06 AM IST 1.09 meters F{ieh Tide2008-01-01 6:27 ANd nST Sunrise

2008-01-01 8:32 AM IST 0.42 meters I-ow Tide2008-01-01 3:24 PM XST 1.03 meters F{ieh Tide2008-01-01 5:32 PM IST Sunset

2008-01-01 8:58 PM IST 0.66 meters Low Tide2008-01-02 3:02 AM IST 1.00 meters Hieh Tide

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6. Summarl an[ Conctu"rion:

Gangavaram-Visakhapatnam shoreline changes are studied in two stages, firstly decadal

changes on regional scale and secondly short- term changes at cell level with IRS-1D/P6,

LISS 11VIV and PAN merged and resampled data to 5 metres. Based on the sediment

transport boundaries, the study area is divided into four cells. Study of each cell is carried

out at an interval of nvo/three years in 10, 000 scales. The studies include coastal

morphology and shoreline changes and beach profiling. At each cell, the beach widtl4are

calculated for 1998-i001, 2001-03, 2003-05 and 2005-08 and compared with summer

2009 beach profiles. This helped to ascertain shoreline changes in the field with respect

to satellite derived shoreline. The overall accuracy of this investigation estimate around

75 to 85o/o with 5 meter resolution resampled data acquired during low tide provided

reasonably good details about significant locations of shoreline changes and associated

morphodynamics. The short term shoreline changes at each coastal cell are carried out.

The results show that over a decade, the regional shoreline changes follow the normal

long shore transport with the net sediment drift to the north. The estimated change in the

beach with computed in the satellite data at critical transects is as follows, SZYo in

southem Gangavaram Coastal cell, 30.84%in southem tip of RK beach, 17.69%o in

Bhimunipatnam and 5.98 % and 15.90 %o north and south Rishigonda respectively. In

Rishigonda coastal cell, at places, the beach has completely eroded (100%) Table-2) with

negligible recovery. However, shore-term changes are subjective of local activities such

as constructi"r,#"* port, cultivation of coastal plantations and amusement parks mostly

along Gangavaram and Nshigonda coast. The Bhimunipatnam beach (width) had

moderately decreased during 1998-2005, but recovered later in 2008. The southem RK

and northern Rishigonda bachgnrid,& have moderately decreased from 1998-2008. The

32

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northern part of RK-beach remained stable than

beach in the south part of visakhapatnam port at

beach resorts and cultivation of vegetation.

southern part during ZA05-200g. The

Yerrada shows developments such as

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33