Shoreline Change Assessment for Odisha Coast

The coastline of India is undergoing changes due to various anthropogenic and natural interventions. Most of the shoreline changes are on account of

Coastal erosion is a chronic problem and is often thought of as inevitable along most open shores of the country. Shorelines and coastal processes are

This computer-generated perspective view of the Odisha coast highlights the locations of major ecological and deltaic systems along this coast. The image shows “Chilika Lake” (shown in blue) the largest brackish water lagoon in India, Mahanadi delta, the second largest delta in India and the Bhitarkanika Mangroves. This image combines offshore bathymetric data of GEBCO and SRTM ASTER Digital-Elevation data.

not restricted by administrative borders, and constantly change in response to wind, waves, tides, sea level fluctuation, seasonal and climatic variation, human alteration, and other factors that influence the movement of sand and material within a shoreline system. The loss (erosion) and gain (accretion) of coastal land is a visible result of the way shorelines are reshaped in the face of these dynamic conditions. How and Why Shorelines Change?As the waves gently lap the shore of a sandy beach, do you ever wonder where that sand came from? The answer is: “erosion”The source of the sand that created and continues to feed the beaches, dunes, and barrier beaches in India, comes primarily from the erosion of coastal landforms. All sedimentary coasts tend to erode at one time or another and this basic tenet of coastal science, reflects the complex interactions that occur at the land-ocean interface. Wherever shorelines are composed of discrete grains of sediment, the processes of winds, waves, currents and changing water levels combine to mobilize particles and move them around by

varying degrees. Erosion, transport, and the accretion that results are continuous and interrelated processes.

Shorelines also change seasonally, tending to accrete slowly during the summer months when sediments are deposited by relatively low energy waves and erode dramatically during the winter when sediments are moved offshore by high energy storm waves. In addition, attempting to halt natural coastal process with seawalls and other hard structures, only shifts the problem, subjecting downdrift coastal areas to similar losses. Also, without the sediment transport, some of the beaches, dunes, barrier beaches, salt marshes, and estuaries—are threatened and would disappear as the sand sources that feed and sustain them are eliminated.

As populations continue to grow and community infrastructures are threatened by coastal erosion, there is increased demand for accurate information regarding past and present trends and rates of shoreline movement. There is also a need for a comprehensive analysis of shoreline movement that is

National Centre for Sustainable Coastal Management (NCSCM) Society of Integrated Coastal Management (SICOM)Ministry of Environment and Forests (MoEF), Government of India

the structures which have been developed/ constructed along the foreshore of the country. Several of these developments are not compatible with the dynamic nature of the shoreline. Because of these factors, it has become imperative to identify areas subject to both long- and short-term erosion, since in most cases, rates of erosion have enhanced during the past decade. The Ministry of Environment and Forests is mapping the coastline to enhance the country’s preparedness to face sea hazards like storm surge and Tsunami.

The National Assessment of Shoreline Change for Gujarat and Puducherry has been released by the Honourable Union Minister Shri. Jairam Ramesh, Minister of State for Environment and Forests, on 29th December 2010. Today, the 29th April 2011, the shoreline change maps for Odisha is being released and major highlights are provided in this factsheet.

General Facts and Figures

Latitude 17°49' N and 22°34' N Longitude 81°27' E and 87°24' E Area 156,000 km2 Odisha State Population

36.7 million (2001 census)

Population Density 236 persons/km2 (2001 census)

Length of Coastline (km)

480.40

Coastal Districts of OdishaGanjam 60.85Puri 136.48Jagatsinghpur 58.95Kendrapara 83.55Bhadrak 52.61Baleshwar 87.96Population in Coastal Districts

8,975,581

Area of Coastal Districts

21,887 km2

Population Density in Coastal Districts

410 persons/km2 (2001 census)

Major Ecological Systems

Chilika Lagoon (672 km2)Bhitarkanika wildlife sanctuaryGahirmatha and Rushikulya Olive Ridley Nesting Sites

Rivers of OdishaDistrict RiversGanjam Bahuda

RushikulyaPuri Chilika Lake mouth

Mangala NadiBhargavi NadiKushabadra NadiPrachi/Kadua Nadi

Jagatsinghpur Devi RiverBalijhori NadiBitikolia NadiJatadharMohan NadiMahanadi River

Kendrapara Hansua NadiBansgarh NadiMaipura Nadi

Bhadrak Dhamra NadiGamai Nadi

Baleshwar Kantiachara NadiNunia NadiKamachara NadiKhandita NadiBurhabalang RiverPanchpara NadiHanskara NadiSubarnareka River

Ports of OdishaDistrict PortsGanjam Gopalpur

Palur Fishing HarbourPuri AstarangaJagatsinghpur ParadipKendrapara NilBhadrak DhamraBaleshwar Anantpur

The coastline of the state of Odisha is ~480km long and consists of six coastal districts. The southern tip of the Odisha coast borders the state of Andhra Pradesh and the northern end connects to the state of West Bengal.

Shoreline Change Assessment of Odisha

Shorelines are subjected to dynamic changes due to coastal processes, that are controlled by wave characteristics and the resultant near-shore circulation, sediment dynamics, beach form, etc. For the rates reported herein, erosional trends are presented as “negative” values and accretional trends are presented as “positive” values. Coastal erosion is considered as more vulnerable because of the resultant loss of coastal infrastructure and important natural habitats such as beaches, dunes, and mangroves. It also reduces the distance between coastal population and ocean, thereby increasing the risk of exposure of population to coastal hazards.

The shoreline change assessment of Odisha Coast represents long-term shoreline change for a period of 38 years from 1972-2010. Shoreline change evaluations are based on comparing four historical shorelines extracted from satellite imageries for the above time period, with recent shoreline derived from LISS III images and limited field surveys.

consistent from one coastal region to another. Prediction of shoreline retreat and land loss rates is critical to planning future coastal management strategies. To date, long-term planning for India’s shoreline has been done in piecemeal, if at all. Consequently, entire communities are being developed without adequate consideration of the potential costs of erosion, flooding, and storm damage related to sea-level rise.

In order to correctly interpret shoreline change, all shoreline data were analyzed and evaluated in light of current shoreline conditions, recent changes in shoreline uses, and the affects of human-induced alterations to natural shoreline movements. In areas that show shoreline change reversals (i.e., where the shoreline fluctuates between erosion and accretion) or areas that have been extensively altered by human activities, knowledge of natural and human impacts are typically required for proper interpretation.

The historical shorelines represent the following periods: 1972 (Survey of India toposheet) used as base map, satellite imageries of 1990, 2000, and 2010. For the coast of Odisha, base maps were prepared on 1:50,000 scale using the toposheet of the Survey of India. Onscreen digitization of coastline was made using various satellite imageries on 1:50,000 scale and stored as different layers in GIS environment for the years 1990, 2000, and 2010. Depending on location and data source, different proxies for shoreline position were used to document coastal change, including high water line, wet-dry line, vegetation line, dune toe or crest, toe or berm of the beach, cliff base or top, and the instantaneous water line as extracted from satellite imagery.

These multi-date shorelines served as input into the USGS Digital Shoreline Analysis System (‘DSAS’) software to cast various transects along the coast of Odisha. A distance of 300m intervals from the baseline was assigned to calculate the erosion/ accretion statistics in ArcGIS 9.3 software. The results obtained were categorized into eight classes of “Zones of erosion/ accretion” as follows:

Of the zones on which the shoreline was eroding, ‘high erosion’ was observed at north of river mouths along the Odisha coast. High erosion was also observed on the southern part of the breakwaters of ports, where such coastal engineering structures have greatly altered the natural shoreline movement. Presence of major mangrove systems at the Mahanadi delta and the Bhitarkanika Mangrove Forest have resulted in ‘high accretion’ areas along the Odisha coast.

Seawalls and/or riprap revetments have been constructed in as much as 9.78 km of the coastal stretch of Odisha to protect coastal infrastructure from erosion and these areas have been classified as ‘Artificial Coast’. Statistics indicate that

National Centre for Sustainable Coastal Management (NCSCM) Society of Integrated Coastal Management (SICOM)Ministry of Environment and Forests (MoEF), Government of India

Classification of Coast Extent (km) % of Coast Cumulative (%)Total length of coastline 480.40 High Erosion Zone 39.33 8.19 Medium Erosion Zone 51.96 10.82 Low Erosion Zone 85.41 17.78 36.8#

Artificial Coast: Seawalls/ Riprap 9.78 2.04 2.04Stable Coast 69.06 14.38 14.38High Accretion Zone 85.90 17.88 Medium Accretion Zone 55.15 11.48 Low Accretion Zone 83.80 17.44 46.80#

Number of Ports/ Harbours 13 Number of Fish Landing Centres 57 Number of Groynes / Breakwaters

14

Number of Jetties 8

Table 1: Shoreline Characteristics and Statistics for Odisha Coast

#(Sum of High erosion + Medium erosion + Low erosion)$(Sum of High accretion + Medium accretion+ Low accretion)

Table 2: Erosion/ accretion characteristics near Ports

District Ports South NorthGanjam Gopalpur High Accretion Low Erosion

Palur Fishing Harbour Stable coast Stable coastPuri Astaranga High Erosion Jagatsinghpur Paradip High Accretion Artificial CoastKendrapara Nil Bhadrak Dhamra Medium Erosion Stable coastBaleshwar Anantpur Stable coast Medium Erosion

District-wise erosion/ accretion characteristics

There are six coastal districts in Odisha, which have key infrastructure facilities and ecologically sensitive areas. District-wise statistics indicate that erosion is dominant in the coastal districts of Puri and Jagatsinghpur and accretion dominant in Ganjam, Kendrapara, Bhadrak and Baleshwar (Fig. 2). Due to the presence of dense mangrove vegetation, the coastal districts of Kendrapara, Bhadrak and Baleshwar show accretion of >50% of the coast. The coast is protected by riprap and other structures in the coastal districts of Jagatsinghpur and Baleshwar (Fig. 2). Table 3 provides details of shoreline change dynamics observed at river mouths. Erosion was dominant on the southern side of river mouths while accretion was observed north of the river mouths. River mouths such as Subranarekha, Bansgarh and Balijohri showed high erosion phenomena in the north. High accretion was observed

2.04% of the coast (Table 1) of Odisha is managed artificially, located near Paradip and Dhamra Ports respectively.

Overall statistics indicate that the coast of Odisha is largely accreting (46.8%) and 14.4% is stable. Erosion (High, medium and low erosion) accounts for 36.8% of the coast (Table 1). This assessment indicates that accretion is dominant in the central and northern part, while erosion dominates the southern part of the coast of Odisha. Low to medium erosion is found to occur along ~137 km of the ~480km coast of Odisha, representing nearly 28.6% of the total coast of Odisha. It could be observed that zones of erosion is obvious to the north of ports such as Gopalpur, Paradip and Anantpur Ports and to the south of Dhamra and Astranga Ports. Accretion is observed on the southern side of Paradip and Gopalpur Ports and stable coast is observed at Anantpur Port. On the northern side of Paradip Port, riprap structures are dominant (Table 3).

south of river mouths such as Devi, Gamai, Kantiachara, Nunia, Panchpara and Subarnarekha. This indicates that shoreline change was very dynamics along the mouth of rivers, suggesting that the inflow pattern determined the nature of shoreline.

National Centre for Sustainable Coastal Management (NCSCM) Society of Integrated Coastal Management (SICOM)Ministry of Environment and Forests (MoEF), Government of India

Table 3: Erosion/ accretion characteristics near river mouthsDistrict Rivers South North

Ganjam Bahuda Stable coast Low AccretionRushikulya Medium Accretion Low Erosion

Puri Chilika Lake mouth Stable coast Low ErosionMangala Nadi Low Accretion Low AccretionBhargavi Nadi Medium Accretion Medium AccretionKushabadra Nadi Low Erosion Low ErosionPrachi/Kadua Nadi Medium Erosion Low Erosion

Jagatsinghpur Devi River High Accretion High ErosionBalijhori Nadi Medium Erosion High ErosionBitikolia Nadi High Erosion Medium AccretionJatadharMohan Nadi Low Accretion Low ErosionMahanadi River Artificial Coast High Accretion

Kendrapara Hansua Nadi Medium Erosion Medium ErosionBansgarh Nadi High Erosion High ErosionMaipura Nadi Medium Erosion Medium Accretion

Bhadrak Dhamra Nadi Low Erosion Low AccretionGamai Nadi High Accretion High Accretion

Baleshwar Kantiachara Nadi High Accretion High AccretionNunia Nadi High Accretion Medium ErosionKamachara Nadi Stable coast Medium ErosionKhandita Nadi Low Erosion High AccretionBurhabalang River Medium Accretion Medium AccretionPanchpara Nadi High Accretion Medium AccretionHanskara Nadi Stable coast Medium AccretionSubarnareka River High Accretion High Erosion

In summary, this assessment indicates that the a major stretch of Odisha’s coastline (~61%) is either accreting or stable. However, 8.2 % (39.3 km) of the coast is undergoing high erosion. Based on the above information and data it is advised that proper precautions be taken prior to erecting any further structures along the eroding and vulnerable coastal stretches of Odisha.

Prepared by: Ramesh, R., Purvaja, R and Senthil Vel, AGraphic Design by : Swamynathan, S.A. & Chakravarthi P.Contributed by : Mary Divya Suganya, Sathiyabama, V.P. & Sathish Kumar S. COOPERATING ORGANIZATIONSNational Centre for Sustainable Coastal Management [NCSCM], ChennaiSociety of Integrated Coastal Management [SICOM], New Delhi &Institute for Ocean Management, Anna University, ChennaiENVIS Centre for Coastal Management and Coastal Shelterbelt (COAST)

For more information contact:Prof. R. RameshNational Centre for Sustainable Coastal ManagementMinistry of Environment and ForestsGovernment of IndiaKoodal Building, Anna UniversityChennai 600 025 http://www.ncscm.org/

This fact sheet is also available online at http://www.ncscm.org

National Centre for Sustainable Coastal Management (NCSCM) Society of Integrated Coastal Management (SICOM)Ministry of Environment and Forests (MoEF), Government of India