Long-term coastal erosion assessment along the coast of Karnataka, west coast of India

Author’s Accepted Manuscript Long-term coastal erosion assessment along the coast of Karnataka, west coast of India K. Sowmya, M. Dhivya Sri, Aparna S. Baskaran, K.S. Jayappa www.elsevier.com/locate/ijsrc

PII: DOI: Reference:

S1001-6279(17)30282-2 https://doi.org/10.1016/j.ijsrc.2018.12.007 IJSRC223

To appear in: International Journal of Sediment Research Received date: 9 September 2017 Revised date: 5 September 2018 Accepted date: 28 December 2018 Cite this article as: K. Sowmya, M. Dhivya Sri, Aparna S. Baskaran and K.S. Jayappa, Long-term coastal erosion assessment along the coast of Karnataka, west coast of India, International Journal of Sediment Research, https://doi.org/10.1016/j.ijsrc.2018.12.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Long-term coastal erosion assessment along the coast of Karnataka, west coast of India

Long-term coastal erosion assessment along the coast of Karnataka, west coast of India

K. Sowmyaa, M. Dhivya Srib, Aparna S. Baskaranc, K.S. Jayappad* a

Department of Marine Geology, Mangalore University, Karnataka, India

b

National Institute of Oceanography, Goa

c

Department of Civil Engineering, SRM Institute of Science and Technology, Chennai, India

d

Department of Marine Geology, Mangalore University, Karnataka, India

Corresponding Author: [email protected]

Abstract Coastal areas are always under frequent threat from various natural processes and man-induced activities. Coastal erosion is recognized as the permanent loss of land along the shoreline resulting in the transformation of the coast. The current study focuses on long-term coastal erosion analysis of the entire Karnataka coast using Remote Sensing, Geographical Information System (GIS), Linear Regression Rate (LRR), and End Point Rate (EPR) techniques. Analysis of 26 (1990 to 2016) years of erosion using Landsat images by the use 1

of the Digital Shoreline Analysis System (DSAS) tool has been done. The results show a high erosion rate at Ullal during this period (LRR -1.3 m/yr) and accretion at Devbagh (LRR 3.2 m/yr). The southern Karnataka coast faces severe erosion especially at Ullal, where the settlement is high. At Thanirbhavi, Mukka, Kota, and Om Beaches erosion also is noticed. Both anthropogenic activities like ports, seawalls, breakwaters, etc. and natural processes like long shore drift, seasonal variation, etc. are factors affecting the shoreline change along the Karnataka coast. Key words: Karnataka coast, Landsat images, Erosion, Linear Regression Rate, End Point Rate

1. Introduction The accuracy of shoreline change rate assessment reflects concrete changes and prediction of future changes depends on the following factors: the accuracy of shoreline data, irregularity of the shoreline change, number of measured shoreline data points (Kumar et al., 2010b), total time duration of the coastline data acquisition (Douglas et al., 1998), temporal and spatial bias in estimation of the statistics of the rate-of-change in the shoreline (Eliot & Clarke, 1989), and methodology of calculation (Akshaya & Arkal, 2016; Dolan et al., 1991; Hegde & Akshaya, 2015). The causes of variation in the rate of change include geomorphic

features such as inlets, wave energy, engineering changes, weather conditions, etc. (Douglas & Crowell, 2000). To assess the anthropogenic impact or to plan and implement management strategies, monitoring of shoreline change is necessary and it is useful to recognize the shoreline character and processes that induced these changes in specific areas (Vaidya et al., 2015). Remote Sensing (RS) and Geographical Information System (GIS) techniques can

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facilitate the complications of detecting shoreline position and completing the shoreline change analysis (Aedla et al., 2015; Maiti & Bhattacharya, 2009). Along the Karnataka coast 75% of the shoreline is covered with sandy beaches (Kumar et al., 2006), especially the southern coast and Uttara Kannada beaches (those are pocket-types - they lie between rocky headlands) (Sowmya & Jayappa, 2016). The intertidal region of sandy beaches is a highly dynamic zone caused by natural processes (tide, waves, long shore current, and wind) as well as human activities (Capo et al., 2006; Larson et al., 2000; Poornima & Chinthaparthi, 2014; Scott et al., 2011; Short & Hesp, 1982; van Rijn, 2011; Wright & Short, 1984). The entire Karnataka coast is exposed to an onslaught of the southwest monsoon, so the coast has to face high wave conditions during the monsoon period which develops strong southwards littoral currents. These littoral currents, distribute the sediment along the shoreline which is easily available for future erosion. The ports obstruct sediment flow and get sediment enriched on the up-drift side, whereas the down-drift side gets eroded during the monsoon period (Boak & Turner, 2005; Kumar & Jayappa, 2009). The seasonally reversing wind pattern influences northward drift during the northeastern monsoon, which gradually redistributes the sediment and regains sediment at eroded sites (Ateeth et al., 2015; Naik & Kunte, 2016). Coastal engineering structures like breakwaters, seawalls, and groins act as a barrier against alongshore transport (Kunte, 1994). These manmade structures accumulate sediment on the up-drift side and the down-drift side experiences sediment starvation and subsequent erosion (Salghunna & Aravind, 2015; Taggart & Schwartz, 1988). The study done by Kunte and Wagle (1991) along the southern Karnataka coast based on the spit growth direction indicates that alongshore drift is either towards north or south depending upon the monsoon season. According to Reddy et al. (1978, 1982) the 3

predominance of southerly drift of the coastal currents during a major part of the year could be responsible for the growth of the Bengre Spit. According to Ateeth et al. (2015), Ullal showed high erosion during 1967–2013. Naik and Kunte (2016) revealed that 22 out of 90 beaches of the Karnataka coast are out of condition for use due to erosion, human settlements, and activities linked to ports/harbours, industries, and fisheries. According to them the erosion rate in and surrounding the area of the Karwar Port was -1.65 m/yr and accretion was +3.31 m/yr during 1973 to 2014. Naik and Kunte (2016) stated that 28% of the total coastal stretch of Dakshina Kannada and Udupi districts and 8% of Uttara Kannada district is experiencing severe erosion. Hegde and Akshaya (2015) stated that the coastal stretch of Mangalore is under the very high risk rating and that of Kundapur, Kumta, northern Udupi, and Bhatkal are in the high risk rating in Digital Shoreline Analysis System (DSAS) calculation. The

Karnataka coast generally faces severe erosion during the southwest (SW)

monsoon because of high wave activity and accretion during the fair weather season (Jayappa et al., 2003; Manjunatha & Balakrihna, 1999). Previous research has revealed that most of the sand lost during the SW monsoon is regained in the next season along the southern Karnataka coast (Jayappa et al., 2003; Kumar et al., 2006; Kumar et al., 2010a, b). Constant and major erosion has shown in some parts of the Karnataka coast (Dwarakish et al., 2009). Because of the reduction in sediment supply due to various anthropogenic activities like sand mining and daming of rivers, the beach width decreased to zero in some locations (Kumar & Jayappa, 2009). Vinayaraj et al. (2011) have noticed severe erosion at Devbagh (north of the Kali River), Pavinakurve (north of the Sharavathi River), Kundapur, and the coastline at Malpe is almost constant with minor erosion and deposition. Lars and Thomas (2015) have assessed multi-hazards along the Karnataka coast and stated that coastal erosion is a major hazard compared to other hazards, especially along the southern Karnataka coast. A study on long-term and short-term shoreline 4

changes using Weighted Linear Regression Rate (WLR) and End Point Rate (EPR), respectively, done by Selvan et al. (2014) for the period of 1973 to 2006 revealed that an average of 1.5 m/yr of accretion and 1.0 m/yr of erosion and a high rate of erosion close to river mouths have taken place along the Karnataka coast. In the current study, an attempt has been made to determine the rate of shoreline change, especially erosion along the Karnataka coast using RS and GIS as tools and Linear Regression Rate (LRR) analysis focusing on the 1990 to 2016 time period. 2. Study area The coast of Karnataka is situated between 74° 51’E, 12° 45’N and 74° 05’E, 14° 53’N in the west central part of peninsular India (Fig. 1). It has a coastline of about 300 km from Talapady in the south to Karwar in the north shared by three districts - Dakshina Kannada, Udupi, and Uttara Kannada. The coast is bordered by the Arabian Sea on the west and Western Ghats in the east without any major delta formation. Sand bars are found in most of the estuaries (Kumar et al., 2012). The coast is exposed to seasonally reversing monsoon winds, with an average annual rainfall of 4,200 mm. Of the total rainfall, 80% is received during June to August (Dwarakish et al., 2009; Kumar et al., 2010b; Lars & Thomas, 2015). The temperature ranges from 21° C in December to 36° C in April. Significant wave height is up to 6 m during the SW monsoon (Avinash et al., 2012; Kumar et al., 2006, 2010b; Lars & Thomas, 2015) and is < 1.5 m during rest of the year along the west coast of India. Tides are semidiurnal with a mean tidal range of 1.2 m and a spring tidal range of 1.8 m (Kumar et al., 2010b). Alongshore currents are found to be strongest and towards the south during the SW monsoon (Narayana et al., 2001).

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The coastline displays characteristics of submergence with drowned river valleys, estuaries, and many small inlets (Nayak & Hanamgond, 2010). The southern part of the Karnataka coast has extensive straight beaches backed by estuaries with low estuarine islands and mangroves. Sand spits growing northwards often boarder the estuaries (Nayak & Hanamgond, 2010). 3. Methodology The erosion and accretion of the coast in the study area was analyzed for a period of 26 years (1990 to 2016). Ortho-rectified satellite images of the study area from sensors Landsat Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Operational Land Imager - Thermal Infrared Sensor (OLI-TIRS) for the years, 1990, 2000, 2010, and 2016 were downloaded using the U.S. Geological Survey Earth Explorer web tool. Additional information about the specifications of satellite data used in the current study is listed in Table 1.

3.1 Data Preparation All satellite images were layer stacked using ERDAS imagine layer stack tool. Scan Line Corrector (SLC) of Landsat 7 failed in 2003, and, hence, there is a gap in the images taken after that. In current study, the SLC of data is used to delineate the shoreline of 2010. The Landsat 7 image of 2010 has been destripped by filling the gap in the images of same dates of 2008 and 2009 using the model maker tool of ERDAS imagine software. The output image was geo-rectified with the use of Ground Control Points (GCPs) taken at permanent features such as road intersections and bridges. Eighteen GCPs spread evenly over the coastal region of the image were taken to give the best coverage for calculating the transformation. 6

For all these images Root Mean Square Error (RMSE) was maintained within a pixel (±3.1 m) (Hegde & Akshaya, 2015; Kumar et al., 2006, 2009, 2010b, 2012). Table 1. Details of the satellite images acquired for shoreline delineation Satellite

Sensor

Landsat 5

TM

Spatial resolution 30X30 m

Acquisition date and time (GMT) 23/02/1990

Geo-referencing error

Digitizing error

-----

±1m

------

±1m

±3.1 m

±1m

-------

±1m

04.53.52 a.m. Landsat 7

ETM+

30X30 m

14/03/2000 05.15.34 a.m.

Landsat 7

ETM+

30X30 m

22/02/2010 05.14.59 a.m.

Landsat 8

OLI-TIRS

30X30 m

30/01/2016 05.22.37 a.m.

Fig. 1. Study area map

7

3.2 Shoreline Extraction and change estimation

8

A binary image of each image was formed using the near infrared band using the histogram splicing method and these images were classified unsupervised to form an image with absolute separation between land and water classes (Kumar et al., 2009, 2010b, 2012). The vector layer of the shoreline has been extracted from the classified images by using ERDAS Imagine 9.3 and ArcMap 10.3. The high water line (HWL) mark, i.e. the effectual coastline is equal to the "wet/dry line" of the previous tide, which is clearly identifiable from all images is used to delineate the shoreline (Kankara et al., 2014; Selvan et al., 2014). In this study, the effective water-land demarcation was made in the vector format of 1990, 2000, 2010, and 2016 shorelines, which were used as an input to the DSAS 4.0 extension of ArcGIS for assessing the rate of shoreline change. By using multiple historic shoreline positions, DSAS computes rate of change statistics (Thieler et al., 2005). Transects in DSAS were directly perpendicular to the baseline at 100 m intervals all along the shore. Relations of these transects with shoreline along the baseline is then used to compute the rate-ofchange statistics. The LRR and EPR methods of shoreline change rate estimation were used in the current study. The advantages of the EPR method are ease of computation and minimal requirements of only two shoreline dates, i e the oldest and youngest, ignoring the other data sets. The method is purely computational and the calculation is based on accepted statistical concepts. The LRR method is based on the overall minimum of the squared distance to the known shoreline using all available data to find the best-fit line, and LRR is a recognized technique for computing long-term rates of shoreline change (Crowell & Leatherman, 1999). The total number of transects for Dakshina Kannada is 353, Udupi is 954, and Uttara Kannada is 1466. Total 30 reference points were considered to analyse erosion along the coast of Karnataka. Out of these 30, Dakshina Kannada has 9 reference sites, Udupi has 8, and Uttar Kannada has 13. 4. Results and Discussion 9

In the current study, the LRR and EPR statistical methods are applied to calculate the rate of coastal erosion using DSAS data. The coastal erosion of the entire Karnataka coast is shown in district-wise maps with four categories of shoreline change and graphs (see Figs. 2 to 5(c)). Table 2 lists the EPR and LRR of coastal erosion for 1990 – 2016. The negative values indicate erosion whereas; positive values represent accretion (Table 2). The values listed here are generalized values for each reference site. 4.1. Dakshina Kannada The analysis at Talapady shows the EPR value of is 0.5 m/yr and LRR value is 0.6 m/yr. These results indicate that the beach is slightly accreting. This location is an open shore and there are no shore protecting measures. At Someswara the LRR value is 0.8 m/yr and the EPR value is 0.9 m/yr indicating accretion along this beach. This location is a long open shore with rock headland. A seawall had been constructed but the structure was destroyed. The northern side of the rocky headland is accreting. Ullal shows severe erosion during the study period as LRR is -1.3 m/yr and EPR is -1.3 m/yr. Ullal is protected by a seawall, but the structure is damaged. The Ullal Spit has formed in the Netravathi-Gurpur River mouth. The coastal line has extended very near to households. To prevent beach erosion, a seawall 0.5 km long was constructed on an experimental basis at the Bengre tip in 1984-1985. After this, the beach not only became stable but it also started growing (Kumar & Jayappa, 2009). In order to prevent boats from capsizing and littoral drift from entering the Netravathi-Gurpur Estuary, breakwaters were constructed in early 1990s on either side of the approach channel to the Old Mangalore Port. Subsequently, accretion of sediment and seaward shifting of the shoreline continued on the Bengre side, and severe erosion began at Kotepura Beach (southern side of the river mouth). Many industries are situated along Kotepura Beach. At Bengre, the LRR was found to be 0.2 m/yr and EPR was found to be 0.2 m/yr during 1990-2016. Construction of the New Mangalore Port (NMP) (during 1967–73) 10

periodic dredging of the approach channel might have led to the changes in the areal extent of the Ullal and Bengre spits (Avinash et al., 2010). Thanirbhavi is situated on the northern side of Bengre Beach. The erosion determined during this study period was found to be LRR equals -1.1 m/yr and EPR equals -1.0 m/yr. This location is an open beach without any artificial structures or coastal protection measures. Panambur Beach is situated northern side of Thanirbhavi, where the LRR is 0.7 m/yr and the EPR is 1.1 m/yr and between these beaches the NMP is situated. The breakwater of the NMP plays a significant role in shoreline change. The LRR at Surathkal is 0.1 m/yr and the EPR is 0.0 m/yr, this indicates slight accretion, whereas Mukka Beach is showing erosion because a collapsed seawall was found there. The LRR at Mukka Beach is -0.9 and the EPR is -1.0 m/yr. This is situated near to the Mulki-Pavanje River mouth. The erosion rate at Sasihithlu is a LRR of -0.1 m/yr and an EPR of -0.3 m/yr. This site is the spit of Mulki-Pavanje River where erosion was noticed (Figs. 2 and 5a). 4.2 Udupi Hejamadi is the northern side of the Mulki-Pavanje River, where accretion is noticed as LRR equals 0.2 m/yr and EPR equals 0.2 m/yr, and a collapsed seawall was found along the beach. At Yermal Beach also same type of seawall was noticed where the accretion was high as LRR equals 3.1 m/yr and EPR equals 3.5 m/yr. Kaup and Malpe are very important beaches in the Udupi district where accretion was noticed at both beaches as LRR equals 1.2 m/yr and EPR equals 1.4 m/yr and LRR equals 2.4 m/yr and EPR equals 2.3 m/yr respectively. Malpe port is situated near the Udyavara River mouth and a breakwater was constructed as a channel facility for the port at Malpe. A shipyard also is situated on the shore. These artificial structures influence the erosion-accretion rate along this coast. Kodi Bengre is a spit in the Swarna–Sita River mouth, where the beach is essentially stable with LRR equal to -0.1 m/yr and EPR equal to 0.03 m/yr. The seawall was found along the coast 11

in a collapsed condition. The Swarna-Sita River has a well developed spit on both the north and south sides. The shape and area of the spit has been changing as the shore line changes happen. Kota is another eroding beach situated north of the Swarna-Sita River, where a seawall has been constructed to protect the coast, but it was poorly designed. The LRR at Kota Beach is -0.5 m/yr and the EPR is -0.3 m/yr. Maravanthe Beach was found to be an accretional beach where a seawall has been constructed to protect the beach. The LRR of this beach is 0.2 m/yr and the EPR is 0.5 m/yr. A breakwater 250 m long was found at the site, and the shoreline change rate reflects the effect of the breakwater. Uppunda Beach shows erosion in this study period as LRR equals -0.5 m/yr and EPR equals -0.2 m/yr. Some rock outcrops were found near this site and the beach is an open shore without any artificial structures. Major beaches of the Udupi Coast have shown accretion except Kodi Bengre, Kota, and Uppunda (Figs. 3 and 5b). 4.3 Uttara Kannada The accretion statistics at Nestar Beach are a LRR of 1.5 m/yr and an EPR of 1.3 m/yr. This is a pocket beach and it lies between two rocky headlands. Murudewara is a tourist place where no coastal protection measures have undertaken. The LRR value at the site is 0.6 m/yr and the EPR is -0.1 m/yr. The LRR and EPR of Manki Beach are -0.2 m/yr and -0.5 m/yr, respectively, and the beach shows erosion along the site. Apsarakonda, Pavinakurave, Vanali and Tadari are the beaches along the Uttara Kannada district where accretion is shown as LRR 0.4 m/yr, EPR 0.6 m/yr; LRR 1.4 m/yr, EPR 1.4 m/yr; LRR 1.1 m/yr, EPR 1.0 m/yr; and LRR 0.1 m/yr, EPR 0.4 m/yr, respectively. Apsarakonda is small sandy beach and a rocky headland is situated near to the site. Some rock outcrops are found along Pavinakurave Beach. Vanali and Tadari beaches have rocky headland, where very small pocket beaches have developed. Om Beach is an erosional pocket beach where the LRR is -0.8 m/yr and the 12

EPR is -0.6 m/yr. Gokarna Beach is an open shore where accretion was found in the current analysis, the LRR is 1.2 m/yr and EPR is 1.4 m/yr. Bhavikeri and Harvada beaches are another two pocket beaches along the Uttara Kannada district where Bhavikeri Beach is found to be eroding and Harvada Beach is found to be accreting. The rate of change of these two sites are LRR equals -1.1 m/yr, EPR equals -1.1 m/yr and LRR equals 0.9 m/yr , EPR equals 0.7 m/yr, respectively. Karwar Naval Base is situated near Harvada. The channel dredging and breakwater construction were found to control the erosion and accretion. Karwar is the most important site in the Uttara Kannada district where the LRR and EPR values show erosion as -0.2 and -0.3 m/yr, respectively. The Kali River and Karwar Port are situated north and south to the site. Devabagh Beach is north of the Kali River, where high accretion has been recorded as LRR equals 3.2 m/yr and EPR equals 3.1 m/yr (Figs. 4 & 5c). According to Ateeth et al. (2015) 1991, 2001, 2005, 2009, and 2013 show accretion at the Bengre Spit and erosion at the Ullal Spit. They concluded that 46 years of erosion of beaches is dominant over accretion. The Bengre Spit which was a site of erosion turned into a site of accretion subsequent to the construction of a seawall and breakwaters. The Ullal Spit is subjected to severe erosion (Bhat & Subrahmanya, 2000). Another factor affecting erosion at Ullal is wave height. The significant wave height (Hs) is 0.89 m at Ullal. Rahisha et al. (2016) studied the change detection along the Mangalore coastline and revealed that erosion was observed during 1989 to 2015 at Ullal and accretion at Bengre, Panambur, and Sashithulu. Rahisha et al. (2016) indicated that an area of 0.47 km2 was been eroded during 1982-2015. Bhat and Subrahmanya (2000) stated that the northern part of NMP, which was a stable area prior to construction of the breakwaters during the mid-seventies, shows an accreting trend. Naik and Kunte (2016) studied the impact of ports structures on the shoreline of Karnataka considering one major port, NMP and other minor ports along the Karnataka coast 13

by using shorelines extracted for the years 1973, 1998, 2000, 2003, and 2014. The study indicates that gradual recession and accretion happened at Tadri, Bhatkal, Honnavar, etc. According to Naik and Kunte (2016) Old Mangalore Port has a rate of accretion of 1.3 m/yr and the rate of erosion is not observable during the period of 1973 to 2014. The reference points Vanali, Pavinakurave, and Apsarakona are situated near to Honavar Port, and it shows a rate of erosion of 1.3 m/yr and the rate of accretion is 0.8 m/yr during 1973-2014, where the Tadari Port area shows a rate of erosion 2.0 m/yr and the rate of accretion is 1.4 m/yr. The Manjaguni Port is on the Gangavali River, near to Gokarna and shows a rate of erosion of 1.1 m/yr and the rate of accretion is 1.3 m/yr. Belekari Port, near to Bhavikeri site, shows rate of erosion as 1.267 m/yr and the rate of accretion 4.0 m/yr for the period 1973-2014. Naik and Kunte (2016) stated that the area surrounding Karwar Port has a rate of erosion of 1.7 m/yr and a rate of accretion of 3.3 m/yr during the period of 1973 to 2014. According to Akshaya and Arkal (2016) about 68.65 km of the shoreline is under the very high vulnerable category and 79.26 km of the shoreline is under high vulnerable category. Of the remaining shoreline, 59.14 km and 91.04 km are in the moderate and low vulnerable categories, respectively. About 14.25 km of coastline was of the high risk rating, along the coastal stretches near the southern parts of Mangalore, Kundapur, and Kumta and also in northern Udupi and Bhatkal. Deepika et al. (2013) state that after the construction of breakwaters in 1980s on either side of Udyavara River mouth, significant growth (~45 m/yr) of the southern spit has been recorded. A major shift of Sita–Swarna Rivers mouth toward the south by ~2.30 km has occurred due to the southerly drift. The width of the Kollur–Chakra– Haladi Rivers mouth which was ~600 m in 1910 has been reduced to ~380 m in 2008. Problems associated with erosion include loss of valuable beaches, agricultural land, and palm trees; damage to houses and infrastructure; hindrance to fishing activities; and hardship

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for the people living in the coastal areas who are mostly on the weaker socio-economic side of society (Jayappa et al., 2003).

Fig. 2. Shoreline change from the LRR for Segment 1 and 2 of Dakshina Kannada district

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Fig. 3. Shoreline change from the LRR for Segment 3, 4, and 5 of Udupi district

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Fig. 4. Shoreline change from the LRR for Segment 6, 7, and 8 of Uttara Kannada district

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Table 2. Details of the nature, EPR, and LRR for each reference site District

Reference Sites

Dakshina 1 Kannada

Nature of site

Location Lat.

EPR LRR 19901990Remarks Long. 2016 2016 (m/yr) (m/yr)

Talapady

Open shore

12.77

74.85

0.5

0.6

Accretion

2

Someswara

Rocky headland, seawall

12.79

74.84

0.9

0.8

Accretion

3

Ullal

Spit, seawall, Nethravathi River mouth

12.81

74.83

-1.3

-1.3

Erosion

4

Bengre

Breakwater, Nethravathi River mouth

12.85

74.82

0.2

0.2

Accretion

5

Thanirbhavi

Open shore

12.90

74.81

-1

-1.1

Erosion

6

Panambur

New Mangalore Port Trust (NMPT)

12.93

74.80

1.1

0.7

Accretion

breakwater

Udupi

7

Surathkal

Open sea

13.00

74.78

0.1

0.1

Accretion

8

Mukka

Damaged seawall

13.04

74.78

-1

-0.9

Erosion

9

Sasihithlu

Open sea

13.07

74.77

-0.2

-0.1

Erosion

10

Hejamadi

Poorly designed seawall

13.09

74.77

0.2

0.2

Accretion

11

Yermal

Poorly designed seawall

13.17

74.75

3.1

3.5

Accretion

12

Kaup

Poorly designed seawall, rocky headland

13.22

74.73

1.4

1.2

Accretion

13

Malpe

Open sea

13.36

74.69

2.3

2.4

Accretion

14

Kodibengre

Poorly designed seawall, Swarna –Sita River

13.44

74.69

0.1

-0.1

Erosion

13.52

74.68

-0.3

0.5

Erosion

13.69

74.64

0.5

0.2

Accretion

mouth 15

Kota

Poorly designed

16

Maravanthe

Seawall, breakwater

seawall

18

Uttara Kannada

17

Uppunda

Open sea, rock outcrop

18

Nester

Open sea, pocket beach

13.96

19

Murudeswara

Open sea, rocky headland

20

Manki

21

13.82

74.59

-0.2

-0.2

Erosion

74.53

1.3

1.2

Accretion

14.09

74.48

-0.1

-0.6

Erosion

Open sea, Poorly designed seawall

14.18

74.47

-0.5

-0.2

Erosion

Apsarakonda

Rocky headland

14.23

74.44

0.6

0.4

Accretion

22

Pavinkurave

Rock outcrop, open sea

14.32

74.41

1.4

1.4

Accretion

23

Vanali

Rocky headland

14.41

74.39

1

1.1

Accretion

24

Tadari

Rocky shore

14.52

74.34

0.4

0.1

Accretion

25

Om beach

Pocket beach

14.52

74.28

-0.6

-0.8

Erosion

26

Gokarna

Open shore

14.56

74.30

1.4

1.2

Accretion

27

Bhavikeri

Pocket beach

14.69

74.27

-1.4

-1.1

Erosion

28

Harvada

Pocket beach

14.73

7.25

0.7

0.9

Accretion

29

Karwar

River mouth

14.81

74.12

-0.3

-0.2

Erosion

30

Devbagh

Open sea

14.85

74.11

3.1

3.2

Accretion

Fig. 5(a). Rate of coastal erosion (EPR along with LRR) of Dhakshina Kannada (The numbers below the X axis are the reference sites as per Table 2).

19

Fig. 5(b). Rate of coastal erosion (EPR along with LRR) of Udupi

Fig. 5(c). Rate of coastal erosion (EPR along with LRR) of Uttara Kannda

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As per the erosion assesment, all the beaches of Dakshina Kannada district and some of them in Uttara Kannada district have shown severe erosion. Ullal, Talapady, Someswara, Batkal, and Murudeswara Beaches are found to be heavily populated (Ateeth et al., 2015) (Figs. 6 (a) to (d)), and the shoreline at Surathkal, Kaup, Kodi Bengre and Maravanthe extends very near to households. In Bengre all industries were situated along the coast where poorly designed seawalls are observed. Figures 2, 3, 4 and 6 show the eroded beaches of Ullal, Bengre, Murudeswara, and Devbagh. Both the natural processes and anthropogenic activities are responsible for erosion of this coast. The natural processes include waves, littoral currents, storms, tidal currents, offshore relief, and sea-level changes. The cyclic phenomenon of erosion/accretion is normal along the coast of Karnataka. The width of the beaches is reduced significantly during July/August when minimum sediment storage is noticed on the beaches. The beaches retain the maximum width during April/May when the maximum amount of sediment is stored on them. Even if largescale erosion is found in some locations during the SW monsoon, the lost sand is regained after the monsoon. Anthropogenic activities like construction of ports and harbors, sand and clay 21

mining, and construction of vented dams are also responsible for erosion, reduction in the width of beaches, and shoreline recession in the study area. Substantial increases in the quantity of sand mining have lead to accelerated erosion of the coast in recent years.

Fig. 6(a). Ullal Beach (b). Bengre Beach (c). Murudeswara Beach(d). Devbagh Beach

22

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5. Conclusions Geomorphic processes continuously modify the coastline. Accurate change detection for the coastline is, therefore, very important for planning measures. Remote sensing and geospatial techniques coupled with DSAS are

useful for long-term shoreline change

monitoring and provide a comprehensive view of erosion and accretion patterns of coastal areas. This study shows that during a period of 26 years (1990 to 2016), accretion of beaches is dominant over erosion, but beaches of the southern Karnataka coast are facing severe erosion, especially in Ullal, where the settelement is very high along the coast. The Udupi Coast is dominated by accretion during this period and for the Uttara Kannada Coast some places have experienced erosion and others accretion. Coastal erosion has induced severe damage to public and private property, human lives, and natural resources.

6. Aknowlegements The first author acknowledges the Department of Science and Technology, New Delhi for providing financial support in the form of a Fellowship (DST/INSPIRE Fellowship/2013/364, dated16/08/2013) and the Department of Marine Geology, Mangalore University for providing all needed facilities.

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7. References Aedla, R., Dwarakish, G.S., & Venkat, R.D. (2015). Automatic shoreline detection and change detection analysis of Netravati-Gurpur River mouth using histogram equalization and adaptive thresholding techniques. Proceedings, International Conference on Water Resources, Coastal and Ocean Engineering (ICWRCOE 2015), (pp. 563 – 570), Aquatic Procedia, Vol. 4. Akshaya, B. J., & Arkal V. H. (2016). GIS based approach for vulnerability assessment of the Karnataka Coast, India, Advances in Civil Engineering, 2016, Article ID 5642523. Ateeth, S., Jayappaa, K.S., & Mitra D. (2015). Shoreline change analysis of Mangalore Coast and morphometric analysis of Netravathi-Gurupur and Mulky-Pavanje Spits. Proceeings, International Conference on Water Resources, Coastal and Ocean Engineering (ICWRCOE 2015) (pp.182-189), Aquatic Procedia, Vol. 4. Avinash, K., Jayappa, K.S., & Vethamony, P. (2012). Evolution of Swarna estuary and its impact on braided islands and estuarine banks, Southwest coast of India. Environmental Earth Science, 65(3), 835–848 Avinash, K., Narayana, A.C., &

Jayappa, K.S. (2010). Shoreline changes and

morphology of spits along southern Karnataka, west coast of India: A remote sensing and statistics-based approach. Geomorphology, 120, 133-152.

25

Bhat, H.G., & Subrahmanya, K.R. (2000). Shoreline changes and evolution of the coastal zone in southern Karnataka, India - An analysis based on multi temporal data. International Archives of Photogrammetry and Remote Sensing, Part B7, 191-197. Boak, E., & Turner, I. (2005). Shoreline definition and detection: A review. Journal of Coastal Research, 21, 688-703. Capo, S., Sottolichio, A., Brenon, I., Castaing, P., & Ferry, L. (2006). Morphology, hydrography and sediment dynamics in a mangrove estuary: The Konkouré estuary, Guinea. Marine Geology, 230, 199–215. Crowell, M., & Leatherman, S.P. (1999). Coastal erosion mapping and management. Journal of Coastal Research, 28, 1–196. Deepika, B., Avinash, K., & Jayappa, K.S. (2013). Shoreline change rate estimation and its forecast: Remote sensing, geographical information system and statisticsbased approach, International Journal of Environmental Science and Technology, 11(2), 395-416. Dolan, R., Fenster, M.S., & Stuart, J.H. (1991). Temporal analysis of shoreline recession and accretion. Journal of Coastal Research, 7, 723–744. Douglas, B.C., & Crowell, M. (2000). Long-term shoreline position prediction and error propagation. Journal of Coastal Research, 16, 145–152. Douglas, B.C., Crowell, M., & Leatherman, S.P. (1998). Considerations for shoreline position prediction. Journal of Coastal Research, 14, 1025–1033. Dwarakish, G.S., Vinay, S.A., Usha, N., Toshiyuki, A., Taro, K., Venkataramana, K., … Babita, M.K. (2009). Coastal vulnerability assessment of the future sea 26

level rise in Udupi coastal zone of Karnataka state, west coast of India. Ocean and Coast Management, 52, 467–478. Eliot, I., & Clarke, D. (1989). Temporal and spatial bias in the estimation of shoreline rate-of-change statistics from beach survey information. Coastal Management, 17, 129–156. Hegde, V.A., & Akshaya, J.B. (2015). Shoreline transformation study of Karnataka coast: Geospatial approach. Proceedings, International Conference on Water Resources, Coastal and Ocean Engineering (ICWRCOE 2015) (pp. 151-156). Aquatic Procedia, Vol. 4. Jayappa, K.S., Vijaya, K.G.T., & Subrahmanya, K.R. (2003). Influence of coastal structures on beach morphology and shoreline in southern Karnataka, India. Journal of Coastal Research, 19, 389–408. Kankara, R.S., Selvan, S. C., Rajan, B., & Arockiaraj, S. (2014). An adaptive approach to monitor the shoreline changes in ICZM framework: A case study of Chennai coast. Indian Journal of Marine Sciences, 43(7). 1271 Kumar, A., & Jayappa, K.S. (2009). Long and short-term shoreline changes along Mangalore coast, India. International Journal of Environmental Research, 3(2), 177–188. Kumar, A., Jayappa, K.S., & Deepika, B. (2010a). Application of remote sensing and GIS in change detection of the Netravati and Gurpur River channels, Karnataka, India. Geocarto International, 25, 397–425.

27

Kumar, A., Narayana, A.C., & Jayappa, K. S. (2010b). Shoreline changes and morphology of spits along southern Karnataka, west coast of India: A remote sensing and statistics-based approach. Geomorphology, 120, 133–152. Kumar, V.S., Johnson, G., Dora, G.U., Chempalayil, S.P., Singh, J., & Pednekar, P. (2012). Variations in nearshore waves along Karnataka, west coast of India. Journal of Earth System Science, 121, 393–403. Kumar, V.S., Pathak, K.C., Pednekar, P., Raju, N.S.N., & Gowthaman, R. (2006). Coastal processes along the Indian coastline. Current Science, 91, 530–536. Kunte, P.D. (1994). Sediment transport along the Goa-North Karnataka Coast, western India. Marine Geology, 118, 207-216 Kunte, P.D., & Wagle, B.G. (1991). Spit evolution and shoredrift direction along south Karnataka coast, India. Giomale di Geologia, Series 3, 532, 71-80. Lars, R.A., & Thomas, B. (2015). Application of a new methodology for coastal multihazard assessment & management on the state of Karnataka. Indian Journal of Environmental Management, 152, 1-10. Larson, M., Capobianco, M., & Hanson, H. (2000). Relationship between beach profiles and waves at Duck, North Carolina, determined by canonical correlation analysis. Marine Geology, 163, 275-288. Maiti, S., & Bhattacharya, A.K. (2009). Shoreline change analysis and its application to prediction: A remote sensing and statistics based approach. Marine Geology, 257, 11–23.

28

Manjunatha, B.R., & Balakrishna, K. (1999). The depositional history of late quaternary sediments along Mangalore, west coast of India, Indian Journal of Marine Sciences, 22, 449-454. Naik, D., & Kunte, P.D. (2016). Impact of port structures on the shoreline of Karnataka, West Coast, India. International Journal of Advanced Remote Sensing and GIS, 5(5), 1726-1746. Narayana, A.C., Manojkumar, P., &Tatavarti, R. (2001). Beach dynamics related to the mudbank along the southwest coast of India. In: W.H. McAnnally,& A.J.Mehta, (Eds.), Coastal and estuarine fine sediment processes (pp.495-507),Amsteram; Elsevier Science BV. Nayak, G.N., & Hanamgond, P.T. (2010). India. In: ECF Bird (Ed.), Encyclopaedia of the World's Coastal Landforms.Berlin; Springer. Poornima, K.V., & Chinthaparthi, S. (2014). Detection and future prediction of coastal changes in Chennai using remote sensing and GIS techniques. International Journal of Innovative Research in Science, Engineering and Technology, 3(2), 9456–9462. Rahisha, T., Goud, A. K. C., & Sreedhara, V. (2016). Change detection in Mangalore Coastline using multi temporal remote sensing satellite data and GIS. International Journal of Advances in Mechanical and Civil Engineering. Special Issue, Sep. 2016, 9-14. Reddy, M.P.M.,

Hariharan, V., & Kurian, N.P. (1978). Coastal currents near

Mangalore. Journal of the Institution of Engineers (India), 58, pt. cl 4.

29

Reddy, M.P.M., Hariharan, V. & Kurian, N.P. (1982). Beach stability along the coast from Ullal to Thannirbhavi near Mangalore. Indian Journal of Marine Science, 11, 327-332. Salghunna, N.N., & Aravind, B.S. (2015). Shoreline change analysis for northern part of the Coromandel coast, Proceedings, International Conference on Water Resources, Coastal and Ocean Engineering (ICWRCOE 2015), (pp. 317-324), Aquatic Procedia, Vol. 4. Scott, T., Masselink, G., & Russell, P. (2011). Morphodynamic characteristics and classification of beaches in England and Wales. Marine Geology, 286, 1–20. Selvan, S.C., Kankara, R.S., & Rajan, B. (2014). Assessment of shoreline changes along Karnataka coast, India using GIS and remote sensing techniques. Indian Journal of Marine Sciences, 43(7), 1-6. Short, A., & Hesp, P. (1982). Wave, beach and dune interactions in southeastern Australia. Marine Geology, 48, 259-284. Sowmya, K., & Jayappa, K. S. (2016). Environmental sensitivity mapping of the coast of Karnataka, west coast of India, Ocean & Coastal Management, 121, 70–87. Taggart, B.E., & Schwartz, M.L. (1988). Net shore-drift direction determination: A systematic approach. Journal of Shoreline Management, 3(4), 285-309. Thieler, E.R., Himmelstoss, E.A., Zichichi, J.L., & Miller, T.L. (2005). Digital Shoreline Analysis System (DSAS) version 3.0: An ArcGIS extension for calculating shoreline change. U.S. Geological Survey Open-File Report 20051304. 30

Vaidya, R., Biradar, R.S., Inamdar, A.B., Sudha, S., & Madhavi, P. (2015). Assessment of shoreline changes of Alibag Coast (Maharashtra, India) using remote sensing and GIS. Journal of Marine Biological Association of India, 57(2), 83-89. van Rijn, L.C. (2011). Coastal erosion and control, Ocean & Coastal Management, 30, 1-21. Vinayaraj, P., Glejin J., Udhaba D.G., Sajiv P.C., Sanil K.V., & Gowthaman, R. (2011). Quantitative estimation of coastal changes along selected locations of Karnataka, India: A GIS and remote sensing approach. International Journal of Geosciences, 2, 385-393. Wright, L.D., & Short, A.D. (1984). Morphodynamic variability of surf zones and beaches: A synthesis, Marine Geology, 56, 93

31