Shoreline Change Analysis of Mangalore Coast and Morphometric Analysis of Netravathi-Gurupur and Mulky-Pavanje Spits
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Available online at www.sciencedirect.com ScienceDirect Aquatic Procedia 4 ( 2015 ) 182 – 189 INTERNATIONAL CONFERENCE ON WATER RESOURCES, COASTAL AND OCEAN ENGINEERING (ICWRCOE 2015) Shoreline Change Analysis of Mangalore Coast and Morphometric Analysis of Netravathi-Gurupur and Mulky-Pavanje Spits Ateeth Shettya,*, K.S. Jayappaa, D.Mitrab aDepartment of Marine Geology, Mangalore University, Mangalore – 574 199, Karnataka, India bMarine and Atmospheric Sciences Department, Indian Institute of Remote Sensing, Dehradun – 248 001, Uttarakhand, India Abstract Various developmental projects have come up in the coastal zone of Dakshina Kannada and Udupi districts in the last few decades. A number of beaches are subjected to erosion and lots of coastal properties are destroyed specially during SW monsoon season along the Mangalore coast in recent years. In order to protect the beaches and the properties, a number of seawalls - each ranging in length between 100 m and 2500 m - are built since 1980s. A very few of them built scientifically, but most of them are just dumping of granite blocks directly on the shoreline. In the present study, an attempt is made to understand long-term (1967-2013) shoreline changes as well as erosion / deposition patterns due to natural (including sea-level rise) and anthropogenic activities along this coast. The study area extends from Yermal in the north to Talpady in the south covering a total length of 45.63 km. Topomap of 1967 and multi-temporal satellite images have been analyzed using Remote Sensing and GIS techniques to demarcate shoreline positions and to assess the impact of anthropogenic and hydrological factors on coastal morphology of this region. An integrative approach of Remote Sensing and GIS techniques as well as seasonal field studies clearly illustrates the reasons for shoreline and beach morphological changes. Construction of seawalls has resulted in shifting of erosion sites from one place to another adjacent place, whereas, breakwaters have been acting as barriers for littoral drift. Overall, areas subjected to erosion are higher compared to those subjected to accretion in the study area. Applications of Remote Sensing and GIS have led to understanding shoreline and beach morphological changes. These have also provided data analysis tools and methods to evaluate the geospatial patterns in short-term and long-term changes. The results of this study will be useful for shoreline, coastal zone management and implementation of CRZ act. © 20152015 The The Authors. Authors. Published Published by by Elsevier Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license (Peerhttp://creativecommons.org/licenses/by-nc-nd/4.0/-review under responsibility of organizing committee). of ICWRCOE 2015. Peer-review under responsibility of organizing committee of ICWRCOE 2015 Keywords: Remote Sensing;GIS; Shoreline Changes;Seawalls;Breakwaters. * Corresponding author. E-mail address: [email protected] 2214-241X © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015 doi: 10.1016/j.aqpro.2015.02.025 Ateeth Shetty et al. / Aquatic Procedia 4 ( 2015 ) 182 – 189 183 1. Introduction Coastal areas are very important for human beings since ancient time. About one-third of the human population is living within 100 km from the shoreline. Due to abundant natural resources and urbanization, population increases rapidly on the coastal zones. Various developmental projects have been set up in the coastal zone, placing great pressure on it, leading to diverse coastal hazards like sea erosion, seawater intrusion, coral bleaching, shoreline change etc. Li Ron et al. (2001) state that shoreline is one of the unique features of the earth surface and is one of the 27 features recognized by the International Geographic Data Committee (IGDC). A shoreline is a dynamic system with sediment moving continually, being deposited here and eroded there, as it attempts to establish an equilibrium with respect to available sediment budget and prevailing near shore marine processes (Poulos and Chronis, 2001). Shoreline change monitoring is an issue of concern in coastal management because of the tendency of the ecosystems to support many population (Moran, 2003). The coastal region mainly affected by the cause of wind, tidal current, wave and human factors. So management of coastal region should be considered in a better way and efficiently. According to Griffiths (1988), the coastal zone is increasingly under pressure from human activities such as fishing, coral and sand mining, mangrove harvesting, seaweed farming, sewage disposal, urban expansion and tourism. Of particular note are dynamite fishing, over-harvesting of mangroves, coral and sand mining, all of which have profound negative impacts on coastal stability and are thought to lead to coastal erosion and shoreline change. Among other human activities that impact coastline include dredging and physical development, mineral exploration, and construction of ports and removal of vegetation. It is of paramount importance for coastal settlements to know without bias whether local shorelines are advancing, retreating or stable (Kasinatha et al., 2004). Damming of rivers which cut-off the major source of sediments for many coastal systems and the breakwaters reduce the normal longshore drift (Frihy, 2001). Coastal erosion is a global problem affecting almost every country around the world having a coastline. This problem is expected to accelerate in the future due to the global warming, which most likely will cause a sea-level rise and increase the number of storm events across the globe. Bhat et al. (2000) have studied 100 km stretch of southern Karnataka and reported that the breakwaters of New Mangalore Port, at the mouths of Nethravathi - Gurupur estuaries, Udyavara estuary and seawalls elsewhere have contributed substantially to the modification of shoreline. The use of remote sensing and GIS for mapping and analyzing shoreline changes over a period of time has gained prominence in recent years as high resolution satellite data have become readily available (Adegoke et al., 2010). 2. Scope of the Present Investigation Based on remote sensing techniques, the present study attempts to understand the long-term shoreline changes (from 1967 to 2013) and the processes that operate in bringing about erosion and deposition along this coastal zone. Topomap of 1967, multi-temporal IRS IC/1D/P6 and Landsat – 5, 8 satellite images have been utilized to demarcate shoreline positions. As various developmental projects have been set up recently in the area, the present study will be very useful to assess the impact of hydrological and morphologic factors modifying the shoreline along this coast. The recent systematic tools of Remote Sensing, GIS and GPS are exceptionally important for coastal environmental studies. In the present study, an attempted is made to monitor shoreline changes along the Mangalore coast and morphological changes of Ullal – Bengre and Mulky - Pavanje spits. The results of this study will be useful for shoreline change detection, coastal zone management and implementation of CRZ act. 3. Study Area The coastal zone of Dakshina Kannada district extends for over 46 kms, from Latitude 12O45' to 13O11' N and Longitude 74O44' to 74O52' E with the Arabian Sea in the west and the Western Ghats in the east. The study area enjoys tropical hot monsoon climate due to its latitudinal position. The tropical monsoon climate is characterized by heavy rainfall from June to September ranging from 3000 mm to 3900 mm with high temperature all the year round and a relatively constant high humidity. Mangalore is being a major city on the Karnataka coast gaining economic importance due to urbanization and industrialization. The Netravathi and Gurpur (N-G) rivers encircle the city by flowing on its south and north respectively and debouch into the Arabian Sea at its southern side. The 184 Ateeth Shetty et al. / Aquatic Procedia 4 ( 2015 ) 182 – 189 morphological and shoreline changes in this region are dependent on many factors, such as beach erosion/accretion, human interference with natural processes of longshore sediment transport and beach reclamation. The study area comprising a total length of 45.63 km, extends from Yermal in the north to Talpady in the south (Fig. 1). It is divided into four sectors in order to understand the erosion/accretion patterns, shoreline changes, pollution and impact of anthropogenic activities on beach morphology. Sector-wise information of the study area is provided in Table 1. The beaches are comprising of fine to coarse sand with their width ranging between 20 and 230 m. Bengre and Ullal are the most densely populated zones in the study area. Thannirbhavi and Someshwara beaches have gained recreational importance. Table 1: Sector-wise information of the study area Sector Major areas Latitudes / Longitudes Length (km) A Yermal and Hejamady 13O04' N - 13O11' N / 74O44' E - 74O46' E 10.294 B Sashithulu, Mukka, Surathkal and Panambur 12O56' N - 13O04' N / 74O46' E - 74O48' E 15.937 C Thannirbhavi and Bengre 12O50' N - 12O55' N / 74O48' E - 74O49' E 8.299 D Ullal, Someshwara and Talapady 12O45' N - 12O50' N / 74O49' E - 74O52' E 11.108 Total length 45.638 Fig.1 Study area showing the four sectors, major beaches and estuaries. Ateeth Shetty et al. / Aquatic Procedia 4 ( 2015 ) 182 – 189 185 4. Materials and Methods 4.1 Satellite data The IRS IC/1D/P6 - LISS-III and Landsat - 5/8 – TM / OLI satellite data is well suited for generating land-water boundaries because of the strong contrast between land and water in the infrared portion of the electromagnetic spectrum (Charatkar, 2004) and hence they were used in the present study (Table 2). Table 2: Details of satellite data Satellite (Sensor) Date of acquisition Spatial resolution LANDSAT – 5 (TM) 09-01-1991 30 m IRS 1C/1 D (LISS III) 04-12-2001 23.6 m IRS P6 (LISS III) 07-12-2005 23.5 m IRS P6 (LISS III) 23-10-2009 23.5 m LANDSAT – 8 (OLI) 21-11-2013 30 m 4.2 Topographic map Survey of India (SOI) topomap nos.