31 Application of Remote Sensing and GIS for Coastal Zone Management

Dr. Puneeta Pandey

 

1. Learning Objectives

 

The objective of the module is to understand the application of remote sensing and GIS for mapping, classification and analysis of data pertaining to coastal zones for their effective management and conservation.

 

2. Introduction

 

Coastal zone is an interface between terrestrial and marine ecosystems. These are known to be highly productive regions and comprise of mangroves, sea grasses, coral reefs and sand dunes. These transition zones harbor variety of floral and faunal species, regulate cycling of nutrients, filter pollutants and help to protect shorelines from erosion and storms. Because of dynamic interaction between land and water, coastal zone mark an area of continual change. Increased anthropogenic activities like industrial development, tourism, growth of cities, aquaculture and fishing, disposal of wastes have affected these ecosystems badly as a result of reduction marine bio-diversity and degradation of coasts. Norse (1993) identified five major factors accounting for degradation and depletion of coastal resources as-

 

1.      Habitat degradation

 

2.      Pollution

 

3.      Population pressure

 

4.      Overexploitation of marine resources

 

5.      Multiple resource use conflicts

 

Among all the above issues, population pressure is often recognized as the most serious factor affecting the coastal zones. Apart from anthropogenic factors, episodic events, such as cyclones, tsunamis, floods, pose serious threat to human life and property in the coastal zone. Considering all the above mentioned threats to coastal ecosystems, urgent measures are required to be taken to conserve and protect these region including individual plant species and communities, to ensure sustainable development. Issues that are needed to be addressed in context of coastal zone management and its protection are coastal ecosystems and marine living resources, coastal development, coastal water quality, shoreline protection, coastal hazards and climate change (Nayak, 2000).

 

Another set of processes occurring in the coasts like erosion, deposition, sediment transport and sea level rise also modify the shoreline and affect these regions. Therefore, in order to protect and restore them from various degrading factors, periodic assessment and an up-to-date and comprehensive scientific databases on habitats, protected areas, water quality are required to be developed. Based on these databases, proper planning and policy decisions can be framed. Advanced mapping techniques like those comprising remote sensing, GIS (Geographic Information System) and GPS (Geographic Positioning System) are considered to be more advantageous in mapping of coastal zones and preparation of databases as compared to conventional mapping techniques which can’t provide up-do date information. Data used for remote sensing is easily available, multi spectral in nature, and provides repetitive coverage. Remote sensing techniques generate spatial data which are analyzed in GIS environment for the spatial and temporal analysis. GIS further assists in integration of various data and application of modeling techniques to derive better picture of the study area and framing new policies and development of management plan. Coastal Zone Management calls for planning and organization of development processes and control activities of coastal areas aiming at the sustainable use of natural resources of the coastal zone. It involves various disciplines like hydrology, soil/water conservation, environmental expertise, forestry, agro-economy, physical planning, sociology/anthropology (demography) and economy.

 

2.1 Steps involved in coastal zone management include-

 

1.      Collecting data concerning Coastal Zone

 

2.      Ranking of data reliability (e.g. with maps depending on scale, source, age and material)

 

3.      Maintenance of these information (keep it up to date)

 

4.      Monitoring of inventory studies

 

5.      Generate thematic maps

 

6.      Support management and planning activities of by providing necessary and sufficient information on coastal zone

 

7.      Support the writing policies concerning coastal zone

 

8.      Research to assess the management and planning problem in specific areas.

 

3.  Coastal zone issues and their management using geospatial technology-

 

3.1 Mangroves– are highly productive ecosystems which enrich the coastal waters and support benthic population through recycling of nutrients and production of organic matter. They play an important role in shoreline stabilization, sedimentation trapping, fish breeding, sequestration and storage of carbon pool and remediation of heavy metals. Despite being of such socio-economic and ecological value, these forests face destruction due to expansion of aquaculture farms and demand of wood for construction purposes. They comprise 8% of the world vegetation. India has 4740 km2 of area under mangroves (0.14 % of total geographic area). Forest Survey of India has been instrumental in providing information related to forest cover in country since 1987. Satellite remote sensing has been found to be a very valuable application tool in management and monitoring of mangroves. For distinguishing mangrove cover, spectral resolution of the sensor is of crucial importance and important techniques involved are principal component analysis and band ratio. Change detection analysis using remote sensing data assists in detecting changes in spatial cover of mangroves and conversions into other land use land cover classes due to external interferences. For this purpose, Landsat TM/MSS/ ETM+ and IRS data has been found to be very suitable. The whole study involves two main steps:

 

In the first step, a broad classification of the general land cover, including mangroves is made. This indicates the best approach to dealing with the various types of imagery in order to detect the mangrove deforestation.

 

The second step concentrates on the specific problem of detecting changes in the mangrove areas. It examines different approaches for monitoring the nature of the changes in order to produce maps showing the current and former conditions in an area.

 

Synthetic Aperture Radar (SAR) data, which is independent of cloud, cover and weather interference can be used for mapping mangrove and estimation of mangrove biomass. Mesta et al., 2014 carried out study to provide detailed information of mangroves species distribution along the west coast of India (Bhatkal, Honnavar, Kumta and Ankola taluks of Uttara Kannada district which falls under Honnavar forest division of Karnataka) using geospatial technology. Mangrove forest in the regions maintains a good food supply, and acts as protective nurseries for fish and prawn. Changes in the forest cover and coastline changes were studied 1989–2010. Landsat and IRS data was used for the study (Fig 1). Chief mangrove species in the area (Rhizophora mucronata, Sonneratia caseolaris, Avicennia officinalis, Sonneratia alba, and Kandelia candel) were studied for their spatial distribution. The study provided valuable data for drawing plan for restoration and conservation of mangrove habitats.

Fig. 1 Flow chart of method used in the study mangrove dynamics (Mesta et al., 2014).

3.2. Coral reefs– These are ecosystems with greatest number of species of any marine ecosystem and thus, are regarded as one of the most important critical resources for various ecological, environmental and socio-economic reasons. Employment of a huge number of individuals is reliant on this biologically rich community as a considerable amount of their food and procuring is from the high productivity of coral reef. Along the coastal areas these ecosystems act as a barrier against wave action thereby preventing coastal erosion. Besides this, they protect mangroves and seagrass beds which are the breeding and nursing grounds of various economically important organisms. Coral reef ecosystems are quite vulnerable to external impacts which can be natural or anthropogenic. But a majority of stress is caused due to human influence. Around 57% of the coral reefs globally, are under threat due to anthropogenic causes like over exploitation, coastal development, marine pollution, toxic discharge from industrial and agricultural chemicals (Bryant et.al 1998). Thus, global pressures on coral reefs due to increasing coastal populations; calls for their careful analysis, planning and management. Chandrasekar et al. (2002) classified the major issues for the prevention of degradation of corals as-

 

1.  Monitoring long term trends of dynamic changes,

 

2.  Planning and implementing coastal protection

 

3.    Formulating proper criteria for the location of industries, aqua culture and recreational activities

 

4.  Monitoring and conserving critical environmental features5.

 

5.    Assessing the impact of reclamation of land from the sea, sand mining, dredging and recreational activities on coastal ecology,

 

6.  Controlling pollution of coastal and estuarine

 

7.  Improving navigation systems etc.

 

In India, the coral reef beds are located in Gulf of Kachchh, Gulf of Mannar, Lakshadweep Islands and Andaman and Nicobar islands. These fragile ecosystems could be easily destroyed by pollution, siltation, logging and mining. The main threats to coral reef colonies in India are climate change, algal overgrowth, release of domestic waste and siltation from land based activities. In India, studies on coral reefs in the coastal zone are being undertaken by Indian National Centre for Ocean Information Sciences (autonomous body under the MoES at Hyderabad). The information about their extent and condition is useful for planning strategies required for their conservation and prevention. IRS LISS II and LISS III data has been used to map coral reefs on 1:50000 scale (Nayak, 2004) for uncharted coralline shelf, coral heads, live coral platform and coral pinnacle. The resultant maps were used as a basic input for estimating the boundaries of protected areas and biosphere reserves. Degradation of coral reefs was found to be more disastrous than their total destruction. As both coral and mangrove ecosystems form an integral part of coastal zone, the destruction of one could led to serious consequence on another. Felling of mangroves can led to increase in sediment loading and affect growth of live coral and species diversity. These systems exhibit clear-cut morphological and ecological characters which allow for their proper mapping using remote sensing techniques. Nayak et al. (1996) used IRS-1C LISS III and PAN merged data for coral reef zonation study. Green band (520-590 nm) of IRS LISS III was found to be quite useful for this purpose and corals spread over areas as small as 50m2 were differentiated. Further, very high-resolution data such as IKONOS has yielded better results with enhanced accuracy of classification as well as delineation of boundary (Fig.2).

Fig 2. Coral reef zonation (Gulf of Kachchh, Western India) using IKONOS data (Nayak, 2004).

 

In a study by Warnasuriya et al. (2014) based on mapping of shallow coral reefs in south Sri Lanka Landsat 7 ETM+ images were found suitable to identify the reef areas with the reflectance characteristics of different bands. Coral reef areas can be identified due to high DN values obtained for shallow reefs for due to the bottom reflection. However reef patches could not be identified in the study owing to coarse resolution (30 m) of Landsat, thereby limiting the use of Landsat datasets for reef areas with large spatial extent. Bathymetry maps produced using ‘Depth of Penetration’ method for Landsat7 ETM+ satellite images gave more descriptive details on bottom nature of the reefs (Fig 3). Near infrared band was found to be most suitable band for image classification for identification and distribution of coral reefs (Fig 4).

 

Fig. 3 Bathymetry map of coral reefs in Dondra, Polhena and Madiha (Sri Lanka) (Warnasuriya et al., 2014)

 

Fig. 4 Classified map of coral reefs in Madiha, Polhena and Dondra (Sri Lanka) (Warnasuriya et al., 2014)

 

3.3. Suspended sediment dynamics– Non-point sources of pollution from watershed are often the cause of large proportion of pollutants in various water bodies (estuaries, bays, seas). Degradation in water quality can also be caused by anthropogenic causes like logging, agriculture, irrigation, development etc. Suspended sediments, which affect fisheries, aquatic life and navigation can be easily recognized on remote sensing images. Various satellites (Landsat, IRS, SPOT) allow for detection of any sediment present in shallow coastal waters.

 

3.4. Marine water quality– Various types of wastes generated as result of industrial processes, municipal treatment plants, off-shore exploration and dumping of oil, tourism activity, maritime transport are dumped directly to seas and degrade the marine environment. Suspended sediments which carry absorbed chemicals and affect navigation, fisheries, and aquatic life, are easily detected on the satellite imagery. Other indicators of water quality are turbidity, temperature and colour. Trophic status, nutrient load are indicated by chlorophyll values.

 

3.5. Marine fishery– Aquaculture as well as fishery is the major sources of livelihood especially for people inhabiting the areas surrounding coastal zones. Our country is one of the regions with high potential for marine fisheries development. The present fish production India is chiefly from the coastal waters (up to depth of 50 m). Thus, in order to harness full potential of marine living resources in these zones, an improved knowledge of identification of marine resources is necessary. Third level productivity can be estimated by phytoplanktons that give the idea about the standing stock of green biomass. These days, narrow spectral bands of various satellite sensors provide a better insight into our understanding of the ocean productivity. With the repetitive coverage of two days, IRS P4 Ocean Colour Monitor (OCM) has been instrumental in providing ocean colour data for Indian regions. On the basis of oceanographic features such as thermal boundaries, fronts, eddies, rings, gyres, meanders and up welling regions the Potential Fishing Zone (PFZ) maps are generated (Narain et al. 1992, Solanki et al. 2003). Also, we can gain knowledge about the availability of food in the column using ocean colour data. The sites where gradients of SST and chlorophyll coincide are ideal for fish aggregations.

 

3.6. Shoreline protection- The coastal regions are one of the favorable sites for the people to migrate. Coastal ecosystems have a vital role to play in stabilization of shorelines and buffering coastal environment from the impact of natural calamities like storm. The historical and practical ways to study changes in shoreline along with different landforms help in interpreting the coastal processes operating in the region. Changes in the shoreline have been studies for the entire Indian coast using Landsat (MSS and TM) and IRS (LISS II) data on different scales of 1:250K and 1: 50K. North Visakhapatnam, Paradip, and Ennore, north of Madras, near Nagapattiam and Kanyakumari ports on the East Coast of India showed considerable erosion whereas southern part of these ports witnessed deposition (Fig 5). Construction of artificial barriers like breakwater, jetties led to these changes.

 

Dam construction on rivers interferes with coastal environment as well. Acute erosion was observed in one of the thermal Power Station in the Gulf of Khambhat (located on the Mahi estuary) during 1979-1981. After analyzing the multi-temporal satellite data considerable shoreline changes were evidenced in the Mahi estuary between 1972 and 1988 (Nayak and Sahai, 1985) which were because of construction of dams during 1975 on the Mahi and Panam rivers in upstream regions. Movement of suspended sediment also assists in gaining idea about near shore water flow. Two separate water masses were observed when in Kochi a sediment plume coming out from harbor made a contact with sediments along the coast which led to depict that plume is behaving as a barrier to the sediment transport. The resultant erosion on the southern coast and deposition on the northern coast was observed due to this. Sediment transport and dispersal can be better studied using IRS P4 OCM because of its 2 day revisit time.

 

Fig 5. Changes in shoreline between 1929 and 2001 in the deltaic region of Maha Nadi, Eastern India (Nayak, 2004).

 

Summary

 

Remote sensing, in combination with GIS, is a powerful tool for management of coastal zone ecosystems sustainably which are of great importance and of immense value to mankind. The chapter discussed some highly productive ecosystems that represent coastal zones, the issues these transition zones are currently facing, and their management using geospatial technology. Anthropogenic stress caused as result of various man-linked activities like industrialization, aquaculture, population pressure and over exploitation of marine resources has caused degradation and depletion of coastal resources. Therefore, it becomes essential to protect these valuable ecosystems to ensure sustainable development for which geospatial technology has proven to be of great help. IRS, Landsat and SPOT data have been used to generate information on baseline inventory, change detection, eroded areas and sediment transport. PAN data combined with LISS provides detailed spatial information about any construction activity, reclamation, and ecologically sensitive areas. Wide field sensor (WiFS) provides high temporal resolution data which is very useful in studying suspended sediments in coastal waters and also helps in understanding dispersion and transport of pollutants. FCCs generated through LISS and Landsat assist in biodiversity studies as it helps in differentiating between shrubs and mangroves, hence marking the vital areas for protection under coastal zones. The state and central agencies/pollution boards and NGOs which are committed for the conservation of coastal ecosystems are now increasingly adopting geospatial data for their routine use after realizing the value of the remote-sensing derived information,.

 

Suggested Readings

  • Bryant, D., Burke, L., McManus, J., & Spalding, M. (1998). Reef at Risk: a map based indication of threat to the world’s coral reefs, 56pp. World Resources Institute, Washington.
  • Chandrasekar, N., Victor, A. C. C., Easterson, D. C. V., & Muthiah, P. (2002). Remote sensing and GIS in coral reef environment: An overview. In Proceedings of the National Seminar on Marine and Coastal Ecosystems: Coral and Mangrove: Problems and Management Strategies (Vol. 2, pp. 132-138).
  • Mesta, P. N., Setturu, B., Subash Chandran, M. D., Rajan, K. S., & Ramachandra, T. V. (2014). Inventorying, mapping and monitoring of mangroves towards sustainable management of West Coast, India. J Geophysics Remote Sensing, 3, 130-138.
  • Narain, A., Beenakumari, S. and Raman, M. 1992b. Observation of a persistent coastal upwelling off Gujarat by NOAA AVHRR and its implication on fisheries. Remote Sensing Applications and Geographic Information Systems: Recent Trends. Tata-McGraw Hill, New Delhi. pp. 337-341 Nayak, S. (1996). Monitoring the coastal environment of India using satellite data. SCIENCE TECHNOLOGY AND DEVELOPMENT-LONDON-, 14, 100-120.
  • Nayak, S. (2000). Critical issues in coastal zone management and role of remote sensing. Subtle issues in coastal management, 77-98.
  • Nayak, S. (2004). Role of remote sensing to integrated coastal zone management. In XXth Congress of the International Society for Photogrammetry and Remote Sensing (Istanbul, Turkey), Commission (Vol. 7, p. 18).
  • Norse, E. A. (1993). Global marine biological diversity: a strategy for building conservation into decision making. Island Press.
  • Solanki H. U. et al. 2003. Fishery forecast using OCM chlorophyll concentration and AVHRR SST:
  • AVHRR results off Gujarat coast, India. Int. J. Remote Sensing, 24(18): 3691-3699. Warnasuriya, T. W. S., Kumara, P. P., & Alahacoon, N. (2015). Mapping of selected coral reefs in Southern, Sri Lanka using remote sensing methods. Sri Lanka Journal of Aquatic Sciences, 19.