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Application of GIS technology for Coastal Zone Management: a hydrographer perspective
Lt. Commander R. K. Bhardwaj
NAtional Hydrographic Office, Dehradun
nho@sancharnet.in
Lt. Commander R. K. Bhardwaj
NAtional Hydrographic Office, Dehradun
nho@sancharnet.in
Abstract
The objective of this paper is to outline the importance of GIS technology for coastal zone management. Following a definition of the coastal zone, and , short description of its peculiarities and the urgency of its management, the paper describes the use of GIS technology in coastal zone management, its advantages and the consideration for accuracy. This followed by information and data required for coastal zone management and the application area in coastal management. The conclusion emphases the importance of geographical information system in coastal zone management for efficient data handling and analysis of geographically related data.
Introduction
Coastal zone for the purpose of this paper, shall mean the area, on both side of the actual land water interface, where both territorial as well as Marine environmental influences each other. In addition, interaction between various natural processes and human activity are important factor in the coastal area. The coastal zone shows high population density with large number of urban conglomeration and in consequence, a fast population growth. Again as a consequence, coastal zone are characterised by a high concentration of economic and, in particular, industrial activities with all the resulting problems of resource consumption, waste management and technological risk. On coastal water side, fisheries and aquaculture exploits a generally highly productive system. Very specific, and valuable as well as vulnerable, typical coastal ecosystems include estuaries, salt marshes, mangroves, coral reefs etc. Offshore activities such as oil and gas, as well as mining, are additional forms of exploitation of the coastal zone. In addition, the coastal zone is also the recipient of all water borne waste streams, primarily attributable to agriculture, its fertilizers and agrochemical, and all treated and untreated waste water the hinter land produce in their respective catchment. They all drained in to the coastal waters. Therefore, there is an urgent need for intelligent management of coastal zone.
GIS Technology and Coastal Management
Determining the accurate length of the coastline is important for such coastal zone management application as shoreline classification, monitoring erosion, mapping biological resources, habitat assessment and for the planing and response to nature (e.g. storm surges) and man made disasters (e.g. oil spills). Coastal zone management, by definition, is spatial management. Geo referenced spatial data is map data in a digital form which mean that each of the earth’s features that are stored as spatial data has a unique geographic reference such as latitude and longitude. The increasing use of spatial data and GIS (Geographic Information System) by organizations and researchers is a valuable tool to help solve the planning and management issues in the coastal zone. There are many different Geographic Information Systems in use today and they tend to differ in certain aspects such as “how they link geographic location with information about those locations, the accuracy with which they specify Geographic location, the level of analysis they perform and the way they present information as graphic drawing”.
What is GIS?
At this point it is useful to consider exactly what Geographical Information System is (and what it is not). The definition of GIS are numerous but a useful one is that it is a data base system in which most of the data are spatially indexed and upon which a set of procedures operates in order to answer queries about the spatial entities in the data base. Thus it is an information system whose relation basis is co-ordinate data of the form X, Y, Z, a concept familiar to the surveyor. The function of an information system is to improve a user’s ability to make decision in research, planning and management; a GIS is therefore essentially a management tool.
Why GIS for CZM?
Since the coast all around the world are fast developing and firm management policies have to be established. However, for any management of the shore to be effective, it is necessary for the policies to be based on informed decision-making. This in turn requires ready access to appropriate, reliable and timely data and information, in suitable form for the task at hand. Since much of this information and data is likely to have spatial component, one branch of information technology with apparent potential for contributing significantly to coastal management in a number of ways. These include:
- The ability to handle much larger databases and to integrate and synthesise data from a much wider range of relevant criteria than might be achieved by manual methods. This in turn means that more balanced and coordinated management strategies may be developed for considerably longer lengths of coast.
- GIS encourages the development and use of standards for coastal data definition, collection and storage, which promotes compatibility of data and processing techniques between projects and departments, as well as ensuring consistency of approach at any one site over time.
- The use of a shared database(especially if the access is provided via a data network) also facilitates the updating of records, and the provision of a common set of data to the many different departments or offices that might typically be involved in management of a single stretch of coast. A shared database implies reduction or elimination of duplicated records, and thus the potential for significant economic savings as well as improved operational efficiency.
- Provides efficient data storage and retrieval facilities.
- GIS also offers the ability to model, test and compare alternate management scenarios, before a proposed strategy is imposed on the real-world system. Computer technology allows the consideration of much more complex simulations; their application to very much larger data bases: and also enables compression of temporal and spatial scales to more manageable dimensions.
Map accuracy is relatively a minor issue in cartography, and the map user are rarely aware of the problem. But when the same map is digitised and input to GIS, the mode of use changes. The new uses extend well beyond the domain for which the original map was intended and designed. Therefore, accuracy problem in GIS requires consideration of both object oriented and field oriented views of geographic variations. Moreover, the machine used to make measurement in GIS (Digital computers) are inherently more precise than the machine of conventional map analysis. Error analysis in spatial data base is very important with a direct bearing on the accuracy on GIS and hence require due consideration. One of major requirements in the Digital Topographic DataBases (DTDB) of a large country is consideration of a variety of features. Digital Stereo photogrammetry may be useful in extraction of cartographic features with a greater accuracy. The Digital Elevation data in the form of contours, thus digital monoplotting can be considered as a quicker method of plotting the data for maintenance of DTDB. Some of the other factors that also must be considered are:
- The type of spatial data
- The scale and resolution of the spatial data
- The type of map projection
- The measuring unit
- Horizontal and vertical datum for Geographic co-ordinates
- Metadata
Scale
A map scale is a representation of the ratio between a measurement of distance on a map to the same distance in the real world. For example, a map feature that is 2 centimeters long on a 1:50,000 scale map represent an object that is 100,000 centimeters or 1000 meters in the real world. The larger the scale factor becomes, the smaller the map scale becomes, and the opposite is true as well. As a general rule, as the scale of the map increases, there will also be an increase in the accuracy of the map, and there will also be an increase of the amount of geographic features that can be displayed on the map. When using spatial data for mapping and measuring purposes, the largest scale map and spatial data that cover a selected study area should be obtained for use in a geographic information system.
Spatial Resolution of Data
The degree of resolution of spatial data in important for the user of geographic information system. The spatial resolution of GIS data is also a function of generalisation since small scale map do not usually contain as much geographic details as larger scale map and as a result, the data is most often recorded and stored with less spatial precision. For vector data, spatial accuracy is a function of how many nodes and versions are used to record geographic feature at a particular map scale. The closer the vertices to each other, then the degree of resolution of the spatial data also increases. The farther apart the vertices are from each other, then the reliability of the spatial data to represent the geographical features in their true shape and size will diminish accordingly. This is especially true for rivers and coastlines when their shapes and orientation can constantly change across the earth’s surface.
Projection
The earth is a sphere that is slightly flattened in the Polar Regions, and to draw a large portion of the earth’s surface onto a flat piece of paper has always been a problem. There are over 250 different map projections and each one has its own particular strength and specific uses. Some projections are better for the accurate representation of certain regions of the world, which other projections are designed for specific purpose such as showing true direction for Navigation (but not true distance) such as with the famous Mercator Projection. All map projection will distort the earth’s sphere to a certain degree especially regarding the representation of angles, area, distances and directions.
The Measuring Unit
Different maps can be based on different types of map measuring units. Spatial data can be stored in various types of units such as decimal degrees, metres or feet. It is important to know what unit the spatial data uses so that the correct scale can be applied to the map. If incorrect measuring unit is applied to spatial data that is loaded into a GIS, then a false map scale will be the result. If the map scale is incorrect, then all the measurements using a GIS will be wrong.
Horizontal and Vertical Datum
Map datums refer to the various locations from where geographic measurements are referenced and this is one of the parameters in which individual maps are identified. Many navigational maps/charts will soon be converted to new horizontal datum known as WGS 84. The use of new horizontal datum has meant that maps/charts that are based on Everest datum can be shifted as much as 150 metres in the horizontal direction as compared with WGS 84 based maps that cover the same area. Conversion programmes are available that can update the horizontal position of present maps to match the horizontal position of WGS 84 maps.
Along with horizontal datum, maps are also referenced to vertical datum, which is the level surface to which elevations are referred. In hydrography the vertical datum is known as chart datum. Another type of datum generally used is the MSL(Mean Sea Level), which is based on the average height of the sea’s surface for the complete tidal ranges over a 19 year period.
Metadata
GIS data normally comes with a file of information that describe the contents of the data sets. This particular GIS information file is commonly known as Metadata and it describe the basic features of the GIS data. For the metadata to be useful, it should list the map title, spatial area covered, the map projection, the horizontal and vertical datum, the map unit, the date of map, mapping specification and accuracy limits.
Information requirements for coastal management
In order to be of any value, it is necessary that the information products output from a CZMs should correspond with the actual requirements of the various user communities. But what are these information requirements? Given a number of potential users of coastal zone data and information, what are the main areas of common interest – or significant diversity – regarding both information desired, and the data needed to be processed in order to obtain that information? The various informations required for achieving the goal of an effective management of the coastal zone could be categorised broadly under following headings.
Data Required for Coastal Zone Information
Geographical data: an organised, planned and coherent coastal database should therefore a basic requirement of a good and constant management. Many of the data to be found within a coastal management database will be geographic in nature and can be called a Geographical data. It is a “data, which refers specially to features that describe the earth’s surface”. Geographical data has both location and attributes. This is the Where something is and the What it is. We can define the where something is as the Spatial component of data, and what something is as the Aspatial or Attribute component of data.
| HABITATS | COAST | TRANSPORT |
|
Estuaries Sea grass Macro algae Inter-tidal Salt-marsh Mangroves Waders Rookeries Shellfish All |
Sandy Beach Rocky beach Rocky cliff Inter-tidal Mangroves Salt marsh Others All |
Roads(major) Roads (minor) Major Ports Harbours Marinas Boat ramps Airports Nav channel Nav Markers Ferry routes All |
- Spatial data: It is an explicit spatial/locational reference and can involve absolute or relative locations. These are often referred to as point, lines, areas, or surfaces or can refer to some attribute that is continuous (e.g. elevation), or discrete (e.g. Male/Female or soil categories).
- Attribute Data: Attribute data describes what is a some location and has some link between it and the spatial data.
Example: A map with country boundaries v/s the same map with country names have a spatial dimension to them, and in many cases this spatial component can be harnessed as the common factor, which unites the disparate data elements into a coherent and integrated structure.
| SEABED | INFRASTRUCTURE | RESTRICTED ZONES |
|
Bathymetry < 2 m < 5 m < 10 m Inter tidal Spoil dump Others All Bottom Type Sand Hard clay Rock, mud shell Coral reefs Others All Benthic Flora Sea grass Seaweed Coral All |
Residential Industrial Commercial Recreational Ports Harbours Marinas Mooring Boat ramps Intakes Outfalls Fresh water Power generation Hinterland Education Medical facilities All |
National Parks Terrestrial Marine Cultural features Sacred sites Risk to personnel Navigation Military Zoning Ecologically sensitive area Breeding & spawning ground Historical areas Heritage area All |
| RECREATION | FISHERIES | POLLUTION |
|
Beaches Tourist facility Harbours Marinas Fishing Diving Moorings Boat ramps All |
Commercial Recreational Aquaculture Leases Fishing Ports Spawning ground All |
Oil spills Typical oil characteristics Oil treatment Dispersant use Disposal sites Domestic sewage Industrial waste Eutrophication All |
Classification of Coastal Information Data: Thus, many coastal databases will, in potential or in reality, display many classic characteristics of databases found in GIS. As with any other GIS application, the data involved in creating a coastal GIS database fall into a number of distinct categories. Depending on the method of classification used, these include:
- Basic Geodetic or Planimetric Data: It establishes the geographic referencing system against which coastal entities or processes of interest may be placed.
- Topographic Data: It records the location and distribution of natural and cultural features(beaches, cliffs, dunes, roads, settlements, harbours, etc)within the landscape;
- Qualitative and Quantitative Attribute Data: It provides further information about the properties(size of sediments on a each, morphodynamic indices, tidal range, value of coastal properties, amount of shipping visiting selected ports, etc) of coastal entities and phenomena.
- Time series data: It allows temporal databases to be compiled(Langran,1990), and information to be gleaned about the variability of coastal entities , attributes and relationships in both space and time; and
- Metadata: It allows estimations to be made of currency, completeness, history, ownership, and reliability of information, derived from the system.
Sources of Coastal Information Data: As identified above , two types of data are input into a GIS, spatial and attribute. A wide variety of data sources exist for both spatial and attribute data.
The most common general sources for spatial data are:
- Hard copy maps
- Aerial photographs
- Remotely-sensed imagery
- Point data samples from surveys
- Existing digital data files
- Existing hard copy maps. Sometimes referred to as analogue maps, provide the most popular source for any GIS project. Potential users should be aware that while there are many private sector firms specialising in providing digital data, central and state government agencies are an excellent source of data. Because of the large costs associated with data capture and input, government departments are often the only agencies with financial resources and manpower funding to invest in data compilation. State agencies are also often a good source for base map information.
- An inherent advantage of digital data from government agencies is its cost. It is typically inexpensive. However, this is often offset by the data’s accuracy and quality. Thematic coverage’s are often not up to date.
- Indian Air Force, The Air Survey Company, DumDum, Kolkata, and the National Remote Sensing Agency(NRSA) Hyderabad carryout the flying operations for aerial photography
- Point data samples are collected by actually carrying out survey in the area of interest. This is generally done not only to collect the missing information in the available data but also to validate and authenticate the same.
- Existing digital files with various government and non-government organizations are an important source of information for creating any GIS database. These include central and state ministries, organisations like National Institute of Oceanography ,Survey of India.
- National Hydrographic Office, National Remote Sensing Agency and various private firms like Roalta, Elcome Surveys, Decca Surveys etc.
Attribute data has an even wider variety of data sources. Any textual or tabular data than can be referenced to geographic features, e.g. a point, line, or area, can be input into a GIS. Attribute data is usually input by manual keying or via a bulk loading utility of the Data Base Management System (DBMS) software. ASCII format is a de facto standard for the transfer and conversion of attribute information.
Application areas for coastal zone management systems
Given the diversity of tasks facing the coastal manager and also the range of data processing functions that may exist in a typical GIS, there is a multiplicity of potential application areas for coastal GIS technology. However, from this plethora of applications, a few generic areas are as follows:
Coastal resource survey and management: Continuing expansion of human population increases pressure on the shore for living space, leisure and recreation, and a host of the purposes. At the same time, the oceans and coastal waters of the world are also important hunting grounds for a wide range of economic resources, of value to society. As these resources gradually depleted, there is a corresponding increase in the need to explore conservation measures on remaining sticks. GIS has considerable potential to assist in these tasks. Few examples are as follows:
- Within the leisure and recreation sectors, GIS has been used to assist in the development of new or improved infrastructure including development of new shore-based facilities such as marinas, and the management of recreation activities in the areas of fragile coastal dune systems.
- In the fishing and aquaculture industries, GIS may be used to find optimal locations for fish-farms, through the analysis of salinity, bathymetry, shelter, land uses, proximity to other facilities, etc.
- GIS is also a major technology within the mining and oil exploration industries, where it is harnessed to assist in the discovery, assessment and exploration of new mineral wealth.
In monitoring studies, the primary objective is to record what aspects of the coast are changing, and where and why these changes are taking place. Monitoring at its simplest involves recording what is present at one baseline instance in time, and then comparing this pattern with that of subsequent stages.
GIS has been applied at the coast in order to keep track of a wide range of natural and human-induced changes, including:
- Changes in the extent and ecology of wetlands
- Analysis of erosion and shoreline changes
- Assessment of potential and actual flood hazard and damage.
- The silting up of harbours and the effectiveness and impacts of mitigation efforts such as dredging.
- Monitoring the changes of land use in the coastal hinterlands, in particular the growing urbanisation of the coastal fringe; and
- Monitoring the behaviour of oil spillages in coastal environments.
Traditional modeling of coastal phenomena has mostly relied on experiments with wave tanks and other large physical models. However, it is becoming increasingly common to us computer-based simulation modeling techniques wherever appropriate. Amongst other benefits, computerised simulation has the potential to overcome scale limitations that may be present in a physical model; may avoid the need for physical destruction or alteration of materials under study; can provide greater degree of control over the temporal aspects of the simulation (including compression of long time periods into more manageable extent, temporary halting or even reversal of the model to examine specific aspects in greater detail; etc.); and may be much cheaper and more manageable than construction of a physical model. Furthermore, development of a successful computer simulation depends on the creation of a robust data model for representing the system variables within the GIS, and this in turn requires a meaningful conceptualisation of the phenomena under study. Thus, the process of setting up the simulation can, itself, promote greater awareness of the constituent and relationships at work within the coastal system.
A number of examples are documented in the literature, describing the use of GIS technology for modeling processes and events within the coastal zone. Typical applications include the use of GIS for assessing the threat of sea level rise on the coast of Maine, and the likely responses of coastal sand dunes to such rise. Modeling of oil spills with a view to minimising their environmental impacts, modelling possible impacts of dredge spoil dumping, modeling for multiple use of estuarine waters, and assessment of possible sites for aquaculture development.
GIS for coastal decision-making and policy formulation: By combining rapid data retrieval with analytical and modeling functions, GIS has the ability to respond rapidly and flexibly to ad hoc ‘what if type questions’. Thus, a well-designed coastal zone information system could be significant as a decision-support tool, to aid development of integrated and sustainable coastal management strategies.
Conclusion
GIS should be viewed as an opportunity for the marine community to advance in the field of coastal zone management. GIS represents the latest weapon in the arsenal of tools to solve the spatial data-handling problem. Proper use of GIS required the data knowledge of the salt grimed hydrographic surveyor, the map composition skills of the experienced cartographer, the data base management skill of the data processing person, the scientific insight of geographer, the computer knowledge of a system analyst, and the personnel and organisation skill of the manager. The coastal zone GIS are currently enjoying a major upsurge in the level of interest and there are grounds for optimism in believing that the significant advances in this direction is not too far away. At the end, it is concluded that the use of GIS in coastal zone management in interesting and stimulating. Get in to it, (but with your eyes open).
References
- Dr. Robin K H Falconer “ Experience with Geographic Information System (GIS) in the marine world”. Hydrographic Journal No. 58 Oct 1990.
- R G Humphreys A. R. I. C. S., Dip. H. S. “Marine Information System” the Hydrographic Journal No.54 Oct 1989.
- “ GIS technology and special analysis in Coastal Zone Management” by Kurt Fedra & Endrico Fedli. EEZ Technology Edition 3.
- GIS@Development Feb 2000 Vol. 2 Issue 2 “ Some aspects of Accuracy in GIS” by MD Joshi and R Shivakumar
- “The use of GIS for CZM” by Michael Kostiuk