Tidal wetland mapping using remotely sensed data
V. Shreedhara, A.N. Sherieff, M. Sabappa Reddy
Karnataka State Remote Sensing Technology Utilization Centre, Bangalore, India
C. R. Bannur
karnataka State Council for Science & Technology, Bangalore, India.
S. R. Nayak,Baldev Sahahi
Spalce Application Centre, Ahmedabad, India.
Source : http://www.gisdevelopment.net/
Information on the coastal zone is essential for the regional planning, decision and policy making for futuristic development and constructive management plans. Wetland, the prime component of the coastal zone is a dynamic ecosystem having complex inter-relationship of hydrology, soil and vegetation. They are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or land covered with shallow water. Tidal Wetlands have been recognized as a significant ecosystem which play an important role in Bio-geochemical cycle by trapping the silt and clay, recharging the groundwater and even cleansing certain toxic components from effluent water, to which they are aptly called as “Kidneys of landscape”. The tidal wetlands also provide a unique habitat for flora and fauna at different trophic level and are responsible for conserving reproductive fisheries not only by way of catch but as feeding, spawning and nursery grounds. Besides, mangroves and coral reefs are the economical and major ecosystem of the wetland. Conservation of these lands lies in their precise identification and periodically monitoring them over time and space.
Karnataka forms a part of the Malabar Coast in the West with extensive coastline running 320 kms, placed 12 30-150 00 N and 740 00 750 00 E. indented with promontories, headlands, picturesque estuaries, encompassing tidal wetlands essaying complex “Mangroves” and lengthy linear beaches. The coastal berm is narrow due to the descending western ghats, which are aboutted by the sea particularly in Uttara Kannada part of the coast. The region comes under the direct influence of the Southeswest monsoon, receiving very heavy rainfall during June to August. The climate is humid. Soil is alluvial in the plain region and Lateritic down the hilly slopes.
Nevertheless, the coast has foreseen over the period of time, the growth of undustry and urbanisation due to its natural harbors and ports in particular New Mangalore Port, which has opened new vistas in trade ad commerce, which along with the commissioning of the sea Bird has gone to deplete and destruct the virgin environment, in particular, the wetland ecosystems by way of discharging the industrial effluent into the sea, which needs a constant monitoring, to which remote sensing is an ideal tool.
The main objectives of the present study is :
All along the beaches rectangular shaped, characterized with cherry red tone features were identified as beach plantations, comprising of Casuarina, grown under afforestation programme to protect the coast. They were predominantly seen along the Mangalore Udupi, Honnavar & Karwar area.
It comprises of swamp/marsh / coconut plantation. scrub vegetation, within the confluence of the wetland, related to the phenomenon of regression of the sea. They may be sites of older mudflats which are under the sea in the age past.
Estuaries, logoons, creeks and bays which form the major water bodies are easily identified by their characteristic blue tone. Estuaries usually defined as that part of the lower river course that is affected by the maxing of salt water with the fresh water. about 9 major estuarine complex were identified along the Karnataka coast, most of them draining parallel to the coast. lagoon is an elongated body of water lying parallel to the coast. Lagoon is an elongated body of water lying parallel to the coastling and separate from the open sea by barren islands. They are predominantly seen in the Kundapur, Mangalore and Karwar regions. Creeks are a low land water course of medium size, originating from any natural streams or Bay or a narrow inlet of sea that extends inland and are commonly seen along the coast.
Features like paleomudflat, coastal dunes, coastal dune with vegetation and strandlines are classified under this category.
They are defined as mudflats lying above high tide flats and are formed by marine deposition of the past sea level (Nayak & Sahai, 1984-85).
Coastal dunes are defined as topographical feature of eolian origin composed of sand grains deposited down by wind from a natural sources of sad. The mode of transportation of these sand particle could not be identified but the dunes are identified based on photo characters and are extensively seen in the Kumta, Honnavar, Kundapur and Udupi regions. Denuded dunes, a small distance away in the coast which are cultivable, are classified as dunes with agriculture which are frequently seen.
It is an ancient shorelines, refers collectively to the assemblage of various features characteristics of former coastal areas. It is observed all around karwar and Honnavar coast, featuring like a lineament in the image.
They include saltpans, Aquaculture ponds, Islands, high water and low water line.
An undrained usually small & shallow, rectangular, man-made depression or hollow in which saline water accumulates & evaporate leaving salt deposits. These features are very well delineated in the image based on their characteristic features & vast stretches of them are identified along the Tedri and Kali estuaries.
Many tiny offshore Islands are clearly visible near Maple, Kundapur, Bhatkal, Honnavar & Karwar regions. Estuarine islands locally called as “kudrus” which are generally muddy, low and flat often support good growth of mangroves, coconut plantation and agriculture were also identified in this category.
High water & Low water line:
Water at the maximum & minimum level reached during the tidal cycle is coined as high and low water line, which can be demarked by the analysis of satellite data.
It is evident from the present study, the usefulness of 1:50,000 scale, albeit with certain limitations. the information culminated is very informative & resourceful for the planners & decision makers, in taking constructive measures to conserve and apt management of the coastal environment. As been said earlier, tidal wetlands are very unique ecosystems by itself, interfacing land & water, none others to it can speak about the their resources potentiality, need continues monitoring & inventory for maintaining the eco-balance. The studies were useful in identifying vulnerable points along estuaries where afforestation of mangroves are being presently carried out by the Udupi regions of the coast Along with brackish water aquaculture sites were too demarcated to carry out pisciculture activities as a socioeconomic measure near the Kumta & Ankola regions of Uttara Kanada coast. Marine regressions over the period of time is indicated by the presence of place-mud flats, strandlines & lagoons identified by the studies.
Davies J.L., 1972: Geographical variation in coastal Development, Oliver & Boyd, Edinburgh.
King C.A.M. 1972: Beaches & Coasts. 2nd Edition. University of Nottingham Edward Arnold, London.
Nayak. S.R. & Sahahi, B., 1985: Coastal Morphology: A case study of the gulf of Kambhat (Cambay). Int. Jurn. Remote Sensing, 6 (3 & 4), 559-567.
SAC, 1991: Manual for mapping of Coastal Wetlands/land forms & shore line changes using satellite date.
Sheikh M.G., Nayak S.R, Shah, P.M. & Jambusarai B.B. 1985: Coastal land form mapping around the Gulf of Khambhat using landsat TM data. Jurn, Ind. Society of Remote sensing, Vol. 17. No. 1.