Management of Wetlands – A Remote Sensing Approach
S. Sudhakar, V. Jayasree, M. Prithviraj
Regional Remote Sensing Service Centre, IIT Campus Kharagpur
A. K. Raha
State forest department, Calcutta
Abstract
Sunderbans, one of the world’s major mangrove ecosystem needs proper planning and timely execution of conservational measures to control further degradation. Satellite Remote Sensing, with its repeatability and synoptic coverage in separate spectral bands, has opened new vistas in the survey and monitoring of the inaccessible areas. Realizing the importance of data base on the condition and areal extent of mangroves for a scientific forest management strategy, an attempt has been made in this work, to segregate three density classes within complex mangrove ecosystem in the district 24 Paraganas (South), West Bengal using IRS-1A, LISS-II data pertaining to November 1988. The overall classification accuracy was more than 85 percent.
Introduction
The terms “Wetland” is quite often used to cover wide range of aquatic habitats like marshes, swamps and bogs. It is defined as “the lands transitional between terrestrial and aquatic systems where the water table is usually at or nears the surface or the land is covered by shallow water” (Cowardian et. al. 1979).
The mangrove, a distinct type of vegetation dispersed on relief lying under constant influence of tidal and fresh water, constitute a part of wetland ecosystem. The mangroves comprises of physiologically specialized and ecologically adapted plants to survive in salt / blackish water conditions. Most of the species are characterized by high osmotic and suction pressure in the leaves, vivipary and presence of specialized roots of stilt/pneumatophers with buttress nature of stem to withstand the adverse conditions of the costal wetland environment.
The general distribution of mangroves is restricted to the tropical and temperature zones of the world and their exuberant growth and development requires primarily the following conditions:
- Air temperature near about 200C during coldest months with the seasonal temperature range not exceeding 4°C;
- Shallow shores free form strong wage and tidal action;
- A wide horizontal tidal range with substratum containing fine grained alluvium.
India has got an extensive coverage of total wetlands where characteristic vegetation – the mangroves, grow. They cover an area of 6740 sq. kms, which is about 7 percent of the world’s mangrove population. About three mangrove population. About three fourth occur in Sundarbans, in the 24 Paraganas (south) district of West Bengal and the remaining major patch is found in the Andaman and Nicobar group of islands (Mang Sanjoy, 1991; Thothathri, 1981).
Mangrove being an important component of the complex wetland ecosystem needs to be protected and conserved. Therefore. Periodic monitoring of this coastal environment is of paramount importance to obtain the knowledge about their areal extent and condition. The acquisition of data pertaining to these changes in the wetland condition through conventional means is costly, time consuming and difficult due to inaccessibility. But with aid of satellite Remote Sensing methods, having the advantages like synoptic view and repetitive coverage, the task of regular monitoring of this coastal environment has become simpler.
In this paper the successful accomplishment of segregation of the different density classes of the canopy cover of the Sunderbans by following the digital classification scheme (maximum likelihood algorithm) in VAX-11/780 computer with VIPS – 32 Software on the IRS- 1A LISS-II data ahs been highlighted.
