How we can better estimate environmental changes
Remote sensing is the quick technique of obtaining information about objects on the surface of the earth without physically coming into contact with them. This process involves making observations using sensors mounted on platforms (aircraft and satellites), which are at a considerable height from the earth surface and recording the observations on a suitable medium.
Remote sensing data has been used for a wide range of applications in Bangladesh, although in limited institutions, partly due to lack of expertise and financial support to obtain updated image and logistics.
Bangladesh Space Research and Remote Sensing Organization (SPARRSO) is responsible for research, development, and operational activities in space science and remote sensing technology in Bangladesh.
This multi-sectoral program involves several government departments and agencies. The National Space Research and Remote sensing committee decides the policy matter of the program and also do the inter-ministrial coordination.
One of the most popular applications of remote sensing data is the environmental sector in Bangladesh. Several government and non-government organizations such as LGED, SPARSO, WARPO, SRDI, Brac, SOB, GSB, and CEGIS are included in the study of the environment.
Flood monitoring: CEGIS has initiated using RADARSAT imagery for flood monitoring during wet seasons. Mapping flood and damage extent has also been done by SPARSO and others using NOAA-AVHHR.
River bank erosion: Riverbank line and bank erosion are relatively easier in detection, identification, and monitoring with remote sensing data and can easily be vectorized in GIS format.
Charland monitoring: Distribution of Jamuna charlands and Meghna estuary charland shifting tendency have been studied using remote sensed data.
River morphology: Satellite images like SPOT and Landsat TM are being used for identifying the bank line shifting tendency and erosion and siltation behaviour of rivers in Bangladesh.
Coastal zone monitoring: Estuarine bio-geomorphology, ecology, and land degradation due to shrimp farming, salt manufacturing, and water logging, and coastal change detection are some of the recent issues covered using high resolution remote sensing data in Bangladesh, particularly IRS-LISS, SPOT, Landsat TM, and IKONOS.
Drought stress: Thermal infrared data was applied in the barind tract in the north-western part of Bangladesh for mapping and monitoring drought-prone areas.
Wetland monitoring: Basin-wise wetland monitoring with remote sensing have been attempted in Bangladesh.
Salinity/Water logging: CEGIS (2002) has initiated a study called the Khulna-Jessore Drainage Rehabilitation Project wherein Landsat TM and IRS ID LISS images have been used for identifying changes in the land cover of the area.
Urban land use and land cover information on a regular basis is crucially important for map updating and planning for development initiatives. High resolution Landsat ETM, IRS, QUICK bird, IKONOS, SPOT is found to be extremely useful in urban land cover mapping. One of the limitations of these satellite images in Bangladesh is their prohibitive cost.
Agricultural application of remote sensing in Bangladesh mainly focused on mapping shrimp farm area and estimation of boro paddy area. Other crop inventorying through remote sensing has been attempted sporadically but has not progressed much.
Forestry applications include monitoring of forest area mapping, identifications of actual forest cover extent, preparation of forest working plan, identification of vulnerable sites of forest encroachment, mapping extent of jhum cultivation sites, state of coastal forest, identification of new plantation sites and monitoring forestation program.
Geological applications of remote sensing data are mainly limited to the identification of lineaments, fault line, and landforms. The geological survey of Bangladesh has been using remote sensing data on selected fields of research.
Coastal shrimp farming area management
The shrimp farming and mangrove forest areas are identified and located by remote sensing techniques. The Landsat (MSS & TM) data are used to delineate the surface feature of the coastal area.
Infrared colour (IRC) aerial photographs provided the most revealing information. Sequential aerial photographs provided information on change in time and places. This study reveals that the shrimp farming areas are expanding through destruction of the mangrove forest of Chokoria Sundarban and agricultural land of Rampai and Paikgachha area.
For scientific development of the coastal area, intensive shrimp culture methods are to be encouraged rather than horizontal expansion.
Estimation of surface water in Bangladesh
Remote sensing data is used to estimate the surface water in Bangladesh. Estimation of precipitation is very essential for its various important features such as flood and drought which are very common natural disasters in Bangladesh.
Precipitation is invaluable as a source of renewable fresh water and the importance is much more realistic in a region like Bangladesh which suffers from excessive rate of arsenic in its ground water.
At present, low-dense rain-gauge network over Bangladesh is the only tool to measure rainfall. The information from low-dense rain-gauge network sometimes is not sufficient for quantification of the exact amount of precipitation and for monitoring flood situations.
Shishir Reza is an Environmental Analyst and Associate Member, Bangladesh Economic Association.