Approaches and methods of the study: The study was designed to assess the impact of agricultural encroachment on the livelihoods of fishermen based around the three beels in Naogaon Sadar upazila of Naogaon district, Bangladesh. The major task was to analyze the trends of agricultural encroachment over the years, changes in water areas for 30 to 35 years to the present time in the beels, changes in livelihoods of the fishermen, adoption of alternate livelihoods and institutional context in relation to the sustainable livelihoods.
The study conducted on two different methods such as Remote Sensing (RS) image interpretation and Participatory Rural Appraisal (PRA). Remote Sensing (RS) image interpretation carried out following Salam (2007) method which is supported by the secondary data collected from a range of sources like field visits, literature review, internet search and consultation with the relevant reports. Primary data collected by livelihood analysis through PRA and FGD method and interviews with the individual stakeholders. Information collected using FGD at the household level through a structural questionnaire interview. The complete method for the study presented and the details are as follows: Multi-temporal Thematic Mapper image data obtained from Landsat-5 and Landsat-7 launched by NASA, USA was used. Landsat TM/ETM image has 7 bands with 3 visible and 4 infrared channels including one thermal band. The spatial resolution of one pixel of TM image is 30m by 30m except for thermal band with 120m by 120m.
Study area:
The three existing beels of Sadar Upazila of Naogaon district selected for the assessment, located at the 24°42′ to 24°56′ north latitudes and 88°48′ to 89°00′ east longitudes. The main rivers in this Upazila are Little Jamuna and Tulsi Ganga. Land uses are single crop 41%, double-crop 47% and triple crop rest 12%. The main crops in area are paddy, wheat, potato, brinjal, patal, onions, garlic, and pulses. The Digholi Beel located on the southwest corner of Naogaon district town, which was a large wetland having more than 200 hectares of water area about 100 years ago.
GIS based image processing: The image-processing carried out in the Geographical Information System (GIS) laboratory, Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University (BAU), Mymensingh, Bangladesh. The Remote Sensing (RS) satellite images integrated into the GIS database. The satellite images collected from the Global Land Cover facilities of Maryland University, USA. The Landsat TM/ETM images used in this study are from the Path of 138, and Row of 43 which obtained on 09 February 1977, 11 November 1989, and 17 November 2000.
Data processing and software used in the study: IDRISI KILIMANJARO, the GIS and image processing software used for Landsat satellite image processing in this study which developed by the Graduate School of Geography at Clark University, Worcester, MA, USA. Moreover, the vector-based ArcGIS Desktop 10 GIS software used to edit and digitize the map boundary to separate the area of interest from the RS image. Paint Shop Pro 10, a raster-format image editing software also used for image processing and editing purposes. The manipulated and edited images imported in to IDRISI KILIMANJARO GIS software and resampling of the images done in the IDRISI environment to bring all the images in a single reference system.
Data analysis: All the collected data compiled, transferred into the computer in MS Excel Programme, cross-checked for any mistake and analyzed in MS Excel 2016 version. The indicators in data analysis were area of beels in different years, water holding capacity in different seasons and years, amount of fish and fish species harvested in different periods, assets, income and expenditure, the social and financial status of fishermen and crop farmers in the beel areas.