Lateral migration of the Bhagirathi River temporally creates unavoidable geomorphic hazards in West Bengal, India. The Bhagirathi River flows SW for ～67.30 km between the confluence point of Ajay and Jalangi rivers i...Lateral migration of the Bhagirathi River temporally creates unavoidable geomorphic hazards in West Bengal, India. The Bhagirathi River flows SW for ～67.30 km between the confluence point of Ajay and Jalangi rivers in East Burdwan and Nadia districts of West Bengal. The course of Bhagirathi is notably migration prone and cultivates problematic changes along its course over time. In the study, we have looked into its migration tendency and unpredictability for past 238 years and then predicted the lateral shifting of river centerline using temporal satellite imageries – Landsat-5(TM) of 1987(8, December), 1995(28, January), 2005(7, January) and LISS-IV satellite imagery(2017, 5 January);SOI Toposheet – 1968–1969(79 A/2, 79 A/3, 79 A/6 and 79 A/7) and Rennell's map of 1779. Other highlights are the quest of fluvial features, oxbow lakes, mid-channel bars, channel migration rate, meander geometry, channel sinuosity in different parts of river course and the parts that experience intensive bank erosion. The entire river course has been subdivided into three segments; viz. reaches A, B and C. Investigation displays that degree of sinuosity decreases from its anterior course(1968) to the existing course(2017). Reach-specific outputs display that reach B is highly sinuous(SI value 1.94 in 2017) and SI increases temporarily, whereas for reaches A and C it decreases with time. The rate of migration is higher in reach B than that in reaches C and A. The study displays a notably decreasing trend of migration in comparison with its previous lateral migration and shows that the migration nature over time is intensively inconsistent and unpredictable except very few portions of the river course. The nature of deposition within the river channel shows an unstable behavior during the entire period of the study. Meander geometry depicts a rapid change of river course innate to meander bends and shows a higher rate of migration by meander loop cut-off rather than lateral migration that reflects the inconsistency, erosion vulnerability and unpredictable nature of migration. The present work offers a valuable source to comprehend channel changes in Bhagirathi River and serve as an efficacious base for river-bank migration and erosion hazard planning and management.展开更多
This case study evaluates the seasonal variability of the Pearson's linear correlation coefficient of land surface temperature(LST)with some spectral indices like NDVI,NDWI,NDBI,and NDBaI by using a series of Land...This case study evaluates the seasonal variability of the Pearson's linear correlation coefficient of land surface temperature(LST)with some spectral indices like NDVI,NDWI,NDBI,and NDBaI by using a series of Landsat images for 1991-92,1995-96,1999-00,2004-05,2009-10,2014-15,and 2018-19.The results from the average correlation of the entire period of all-season show that the LST builds a positive correlation with NDBI(0.71)and NDBaI(0.52)while it builds a negative correlation with NDVI(-0.44).The LST-NDWI correlation is insignificant.The best correlation is noticed in the post-monsoon period,while the least correlation is observed in the winter season.This study can support the environmental planning to build a sustainable city under a similar environment.展开更多
Mining operations result in the generation of barren land and spoil heaps which are subject to high erosion rate during the rainy season. The present study uses the Revised Universal Soil Loss Equation (RUSLE) and SCS...Mining operations result in the generation of barren land and spoil heaps which are subject to high erosion rate during the rainy season. The present study uses the Revised Universal Soil Loss Equation (RUSLE) and SCS-CN (Soil Conservation Service - Curve Number) process to estimate in Kiruburu and Meghahatuburu mining sites areas. The geospatial model of annual average soil loss rate was determined by integrating environmental variables parameters in a raster pixels-based GIS framework. GIS layers with, rainfall passivity and runoff erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management(C) and conservation practice (P) factors were calculated to determine their effects on annual soil erosion in the study area. The coefficient of determination (r2) was 0.834, which indicates a strong correlation of soil loss with runoff and rainfall. Sub -watersheds 5,9,10 and 2 experienced high level of highly runoff. Average annual soil loss was calculated (30*30 m raster grid cell) to determine the critical soil loss areas (Sub-watershed 9 and 5). Total soil erosion area was classified into five class, slight (10,025 ha), moderate (3125 ha), high (973 ha), very high (260 ha) and severe (53 ha). The resulting map shows greatest soil erosion of >40 t h-1 y-1 (severe) through connection to grassland, degraded and open forestry on the erect mining side-escutcheon. The Landsat pan sharpening image and DGPS survey field data were used in the verification of soil erosion results.展开更多
文摘Lateral migration of the Bhagirathi River temporally creates unavoidable geomorphic hazards in West Bengal, India. The Bhagirathi River flows SW for ～67.30 km between the confluence point of Ajay and Jalangi rivers in East Burdwan and Nadia districts of West Bengal. The course of Bhagirathi is notably migration prone and cultivates problematic changes along its course over time. In the study, we have looked into its migration tendency and unpredictability for past 238 years and then predicted the lateral shifting of river centerline using temporal satellite imageries – Landsat-5(TM) of 1987(8, December), 1995(28, January), 2005(7, January) and LISS-IV satellite imagery(2017, 5 January);SOI Toposheet – 1968–1969(79 A/2, 79 A/3, 79 A/6 and 79 A/7) and Rennell's map of 1779. Other highlights are the quest of fluvial features, oxbow lakes, mid-channel bars, channel migration rate, meander geometry, channel sinuosity in different parts of river course and the parts that experience intensive bank erosion. The entire river course has been subdivided into three segments; viz. reaches A, B and C. Investigation displays that degree of sinuosity decreases from its anterior course(1968) to the existing course(2017). Reach-specific outputs display that reach B is highly sinuous(SI value 1.94 in 2017) and SI increases temporarily, whereas for reaches A and C it decreases with time. The rate of migration is higher in reach B than that in reaches C and A. The study displays a notably decreasing trend of migration in comparison with its previous lateral migration and shows that the migration nature over time is intensively inconsistent and unpredictable except very few portions of the river course. The nature of deposition within the river channel shows an unstable behavior during the entire period of the study. Meander geometry depicts a rapid change of river course innate to meander bends and shows a higher rate of migration by meander loop cut-off rather than lateral migration that reflects the inconsistency, erosion vulnerability and unpredictable nature of migration. The present work offers a valuable source to comprehend channel changes in Bhagirathi River and serve as an efficacious base for river-bank migration and erosion hazard planning and management.
文摘This case study evaluates the seasonal variability of the Pearson's linear correlation coefficient of land surface temperature(LST)with some spectral indices like NDVI,NDWI,NDBI,and NDBaI by using a series of Landsat images for 1991-92,1995-96,1999-00,2004-05,2009-10,2014-15,and 2018-19.The results from the average correlation of the entire period of all-season show that the LST builds a positive correlation with NDBI(0.71)and NDBaI(0.52)while it builds a negative correlation with NDVI(-0.44).The LST-NDWI correlation is insignificant.The best correlation is noticed in the post-monsoon period,while the least correlation is observed in the winter season.This study can support the environmental planning to build a sustainable city under a similar environment.
文摘Mining operations result in the generation of barren land and spoil heaps which are subject to high erosion rate during the rainy season. The present study uses the Revised Universal Soil Loss Equation (RUSLE) and SCS-CN (Soil Conservation Service - Curve Number) process to estimate in Kiruburu and Meghahatuburu mining sites areas. The geospatial model of annual average soil loss rate was determined by integrating environmental variables parameters in a raster pixels-based GIS framework. GIS layers with, rainfall passivity and runoff erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management(C) and conservation practice (P) factors were calculated to determine their effects on annual soil erosion in the study area. The coefficient of determination (r2) was 0.834, which indicates a strong correlation of soil loss with runoff and rainfall. Sub -watersheds 5,9,10 and 2 experienced high level of highly runoff. Average annual soil loss was calculated (30*30 m raster grid cell) to determine the critical soil loss areas (Sub-watershed 9 and 5). Total soil erosion area was classified into five class, slight (10,025 ha), moderate (3125 ha), high (973 ha), very high (260 ha) and severe (53 ha). The resulting map shows greatest soil erosion of >40 t h-1 y-1 (severe) through connection to grassland, degraded and open forestry on the erect mining side-escutcheon. The Landsat pan sharpening image and DGPS survey field data were used in the verification of soil erosion results.
