Papers by Dhrubajyoti Sahariah
Floodplain wetlands are very important for ecological and socio-economic services and, in Assam l... more Floodplain wetlands are very important for ecological and socio-economic services and, in Assam large number of people living in-and-around wetlands, often depends on the wetland ecosystem services for their livelihoods. To understand the ecological condition of floodplain wetlands, in the Upper Brahmaputra valley, Assam, assessment were carried out during the pre-monsoon and post-monsoon from October 2016 to May 2017 in six important wetlands. The paper highlights integrated approach to study the landscape status of the catchment area; physico-chemical characteristics of the water and soil. Over the time period of 2016-17, water and soil samples were collected and analysed from six-selected wetlands; and for the image based analysis of these wetlands have been carried out using Landsat-8 image 2016. The study revealed that, in spite of decreasing size, the Fuklai beel is in better condition among all of the wetlands based on the landscape assessment and the Water Quality Index (WQI...
Assessment of the land use/land cover and climate change impact on the hydrological regime of the Kulsi River catchment, Northeast India
Sustainable water resources management, Feb 27, 2024
Earth Systems and Environment, Nov 30, 2023
Global planted trees extent 2015
We provide a global extent of planted trees landscapes (aggregated land use classes of planted fo... more We provide a global extent of planted trees landscapes (aggregated land use classes of planted forest, woody plantations and agroforestry). The layer has binary value and represents the status for the year 2015 at a spatial resolution of 100 m. The layer has been derived from a global forest management map produced by the Nature Map project (https://naturemap.earth/). The description of the methodology could be found here: https://doi.org/10.5281/zenodo.3933966
The first ever global map of forest management was generated based on remote sensing data. To col... more The first ever global map of forest management was generated based on remote sensing data. To collect training data, we launched a series of Geo-Wiki (https://www.geo-wiki.org/) campaigns involving forest experts from different world regions, to explore which information related to forest management could be collected by visual interpretation of very high-resolution images from Google Maps and Microsoft Bing, Sentinel time series and normalized difference vegetation index (NDVI) profiles derived from Google Earth Engine. A machine learning technique was then used with the visually interpreted sample (280K locations) as a training dataset to classify PROBA-V satellite imagery. Finally, we obtained a global wall-to-wall map of forest management at a 100m resolution for the year 2015. The map includes classes such as intact forests; forests with signs of management, including logging; planted forests; woody plantations with a rotation period up to 15 years; oil palm plantations; and ag...
Water
Illegal sand mining has been identified as a significant cause of harm to riverbanks, as it leads... more Illegal sand mining has been identified as a significant cause of harm to riverbanks, as it leads to excessive removal of sand from rivers and negatively impacts river shorelines. This investigation aimed to identify instances of shoreline erosion and accretion at illegal sand mining sites along the Chambal River. These sites were selected based on a report submitted by the Director of the National Chambal Sanctuary (NCS) to the National Green Tribunal (NGT) of India. The digital shoreline analysis system (DSAS v5.1) was used during the elapsed period from 1990 to 2020. Three statistical parameters used in DSAS—the shoreline change envelope (SCE), endpoint rate (EPR), and net shoreline movement (NSM)—quantify the rates of shoreline changes in the form of erosion and accretion patterns. To carry out this study, Landsat imagery data (T.M., ETM+, and OLI) and Sentinel-2A/MSI from 1990 to 2020 were used to analyze river shoreline erosion and accretion. The normalized difference water in...
ISPRS International Journal of Geo-Information
The alteration of land use and land cover caused by human activities on a global scale has had a ... more The alteration of land use and land cover caused by human activities on a global scale has had a notable impact on ecosystem services at regional and global levels, which are crucial for the survival and welfare of human beings. Merbil, a small freshwater wetland located in the Brahmaputra basin in Assam, India, is not exempt from this phenomenon. In the present study, we have estimated and shown a spatio-temporal variation of ecosystem service values in response to land use and land cover alteration for the years 1990, 2000, 2010, and 2021, and predicted the same for 2030 and 2040. Supervised classification and the CA-Markov model were used in this study for land-use and land-cover classification and future projection, respectively. The result showed a significant increase in built-up areas, agricultural land, and aquatic plants and a decrease in open water and vegetation during 1990–2040. The study area experienced a substantial rise in ecosystem service values during the observed...
Distribution mapping of five threatened medicinally important plant species of Arunachal Himalaya
Vegetos
When the Bough Breaks: Spatial Variability of Tropospheric Ozone in the Indian Sub-continent
Springer eBooks, 2022
Assessing the impacts of current and future changes of the planforms of river Brahmaputra on its land use-land cover
Geoscience Frontiers
Land
Bank erosion hazard is a frequent occurrence that poses threats to floodplain ecosystems. This an... more Bank erosion hazard is a frequent occurrence that poses threats to floodplain ecosystems. This analysis examined changes to the Jia Bharali River channel in India using the GIS-based Digital Shoreline Analysis System [DSAS]. The Jia Bharali’s future channel was predicted so as to identify the most erosion-susceptible zones. The rate of bankline movement was calculated using remotely sensed data collected over a period of 45 years (1976–2021). The results show that the river’s erosion and deposition rates were higher in the early years than towards the later part of the period under analysis. On the right and left banks of the river, the average shift rate was −9.22 and 5.8 m/y, respectively, which is comparatively high. The chosen portion of the river was evenly divided into three zones, A, B, and C. The most positively affected zone was zone A. The left bank of zone B exhibited a higher rate of erosion than the right bank, indicating that the river was moving to the left [eastward]...
Environmental Science and Pollution Research, 2022
Satellite remote sensing and geographic information system (GIS) have revolutionized the mapping,... more Satellite remote sensing and geographic information system (GIS) have revolutionized the mapping, quantifying, and assessing the land surface processes, particularly analyzing the past and future land use-land cover (LULC) change patterns. Worldwide river basins have observed enormous changes in the land system dynamics as a result of anthropogenic factors such as population, urbanization, development, and agriculture. As is the scenario of various other river basins, the Brahmaputra basin, which falls in China, Bhutan, India, and Bangladesh, is also witnessing the same environmental issues. The present study has been conducted on the Brahmaputra Valley in Assam, India (a sub-basin of the larger Brahmaputra basin) and assessed its LULC changes using a maximum likelihood classification algorithm. The study also simulated the changing LULC pattern for the years 2030, 2040, and 2050 using the GIS-based cellular automata Markov model (CA-Markov) to understand the implications of the ongoing trends in the LULC change for future land system dynamics. The current rate of change of the LULC in the region was assessed using the 48 years of earth observation satellite data from 1973 to 2021. It was observed that from 1973 to 2021, the area under vegetation cover and water body decreased by 19.48 and 47.13%, respectively. In contrast, cultivated land, barren land, and built-up area increased by 7.60, 20.28, and 384.99%, respectively. It was found that the area covered by vegetation and water body has largely been transitioned to cultivated
land and built-up classes. The research predicted that, by the end of 2050, the area covered by vegetation, cultivated land, and water would remain at 39.75, 32.31, and 4.91%, respectively, while the area covered by built-up areas will increase by up to 18.09%. Using the kappa index (ki) as an accuracy indicator of the simulated future LULCs, the predicted LULC of 2021 was validated against the observed LULC of 2021, and the very high ki observed validated the generated simulation LULC products. The research concludes that signifcant LULC changes are taking place in the study area with a decrease in vegetation cover and water body and an increase of area under built-up. Such trends will continue in the future and shall have disastrous environmental consequences unless necessary land resource management strategies are not implemented. The main factors responsible for the changing dynamics of LULC in the study area are urbanization, population growth, climate change, river bank erosion and sedimentation, and intensive agriculture. This study is aimed at providing the policy and decision-makers of the region with the necessary what-if scenarios for better decision-making. It shall also be useful in other countries of the Brahmaputra basin for transboundary integrated river basin management of the whole region.
PeerJ
Inland water plants, particularly those that thrive in shallow environments, are vital to the hea... more Inland water plants, particularly those that thrive in shallow environments, are vital to the health of aquatic ecosystems. Water hyacinth is a typical example of inland species, an invasive aquatic plant that can drastically alter the natural plant community’s floral diversity. The present study aims to assess the impact of water hyacinth biomass on the floristic characteristics of aquatic plants in the Merbil wetland of the Brahmaputra floodplain, NE, India. Using a systematic sampling technique, data were collected from the field at regular intervals for one year (2021) to estimate monthly water hyacinth biomass. The total estimate of the wetland’s biomass was made using the Kriging interpolation technique. The Shannon-Wiener diversity index (H′), Simpson’s diversity index (D), dominance and evenness or equitability index (E), density, and frequency were used to estimate the floristic characteristics of aquatic plants in the wetland. The result shows that the highest biomass was ...
Land Use and Land Cover Change Monitoring and Prediction of a UNESCO World Heritage Site: Kaziranga Eco-Sensitive Zone Using Cellular Automata-Markov Model
MDPI land, 2023
Geospatial modeling to assess the past and future land use-land cover changes in the Brahmaputra Valley, NE India, for sustainable land resource management
Environmental Science and Pollution Research
Satellite remote sensing and geographic information system (GIS) have revolutionized the mapping,... more Satellite remote sensing and geographic information system (GIS) have revolutionized the mapping, quantifying, and assessing the land surface processes, particularly analyzing the past and future land use-land cover (LULC) change patterns. Worldwide river basins have observed enormous changes in the land system dynamics as a result of anthropogenic factors such as population, urbanization, development, and agriculture. As is the scenario of various other river basins, the Brahmaputra basin, which falls in China, Bhutan, India, and Bangladesh, is also witnessing the same environmental issues. The present study has been conducted on the Brahmaputra Valley in Assam, India (a sub-basin of the larger Brahmaputra basin) and assessed its LULC changes using a maximum likelihood classification algorithm. The study also simulated the changing LULC pattern for the years 2030, 2040, and 2050 using the GIS-based cellular automata Markov model (CA-Markov) to understand the implications of the ongoing trends in the LULC change for future land system dynamics. The current rate of change of the LULC in the region was assessed using the 48 years of earth observation satellite data from 1973 to 2021. It was observed that from 1973 to 2021, the area under vegetation cover and water body decreased by 19.48 and 47.13%, respectively. In contrast, cultivated land, barren land, and built-up area increased by 7.60, 20.28, and 384.99%, respectively. It was found that the area covered by vegetation and water body has largely been transitioned to cultivated land and built-up classes. The research predicted that, by the end of 2050, the area covered by vegetation, cultivated land, and water would remain at 39.75, 32.31, and 4.91%, respectively, while the area covered by built-up areas will increase by up to 18.09%. Using the kappa index (ki) as an accuracy indicator of the simulated future LULCs, the predicted LULC of 2021 was validated against the observed LULC of 2021, and the very high ki observed validated the generated simulation LULC products. The research concludes that signifcant LULC changes are taking place in the study area with a decrease in vegetation cover and water body and an increase of area under built-up. Such trends will continue in the future and shall have disastrous environmental consequences unless necessary land resource management strategies are not implemented. The main factors responsible for the changing dynamics of LULC in the study area are urbanization, population growth, climate change, river bank erosion and sedimentation, and intensive agriculture. This study is aimed at providing the policy and decision-makers of the region with the necessary what-if scenarios for better decision-making. It shall also be useful in other countries of the Brahmaputra basin for transboundary integrated river basin management of the whole region.
Habitat suitability of Gymnocladus assamicus - A critically endangered plant of Arunachal Pradesh, India using machine learning and statistical modeling
Acta Ecologica Sinica
The present study sought to identify the potential distribution range of critically endangered Gy... more The present study sought to identify the potential distribution range of critically endangered Gymnocladus assamicus in Arunachal Pradesh based on published data and field collection. We used the Maxent model to estimate the range of distribution and the result was then compared with three other models, i.e., the Generalized Linear Model (GLM), the Bioclim and the Random Forest model to assess the species' habitat suitability. A total of 23 different environmental variables were used, including bioclimatic ones, monthly minimum and maximum temperature, monthly precipitation and elevation data. The Maxent output listed 12 variables explaining 99.9% variation in the model. In comparison, Maxent showed the maximum region under habitat suitability criteria (1884.48 km 2), followed by Random Forest (70.73 km 2) and Bioclim (11.62 km 2) model. Except for the Maxent model, suitable habitats predicted by other models are highly restricted within and across the study species' current distribution range. The average model prediction shows an expanded distribution range for the species up to Tawang which is the closest district of currently known distribution of the species in the state. Thus, the present study recognizes the importance of the geographic range of G. assamicus, a critically endangered species with very limited spatial distribution range and also provides some specific details to explore possible habitats for the species in new areas of potential occurrence in Arunachal Pradesh, India.
Global forest management data at a 100m resolution for the year 2015
We provide four data records: 1.The reference data set as a comma-separated file ("reference... more We provide four data records: 1.The reference data set as a comma-separated file ("reference_data_set.csv") with the following attributes: "ID" is a unique location identifier "Latitude, Longitude" are centroid coordinates of a 100m x 100m pixel. "Land_use_ID "is a land use class: 11 - Naturally regenerating forest without any signs of human activities, e.g., primary forests. 20 - Naturally regenerating forest with signs of human activities, e.g., logging, clear cuts etc. 31 - Planted forest. 32 - Short rotation plantations for timber. 40 - Oil palm plantations. 53 - Agroforestry. "Flag" identifies a data origin: 1- the crowdsourced locations, 2- the control data set, 0 – the additional experts' classifications following the opportunistic approach. 2. The 100 m forest management map in a geoTiff format with the classes presented - "FML_v3.2.tif ". 3. The predicted class probability from the Random Forest classification ...
Acta Geophysica, 2020
The study examines the effects of urbanization on land surface temperature (LST) in Guwahati, a c... more The study examines the effects of urbanization on land surface temperature (LST) in Guwahati, a city in India using satellite data. Landsat images were utilized for LST retrieval, land-use land-cover (LULC) classification and the normalized difference built-up index mapping. Surface Energy Balance Algorithms for Land and support vector machine methods were used in the study. Results showed that the city has gone through massive changes in its LULC pattern with a high degree of urbanization during the period 1992-2015. The built-up area (BUA) increased to 87.8 km 2 in 2015 from 11.6 km 2 in 1992 while vegetation decreased from 143.3 to 76.6 km 2. Open spaces and water bodies decreased from 14.5 to 5 km 2 and to 6.6 km 2 from 6.7 km 2 , respectively. Conversely, an increasing trend of LST was observed. The mean LST which was 18.5 °C in 1992 rose to 29.03 °C in 2015. Linear regression used in quantifying the relationship between urbanization and LST showed a positive relationship between LST and BUAs in the city.
Impacts of temperature–rainfall and land use/land cover changes on the hydrological regime in the Muhuri River basin, Northeast India
Sustainable Water Resources Management
The present study aims to assess the impact of temperature-rainfall (TR) and land use/land cover ... more The present study aims to assess the impact of temperature-rainfall (TR) and land use/land cover (LULC) on the hydrological regime of a forested watershed. The authors consulted meteorological, hydrological, and remote sensing data in this research work. The study applied statistical techniques like regression and analysis of variation (ANOVA), which have been used to analyze the variability of TR and LULC and their impact on the hydrological regime of the river. To analyze the variability, the whole study period (1986-2016) was divided into two phases, i.e., 1986-2000 (Phase I) and 2001-2016 (Phase II). The statistical analyses proved that within the study period, water discharge, water level, hydraulic radius, and flow velocity experienced variation significantly (p value < 0.05) except for wetted perimeter (p value > 0.05). All the variables have decreased considerably in the second phase of the study period, i.e., in the 2001-2016 periods. Moreover, phase-wise seasonal analysis proved that the variations during monsoon and non-monsoon are lacking and prominent, respectively. The response of hydraulic variables to temperature-rainfall proved that the hydraulic variables had an insignificant correlation (R = 0.15 to 0.41) with the annual and the monsoon rainfall, while significant relation (R = − 0.26 to 0.78) was observed with the non-monsoon rainfall and temperature (maximum and minimum). There was a significant variation (p value 0.00) of LULC change in both phases. Statistical analyses proved that among the two phases of the study, the mean value of the forest class decreased significantly (from 550.37 to 425.67 km 2). In contrast, rubber plantations increased extensively (from 21.36 to 128.36 km 2) in comparison to the other LULC classes. Statistical analysis proved that the LULC change is very much responsible for the hydrological modifications rather than the rainfall.
PLOS ONE
A common phenomenon associated with alluvial rivers is their meander evolution, eventually formin... more A common phenomenon associated with alluvial rivers is their meander evolution, eventually forming cutoffs. Point bar deposits and ox-bow lakes are the products of lateral bend migration and meander cutoff. The present study focuses on identifying the meanders of River Manu and their cutoffs. Moreover, this study compares the temporal evolution and predicts the progress of selected meanders of River Manu. In the present research, the Survey of India topographical map, satellite imagery, and geographic information system (GIS) technique were used to examine the evolution of the Manu River meander. Subsequently, a field visit was done to the selected cutoffs and meanders of River Manu to ascertain the present status and collect data. It has been observed that many cutoffs have undergone temporal changes, and their sizes have decreased. Some have become dried or converted to agricultural fields. The width of River Manu has decreased in all the selected bends from 1932 to 2017. The sinu...
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Papers by Dhrubajyoti Sahariah
land and built-up classes. The research predicted that, by the end of 2050, the area covered by vegetation, cultivated land, and water would remain at 39.75, 32.31, and 4.91%, respectively, while the area covered by built-up areas will increase by up to 18.09%. Using the kappa index (ki) as an accuracy indicator of the simulated future LULCs, the predicted LULC of 2021 was validated against the observed LULC of 2021, and the very high ki observed validated the generated simulation LULC products. The research concludes that signifcant LULC changes are taking place in the study area with a decrease in vegetation cover and water body and an increase of area under built-up. Such trends will continue in the future and shall have disastrous environmental consequences unless necessary land resource management strategies are not implemented. The main factors responsible for the changing dynamics of LULC in the study area are urbanization, population growth, climate change, river bank erosion and sedimentation, and intensive agriculture. This study is aimed at providing the policy and decision-makers of the region with the necessary what-if scenarios for better decision-making. It shall also be useful in other countries of the Brahmaputra basin for transboundary integrated river basin management of the whole region.