Faculty Publications
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Publications by NITK Faculty
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Item Erosion and Accretion in the Netravati River Stretch: Spatiotemporal Analysis Using Geospatial Approach(Springer Science and Business Media Deutschland GmbH, 2024) Makhdumi, W.; Shwetha, H.R.; Dwarakish, G.S.Understanding erosion and accretion, which are critical geomorphic processes, is essential for effective river management and conservation. Erosion by removing soil and rock changes the river's shape, depth, and course. Accretion, conversely, involves the deposition and accumulation of sediment, shaping features like riverbanks and floodplains. Focused on a 30 km stretch of the Netravati River, in the southwestern region of India, this study used Survey of India toposheets and Landsat images to track changes over time (1973, 1998, 2022). The Normalised Difference Water Index (NDWI) and image classification were employed for the analysis which revealed notable spatiotemporal variations in these processes. From 1973 to 2022, the analysis estimated a total erosion of 510.43 hectares and an accretion of 317.71 hectares. The years 1973–1998 witnessed more accretion (417.6 hectares) than erosion (229.08 hectares). And, from 1998 to 2022, erosion dominated at 438.37 hectares, with only 56.97 hectares of accretion. These variations can be attributed to both natural processes and human interventions. Notably, the construction of a vented dam in 1993 at Thumbe, followed by the subsequent dam in 2016, 50 m downstream of the old dam, influenced the sediment dynamics and flow patterns in the Netravati River, potentially impacting erosion and accretion processes. This research adds to our understanding of erosion and sediment changes in the Netravati River over time. The dams and hydraulic structure upstream along with geospatial techniques offer researchers and river managers a unique opportunity to examine river shape impacts and thus develop sustainable strategies for river preservation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Estimation of daily actual evapotranspiration using vegetation coefficient method for clear and cloudy sky conditions(Institute of Electrical and Electronics Engineers, 2020) Shwetha, H.R.; Nagesh Kumar, D.N.Actual evapotranspiration (AET) can be studied and estimated using remote-sensing-based methods at multiple spatial and temporal scales. Reflectance and Land surface temperature are essential in these methods. However optical and thermal sensors fail to provide these data under overcast conditions and this creates gap in the AET product. Besides, there is a necessity of the AET method that requires less data and estimates AET with better accuracy. In this regard, AET was estimated for all-sky conditions using the vegetation coefficient (VI-Kv) method utilizing microwave, thermal, and optical data. Essential reference evapotranspiration (ET0) under cloudy conditions was estimated using LST-based Penman-Monteith temperature (PMT) and Hargreaves-Samani equations. Furthermore, LST predicted using the microwave polarization difference index (PLST) and LST of moderate resolution imaging spectroradiometer (MODIS) cloud product (MLST) were evaluated with in-situ air temperature (Ta) under cloudy sky conditions. Results revealed that the PLST correlated better with Ta than MLST with correlation coefficient (r) values of 0.71 and 0.81 for day and night times, respectively. Hence, PLST-based solar radiation (Rs) estimation yielded better accuracy with observed Rs with r and root mean square error values of 0.864 and 0.07 for Berambadi station under cloudy conditions, respectively. PMT-based ET0 values corresponded well with the observed ET0 under cloudy sky condition during this study. In addition, AET estimated using the VI-Kv method was compared with the simple two-source energy balance (TSEB) method under clear sky conditions. It was found that the improved VI-Kv method performed better than the TSEB method and could also fairly estimate AET even under cloudy sky conditions. © 2008-2012 IEEE.Item Integrating Soil Spectral Library and PRISMA Data to Estimate Soil Organic Carbon in Crop Lands(Institute of Electrical and Electronics Engineers Inc., 2024) Reddy, B.S.; Shwetha, H.R.The increasing demand for precise soil organic carbon (SOC) monitoring in croplands is crucial for food security (SDG 2), and has led to the exploration of fusing soil spectral libraries (SSLs) with hyperspectral sensing data for SOC estimation. However, the widespread adoption of SSL for SOC estimation faces challenges, particularly in developing nations, due to inconsistent calibration libraries and reliable estimation models. Furthermore, SSL rely on regular soil sample collection and spectral data recording using spectroradiometers, which is impractical in agricultural-predominant countries, such as India, with limited time for sample collection between crop rotations. To address this challenge, we developed synthesized SSL in laboratory conditions and integrated it with hyperspectral data using machine learning (ML) algorithms to bridge the gap between synthesized SSL and hyperspectral data for local-scale SOC mapping. This approach was tested by mapping SOC in Mysore, India, using spectroradiometer hyperspectral measurements and PRISMA sensor data. The proposed approach and synthesized SSL exhibited better performance prediction accuracies, R2 of 0.92 and 0.79, and the RMSE values of 2.31 and 9.91 g/kg, respectively, for PRISMA and laboratory spectroscopy data. These results highlight the potential of synthesized SSL for SOC prediction in alluvial soils, leveraging local datasets, and hyperspectral data. Our future work will expand the synthesis approach to other study areas, particularly those with alluvial soil origins, further enhancing the applicability of this methodology for SOC estimation and aiding food security efforts. © 2004-2012 IEEE.