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ABSTRACT. A glacierized terrain comprises different land covers, and their mapping using satellite data is challenged by their spectral similarity. We propose a hierarchical knowledge-based classification (HKBC) approach for differentiation of glacier terrain classes and mapping of glacier boundaries, using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery and Global Digital Elevation Model (GDEM). The methodology was tested over Kolahoi Glacier, Kashmir Himalaya. For the sequential extraction of various glacier terrain classes, several input layers were generated from the primary datasets by applying image-processing techniques. Noticeable differences in temperature and spectral response between supraglacial debris and periglacial debris facilitated the development of a thermal glacier mask and normalized-difference debris index, which together with slope enabled their differentiation. These and the other layers were then used in several discrete tests in HKBC, to map various glacier terrain classes. An ASTER visible near-infrared image and 42 field points were used to validate results. The proposed approach satisfactorily classified all the glacier terrain classes with an overall accuracy of 89%. The Z-test reveals that results obtained from HKBC are significantly (at 95% confidence level) better than those from a maximum likelihood classifier (MLC). Glacier boundaries obtained from HKBC were found to be plausibly better than those obtained from MLC and visual interpretation.

This study assimilates data from historical records (1857-1961/84), survey of India topographic maps, and a series of multispectral satellite data (1962-2014) for analyzing the shrinkage and dimensional changes of the Kolahoi glacier, Jammu and Kashmir, between 1857 and 2014. The composite results show that the glacier has receded by ∼3423 m (21.8 m/year) in the past 157 years. The historical records reveal that the glacier retreated by >1609 m from 1857 to 1909, 800 m from 1912 to 1961, and 210 m from 1961 to 1984. From 1962 to 2014 (52 years), we observed a retreat of 1014 ± 64 m (19.5 ± 1.1 m/year). We noted a marked disparity in the retreat rates of primary snout (PS) and secondary snout (SS) which was found to be 19.5 ± 1.1 m/year for PS and 11.34 ± 1.1 m/year for SS. Further, our investigations reveal that the changes in the length are accompanied by considerable changes in the area. The area of the glacier reduced from 14.46 ± 0.34 km (1962) to 11.28 ± 0.21 km (2014) amounting an overall deglaciation of 3.18 ± 0.34 km or 22.99 ± 2.3% in the past 52 years. Besides, the glacier has started degenerating at a much accelerated pace showing a deglaciation of 11.1 ± 1.9% and a recession rate of ~27.8 ± 3.2 m/year in just 14 years (2000-2014). These results warrant the detailed studies regarding various controlling factors, besides the climate change.

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