Mapping of Debris-Covered Glaciers Using Remote Sensing Techniques—A Review

Understanding the health and dynamics of Himalayan glaciers has become a global scientific priority due to their critical role in sustaining freshwater supplies for drinking water, agriculture, industry, and hydropower across densely populated downstream regions. Accelerated glacier change under a warming climate has intensified the need for systematic monitoring and improved understanding of glacier responses to climatic variability. Consequently, global-scale glacier mapping, monitoring, and inventory development have emerged as essential components of cryospheric research and water resource assessment. Given the vast extent, complex terrain, and inaccessibility of mountain glaciers, remote sensing remains the most effective and economically viable approach for repeated, large-scale glacier mapping. A wide range of techniques has been developed, including spectral band ratios, index-based classifications, morphometric analysis using topographic attributes, multi-source and texture-based approaches, and supervised classification methods. While these techniques have proven effective for clean-ice and snow-covered glaciers, their applicability is significantly constrained in regions dominated by debris-covered glaciers. Debris-covered glaciers present a major challenge for satellite-based mapping due to the spectral similarity between supraglacial and periglacial debris and the surrounding valley rock, which severely limits discrimination using conventional multispectral imagery. This complexity often leads to underestimation of glacier extent and uncertainty in glacier inventories, with implications for mass balance assessment, hydrological modelling, and hazard evaluation. Over the past decade, substantial methodological advances have been made to address these challenges, incorporating thermal data, surface morphology, texture measures, multi-temporal analysis, and data fusion techniques. This chapter critically reviews the evolution of remote sensing–based methods for mapping debris-covered glaciers, evaluating their strengths, limitations, and suitability across different physiographic and climatic settings. By synthesizing methodological progress and remaining challenges, the chapter highlights key research gaps and outlines future directions for improving the accuracy, automation, and reliability of debris-covered glacier mapping in high-mountain regions.