Scale-dependent Geomorphometric Analysis for Glacier Mapping at Nanga Parbat: GRASS GIS Approach.

Mountain environments are the result of complex interactions involving climate, tectonic and surface processes. Unfortunately, scientists do not understand a variety of processes and feedback mechanisms that control the geodynamics of topographic evolution, and dictate the nature of environmental change, and resource related issues. Thus the analysis of topography is essential for studying the role of surface processes in topographic evolution. Numerous scientists have tried to utilize morphometric parameters to automate geomorphological mapping at different scales [23, 25]. While physically-based models have produced promising results [16, 18], they do not consider the hierarchical organization of the topography. Many of the issues fall in the category of formalizing the concept of homogeneous terrain units at a variety of scales. Current software cannot automatically extract meaningful terrain units or objects from a DEM. There have been attempts to extract homogeneous units such as valley bottoms, ridges, pits and saddles [1, 26, 45], and higher-order geomorphologic features such as landform types [40, 41]. Various methods, however, are not appropriate for extracting complex terrain features such as slope facets, river terraces, or the active extent of a modern-day glacial valley. Unfortunately, hierarchy theory is generally described with no formal mathematical guidelines or rules established to define the organizational structure [31]. Issues include defining the concept of homogeneous terrain properties [22, 23], defining the various scale ranges that determine the number of levels in the hierarchy [38], solving the problem of indeterminate boundaries, addressing topological relations, and identifying and using appropriate geometric and contextual attributes to characterize terrain objects [23, 25]. The basic problem represents the transformation of theory and concepts into mathematics and models that effectively transform continuous fields of morphometric properties into real entities that can be observed on the landscape.The overall objective of this research is to develop an objectoriented approach at modeling the topography to determine if hierarchy theory and terrain objects can be used to accurately map alpine glaciers at Nanga Parbat in northern Pakistan. Specific research objectives were too: 1. Determine the significance of firstand second-order derivatives of the elevation field. 2. Examine the inherent statistical properties of terrain objects to determine if geometry and contextual relationships can be used to characterize landforms. 3. Determine if a simple hierarchical model can be used to map alpine glaciers at Nanga Parbat. The research presented here is a selection of the most critical and key ideas from my Master’s thesis, for more in depth information please see and refer to [37]. Here the problem is not presented in full details and special focus is given to the role of GRASS (Geographic Resources Analysis Support System) GNU/GPL GIS in the research.