GIS-MORPHOMETRY: A GIS FRAMEWORK FOR DIGITAL TECTONIC GEOMORPHOLOGY STUDIES

Digital terrain modelling and landform analysis are carried out by means of (1) general geomorphometry of DEM, (2) digital drainage network analysis, (3) digital image processing, (4) lineament extraction and analysis, (5) spatial and statistical analysis and (6) 3D surface modelling. These approaches defined the growing domain of digital tectonic geomorphology. Most of its investigations include visualisation of imagery and geology with topography, raster calculations with Map Algebra procedure, and the integration of fault model calculations for surface uplift. Analysis of digital elevation models (DEM) by means of geomorphometry provides an efficient tool of recognizing fractures and characterising the morphotectonics and the morphodynamics of an area in a quantitative way.

Topographic attributes extracted from the DEM allow general and specific characterisation of relief in term of coupled and inherent interaction between surface processes and tectonic. The DEM manipulations illustrate the basic evidence of deformation and surface processes recorded in the topography. In addition, digital drainage network and digital image processing allow, via morphometric parameters extraction and integration, morphotectonic investigations of the landform. Though, this large amount of quantitative attributes requires a well-organized digital system to ensure, numerically, their systematic extraction and manipulations. The implementation of an adequate framework using the available GIS technology is the motivation and the primary goal of our work.

A GIS architecture and database has been designed and developed to ensure many quantitative procedures and approaches. They are originally based on landform investigations and geomorphological characteristics which are translated into mathematical and numerical algorithms. The general framework of the developed GIS is composed of three core “moprhomtric components”: (1) DEM-morphometry, (2)Digital Drainage Network (DDN)-morphometry and (3) Digital Image (DI)-morphometry (Fig. 1). A large set of morphometric parameters are extracted from these GIS sub-structures. However, classical operations and GIS functions are also ensured: data integration and interoperability, data management and spatial analysis, topology and interactive visualisation. This “GIS-Morphometry” framework was developed under ArcGIS package using ModelBuilder tool and Python programming language. The GIS object-oriented technology has been used to extract automatically most of moprhomtric parameters and attributes (Fig. 2). A comprehensive Geodatabase was structured for the purposes of data integrity and effectiveness of data manipulation. The system's totally digital nature ensures that it will be flexible so that it can grow and evolve as new data, processing procedures, and modelling and visualization tools become available. A set of morphotectonic and morphostructural maps of test sites into northern Tunisia was created. The neo-morphodynamic model of folded and faulted structures was particularly emphasized and mapped.