CalHypso: An ArcGIS extension to calculate hypsometric curves and their statistical moments. Applications to drainage basin analysis in SE Spain

We present the GIS extension CalHypso to automatically extract multiple hypsometric curves from digital elevation models (DEM). This extension is programmed in Visual Basic 6 and uses the ArcObjects architecture of ArcGIS. It employs a new and easy methodology to extract the hypsometric curve by using the integer data-model properties of ArcGIS and summations algorithms. This provides an optimal integration within the program environment, allowing the representation and comparison of curves directly within the GIS main program. The CalHypso extension can also calculate the main statistics related to the hypsometric curve by applying polynomial fits. We have tested this tool in several basins of the eastern border of the Sierra-Nevada dome in the Betic Cordillera (SE Spain), showing important differences in the north- and south-slope hypsometric curves. These variations are probably related to the tectonically controlled drainage evolution of the southern border of Sierra Nevada. An eastward decrease in tectonic-driven erosion is also suggested by the hypsometric curves analyzed.