The land morphology concept and mapping method and its application to mainland Portugal

Abstract

Land morphology influences and shapes the distribution of biodiversity, agricultural production and economic activity. It can be systematized into landforms and quantitatively categorized using the land morphology concept (LMC). The LMC classifies landforms according to their hydrological position in the watershed. This paper presents an automated method to categorize LMC in a way that facilitates land morphology mapping (LMM) by using three criteria: flat areas, surface curvature and hydrological features. The LMM presents a different view to evaluate and describe landforms by distinguishing valley bottoms and hilltops from flat areas considered as a landform per se in common practice in landform classification.The main goal is to establish and validate criteria to automatize LMM method and create a 25 m spatial resolution GIS map of mainland Portugal's land morphology and landforms. The validation of the automated LMM method was done by comparison between automated and manual procedures in three representative Portugal landforms. To evaluate the compatibility between national and local scales, the LM map was compared with two local level applications using the same automated LMM method, for the Lisbon and Loures municipalities. The LM map was also compared with the distribution of soils from wet system in order to interpret local relationships between soils distribution and landforms, and two widely known automated landform classifications.The results show that the automated LMM method and data used is robust enough to map landforms on a national scale, with sufficient detail to capture finer landforms details at the local scale. This method can be applied across regions and countries (simply by modifying slope gradient) and is a complementary tool to other landform classifications to solve the mapping issues that occur in flat areas when the hillslope is absent. It also may contribute to enhance ecological land unit's maps and soil maps, by modelling natural systems and map ecosystem services accurately, e.g. valley bottoms and floodplains, give information about flood risk areas. It may contribute to support environmental and planning authorities in taking decisions based on a more thorough analysis of land value and ecological functions, across scales.