Palavras-chave-arqueogeografia; foto-interpretação; multidisciplinaridade; sistemas de informação geográfica (SIG); parcelário romano Abstract-The observation of metric patterns present in the current rural land parcelling in Alenquer (Portugal) floodplain, visible from the mapping and aerial photography, identified the existence of metric 8 x 8 actus corresponding to land Roman standards, which leads us to infer the possibility of rural land parcelling ever since the Roman period. The methodologies, and the placing of archaeological settlements in the long term, allow us to infer the drainage of alluvial area-along the Tagus river-in a subsequent period to the Iron Age. The change of settlement in the Roman period, moved to lower elevations (altitudes lower than 10 meters), in areas with higher flood possibilities, allow advance the possibility that drainage is also associated with the construction of the land parcelling ever since that period.