Depositional environment mapping in alluvial plains is a basic step in geomorphological, pedological and archaeological studies, where remotely sensed data give an indirect contribution in assessing soil moisture, which could be correlated to sediment texture. However, a textural discrimination based on soil wetness is strictly season- dependent, and any procedure used to map different deposits from remotely sensed data fails when the acquisition time is not appropriate, and the appropriate time is generally different for the various sediments in a study area; hence the need for a multitemporal approach. In the present study a multitemporal Wetness (Tasseled Cap Transformation, TCT) analysis has been performed on the Pisa plain (Central Italy), in order to reconstruct the environment hosting a Roman harbour which seems to be one of the most important Roman harbors ever discovered, as is emerging from the archaeological excavation in progress. Four geocoded and atmospheric corrected images, acquired in March, July, October and December 1991, were processed to obtain just as many Wetness maps. Wetness multitemporal images were produced, and the seasonal changes of this parameter were correlated with grain-size characteristics in selected points in which the soil was bare at each flying over. A Principal Component Analysis on Wetness images was also carried out and synthetic images were produced. Out of all the images, a reliable textural discrimination in the study area was obtained, together with palaeo-geographical information useful in order for a better understanding of the role of the ancient harbor.