Correlation between environmental evolution, historical settlement and cultural heritage upgrading in Valle Umbra (Central Italy)

Abstract

In Central Italy, the «Valle Umbra» (remnant of the south-eastern arm of the plio-pleistocenic Tiberino basin) is a wide depression characterized by a very low declivity causing difficult drainage. During three millennia the zone became alternately partially or totally flooded, with lakes, swamps, and marshland, or sometimes quite dry and easily accessible and exploitable by man. The variation was caused by: a) climate changes, with rainfall increase or decrease; b) tectonic movements tending to rise or to lower the outflow threshold; c) Man who attempted to lower the outflow threshold and canalize streams and creeks for land reclaiming. From the first millennium BC, the Umbrians, Etruscans, Romans, Goths, Byzantines, Longobards and Franks lived at different times in this valley and left traces in various places depending on the environment. From the 7^th to the 3^rd Century BC, traces of Etruscan and Roman settlements have been found on the surrounding hills or on slightly raised ground (Mevania). It is probable that the lowlands were swampy and so not easy to traverse. In the 3^rd Century BC a huge lake is documented (Lacus Umber) which covered a great part of the valley bottom, where there were also numerous meandering streams. On the plain (at Aisillo) the ruins of a Roman temple have recently been discovered which was in use from the 2^nd Century BC to the 3rd Century AD. This corresponds to the period of Roman domination. There is also much evidence of human dwellings in the plain which was easily accessible in Roman times. In 220 BC the most important road which crossed the zone (the Via Flaminia) was built. Traces of a Roman centuriation, for agricultural purposes, but also carried out in order to drain the swamps, have been discovered. We know that the valley was well organized, with plenty of well channelled water courses. In Bevagna a Roman mosaic testifies to a thermal establishment here. A river (the Clitumnus) was navigable as far as the Tiber and Rome, and there were some river ports near the towns. In this healthy environment there were several villas and temples alongside the river some of which are still preserved. The Aisillo temple is now covered by about 2 meters of marshy, clayey and peaty sediments indicating that from the 4^th Century AD onwards the valley plain became an impassable swamp. This is also confirmed by signs of a climatic deterioration with increased rainfall and decreasing temperatures, which lasted right up to the Middle Ages. Close to the end of the 5^th Century AD Teodoricus reclaimed part of the Valle Umbra but during the subsequent Longobard invasion, lack of maintenance caused the valley to become a swamp once again. Later history is characterized by various attempts at reclamations attempts made by different municipalities, but lacking coordination. These often led to disputes and fights between neighbouring communities since they sometimes caused damage to the land nearby. In conclusion, in each period it is possible to trace the influence of the environment on inhabited areas and on the activities of the local populations. An historical reconstruction can provide the foundation for our knowledge of the territory and if properly used can help to develop knowledge of our cultural heritage and thereby the development of tourism.