Natural and Anthropic Middle-term Variations in the Delta System at the Mouth of the Goro River (Po Delta, Italy) Carlo Del Grande* ,1 , Giovanni Gabbianelli 1 & Umberto Simeoni 2 1 Scienze Ambientali, Universita Á di Bologna, via degli Ariani, 1, I-48100 Ravenna, Italy. 2 Dipartimento di Scienze Geologiche e Paleontologiche, Universita Á di Ferrara, C.so Ercole I d'Este, 32, I-44100 Ferrara, Italy. With 14 figures and 1 table Keywords: Po River delta, climatic change, natural and anthropic factors, river mouth morphology, fluvial processes and regimes, wave-induced pro- cesses. Abstract. The modern delta system of the Po River is the result of an evolution strictly controlled by anthropic factors and mainly developed during a period of climatic deteri- oration (Little Ice Age 1550/1850). At the beginning of the 17 th century the main branch of the Po River, Fornaci Po, was modified with the ªCut of Viroº in order to avoid landfill of the Venetian Lagoon. Si- multaneously, the southernmost branch of Ariano, or Goro, was forced to flow south- wards. Subsequent sedimentary variations, caused by changes in the climatic condi- tions, contributed to make the area supplied by the Goro Po River increasingly lagoonary. In the second half of the 19 th century (end of the Little Ice Age ± L.I.A. ±), the first coastal spits started to take shape and developed in different systems through- out the entire following century. Coastal spits turned out to produce in the original bay, a progressive closure towards the sea. The strong decrease in solid loads, characterising thesecondhalfofthe20 th century and mainly due to anthropic factors, marks the begin- ning of a new phase extending to the overall Po Delta system, in which the mouth lay- out is controlled by wave energy. Problem The morphological evolution of the modern Po Delta system (Fig. 1) represents a typi- cal example of a deep interaction between natural and anthropic factors, above all dur- ing the last four centuries (Ciabatti, 1968; Bondesan, 1985; Simeoni et al., 2000; Gabbianelli et al., 2000). Among these factors, a crucial role is played by short- and U. S. Copyright Clearance Center Code Statement: 0173-9565/02/S2301±169$15.00/0 P.S.Z.N.: Marine Ecology, 23, Supplement 1 (2002), 169±183 Ó 2002 Blackwell Verlag, Berlin ISSN 0173-9565 * Author to whom correspondence should be addressed: c.delgrande@ambra.unibo.it