Extraordinary flooding inundated much of the Upper Mississippi River basin during the Summer of 1993. All time high streamflows, some much larger than the previous historical floods, were recorded at 42 gaging stations on 33 streams in seven states. It has been reported that 100-yr floods were exceeded at 46 stations in nine states. The flood lasted for a long time bringing enormous physical, environmental, and socio-economic losses. Indeed, the magnitude of the damages in terms of property, disrupted businesses, and personal trauma was unmatched by any other flood disaster in the history of the United states. The Mississippi River is one of the river systems in the United States where extensive flood control development has taken place especially since the nineteen hundreds in order to cope with recurrent flood losses. Thus, for over one hundred years a system of about one thousand five hundred levees (including those built with federal, state and private funds) was created all the way from Cairo, Illinois to the Delta in the Gulf of Mexico. While over the years, many other flood control measures have also been developed such as reservoirs, floodways, channel improvement, and flood insurance, the system of levees has remained an important aspect and a center piece of the strategy for a comprehensive flood control program along the Mississippi River Basin.

However, the 1993 Mississippi flood brought to light and clearly emphasized the fragility of a levee-oriented flood control program. In fact, the very use of river engineering works was brought into question and it has been suggested that it may be timely for the U.S. to take a fresh look at the flood problem. Instead of flood control, it may be wiser to approach the flood hazard problem on a broader perspective of floodplain management, non-structural approaches, and institutional innovations which may be used for integrated, comprehensive flood control strategies. While the Mississippi flood of 1993 has been the most recent example of a summer flood of extraordinary magnitude and consequences, other recent flooding events in many other parts of the United States are vivid examples of society's vulnerability to extreme flood events.

Europe has not been spared from extraordinary flood events. During 1994, extreme summer storms caused major floods in Spain, and severe Fall storms caused floods of extraordinary magnitude and of far-reaching impacts in Italy. Likewise, at the beginning of 1995, a Winter storm, has battered several Northern European countries such as Germany, France, and The Netherlands causing extreme flooding and extensive damages and disruptions in these countries. In Italy, at the beginning of November of 1994, a severe storm hit the upstream catchment of the Po River and orographic enhancement of a cyclonic circulation off the Gulf of Genoa produced intense precipitation over the northern slope of the Apennine divide. Tanaro River (a tributary of the Po River) inundated the floodplain before entering the Po River flooding several towns along the way and causing numerous deaths and extensive damages and losses. Apparently the flood warning system did not work properly which led to extensive post-flood litigation between the responsible federal, regional, and local institutions.

The flood in Northern Europe in January of 1995 has been called the flood of the century because of its extreme magnitude and damages. However, just about a year before, in December of 1993 another extreme flood occurred in much of the same region. Thus, an immediate question became clear, how could two "century floods" hit the same region within a 13-months time frame? The cause of the 1995 flood was natural, i.e. extreme rainfall and snow melted by unexpected sunshine. But a number of man-made factors made the disaster worse than it would otherwise have been. These factors have been directly related to the construction of dikes and levees, which in turn have been associated with the further development of residential and industrial property, increased urbanization and changes in agricultural practices, and straightening of the channel and the raising of the banks of the Rhine River, which cut down many miles of the original length of the river. All such developments have increased the magnitude of the flood peaks and volumes per unit rainfall intensity, and helped produce floods quicker as water traveled faster down the channels. These apparent problems, brought about by a number of structural flood control measures and a conflicting overall flood management strategy, are quite similar to the US experiences associated with the 1993 Mississippi flood.

Because both the United States and several European countries have in recent times experienced the occurrence and the consequences of extreme flood events, a bilateral United States-Italy Research Workshop was organized where a selected group of specialists discussed and exchanged experiences in relation to recent catastrophic flood events. The research workshop was held at the Water Research and Documentation Center of the University for Foreigners, La Colombella, Perugia, Italy, during November 13-17, 1995. Specific outcomes of the research workshop are described under Research Workshop Objectives and Summary, Conclusions and Recommendations sections. A number of organizations in the United States and Europe have directly and indirectly supported the realization of the workshop. Particularly, the U.S. National Science Foundation (Natural and Technological Hazard Mitigation Program) and the Italian National Research Council (National Research Group for Prevention of Hydrogeological Disasters) have provided financial support. The organizers and editors of this proceedings gratefully acknowledge their support. The complete list of supporting organizations are shown under the section Supporting Organizations. The Research Workshop was attended by 41 experts in the field from the United States (14), Italy (17), and other European countries (10). The list of participants are shown under the section Workshop Participants List. The workshop participants prepared written material on pre-determined subjects related to the theme of the workshop which were presented during plenary sessions. The abstracts of all papers and oral presentations are shown under the section Abstracts. Likewise, the edited text of the papers prepared for the workshop are shown under the section Full Papers. In addition, several pictures related to the occurrence and impacts of extreme floods, which have been extracted from some of the papers, have been included under the section Pictures of Extreme Floods. Furthermore, a CD-Rom containing all the material referred to herein has been developed.

Jose D. Salas and Franco Siccardi
Editors