The human-environment system in the small and large context, into analysis of the global warming

The complexity of the human-environment system leads to repercussions on the territory at different time scales. This is observed in reverse scale in relation to the extension of the analyzed system: smallest is the system, greatest is the evidence of the effects induced in a short-to-medium term (eg. in mountain areas); in case of greater extent, more and more the chain of the observable processes will extends over the medium-to- long term, since the possibilities of adaptation are liable to occur in large number. Under this regard some study areas are presented, ranging from the Po plain to a small mountain basin, in which anthropogenic effects show relationships with paroxysmal floods with harmful effects. The effects of global warming are becoming more and more evident, through extreme meteorological phenomena characterized by the development of severe events concentrated in limited time spans. A lack of attention to land management and geo-morphological conditioning of the Italian territory tend to be closely linked to the occurrence of landslides and floods. The latter seriously impact on security and safety of local communities, services activities as well as inhabitants/population. The researchers of IRPI-CNR are called to focus their effort on prevention and prevision of disasters following the development of extraordinary meteorological events, improve the knowledge of the hydro-geological basins and develop instruments allowing a better and more efficient observation of the landscape. Two very different situations are presented. In the first one has prevailed human activity where several conditioning are been imposed for a long time in a large river (the Po River watercourse is about 650 km long and the Po alluvial plain area is approximately 70,000 km2). The regulation have developed to stabilize the channel bottom level during the last Century. Fluvial hazard still recently has characterized the Upper Po river system, related to scouring at the bridges. The River Po exceeded previous peak flows and showed changes towards floods more frequent, shorter and higher in water levels, depending on Northern Italy rainfall new trend. Hydrographical response was highlighted by flooding of speedy flow waters into the abandoned channels and scratching the flood plain top, destroying roads and a railway. Flood speed links with shorter length in water courses measured along the rivers. River network contraction has involved reduction to the fluvial waters mobility and sediment availability in deposition processes. Hydrological changes have accelerated the flood occurrence. The substrate exposure and scouring has changed the hydro-sedimentary system. Scouring at the channel bottom and bridge pier and abutments is observed in the upper alluvial plan. Environmental relapse develops at the water balance by water loss at the surface drainage. Surface water table deepening and water losing involves water lack in the river biomasses maintenance. The morphological response was highlighted by channel length shortening, channel bottom deepening and river bank destabilization. Hazard at the floodplain and at the channel allows risk for safety of roads and walls and accounts breaks at the public communications and expenses at the management to reconstruction: more than 100 bridges were damaged or destroyed at the upper alluvial plain in the last 100 years. In second one case is the climate-geomorphological factor, in a high-altitude in an experimental basin of reduced size (6.6 km2; max altitude 3538 m a.s.l.) monitored since 1995 until the redundancy of the data itself, to explain the recrudescence of meteo-pluviometric intense events. The increase of instability processes also in the high altitude areas could be the answer to the effects of global warming. The monitoring results in the experimental basin allowed to appreciate by a high weather-climatic conditions of the last 20 years and the other as the secondary effects especially in relation the triggering of debris flows and rockfall. The study site lends itself to considerations on increasing the hazardous conditions in the Alps, mostly in built-up areas (torrential fan) that over the years have expanded with amplification of the risks related to potential phenomena of debris flow, landslides and floods. Landslides and floods are the result of very complex phenomena as they involve processes related to interaction atmosphere-soil-land and mainly concern the geology, hydrology and hydraulics of the soil and subsoil, the climate, the human settlement and cannot be treated separately, but they must be addressed by means of transverse and synergistic research. Improve knowledge of the processes is to understand which variables to monitor, track where and what accuracy and resolution in time and space to take to the study of natural hazards.