Torrential rains and downpours devastated Europe over the course of 2014. Recent studies demonstrate that these kinds of phenomena may double by 2050, for an estimated 23 billion euro in collateral damages. Prevention is of paramount importance in order to limit the social costs of these events, and must be planned in a strategic manner in order to avoid hydrogeological instability .

From a climatic point of view, 2014 was an annus horribilis for Europe: torrential rains, thunderstorms and downpours cost numerous human lives and caused damage in the millions of euro in France, Spain, Italy, Germany, Austria, Romania, Hungary, Serbia, Croatia and the Czech Republic.
This atmospheric turbulence cannot be viewed as a rare event, but as an expression of trends already underway and due to climate change, which in densely populated and heavily industrialized territories – where human activity has significantly modified the original geographic terrain – all too often produces situations of hydrogeological instability.

This fear was confirmed in a recent study conducted on natural climate change.
Read the article:Science – David M. Romps et al. – Projected increase in lightning strikes in the United States due to global warming
Coordinated by researchers at the Institute for Environmental Studies in Amsterdam, a study entitled “Increasing stress on disaster-risk finance due to large floods” conducted the first full evaluation of torrential rain risk in Europe, providing forecasts as far ahead as 2050. The study underlines several aspects in particular: the profound interdependence of European fluvial systems, and the need to intervene in order to strengthen protection measures in all watersheds, thereby reducing future costs. Prevention, therefore, is the primary path to follow in order to reduce hydrogeological instability.
These interventions must be organized taking into account a transnational plan to reduce risks, and correctly calibrated in each nation.
This assessment, based on objective technical criteria (including environment, territorial safety, and engineering) must make it possible to identify clear priorities, evaluate alternative designs and select buildable works upon which to focus available resources.
An innovative approach is the best way to proceed
The kinds of interventions useful for reducing hydrogeological instability can be subdivided into three macro-categories: those designed to mitigate flood risk; those designed to mitigate landslide risk; and those designed for urban sewage treatment and river and lake clean up operations.

Multi-criteria approach is based on the “weighting method” for the reduction of various different target functions (to be minimized or maximized) into one single function.
In order to assign these coefficients, which will be allocated to the various objectives, we’ll apply the “Analytical Hierarchy Process,” which defines weights to be used in the analysis, based on their relative importance, both of the areas and of the targets, provided by institutional (and non-institutional) decision makers, who may even belong to categories defined by conflicting interests.
The next step is an analysis based on “compromise programming”, aimed to identify those design solutions closest to ideal, which may not necessarily belong in the group of feasible solutions. This methodology allows the selection of projects on the basis of an assessment of the inherent risk.
Defining criteria
The criteria upon which decision making processes can be structured on a territorial basis belong to areas that can be quite different from one another: design (construction time and risks); economics (cost and extent of compensation for local authorities); environment (the presence of protected areas, areas with special qualities, realization of ancillary infrastructures, waste, etc.); as well as social; political; and administrative.
Defining these criteria in detail for each application area represents the first and most important activity to be addressed.
Evaluation of analysis results
The evaluation process should involve decision makers and all stakeholders.
This approach makes it possible to create consensus for design choices, as well as build an evaluation framework within which evaluation criteria and values are shared and appropriately weighted and harmonized.
In this manner the methodology can define ratings for buildable projects, as well as identify design solutions closest to ideal, creating a ranking for a definitive choice for the projects to be realized based on real, actual economic resources.
A working hypothesis
Initially, the methodology described here above could be applied to a test case, and subsequently extended to all of Italy’s national river basin districts in order to define priority action areas for planned interventions.
An inclusive approach and shared construction of an evaluation framework (working together to define objectives, criteria and relative importance) would make it possible to overcome the kinds of impasses that were created in the past due to the presence of multiple and often conflicting interests in play within the river basin area .