(Prof. Francesco Ballio, Politecnico di Milano)
“How many years can a mountain exist – before it is washed to the sea?”. This beautiful verse of Bob Dylan, taken literally, captures the essence of what we call hydrogeological risk: the territory evolution is a natural and inevitable process: it is only a matter of time. How much time?They are very long-term processes, “geologic time” as they say: that’s why we are not worried about that. But, at the detail level there can be significant evolutions even in shorter periods, ranging from a few hours to hundreds of years: a piece of slope collapse, the water floods lands that are normally dry, a river changes its course, a level ground falls or rises gradually.
More than we had imagined in the past, we are realizing that our strategies to mitigate hydrogeological risk must be able to adapt to changes: the territory will change despite of our actions and, at times, because of them; but also changes in anthropogenic pressures, our desire to use the land; and, in recent years, climate changes, that are changing the characteristics of the natural forcings. In addition to traditional defense works, inflexible by nature, it is important to increase the range of solutions by giving more importance to territorial planning, planning and emergency management, the design of structures and infrastructure less vulnerable to flooding. These actions are typically much more adaptive to changes in the system; they do not necessarily prevent the flood fulfillment but, at least, they can mitigate its effects, and, above all, avoid the loss of lives.
What is the role of technology in this? It always provides the tools and infrastructure for environmental monitoring, an essential basis for the understanding and control of the territory and of the processes that affect them. The development of the last decades allows us to measure the force and the effects in real time, providing evolutionary scenarios used for the dynamic risk management, supporting decisions in an emergency. These capabilities set new challenges in mitigating risks and require a more complex approach than the passive protection provided by a bank; in return, the technology typically requires lower investment while offering excellent adaptability to climate , territorial and social changes.
Conclusion: there are no simple answers to complex problems such as those posed by natural hazards. Or to say it in Bob Dylan style , “the answer is blowing in the wind.” Catch it is not easy.