Sandro passed away last sunday for an heart attack. He was 76. As many knows, I due to him my being here in this field.

After my master in Physics I had a grant for working with him to "Statistical Models of the Quality of the Atmosphere of Venice Lagoon". Apparently far from Hydrology. But not in the mind of Sandro who looked at the diffusion processes from a geometrical point of view. He believed, after reading Mandelbrot works, that diffusion patterns could be understood better with fractal geometry. However, to understand these patterns we had to visualise them: and what better than rivers networks ? In fact, river networks could have been thought, in his view, as a "reverse diffusion" pattern from which we could learn a lot. From diffusion patterns therefore we moved to study hydro-geomorphology, and published together with Andrea Rinaldo the paper: A note on fractal channel networks. Others arrived a little before us on the subject (e.g. Tarboton et al., 1988, and La Barbera and Rosso, 1989) but Sandro path was quite independent, and the "discover" that the flow-path distances (i.e. the width function) have a multifractal statistical structure was ours.

He was always intrigued with geometry being the inner explanation of many phenomena and therefore his interested in the geomorphic unit hydrograph (Rodriguez-Iturbe and Valdes, 1979, Gupta et al., 1980) was natural. He saw in it both the mathematical way to fit geometry into equations, and as a theory suitable to generalisations for coupling water flow and nutrients transport (and diffusion). His work on the Mass Response Function with Andrea Rinaldo (Rinaldo et al,1988) was decades in advance with respect to the interest that eventually was raised on the topic. I believe that also Geomorphological dispersion was quite an achievement that can be listed in the "gemoetrical" effort. That work reflected the idea that, at catchment scale, geometry is as much or more important than flow dynamics to produce the form of the hydrograph.

He was a man of innumerables ideas and initiatives. Always in advance of times (maybe too in advance). The School of Environmental Dynamics at IVSLA founded with Andrea Rinaldo was the field where many of us met with science not simply with hydrology. Any edition had an eye to new insights and paradigms (the recent editions were organized by his son Marco, and maintain the same standards and vision). How much I miss those times!

In his effort to promote modelling, he around the end of the eighties organized a "modelling connection" among environmental scientists, hydrologist , geophysicists, economists, urban planners. The most exciting guys of the Universities of Venice who met for talking about quantitative modeling.

Some colleagues choose the particulars or the details of a discipline: he chose to look at the whole ! Ideas, ideas, ideas. That he was.

As everybody can realize, my recent work has been strongly influenced by working with him. What else was building JGrass, if not giving body to Sandro's vision about processes representation and the idea that spatial explicit modeling was necessary for any environmental problem? What else is my commitment with modeling frameworks like OMS3? What else is my recent involvement with thermodynamics?

He used to say: "Models are wrong ? (Sbaiemo coi modei ?) We do mistake by doing models. (Sbaiemo.) But let's imagine without! (Ma figuresemose sensa!). We should then rely just on qualitative arguments, of ignorant people, based on unformalised belief ?"

Sandro I'll miss you.

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