Monday, June 29, 2020

A practitioners’ view on the application of water and flood directives in Italy

This is the preprint of a chapter of the book: P. Turrini, A. Massarutto, M. Pertile and A. de Carli (eds.), Water Law, Policy and Economics in Italy: Between National Autonomy and EU Law Constraints, Springer (forthcoming 2021). In the chapter we talked about the application of the Water Framework Directive and the Flood directive in Italy, from the point of view of engineering, hydrology and hydraulics. It derives from our experiences in working in the directives' application in the last ten years and hope it could be a contribution for a better application for the next deadline, expected in 2022. The preprint is available through OSF preprints by clicking on the Figure below. 
The directives are a complex topic that has interplay with the organization and legislation of Italy. Here our Abstract: "The commonly called Water Framework Directive1 (WFD) and Flood Directive2 (FD) represent pivotal points for European water policies. They do not need any further introduction here since there are other contributions to this book that present them in detail. In this chapter, we briefly describe how they affect people working in Italy in water resources management, exploitation and protection of and from water bodies. In this contribution, we try to present the work needed to fulfil the directives generally, who did the work and with what responsibilities in past implementation cycles, and what was actually done in implementation cycle for both directives up to 2016. The result is a picture of the Italian water management system; a system not only defined by laws and norms, but also by habits and the way Institutions have developed during recent history through their interplay with growing technical knowledge, the implementation of policies, and the evolution of Italian society. This chapter is divided as follows: section 1 reports what has to be done to accomplish the directives generally; section 2 summarizes who performed the actions connected to the directives in past implementation cycles; section 3 and 4 report and discuss the Italy’s application of the directive; section 5 covers the role of science in the implementation of the directives; and, finally, section 6 contains some considerations on the main critical aspects and on the challenges the future application of the directives (2021- 2027) is going to face." 

Monday, June 8, 2020

Concentration time, if existent, is a statistical concept

Among the various times we use in describing the catchment, concentration time is one of them. It is referred, in the old textbooks, as the largest travel time of water parcels (i.e. statistically significant amount of water molecules that are though to move together) in a catchment. Travel time, in turn is the time a parcel of water employs to across the catchment from its injection (as rainfall) to its exit (as part of discharge). The Figure 1 below illustrate two parcels with different travel times, with parcel 1 arriving faster to the outlet, for being close to it.
The concept of concentration time gained its importance since the Mulvaney theory of "the rational method" reported, for instance,  in K. Beven book (2012). For giving a meaning to it, we can assume that,  if parcels are though to move with constant velocity in a catchment, then, once their distance from the outlet along the drainage directions (see the width function concept) is known,  travel times is obtained by dividing  that distance by the parcels’ velocity.
Rigon et al., 2016 gives a review of this concept in the framework of the geomorphological unit hydrograph based on the width function (or WFIUH). The oldest hydrologists would also remind a simplified version of the story, where, essentially the catchment is seen as a rectangular planar hillslope and the flow is though to be parallel as in Figure 2 below.
Parcels move in essentially rectilinear paths, with constant velocity. Parcels like the no  2 are on the divide and parcel like the no 1 very close to the outlet, that is in Figure 1 a sort of trench. In this case, varying the duration of precipitations, we obtain a hydrograph  which is a triangle or a trapeze. It can be demonstrated that when a rain of constant fixed intensity falls on this catchment, we obtain the maximum discharge possibile when its duration equals the parcels no2 travel time, the largest one. Continuing to argue about models, not about what happens in reality, it can be seen also that, from the point of view of the instantaneous unit hydrograph theory (IUH),  concentration time is the extension of the domain of definition of the IUH distribution function ($t_c$  in Figure 3). 
Unfortunately, most of IUHs do not have a finite domain but an infinite one, the simplest being probably the exponential IUH $$IUH(t;\lambda) = \frac{1}{\lambda} e^{-t/\lambda}$$ (see also Rigon et al., 2011). This implies that for most IUHs, the concentration time does not exist as a rigorous concept.   Besides, the dynamics of water parcels as depicted in simplified theories was completely screwed up by tracers experiments that have determined that the age of water in floods is very much larger than believed, and usually what we see in rivers and torrents is old water not the one just fallen during the last precipitation (though undoubtedly was the rainfall to trigger it). 
The concept of concentration time,  resists in operational hydrology because there is a certain evidence that floods are generated by precipitations of increasing duration with increasing basins area,  and this correlates with the idea of concentration time exposed above for the planar hillslope.  However,  in complex catchments, it cannot be something different from a statistical concept. We already mentioned briefly that a catchment is not a huge planar hillslope and that water parcels move in complicate ways through it.  Moreover, the expansion of the river networks during storms (e.g. Durighetto et al.,  2020)  implies the necessity to add a further dynamic to concentration times perceptual model.

After all the above considerations, if something like the concentration time exists, it is a characteristic statistical time which identified the duration of the rainfalls that generate the  largest peak discharges. It should depend on catchment size and topology (besides on the rainfall). We believe that it increases with catchment size, but being any catchment different, it remains a slippery concept. A solid statistical study would be required to clarify, once for all, the issue.


Friday, June 5, 2020

The Zero Notebook for GEOframe components

There is the necessity to properly document the code we developed.  The state-of-art is that many Jupyter Notebooks were written to document may of the actions requested for running them. These Notebooks are made available when to sample projects are downloaded through their osf (which stands for Open Science Framework)  repository. This is probably a temporary solution which will be unified once forever in Github. However, these notebooks, see for instance the case of the Winter School  ofter are missing of an overall description which conveys all the information regarding the Component, part of which, for some component, was written in a custom LaTeX format and made available through the GEOframe blog. To make some order, I am proposing here to put the basic information in a Notebook, whose template you can find by clicking on the Figure below.
The notebook is a work-in-progress and who wants to give suggestions is welcomed. There are other two scopes for this Notebook Zero,  one is that the materials it contains can serve for a chapter in a Thesis where the component is described for its informatics and its content, with minimal modifications;  the other,  that it could be used for a possible submission of the component code to JOSS.  The latter goal would require some improvement in our GEOframe component Github site though in order to have tagged version of the software, a clean way to submit issues (a issue tracker), a set of unit test for the continuous integration of the components. We made a lot of progresses in recent years, but we are not yet there, really operational. A companion issue is where we do upload the .sim files and the data corresponding to tagged version of the components. So far they were assembled together in someone computer, compiled, eventually uploaded to Zenodo (or OSF) and made public. Streamlining the whole process in Github would be probably convenient. Going even more general, there is an installing problem of the OMS/GEOframe stuff. So far we replicated the jars (i.e. the Java executable) several times, each time we needed a a new project. It is time, I guess, to have the executable in a unique place, at Computer or User level, while the directories with data etc (so fare recognised as the OMS projects), freely replicable for different simulations, but without having to get along any time with copies of the executables.

Fair use: It is easy to make custom versions of our software components and embed it into some "proprietary platform" or "commercial" product.  We do not prohibit this use. However, it should be reminded that GPL 3.0 of the component would require a redistribution of modifications of our codes. 
Besides, even its use would require a note, somewhat visible that makes clear the product is powered by GEOframe. So we expect that fair use of our software in some enterprise would be acknowledged by: "Powered by GEOframe and OMS3".