**5. Conclusions**

The multidisciplinary study carried out in the SE area of Ceggia (VE), in the eastern part of the Venetian Plain, provides numerous details about the high hydraulic instability that a ffected the area during the times, with the alternation of stable phases (land inhabited and cultivated) with unstable phases (presence of marshes).

This condition probably defined the fertility of the soils and the consequent occupation of the area for its cultivation, despite the dependence from continuous works to force and regulate the flow of water. On the other hand, it is clear that only with the beginning of modern times, with new technologies, the managemen<sup>t</sup> of the hydraulic problems have become fully solvable. It can be easily understood, however, thanks to the data collected here, that in more ancient times, until the Roman age, the managemen<sup>t</sup> of this instability had to be not simple and, in any case, temporary.

The survey conducted has made it possible to identify the timing of landscape transformation and to outline, albeit still with some interpretative uncertainty, the di fferent physiognomies that the sector has been acquiring.

Starting from aerial images, it was possible to detect ancient buried traces, and thanks to the comparison with cartographic documents, ancient sources, and data acquired in the field, it was possible to formulate a hypothetical interpretation of the evidence, as well as the transformations that have a ffected an environment poised between land and water.

It has been highlighted that the periods of hydraulic instability were followed by periods of relative stability conditioned by the incessant anthropic intervention of regulation and maintenance of the water system. Moreover, it has been noted that in these sectors, as climatic-environmental conditions vary and in the absence of water resource management, it is the natural element that has the upper hand.

In relation to the focus of our investigation, the reconstruction of the geomorphic evolution of the study area highlights the existence of a stable alluvial plain in the 2nd century BC, when most probably the ditches were dug, as part of field systems possibly in relation with the construction of the *Via Annia* and with the occupation of the sector highlighted by a series of productive-residential settlements.

In post-Roman times, as also demonstrated by the cartography, the alluvial plain was covered by wetlands with the sedimentation of a thin veneer of organic-rich swamp deposits. Higher subsidence in the compressible soft clays and peat lowered the topographic surface along the post-LGM incised valley, allowing larger accommodation space and better preservation of the swamp deposits.

After land reclamation and areal erosion by modern agriculture, the Roman infrastructures became again visible at the surface. Locally, the remnants of the swamp persisted, producing dark-tone soil marks in aerial photographs as well as highlighting the course of low-energy, minor channels of the post-Roman swamps.

As regards the hydraulic-agricultural arrangemen<sup>t</sup> visible in the trace, the data collected so far would sugges<sup>t</sup> a Roman dating. However, there are still several doubts linked both to the modulus of this arrangement, which cannot be traced back to Roman measurements and to the large dimensions of the main axes of the ancient arrangement. Furthermore, there is some discussion about the imperfect orthogonality of the alignments and the different inclination they present with respect to the presumed limits of the centuriation south of *Opitergium*.

Although the alignments of Ceggia can be traced in shape and width to other Roman evidence brought to light in Veneto, it should be noted that most of these comparisons refer to embankments not organized in the system. Even the most stringent comparison, which could be established with the so-called "via di Villadose", considered the *decumanus maximus* of the centuriationn of Adria, does not help for the moment to resolve the interpretative doubts, to which only further investigations can perhaps provide answers.

**Author Contributions:** A.V. contributes to the archaeological research, multitemporal analysis of aerial photos and cartography, R.D. contributes to the geophysical data acquisition, processing, and interpretation, P.M. contributes to geomorphological and geoarchaeological analysis, coring, and interpretation of the alluvial stratigraphy. All authors contributed to the conceptualization and writing of the paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** This paper is a part of the Ph.D. thesis of A.V. supervised by Guido Rosada (University of Padova) and Luisa Migliorati (University of Rome La Sapienza). The authors are grateful to the IGM for authorization to publish the image of Fg.39-Fight GAI 1954 str.14, n.182 (authorization number 7054, date: 27/04/2020) and to Luigi Vacilotto, Silvia Favaro and Guglielmo Strapazzon for their support during the field acquisitions. The use of the ReVen images follows the rules of "Italian Open Data License 2.0" (IODL 2.0 http://www.dati.gov.it/iodl/2.0/), which authorizes the free publication of the aerial photographs after quoting the source: "Regione del Veneto-L.R. n. 28/76 Formazione della Carta Tecnica Regionale".

**Conflicts of Interest:** The authors declare no conflict of interest.
