**4. Conclusions**

Flood events (major and minor) are inevitable, regardless of the amount of existing protection. Flood protection is critical, ye<sup>t</sup> the financial cost of maintaining high levels of protection can prove rather excessive. In major flood events, failures occur, often at different locations each time depending on the spatial distribution and evolution of the phenomenon. However, it is possible to take into account the parameters that highlight the weaknesses and the problematic or insufficient flood protection design so that rational and reliable alternative proposals and solutions emerge.

From the correlations and analyses of the data in this study, it was derived that an important element for the spatial determination of the new measures is the infrastructure already developed for flood protection. The study showed that, despite the existence of multiple structural measures/work, many of them show poor efficiency, as shown by the high rate of repeated maintenance and its cost.

The methodology followed in this study was based on the results of the performance of existing flood protection measures, their characteristics, and their spatial correlation. The evaluation of structural measures by assessing their vulnerability via their yearly maintenance implemented the economic loss and financial impact that flooding events might have on infrastructure. The new measures should be related to the cost of construction and maintenance each time, applying the rule of cost–benefit [10] and life cycle analysis, and infrastructure that costs more to maintain should be replaced.

**Author Contributions:** Conceptualization, E.T.; methodology, E.T., C.S. and A.C.; software, E.T., C.S. and A.C.; validation, E.T., C.S. and A.C.; formal analysis, E.T., C.S. and A.C.; investigation, E.T., C.S. and A.C.; resources, E.T., C.S. and A.C.; data curation, E.T., C.S. and A.C.; writing—original draft preparation, E.T.; writing—review and editing, E.T. and C.S.; visualization, E.T. and C.S.; supervision, E.T. and C.S.; project administration, E.T.; funding acquisition, E.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the INTERREG V-A European Territorial Cooperation Program "Greece-Bulgaria 2014–2020 Flood Protection—Cross Border Planning and Infrastructure Measures for Flood Protection".

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data, models, and code that support the findings of this study are available from the corresponding author upon reasonable request.

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