**5.4 Sinkholes**

Catastrophic collapse features, called sinkholes in the international literature, are a type of instability that affects the surface of the soil as sudden collapses occur over a short period of time (6–24 hours). These differ from the normal karst forms because of their suddenness and conditions of initiation and development. Sinkholes *Introduction to the Sedimentary Geology, Genesis, and Evolution of the Pontine Plain in Relation… DOI: http://dx.doi.org/10.5772/intechopen.111683*

#### **Figure 16.**

*Lazio seismic hazard map (from INGV https://www.google.com/search?q=Mappa+della+pericolosit%C3%A0+s ismica+del+Lazio&tbm=isch&chips=q:mappa+della+pericolosit%C3%A0+sismica+del+lazio,online\_chips:zona zione+sismica).*

can be classified according to their genesis, their interaction with the topographical surface, and the hydrogeological structure of the area in which they form. Their impact on the landscape, and even more on the populations in the areas most at risk, is very high, as demonstrated by the numerous bibliographies available, which often describe huge economic losses and, in some cases, losses of human life, although cases of this type have not yet occurred in Italy. If we also consider the fact that sinkholes are neither random nor extemporaneous phenomena and that their localization, morphometry, and evolutionary typology, as well as their temporal recurrence, clearly demonstrate that they occur in specific geological conditions (sinkhole-prone areas) and in the presence of various geological factors (sinkhole-triggering factors), it is clear that, even in areas such as Italy, it is necessary to reach a profound understanding of the development and triggering modalities these phenomena, even more profoundly if we consider that many of the sinkholes that occur in the susceptible areas of Italy have some peculiar characteristics that substantially differentiate them


*\* Terms used to describe the sinkholes, the main genetic processes, the sedimentological setting and the morphology (partly taken from Gunn, 2004).*

#### **Table 2.**

*Terminology of sinkhole.*

from those studied in the rest of the world [20]. The terminology, which is vast, was schematically classified in **Table 2** [21]. **Figures 17** and **18** illustrate the diverse types and evolutions of sinkholes [20]. **Figure 19** shows the typical sinkhole typology of the Pontine Plain. Doganella's cavity filled with water in a short amount of time. However, the sinkhole of Doganella di Ninfa did not change very much during the few months after its formation. The Doganella chasm appeared in December 2003 [21]. Additional details on all sinkholes in the Piana Pontina are available in several sources (**Figure 20**) [22–24].

#### **5.5 Drinking water quality**

Water analyses from the Agenzia Regionale per la Protezione dell'Ambiente del Lazio (ARPA) broadly provided data (shown in **Table 3**) of the turbidity, microbiology, arsenic content, and fluoride content of the drinking water of villages within the Latina province including Aprilia, Sermoneta, Latina, Cisterna di Latina, and others. These waters are extremely hazardous. As shown by these data, the relevant institutions must take major control of these waters, especially given the concern about contaminants that would be highly dangerous if consumed in drinking water. The hazards of these waters have been confirmed by the Azienda Sanitaria Locale (ASL). In fact, the contamination revealed by ARPA and ASL indicates that the sampling locations are associated with high rates of cancers. The results indicate a need to conduct more in-depth epidemiological studies (resident studies) by initiating a monitoring campaign to estimate the levels of arsenic and fluorine in the resident

*Introduction to the Sedimentary Geology, Genesis, and Evolution of the Pontine Plain in Relation… DOI: http://dx.doi.org/10.5772/intechopen.111683*

#### **Figure 17.**

*Classification of sinkholes based on the literature and field observations of Italian case studies. (a) Anthropogenic sinkhole; (b) solution doline/sinkhole; (c) cave collapse; (d) cover collapse; (e) cover subsidence; (f) rock subsidence; and (g) piping sinkhole [20].*

#### **Figure 18.**

*Schematic of sinkhole evolution. Modified from [20].*

**Figure 19.** *Typical sinkhole of the pontine plain. Dimension 3x3 m.*

#### **Figure 20.**

*Areas in the pontine plain at risk of catastrophic sinking (based on history): (1) Doganella–Via Ninfina (Comuni di Sermoneta e cisterna di Latina). (2) Contrada Ciocco–Contrada Talci, San Michele. (3) Gricilli–Mezzaluna– Tenuta Isabella–Cotarda.*

*Introduction to the Sedimentary Geology, Genesis, and Evolution of the Pontine Plain in Relation… DOI: http://dx.doi.org/10.5772/intechopen.111683*


#### **Table 3.**

*Concentrations of harmful elements in the drinking water of Latina villages.*

population. Survey results indicate plausible health effects in the resident populations of the municipalities of Rome and the Latium provinces, which have high arsenic levels. The effects refer to chronic exposures through the past decades, during which arsenic levels could have been higher than the current levels. The results indicate the need for continuous monitoring of water arsenic levels and public health interventions to ensure compliance with the limits established by the legislation currently in force (directive 98/83/EC, As <10 μg/L).
