# Geohydroology of a Reference Mediterranean Catchment (Cilento UNESCO Geopark, Southern Italy)
## 4 Discussion  
The paper focused on the analysis of the Mediterranean reference Ciciriello catchment in terms of geology, geomorphometry and hydrology to derive a geo-hydrological perceptual model of the experimental catchment. The studied catchment was characterized by different geo-structural and morphological assets between the right and left side of the catchment, also due to the presence of landslides on the left side, as confirmed during field surveys. From the TPI map, we derived that the reference catchment was composed of a prevalence of ridge or summit (33%), 25% of the catchment was incised stream and riparian corridor and 15.4% and 10% were respectively upper slopes and U-shaped (or headquarters) valleys. The drainage network and the riparian corridor were at 450-550 m asl while, up to 650 m asl we identified hillslope with a gentle slope gradient. At elevations larger than 650 m asl we identified the hillslope with a steeper slope gradient. A higher number of first-order streams was observed in the catchment, which pointed towards terrain complexity and the compact nature of the bedrock lithology. The catchment was characterized by potential wet areas with WI values from 5 to 8 indicating a sub-surface flow mechanism localized in the convergent-concave areas and in the hollow land unit. The streamline network was well identified with the highest WI values up to 8. The authors classified the values ranging from 4 to 5 as a parallel flow or Hortonianerland flow occurring in a linear land unit as open slope or hillslopes. The WI less than 4 was localized in the permeable convex landforms (as ridge or summit) where the deep percolation dominantly occurs. The geomorphometric analysis seemed to highlight the different geologic characteristics of the two sides of the catchment. In particular, the TPI map revealed the difference between the left and the right side of the catchment with a higher presence of hollows and hillslopes on the left side than the right side. These differences were further confirmed by the slope map analysis where the higher slope gradient was on the right valley characterized by very incised stream beds, while lower slope gradients were on the left valley of the catchment, where landslides occur. The presence of a large number of streams in the left valley indicates that the topography is still undergoing erosion and at the same time, the lower number of streams on the right indicates a mature topography. These results are also linked to the structural asset of the bedrock that is characterized by dip slope layers on the left valley where a higher presence of landslides than the right valley was verified in the field. The analyses of the events--achieved by comparison of the hydro-chemograph pattern, the daily EC-Q chart of [8] and the hysteretic behavior--to understand the geo-hydroologic behavior of the reference catchment highlighted the occurrence of two types of events: the ordinary and the affected events (Table 3). The ordinary events were identified if the hydro-chemograph pattern respected the well-known Q-EC inverse power law. This condition was reflected in the daily chart for the three types of runoff mechanisms, if the data events fell under the characteristic curves. When this condition was not met, the data fell outside the fields of the chart, and the Q-EC pattern did not respect the inverse relation, the event was defined as affected. The presence of affected events highlighted the limit of the daily chart to represent certain physical mechanisms as more identifiable at high frequency analysis. In Table 1, the event types are summarized. The ordinary events were classified considering their hydrologic pattern into: compound events, occurring during the rainy period and for which it was impossible to isolate a single peak event; sub-events, occurring within a rainy period and for which it was possible to identify one isolated peak; and pure ordinary events, for which it was possible to identify an isolated peak.