For our study case, if we consider the average NSI and the network conformation in 2006 (Fig. 13a), and an event with a 200 year return period versus an event with a 3 year return period, we register a decrease of the NSI of about 20 min. If we compare the average response of the 2006 network to an event having a 3 year return period, respect to the average response of the 1954 network to the same event (Fig. 13b), we have an advance of about 20 min. It appears, therefore, that the loss of storage

capacity might have, on the area response, the same effect of a drastic (200-year return period VS 3-year return period) increasing in the intensity of the rainfall. This result highlights a situation already faced in other areas. Changnon and Demissie (1996), for example, underlined

how drainage PD0332991 changes in the last 50 years explained more of the increasing trend in annual flows (70–72%) than precipitation values. Fig. 13b shows how the changes in storage capacity have a greater effect for events with a shorter return period: the NSI changes mostly for MDV3100 the events with a return period of 3 year. This is in line with older studies from e.g. Hollis (1975) that already underlined how the effect of urbanization declines in relative terms as flood recurrence interval increase, and that small floods may be drastically increased by urbanization. In Italy, the study of Camorani et al. (2005), using a hydrological model, underlined how the hydrologic response of a reclamation area was more pronounced for less severe rainfall events.

Another study by Brath et al. (2006) indicates that the sensitivity of the floods regime to land use change decreases for increasing return Pregnenolone periods, and that the events with the shorter return period are more influenced by land-use changes. The NSI, as well, underlines how the changes in the network storage capacity tend to increase the rapidity of the response in case of events having a lower recurrence interval. From Fig. 13b, it appears also that the loss of storage capacity from 1954 to 2006 has greater effects on events that implied in the past a higher delay in the area response (Sym18): for the most frequent events (return period of 3 years), we have an anticipation of about 1 h and 10 min in 2006, respect 1954. This result suggests a careful land management planning, underlining how conditions that are not necessarily associated with the worst case scenario, can drastically change and seriously constrain the functionality of the reclamation system for rather frequent rainfall events. This work proposed an analysis of changes in the channel network density and storage capacity within a reclamation area in the Veneto floodplain (Italy).