Abstract
Pluvial floods occur when heavy rainstorms cause the surcharge of the sewer network drainage, representing one of the most impacting natural hazard in urban watersheds. Pluvial flood hazard is usually assessed considering the effect of annual maxima rainfall of short duration, comparable with the typical concentration times of small urban watersheds. However, short duration annual maxima can be affected by an error of underestimation due to the time resolution as well as the aggregation time of the rainfall time series. This study aims at determining the impact of rainfall data aggregation on pluvial flood hazard assessment. Tuscany region (Central Italy) is selected as a case study to perform the assessment of the annual maxima rainfall underestimation error, since the entire region has the same temporal aggregation of rainfall data. Pluvial flood hazard is then evaluated for an urban watershed in the city of Florence (Tuscany) comparing the results obtained using observed (uncorrected) and corrected annual maxima rainfall as meteorological forcing. The results show how the design of rainfall events with a duration of 30 min or shorter is significantly affected by the temporal aggregation, highlighting the importance of correcting annual maxima rainfall for a proper pluvial flood hazard evaluation.
Highlights
Dense urban development is causing major difficulties worldwide to cope with sudden and intense rainfall events of short durations
This section follows the same scheme as the case study section and it is composed of two parts
Hydrological Results The underestimation of the annual maxima rainfall with a duration d depends on the temporal aggregation ta of the time series
Summary
Dense urban development is causing major difficulties worldwide to cope with sudden and intense rainfall events of short durations. These kinds of events cause the surcharge of the sewer network overcoming its drainage capacity (i.e., pluvial flooding [1,2]). Climate change is expected to exacerbate weather-related hazards, increasing the number and frequency of extreme rainfall events that can cause urban pluvial flood events [3,4,5]. The effective analysis of pluvial flood hazard (i.e., quantitatively defining rainfall events and their flood impact in a spatially explicit manner [11]) requires an accurate simulation of precipitation events with their corresponding frequencies [12]. Pluvial flood analysis is usually carried out using hydrologic and hydraulic models in which the precipitation, usually of sub-hourly duration, is among the main influencing factors [13,14,15]
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