Probabilistic analysis of spills from stormwater detention facilities

Abstract

Stormwater detention facilities are important tools for flood control in modern urban drainage systems, since they reduce uncontrolled discharges into receiving water bodies and improve the efficiency of stormwater treatment plants. In their modelling it is important to limit the number and the amount of spills to ensure the maximum efficiency of the storage capacity. In this paper, the overflow probability distribution function from a stormwater detention facility is derived; the possibility of pre-filling of the storage capacity from previous runoff events, that can strongly influence spilled volumes, is considered. Effects of the control variables and of two different regulation rules on resulting expressions are investigated and discussed. Finally, an application to a case study is presented.

Performance of Green Roofs for Rainwater Control

“…Bacchi et al (2008) tested that for most Italian basins the Weibull probability distribution function fits the frequency distribution of meteorological input variables better than the exponential probability distribution function; however, its use involves a considerable complication in the equation's integration. Becciu and Raimondi (2014) verified that the double-exponential probability distribution function complies with the frequency distribution of observed data for the main rainfall characteristic parameters; such distribution may be easily integrated but derived expressions are quite complex. Moreover, its application to a case study highlighted the fact that using the double-exponential probability distribution function does not improve so much the accuracy of results and that the bias due to the use of the exponential probability distribution function is negligible when compared to the simplicity of equations integration.…”

“…Mean μ, standard deviation σ and a coefficient of variation V of the three hydrologic parameters used in the modeling rainfall depth h, rainfall duration θ and interevent time d have been reported in Table 1. The hypothesis of characteristic rainfall variables as exponentially distributed, while well suited for rainfall duration, is not perfectly respected for rainfall depth and interevent time, however the bias on results due to its use can be considered negligible, as discussed and tested by Becciu and Raimondi (2014). Table 2 contains the correlation coefficients with the three hydrological parameters.…”

Probabilistic modeling of the efficiency of a stormwater detention facility

“…While correlation between rainfall depth and interevent time and rainfall duration and interevent time is quite low, there is a strong correlation between rainfall depth and rainfall duration. As discussed by Becciu and Raimondi [23], this can lead to a deviation of results of derived formulas from those from the continuous simulation. However, since the assumption that the stormwater detention facility is emptied only after the end of each runoff event has been considered, the dependence of the probability distribution function of spilled volumes from rainfall duration is excluded, and the correlation between rainfall depth and duration does not influence the results.…”

Vegetation Survival in Green Roofs without Irrigation

“…Raimondi and Becciu have evaluated green roofs performances for stormwater control estimating the runoff probability distribution function by mean of an analytical probabilistic approach. This kind of methodology, first proposed by [18] has been applied by different authors also to SUDS: Rain Water Harvesting Systems [19] infiltration trenches [20], permeable pavements [21] bioretention systems [13], green roofs [13,20,22], stormwater detention facilities [23]. Generally, these studies consider a couple of rainfall events at time and neglect or only partially consider the possibility that storage volume is not completely empty at the beginning of considered rainfall.…”