1,721,013 research outputs found
On the efficiency of stormwater detention tanks in pollutant removal
Full text linkIn the design of a stormwater detention tank is important to guarantee a sufficient retention time for the sedimentation of suspended solids, the biological uptake of nutrients and the die-off of bacteria carried in rainwaters. Long retention times increase the capacity of pollutant removal, but also the possibility of spills in downstream receivers and the risk of environmental pollution. In this paper, an analytical probabilistic approach, to estimate the probability distribution function of the average retention time and the efficiency in pollutant removal of stormwater tanks has been proposed. The possibility of water mixing from consecutive runoff events and storage carryover due to successive rainfall events has been considered. The method has been applied to a case study in Milano, Italy
Modelli Probabilistici Regionali per la valutazione delle Piene in Sardegna - Rapporto 1987 Gruppo Nazionale Difesa Catastrofi Idrogeologiche (GNDCI)
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Functional feasibility in optimal evaluation of water distribution network performances
Full text linkThe traditional approach for the optimization of water distribution networks (WDNs) does
not always lead to consistent solutions from an operational point of view. The latest optimization
algorithms identify solutions that are “the best solutions” in mathematical terms but that can be
less than robust against changes in operating conditions, resulting in the worst case in hydraulically
infeasible configurations. Thus, this paper aims to provide a methodology that can synthesize the
network performance capabilities under the change in operating conditions with two convergent
strategies. The first consists of the implementation of new performance indices (PIs), the demand
deficit and the pressure range, and the evaluation of their ability to criticality highlight in operating
conditions. The second is the introduction of a new approach to weight the infeasible solutions in the
final result, which are those inconsistent with the real hydraulic network performances. The analysis
shows that the use of these new indices makes it easier to understand the behavior of the network
and to identify any weaknesses. This is true if these indices consider the hydraulically inconsistent
solutions that may arise from the simulations of different operation conditions; otherwise, results that
poorly represent the real behavior of the network would be obtained
A probabilistic approach to stormwater runoff control through permeable pavements beneath urban trees
Full text link: One of the most current and urgent challenges is making cities sustainable and resilient to climate change. From this perspective, Nature-Based Solutions (NBSs) are well-recognized strategies for stormwater control and water cycle restoration. Urban trees are an example of NBS. However, the high degree of soil sealing typically found in urban environments limits natural processes such as infiltration and hinders the water and nutrient supply for proper root development, which weakens tree stability. Permeable pavements at the base of urban trees, on the one hand, facilitate infiltration, which helps runoff control, and on the other hand, improve stormwater retention and soil humidity, which enhance root feeding. This paper proposes an analytical-probabilistic approach to estimate the contribution of permeable pavements to stormwater management. The equations developed in this study relate the runoff probability to the storage volume, the infiltration rate into the underlying soil, and the average values of the hydrological variables in the input. The model allows us to select different runoff thresholds and considers the possibility that residual volume from previous rainfall events prefills the storage capacity. An application to a case study in Sao Paulo (Brazil) has been presented. It investigates the influence of the different parameters used in the model on the results. The comparison of the outcomes obtained using the developed equations with those obtained from the continuous simulation of measured data confirmed the effectiveness of the proposed analytical-probabilistic approach and the suitability of using permeable pavements at the base of urban trees for improving stormwater retention
Semi-probabilistic design of rainwater tanks: a case study in Northern Italy
Full text linkThe paper proposes a semi-probabilistic approach for the design of rainwater tanks. In particular, the cumulative distribution function of the active storage is derived as a function of rainfall moments. The model is validated through continuous simulation of the hydraulic behaviour of a hypothetical rainwater tank located in Milan (North Italy) using as input a series of rainfall records.</p
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