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  • Open access
  • 71 Reads
Evaluation of simple methodology for piezoelectric sensors protection
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The increasing frequency of extreme storm events have implications for the operation of sewer systems, storm water, flood control monitoring and tide level variations. So, it is necessary to accurate and continuous monitor water level in several environments. Moreover, those sensors must be ready to send data during extreme events. A very common water level sensor is the piezoelectric sensor. These sensors are widely used for water level monitoring. These sensors frequently work submerged in aggressive waters due to the presence of solid particles that can enter the sensor, biological fouling over the sensor surface and oxidation due to saltwater action. This work aimed to develop a simple methodology to protect the sensors for a long-time operation. Three sensors from the same manufacturer with equal specifications were used. The first sensor was used without protection, the second sensor was placed inside a flexible plastic bottle filled with water and the third sensor was placed inside a latex bag filled with water. Over 20,000 readings were recorded on a 3 m depth water column to verify reproducibility of readings with and without sensor protection. The results show that the 3 sensors had similar performance in a fixed position, with amplitudes below 1.5 cm and standard deviation with a value of 0.2 cm. Subsequently, measurements were made by varying the position of the sensors by 50 cm until reaching a depth of 300 cm. The values of the latex-protected sensor reproduced the exact values of the unprotected sensor, while the plastic bottle sensor showed greater variation, with differences of up to 10 cm from the reference sensor. This shows that simple actions costing less than € 2 can protect and extend the life of equipment worth over € 2,500 and still maintain quality measurements.

  • Open access
  • 113 Reads

Recent development dynamics of urban centres, resulting into a substantial increase in the impermeable surface, have forced the administrations to deal more frequently with problems linked to the inability of traditional urban drainage systems to manage rainwater in a sustainable and effective manner.

Several laws currently in force require compliance with the quantitative and qualitative limits to be discharged into watercourses but, in parallel with a "regulatory" approach, integrated strategies, in which sustainable technologies able to reduce the flows conveyed in the network and redevelop the territory come into play, are increasingly being developed.

It is therefore considered essential to change the planning approach or to modify the already consolidated urban contexts using sustainable drainage technologies to bring urban systems back to a configuration that is more similar to the one prior to intensive construction. A fundamental role in the implementation of this strategy is carried out by Sustainable Drainage Systems (SuDS), whose basic principle is the management of rainwater at source through the implementation of prevention, mitigation and treatment strategies.

This study, starting from a project proposal made by SMIA, IRIDRA, Studio Gioia Gibelli, Studio Idrogeotecnico and funded by PoliS-Lombardia, aims to assess the benefits deriving from the widespread application of sustainable drainage infrastructures in the Sesto Ulteriano industrial area through a comparison between a scenario that represents the current configuration of the drainage network and an ideal scenario in which different SuDS techniques have been implemented in the urban system (rain gardens, draining trenches and parking lots, floodable yards, cisterns-planters).

To this aim, therefore, the SWMM5 software was used, which allowed simulations of the behaviour of the drainage network in contexts without and with SuDS techniques after the construction of the synthetic series of precipitation and the urban drainage network model.

Although only event scale simulations have been conducted so far, the encouraging results, assessed in terms of reduction of the flow to be laminated through the implementation of SuDS, suggest that these systems can really contribute to mitigating the effects of flooding in urban areas.

  • Open access
  • 122 Reads
A comparison between conceptual and physically based models in predicting the hydrological behavior of green roofs

One of the consequences of the climate change is the increase in the occurrence and intensity of heavy rainfall events. This condition leads to more frequent and severe urban flooding because of the increasing stormflow volumes that exceed the sewers capacity. In order to mitigate the risk of flooding in urban areas, sustainable urban drainage strategies have been proposed, and among these the use of green roofs. The potential of green roofs to manage urban stormwater has largely been proved. In light of this, modeling the hydrological behavior of vegetated covers appears a crucial issue for urban planners, policymakers and developers so as to quantify stormwater management ability of the green infrastructures before retrofitting existing buildings or planning new settlements. To predict the hydrological performances of a green roofs, different models with different levels of complexity have been introduced by several authors. Among these, the SWMM model has been here selected due to its widespread use and demonstrated efficiency. It has been compared using a number of goodness of fit indices with a basic transfer function approach, the Nash model, typically used to simulate the hydrological behavior of natural river basins and not yet fully explored for what concerns its implementation in predicting the runoff production from green roof systems. The two models have been calibrated against hourly data of thirteen rainfall-runoff events observed at two experimental green roofs, differing for the composition of the drainage layer, located in southern Italy, in a typical Mediterranean climate. Although the lower complexity and input data requirements that characterizes the Nash model, it returns interesting performances. Finally, the existence of a relationship between the errors and the rainfall characteristics has emerged.

  • Open access
  • 77 Reads

The fifth evaluation report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) of the United Nations mentions that extreme rainfall might increase its intensity and frequency in most mid-latitude locations and tropical regions by the end of this century, as a consequence of the rise of the average global surface temperature. Human actions provoked global warming which manifests with an increase in extreme rainfall. These climatic conditions together with the urban development generated a scenario of growing concern for the managers of drainage systems. The objective of drainage networks is preventing the accumulation of rainwater on the surface. Under the new conditions of climate change, the urban drainage systems need to be adapted.

The following article describes a method for flood control by using a rehabilitation model. The method uses a genetic algorithm that iteratively calls the SWMM 5 hydraulic model to perform a hydraulic analysis to search solutions. The results consist of a Pareto front relating investment versus damage. The stakeholders might use this information to adopt the best solution.

This method includes a hydraulic control strategy by using a local head loss in the drainage network, allowing the upstream flow to be retained by decreasing the downstream concentration time. This head loss represents a control device in the beginning of some pipes that come out of storm tanks. As a case study, the method was applied in a section of the drainage network of the city of Bogotá.

  • Open access
  • 396 Reads
Retrofitting of road gutters with an infiltration-exfiltration system for stormwater control

The traditional approach of storm water management on collecting, conveying and discharging runoff is becoming impractical on the current growing urbanization scenario and altered precipitation patterns, with high intensity events being observed more frequently. The contaminants present on runoff after washing off surfaces are an important cause of rivers and streams pollution. To avoid saturation of the urban drainage system and improve water quality the currently strategies for storm water management acts on management water on its source and encouraging systems that also function on water treatment. These systems are often referred as SUDs (sustainable urban drainage systems), green infrastructures, BMPs (best management practices), LIDs (low impact developments). This approach is already mentioned on public policies on urban drainage and land use, specially by limiting the discharge and requiring detention or retention tanks.

Application of these strategies for stormwater control may be difficult, especially in fully developed urban areas. Retrofitting of such areas is usually more expensive and may be limited to few urban spaces. One of the more feasible and effective interventions is the change of traditional road, pavement and parking surfaces with permeable ones.

However, this change is limited by the need to find a trade-off between good infiltration performances and sufficient strength to traffic loads. That’s the reason for which this solution is often applied only to roads with low traffic loads.

An alternative is to limit the adaptations to road gutters, that are less stressed by dynamic loads. The use of an infiltration-exfiltration system as street gutters, consisting of a porous concrete surface with a gravel base, may achieve several goals. First, stormwater runoff to be discharged into the sewer network is reduced. Second, peaks of stormwater flow into the sewer network are reduced, due to the temporary storage inside the porous layers of the part of stormwater runoff that can’t be infiltrated. Third, the porous surface acts as filter, promoting load removal from runoff.

An infiltration-exfiltration system for road gutters is proposed. Test results from an experimental site are also presented. The system was installed on a 15 meters length gutter of a parking lot, with a catchment area of 400 square meters. A comparison with a traditional road gutter with the same dimensions was also performed, by simulation with a hydrologic-hydraulic numerical model.

  • Open access
  • 104 Reads
Checking Procedure of the Trieste (Italy) Submarine Pipeline by Transient Tests
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AcegasApsAmga SpA, of the Hera Group, manages the water systems of Padova and Trieste. Within the water supply system of Trieste, the submarine transmission main (TM) plays a crucial role. In fact it supplies not only the city of Trieste but also the Carsico plateau. Such an iron DN1330 pipe has a length of about 18 km and conveys 700 L/s with a steady-state pressure equal to 7 - 10 bars according to the elevation.

At present divers execute the inspection of the Trieste TM. With the aim of implementing a systematic inspection procedure, AcegasApsAmga SpA decided to proceed with a transient test-based technique (TTBT), which requires small pressure waves to be injected into the test pipe to detect anomalies. Because of the large diameter of the pipeline, the installed valves cannot be closed as fast as required to generate small amplitude sharp pressure waves, which allow precise defect localization. As a consequence, a small side valve has been installed at both the end sections of the pipeline to generate safe transients.

In this paper the first results of the executed transient tests are reported and discussed.

  • Open access
  • 106 Reads
Green Infrastructures in Stormwater Control and Treatment Strategies

Green infrastructures can provide multiple benefits and play an important role in cities’ resilience to extreme stormwater events caused by climate change. Additionally, these techniques can contribute to the protection of transport infrastructures, averting major environmental and economical adversities. Stormwater can be treated through several processes, some processes being more effective than others for specific contaminants. A review of some of the most commonly used GI for stormwater management in urban environments was carried out, with emphasis on their efficiency in reducing peak flow rates, runoff volumes and the following pollutants: total suspended solids, heavy metals, total phosphorus and total nitrogen. The GI studied were green roofs, bioretention systems, filter strips, vegetated swales and trenches. In addition to the advantages in the urban water cycle, benefits of amenity and ecosystem services of these GI have also been identified. The discussion of the results and the comparative analysis of GI performance were carried out taking advantage of a table that summarizes the range of percentages of GI efficiency obtained in the various studies for the different functions.