Propagation of precipitation measurement biases into the hydraulic modelling of urban drainage systems – A case study of the Parco D’Orleans sub-urban catchment

Risultato della ricerca: Conference contribution

Abstract

Aim of this study is to evaluate the impact of Precipitation Measurement Biases (PMBs) of tippingbucket rain gauges onto the hydraulic modelling of urban drainage networks. As a case study, themonitored experimental suburban catchment of Parco d’Orleans located in the University Campusof Palermo, Italy and managed since 1987 by the Department of Engineering of the University ofPalermo is considered. . Two tipping-bucket rain gauges provide a good spatial coverage of thecatchment area and an acoustic level gauge is installed at the outlet of the drainage network forflow mesaurements. Contemporary high temporal resolution rainfall and runoff data series areavailable between 1993 to 1998, and are used for the calibration of the hydraulic model in termsof roughness of the urban surfaces. The total drainage area is 12.8 ha with 68% of imperviousareas; the drainage network is composed of circular and egg-shaped concrete conduits. In thepresent work, the sensitivity of this rapid response system to the accuracy of the rainfall input isstudied, with reference to drainage failures and urban flooding issues. In order to quantify theinstrumental mechanical error of the two available Tipping Bucket Rain-gauges, these werecalibrated at the rain gauge laboratory of the WMO Lead Centre on Precipitation Intensity “B.Castelli” following the procedure described in the recent EN 17277:2019 standard on precipitationmeasurements. For each gauge a calibration curve was provided in order to quantify themeasurement bias and the associated calibration uncertainty.For rainfall-runoff transformation in the urban drainage system, a conceptual model for urbancatchment, which incorporates semi-distributed modelling concepts has been used. The urbanbasin is divided in external sub-catchments connected to the drainage network. Each external subcatchment is modelled as two separate conceptual linear elements, a reservoir and a channel, onefor the pervious part, the other for the impervious part of the investigated area. The drainagenetwork is schematized as a cascade of non-linear cells and the flood routing is simplified in theform of kinematic wave and represented as a flux transfer between adjacent cells. The sensitivityof this rapid response system to the accuracy of the rainfall input has been studied with referenceto drainage failures and urban flooding issues.To examine the effects due to PMBs on the catchment response, a number of simulations werecarried out using raw rainfall data and corrected data obtained after the application of thecalibration curve for each rain gauge. Results, expressed in terms of comparisons between thehydrographs at catchment outlet, show a significant influence of the PMB on the peak flow and thetotal hydrograph volume.
Lingua originaleEnglish
Titolo della pubblicazione ospiteEGU General Assembly 2020
Numero di pagine12
Stato di pubblicazionePublished - 2020

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