Ewa Burszta-Adamiak

Modelling of green roofs' hydrologic performance using EPA's SWMM

Green roofs significantly affect the increase in water retention and thus the management of rain water in urban areas. In Poland, as in many other European countries, excess rainwater resulting from snowmelt and heavy rainfall contributes to the development of local flooding in urban areas. Opportunities to reduce surface runoff and reduce flood risks are among the reasons why green roofs are more likely to be used also in this country. However, there are relatively few data on their in situ performance. In this study the storm water performance was simulated for the green roofs experimental plots using the Storm Water Management Model (SWMM) with Low Impact Development (LID) Controls module (version 5.0.022). The model consists of many parameters for a particular layer of green roofs but simulation results were unsatisfactory considering the hydrologic response of the green roofs. For the majority of the tested rain events, the Nash coefficient had negative values. It indicates a weak fit between observed and measured flow-rates. Therefore complexity of the LID module does not affect the increase of its accuracy. Further research at a technical scale is needed to determine the role of the green roof slope, vegetation cover and drying process during the inter-event periods.

Modelling of percolation rate of stormwater from underground infiltration systems

Underground or surface stormwater storage tank systems that enable the infiltration of water into the ground are basic elements used in Sustainable Urban Drainage Systems (SUDS). So far, the design methods for such facilities have not taken into account the phenomenon of ground clogging during stormwater infiltration. Top layer sealing of the filter bed influences the infiltration rate of water into the ground. This study presents an original mathematical model describing changes in the infiltration rate variability in the phases of filling and emptying the storage and infiltration tank systems, which enables the determination of the degree of top ground layer clogging. The input data for modelling were obtained from studies conducted on experimental sites on objects constructed on a semi-technological scale. The experiment conducted has proven that the application of the model developed for the phase of water infiltration enables us to estimate the degree of module clogging. However, this method is more suitable for reservoirs embedded in more permeable soils than for those located in cohesive soils.

Modern proposal of methodology for retrieval of characteristic synthetic rainfall hyetographs

Modern engineering workshop of designing and modelling complex drainage systems is based on hydrodynamic modelling and has a probabilistic character. Its practical application requires a change regarding rainfall models accepted at the input. Previously used artificial rainfall models of simplified form, e.g. block precipitation or Eulers type II model rainfall are no longer sufficient. It is noticeable that urgent clarification is needed as regards the methodology of standardized rainfall hyetographs that would take into consideration the specifics of local storm rainfall temporal dynamics. The aim of the paper is to present a proposal for innovative methodology for determining standardized rainfall hyetographs, based on statistical processing of the collection of actual local precipitation characteristics. Proposed methodology is based on the classification of standardized rainfall hyetographs with the use of cluster analysis. Its application is presented on the example of selected rain gauges localized in Poland. Synthetic rainfall hyetographs achieved as a final result may be used for hydrodynamic modelling of sewerage systems, including probabilistic detection of necessary capacity of retention reservoirs.

Seasonal variability of basic pollution parameters in atmospheric precipitation in Strzelin

Abstract Electrical conductivity and pH are the basic indices of rainfall pollution, constituting the basis for evaluation of the general nature of rainwater. This article presents an analysis of these two parameters in samples of rainfall collected in the years 2008-2010 (in the heating season and outside it) in three measurement sites P1, P2 and P3, located in the city and commune Strzelin (Lower Silesian Voivodeship). Preliminary results show a high variation of pH and electrical conductivity of rainfall occurring in the analysed area. Approximately 30% of the samples were characterised by a pH that allowed to qualify them, according to JANSEN et al. [1988], as normal rainfall. A similar share in all the collected samples represented rainfall of pH < 5.1 that was classified as slightly, considerably and highly acidic. The problem of acid rain occurred in the analysed area mainly during the heating season, when rainfall of pH < 5.1 accounted for a considerable share in all rainfall samples collected in the said period. The electrical conductivity of most samples fell below 60 μS·cm-1, which allowed us to classify them as slightly polluted rainfall (site P2), considerably polluted (site P3) and highly polluted (site P1). STRESZCZENIE Odczyn i przewodność elektrolityczna należą do podstawowych miar zanieczyszczenia opadów, na podstawie których można dokonać oceny ich ogólnego charakteru. W artykule dokonano analizy tych dwóch parametrów w opadach pobranych w latach 2008-2010 (w sezonie grzewczym i pozagrzewczym) w trzech punktach pomiarowych: P1, P2 i P3 zlokalizowanych na terenie miasta i gminy Strzelin (województwo dolnośląskie). Wyniki badań wykazują dużą zmienność odczynu i przewodności elektrolitycznej opadów występujących na analizowanym terenie. Około 30% prób miało odczyn, który zgodnie z klasyfikacją JANSENA i in. [1988] pozwalał je zakwalifikować jako opady normalne. Podobny udział opadów w całości zebranych prób stanowiły opady o pH < 5,1, klasyfikowane jako mające lekko, znacznie i silnie obniżone pH. Problem kwaśnych deszczów występował na analizowanym terenie głównie w sezonie grzewczym, w którym opady o pH < 5,1 stanowiły znaczną część wszystkich opadów pobranych w tym okresie. Przewodność elektrolityczna większości próbek wynosiła poniżej 60 μS·cm-1, co pozwoliło zakwalifikować je do klasy lekko zanieczyszczonych (stanowisko P2), znacznie zanieczyszczonych (stanowisko P3) oraz mocno zanieczyszczonych (stanowisko P1).

ZIELONE DACHY JAKO ROZWIĄZANIA POPRAWIAJĄCE GOSPODARKĘ WODAMI OPADOWYMI W MIASTACH

The interest in green roof technologies is increasing due to the many tangible benefits that allow to provide. One of them is the ability to improve stormwater management in urban areas, because construction of green roofs can retain and delay in runoff . Due to the fact that the market of green roofs in Poland is relatively young, there is still a need for research to provide detailed information about green roof hydrologic performance in the national climate conditions. The objective of this study is to present the research results on retention capacity of green roofs, carried out at the Wroclaw University of Life Sciences. The results show that the possibility of water retention is considerably improved at green roofs when antecedent dry weather period lasts longer than one day and the rainfall depth does not exceed 10 mm / day.

POMIARY NA CZYNNYCH SIECIACH KANALIZACJI DESZCZOWEJ I OGÓLNOSPŁAWNEJ

Monitoring of the drainage networks is an extremely important tool used to understand the phenomena occurring in them. In an era of urbanization and increased run-off, at the expense of natural retention in the catchment, it helps to minimize the risk of local flooding and pollution. In its scope includes measurement of the amount of rainfall, with the use of rain gauges, and their measure in the sewer network, in matter of flows and channel filling, with the help of flow meters. An indispensable part in this step is their proper calibration calibration. In addition to ongoing monitoring of the sewer system, periodic inspections by the qualified employees of Water and Sewage Company should be done. The following article reviews measurement devices, their calibration methods, as well as the phenomena that occur during operation in the sewer network. It provides a solution for monitoring and

MODELOWANIE ODPŁYWU WÓD OPADOWYCH Z DACHÓW ZIELONYCH

Apart from direct measurements, modelling of runoff from green roofs is valuable source of information about effectiveness of this type of structure from hydrological point of view. Among different type of models, the most frequently used are numerical models. They allow to assess the impact of green roofs on decrease and attenuation of runoff, reduction of peak runoff and value of water retention. This paper presents preliminary results of research on computing the rate of runoff from green roofs using GARDENIA model. The analysis has been carried out for selected rainfall events registered during measuring campaign on pilot-scale green roofs. Obtained results are promising and show good fit between observed and simulated runoff.