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Stormwater is the component of runoff that is generated by human activities, and has gradually become a key issue in achieving sustainability in urban environments. When vegetation and soils are replaced with roads and buildings, less rainwater infiltrates into the ground or is taken up by vegetation, and more becomes surface runoff. A greater area of impervious surfaces leads to increased stormwater runoff volume and velocity, and consequently increases the risk off looding and erosion. Being able to reduce stream flows and pollution of surface flows, green roofs are one technology that may help in alleviating this storm water crisis. This thesis developed a different and effective methodology for quantifying the effects of green roofs on stormwater runoff and calculating the runoff volume and rate for residential housing communities before and after applying green roofs. The method utilizes local climate data like rainfall and evapotranspiration rate, the water use properties of vegetation like crop coefficients of plants, and the areas of impervious surfaces; and then compares the different effects of green roofs in different locations having disparate climatic conditions. It was found that the best way to achieve zero runoff was to green a portion of the total rooftop area and disconnect all impervious surfaces. Implications of this methodology on city planning and site design and for future research are then discussed.

In order to control stormwater runoff engineers and hydrologists have used various techniques to attempt to reduce or delay the volume of water which reaches the sewer system. Recently, international approaches have favoured the idea of "source control" or "on-site" retention. This technique stores water in areas close to the point at which precipitation lands. Permeable pavements and similar stormwater control devices have not been exploited in the United Kingdom. Their adoption has been hindered by a lack of knowledge of their hydrological performance. This research aims to produce information on the hydrological performance of a car park surface and to produce a model which can predict the hydrological response to varying rainfall inputs. The objective of this thesis is to examine the hydrological behaviour of a model car park surface under varying rainfall conditions. The study has involved the construction of full-scale permeable pavement model car park structures and a rainfall simulator for use in the laboratory. A monitoring procedure was developed in order to measure inputs and changes in drainage, storage and evaporation over short (less than 2 hours) and long (up to 3 months) time scales. A range of rainfall simulations were applied to the model car park surfaces which differed in intensity, duration and volume. Hydrological processes were monitored over an 18 month period. Results suggest that evaporation, discharge and retention in the structures were strongly influenced by the particle size of the bedding material and the surface blocks. In general an average of 55% of a 15 mm 11-1 rainfall event could be retained by an initially dry structure. Subsequent simulations suggest that approximately 30% of a 15 mm rainfall event could be stored by an initially wet structure (with a minimum time interval of 72 hours). Sediments were also applied to the car park structures in order to monitor the effects of clogging on hydrological performance and to quantify the ability of the structures to act as a primary screening site for sediments. The application of sediments to the structure showed that evaporation from the structure increased by as much as 25-30%. Laboratory simulation of clogging effects was also compared to data gathered from field sites and the results suggested that laboratory simulations provided a good approximation of the migration of sediments in the structure. A model of the hydrological performance of the structure has been developed to be used as a predictive tool. The model relates rainfall inputs to water retention and discharge output over consecutive rainfall events. It also allows evaporation and long-term retention by the structure to be estimated over differing lengths of dry periods. The model results indicate that discharge was predicted to an accuracy of 78% (based on a percentage difference between the observed and predicted values), and evaporation and retention were predicted to an accuracy of 80%.

Stormwater is the component of runoff that is generated by human activities, and has gradually become a key issue in achieving sustainability in urban environments. When vegetation and soils are replaced with roads and buildings, less rainwater infiltrates into the ground or is taken up by vegetation, and more becomes surface runoff. A greater area of impervious surfaces leads to increased stormwater runoff volume and velocity, and consequently increases the risk off looding and erosion. Being able to reduce stream flows and pollution of surface flows, green roofs are one technology that may help in alleviating this storm water crisis. This thesis developed a different and effective methodology for quantifying the effects of green roofs on stormwater runoff and calculating the runoff volume and rate for residential housing communities before and after applying green roofs. The method utilizes local climate data like rainfall and evapotranspiration rate, the water use properties of vegetation like crop coefficients of plants, and the areas of impervious surfaces; and then compares the different effects of green roofs in different locations having disparate climatic conditions. It was found that the best way to achieve zero runoff was to green a portion of the total rooftop area and disconnect all impervious surfaces. Implications of this methodology on city planning and site design and for future research are then discussed.

Stormwater is the component of runoff that is generated by human activities, and has gradually become a key issue in achieving sustainability in urban environments. When vegetation and soils are replaced with roads and buildings, less rainwater infiltrates into the ground or is taken up by vegetation, and more becomes surface runoff. A greater area of impervious surfaces leads to increased stormwater runoff volume and velocity, and consequently increases the risk off looding and erosion. Being able to reduce stream flows and pollution of surface flows, green roofs are one technology that may help in alleviating this storm water crisis. This thesis developed a different and effective methodology for quantifying the effects of green roofs on stormwater runoff and calculating the runoff volume and rate for residential housing communities before and after applying green roofs. The method utilizes local climate data like rainfall and evapotranspiration rate, the water use properties of vegetation like crop coefficients of plants, and the areas of impervious surfaces; and then compares the different effects of green roofs in different locations having disparate climatic conditions. It was found that the best way to achieve zero runoff was to green a portion of the total rooftop area and disconnect all impervious surfaces. Implications of this methodology on city planning and site design and for future research are then discussed. / Applied Science, Faculty of / Architecture and Landscape Architecture (SALA), School of / Graduate

The following document serves as a design guidebook to assist landscape architects, designers, planners, engineers, and architects in the practice of developing land while preserving water quality. This guidebook outlines methods for maximizing permeable surfaces by providing examples of ways to minimize impervious surfaces. / Master of Landscape Architecture

University of Technology, Sydney. Faculty of Engineering. / Although extensive worldwide literature on urban stormwater runoff exists, very few publications describe runoff development in terms of its basic building blocks or processes and their individual and accumulative significance in response to varying inputs and boundary conditions. Process algorithms should respond accurately to varying input magnitudes and characteristics as well as to changes in antecedent conditions. The present state of estimation errors involved in many current numerical simulation techniques has been reviewed in this thesis. A significant amount of errors that are presently encountered for have been explained in terms of undefined process response not explicitly included within many modelling methodologies. Extensive field monitoring of intra-catchment rainfall and runoff within an urban catchment at Giralang in Canberra, which is typical of Australian urban catchments, was carried out over a 3-year period to define and measure individual runoff processes. This monitoring work led to a greater understanding of the processes driving the aggregation of local runoff from many sub-areas into the runoff observed at full catchment scale. The results from the monitoring process prompted a number of approaches to potentially reduce standard errors of estimate from model-attributable errors based on improvements to definable catchment response mechanisms. The research isolated a number of basic building blocks associated with typical residential allotments, that can be grouped into roof drainage, yard drainage and adjacent road drainage. A proposed modelling approach was developed that allowed these building blocks at an allotment scale to be simply computed using storage routing techniques. This then aggregated via the total catchment’s public drainage system isochronal characteristics utilising a “process tree” approach to provide full catchment scale runoff response. The potential reduction in estimation errors utilising the developed procedure was assessed using a large number of recorded events from the Giralang catchment monitoring data. The proposed numerical modelling approach was found to provide significant improvements over current methods and offered a scale-independent and stormindependent methodology to model catchments of any size without the need for changes to any of the runoff routing parameters. Additionally the approach permits the flexible sequencing and inclusion of a wide range of different urban drainage structures within a catchment that are representative of the local characteristics. The developed procedure also includes a spatially varied water balance approach to infiltration estimation that is more suited to future continuous simulation models. The developed “flexible process tree” approach provides an important step forward in the numerical modelling of complex urban drainage systems. This can reduce errors of estimate by improving intra-catchment process representation.

Extended detention basins are not used for stormwater quality management in many areas of the US because they generally do not achieve the 80% removal of total suspended solids required by many regulatory agencies. The objective of this research was modification of the outlet controls of an existing basin to provide batch treatment of the urban stormwater runoff through efficient control of the hydraulic residence time. A solar powered automated valve and controller were developed and placed on the outlet of an extended detention basin in Austin, Texas to increase the detention time beyond the times achievable using an orifice. This system retained the diverted runoff in the basin for a variable preset period of time. The quality of the influent and effluent of the basin was monitored for concentrations of suspended solids, nutrients, chemical oxygen demand. and total and dissolved metals. The suspended solids concentrations in the basin were controlled by adjusting the residence time of the runoff in the basin to meet the required pollutant reduction. The automated valve can also be used to regulate flow into the receiving waters to control peak flow.

University of Technology, Sydney. Faculty of Engineering. / Although extensive worldwide literature on urban stormwater runoff exists, very few publications describe runoff development in terms of its basic building blocks or processes and their individual and accumulative significance in response to varying inputs and boundary conditions. Process algorithms should respond accurately to varying input magnitudes and characteristics as well as to changes in antecedent conditions. The present state of estimation errors involved in many current numerical simulation techniques has been reviewed in this thesis. A significant amount of errors that are presently encountered for have been explained in terms of undefined process response not explicitly included within many modelling methodologies. Extensive field monitoring of intra-catchment rainfall and runoff within an urban catchment at Giralang in Canberra, which is typical of Australian urban catchments, was carried out over a 3-year period to define and measure individual runoff processes. This monitoring work led to a greater understanding of the processes driving the aggregation of local runoff from many sub-areas into the runoff observed at full catchment scale. The results from the monitoring process prompted a number of approaches to potentially reduce standard errors of estimate from model-attributable errors based on improvements to definable catchment response mechanisms. The research isolated a number of basic building blocks associated with typical residential allotments, that can be grouped into roof drainage, yard drainage and adjacent road drainage. A proposed modelling approach was developed that allowed these building blocks at an allotment scale to be simply computed using storage routing techniques. This then aggregated via the total catchment’s public drainage system isochronal characteristics utilising a “process tree” approach to provide full catchment scale runoff response. The potential reduction in estimation errors utilising the developed procedure was assessed using a large number of recorded events from the Giralang catchment monitoring data. The proposed numerical modelling approach was found to provide significant improvements over current methods and offered a scale-independent and stormindependent methodology to model catchments of any size without the need for changes to any of the runoff routing parameters. Additionally the approach permits the flexible sequencing and inclusion of a wide range of different urban drainage structures within a catchment that are representative of the local characteristics. The developed procedure also includes a spatially varied water balance approach to infiltration estimation that is more suited to future continuous simulation models. The developed “flexible process tree” approach provides an important step forward in the numerical modelling of complex urban drainage systems. This can reduce errors of estimate by improving intra-catchment process representation.

This study investigated the catchment of an urban wetland on sandy soils in Perth, Western Australia. The wetland is of high conservation value but is currently used as a stormwater-compensating basin. The three main aims of this work were to: 1. determine the importance of stormwater drains in the water and pollutant balance of the lake; 2. evaluate pollutant retention rates by the wetland; and 3. identify current land uses in the catchment, determine their impacts on the wetland and identify tolerable levels of urbanisation for a wetland of this type. Stormwater flowing in and out of the lake subcatchments was monitored for two years for background flows and storm events. Water discharge, physical and chemical characteristics —including nutrients and heavy metals — were measured. Water and pollutant mass balances were determined. There was year-round flow at all sites, except from the smallest subcatchment. Flow characteristics differed between sites and were more influenced by catchment characteristics than rain intensity or duration. More water entered than left the lake in spring. In autumn more water left the lake via the overflow than entered. Due to poor maintenance, many drains overflowed during storm events. When compared to Australian and New Zealand Environment and Conservation Council (ANZECC) water quality guidelines for receiving waters, only pH and conductivity met the recommended criteria. The nutrient and heavy metal loads varied with rainfall during both years of study. Suspended solids, total nitrogen and total phosphorus concentrations were proportional to rainfall, while concentrations of dissolved forms of nutrients were not. Background flows contributed significantly to the pollutant load. More than 85% of total suspended solids, nutrients and heavy metals were retained by the wetland — the only exceptions being copper and some forms of dissolved nutrients. An evaluation of the performance of the lake as a pollutant sink, using published data from constructed wetlands, identified phosphorus as the pollutant that requires the largest area for treatment.