Advective water quality model for urban watercourses.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineerrng,As has happened throughout the world. environmental and water quality problems related to developing urban and industrial areas and associated accumulation of waste in built-up areas were the main factors in contributing to sanitary awareness in South Africa. The dwindling water resources and persistent deterioration of water quality, more severely in urban areas, necessitates the review the current practice of storm water management in South Africa. Reliable stormwater drainage models evaluating both the water quantity and quality could be essential in confronting the prevailing pollution problems. The objective of this project was conceived to be the development of a system for the simulation of water quality in urban watercourses, A personal computer compatible model for joint transportation of hydrograph and pollutographs in open channels was developed. The model comprises an operational data handling facility, a user friendly and interactive interface. The study revealed that: Urban and Industrial development results in complication of the urban water system. • Single objectivity approaches in management of urban watercourses are outdated . .. The proposed model is capable of simultaneously routing flood and pollutant condiment waves in open channels. Understanding of aspects of the water quality in urban watercourse can be greatly enhanced by the proposed model. The following recommendations were henceforth made: • Detailed study of the nature. quantity and sources of pollutants in the urban water system. .. Sophisticated (dynamic wave. supercritical flow, complicated ..................... hydrodynamic model snould be considered, • Biological and, chemical process in the urban watercourse be incorporated. • Linking of the water quality model to the storm water drainage model,Andrew Chakane 201

Monitoring and Modeling the Hydrological Performance of Extensive Green Roof Systems

Urban stormwater runoff causes many problems for watersheds located within large metropolitan areas, including such detrimental effects as flooding, erosion, pollution, and the increased risk of combined sewerage overflows. Increased amounts of impervious areas resulting from urban sprawl have also been shown to escalate stormwater flows, which exacerbates water management issues in these metropolitan areas. Water resource engineers have progressively turned toward green infrastructure to solve stormwater problems, and green roof systems represent one type of this green infrastructure. As of current, however, green roof systems are largely underused in as an effective stormwater management tool. The major factor limiting the installation of green roof systems is the unpredictable hydrological response of green roofs to individual storm events. Currently, many municipalities use the Soil Conservation Service model or rational method and associated curve numbers to estimate stormwater flows, with green roofs typically receiving an assigned value ranging from 75-90 within these models. However, these simple models do not accurately predict the hydrological response of green roof systems, where the overall performance is determined by many supplementary factors including geometry, soil media type and depth, initial conditions, and the individual storm hyetograph. The accurate monitoring of green roof stormwater runoff and the use of data to create models are critical to measuring hydrological response, as well as to assess the benefits of the green roof installation to the local watershed. In this study, four 15 m2 test plots were constructed on the roof of the Milwaukee Metropolitan Sewerage District headquarters located in downtown Milwaukee, Wisconsin. An ET 107 weather station manufactured by Campbell Scientific was installed onsite. Stormwater flows were monitored for each plot using a “WeirBox”, a tipping gauge and v-notch weir combination which was developed and calibrated specifically for this project. Three extensive green roof systems manufactured by Vegetal i.D. were tested, including Hydropack, a standard modular extensive green roof, and Hydro Active Smart Roof (HSRP) and Hydro Active Smart Roof Active (HSRA), both of which are extensive green roof systems with additional water storage basins. A control bare roof plot was also monitored to confirm and compare hydrological performance. The WeirBox flow monitoring equipment displayed impressive results with water budget error typically less than 7% for individual storm events when comparing total runoff volume from the control plot to onsite precipitation data. All three of the tested green roof systems exhibited significant hydrological performance in terms of total runoff retention, peak runoff rate reduction, and peak runoff rate delay. However, depending mostly on rainfall characteristics, the responses to individual storm events varied widely. Total runoff retention for the 8 month monitoring period was calculated to be 64%, 87%, and 91% for Hydropack, HSRP and HSRA respectively. In general, both HSR systems with greater water capacities outperformed the standard extensive green roof system, which suggests that optimization through an integrated storage basin can be achieved to improve overall green roof performance. A conceptual simple bucket model was created for the Hydropack and HSRP green roof systems. Data from 6 individual storm events was used to validate the model. While “simple”, the conceptual bucket model successfully reproduced the hydrological response of the green roof systems to individual storm events. Synthesized storm events with return periods ranging from 1 to 100 years were then analyzed using the calibrated models. Hydrological performance diminished with larger storm events, mirroring results from monitoring and literature review. Both monitoring and modeling showed that the integration of extensive green roofs with storage basins greatly improves performance

Impact analysis of urban drainage waters on flood control

This paper analyses the impact of storm water from urban areas on the flood safety issue. In the first capture I will revise the laws that apply to the environmental issue. There is a review of EU directives as well as of the Slovenian law. In the following chapter, I will sum up the theoretical basis of hydrological an hydraulic models, urbane drainage, flood control issues and revise the necessary data to make models using HEC-MHS and HEC-RAS programs. A definition of urbanization impact on the river characteristics and its overland flow is necessary. For the purpose of acquiring detailed data of the flow mentioned, GEN tables have been used. 15 minute storm duration has been used, using various return periods. The HEC- HMS application has enabled me to analyze flood waters. By doing that, I was able to confirm the validity of the river Cereja flow-data. The empirical aspect of the thesis is enhanced by various equations used. The latter enabled me to assess the 100 year return period of flood water. The section of calculations analyzes the flood water hazard for a 10 and 100-year return period, regardless of the storm/rain water impact. However, this impact has been taken into account and was defined in the section following the previous. On account of a multitude of input data combinations, the results have been presented in a form of a chart. They illustrate the changes in Cereja water level and present an analysis of the changes in the level of flood hazard, regarding the additional quantity of storm/rain waters, originating from the urban areas

Climate Change and Sea Level Rise Projections for Boston

While the broad outlines of how climate change would impact Boston have been known for some time, it is only recently that we have developed a more definitive understanding of what lies ahead. That understanding was advanced considerably with the publication of Climate Change and Sea Level Rise Projections for Boston by the Boston Research Advisory Group (BRAG).The BRAG report is the first major product of "Climate Ready Boston," a project led by the City of Boston in partnership with the Green Ribbon Commission and funded in part by the Barr Foundation. The BRAG team includes 20 leading experts from the region's major universities on subjects ranging from sea level rise to temperature extremes. University of Massachusetts Boston professors Ellen Douglas and Paul Kirshen headed the research.The BRAG report validates earlier studies, concluding Boston will get hotter, wetter, and saltier in the decades ahead (see figures below). But the group has produced a much more definitive set of projections than existed previously, especially for the problem of sea level rise. BRAG also concluded that some of the effects of climate change will come sooner than expected, accelerating the urgency of planning and action

Management of an Urban Stormwater System Using Projected Future Scenarios of Climate Models: A Watershed-Based Modeling Approach

Anticipating a proper management needs for urban stormwater due to climate change is becoming a critical concern to water resources managers. In an effort to identify best management practices and understand the probable future climate scenarios, this study used high-resolution climate model data in conjunction with advanced statistical methods and computer simulation. Climate model data from the North American Regional Climate Change Assessment Program (NARCCAP) were used to calculate the design storm depths for the Gowan Watershed of Las Vegas Valley, Nevada. The Storm Water Management Model (SWMM), developed by the Environmental Protection Agency (EPA), was used for hydrological modeling. Two low-impact development techniques – Permeable Pavement and Green Roof – were implemented in the EPA SWMM hydrological modeling to attenuate excess surface runoff that was induced by climate change. The method adopted in this study was effective in mitigating the challenges in managing changes in urban stormwater amounts due to climate change

Stochastic urban pluvial flood hazard maps based upon a spatial-temporal rainfall generator

It is a common practice to assign the return period of a given storm event to the urban pluvial flood event that such storm generates. However, this approach may be inappropriate as rainfall events with the same return period can produce different urban pluvial flooding events, i.e., with different associated flood extent, water levels and return periods. This depends on the characteristics of the rainfall events, such as spatial variability, and on other characteristics of the sewer system and the catchment. To address this, the paper presents an innovative contribution to produce stochastic urban pluvial flood hazard maps. A stochastic rainfall generator for urban-scale applications was employed to generate an ensemble of spatially—and temporally—variable design storms with similar return period. These were used as input to the urban drainage model of a pilot urban catchment (~9 km2) located in London, UK. Stochastic flood hazard maps were generated through a frequency analysis of the flooding generated by the various storm events. The stochastic flood hazard maps obtained show that rainfall spatial-temporal variability is an important factor in the estimation of flood likelihood in urban areas. Moreover, as compared to the flood hazard maps obtained by using a single spatially-uniform storm event, the stochastic maps generated in this study provide a more comprehensive assessment of flood hazard which enables better informed flood risk management decisions

Decision support system for managing stormwater and greywater quality in informal settlements in South Africa

Managing the quality of stormwater and greywater in informal settlements are essential to their growth. In this thesis, methodologies are developed for the assessment and management of stormwater and greywater quality based on the analysis of both nonstructural and structural control interventions. The objectives of the research were as follows: · Review stormwater runoff quality and treatment practices and the extent of runoff and greywater management in rural and peri-urban areas of South Africa. The review was to also determine the extent of quality control awareness and experience among stormwater management professionals and collate information upon which present and future needs can be assessed and addressed. · To develop a methodology to identify factors causing water quality management issues in low-cost, high-density settlements. · To develop a methodology to characterize storm and grey water quality as well as setting ambient water quality and management objectives. · To develop a methodology to identify and select potential non-structural and structural control interventions to manage storm and grey water quality. · Based on the above, to develop a decision support system for evaluation of potential interventions for storm and grey water management at planning level. The methodologies used to achieve the above objectives consisted of: literature review; consultations with stakeholders; data analysis and computations; model development; and model application. The current status of managing water quality pollution in urban areas is outlined and the related problems, specifically those applicable to developing areas are discussed. Management interventions employed to date in the management of water quality effects are set out and the applicability of such interventions to developing areas is identified. The potential of expert systems is evaluated and the application of this system to iii stormwater quality management models is assessed. A decision support system (DSS) was developed for rapid assessment of various water quality management interventions. The model is primarily targeted at those who are involved or are likely to be involved in stormwater quality management including catchment managers, local governments or municipalities, catchment management agencies, private consultants and researchers. The DSS and the related methodologies have been shown through Alexandra Township (north of Johannesburg) case study, to be useful and to satisfy all the objectives set out for the research. The results of the research are summarised and the merits and limitations of the decision support systems are discussed. Recommendations for the direction of future research and the development of the existing model are detailed. Specifically, it is recommended that: · Extensive monitoring be undertaken in order to improve the defaults in the model · A research be undertaken into the extent to which GIS can be integrated to the DSS to select appropriate management interventions and their sites · A research be undertaken into privatization and partnership in the ownership and operation of stormwater management systems. · Selection of least cost strategy with the DSS is presently achieved by trial and error process. The selection process can be improved if the DSS can be linked to an optimizer

Integrating Green Infrastructure Into Stormwater Policy: Reliability, Watershed Management, and Environmental Psychology as Holistic Tools for Success

As cities continue to expand, the issues of flood control and urban water quality have become major modern sustainability challenges. Green infrastructure—the use of nature-based solutions to target, treat, and store stormwater at its source—has emerged as a possible solution. While green infrastructure does offer multiple benefits for urban users, its performance is also highly variable. This Article addresses a key gap in existing literature by explicitly addressing how uncertainty in environmental and anthropogenic factors affects green infrastructure performance and integration within the Clean Water Act’s municipal separate storm sewer (MS4) regulatory program