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The benefits of Low Impact Development (LID) structures in mitigating urban floods and improving water quality have been widely recognized. In the previous chapter, a multicriteria decision analysis was conducted to determine suitable LID options for the study site, by integrating AHP and SWMM. It was found that bioretention cells were among the best choices based on the analyzed criteria, a conclusion supported by other studies. This thesis aimed to achieve flood mitigation and urban water governance goals through a sustainable approach, focusing on LIDs, their selection, and their placements. To further advance this sustainable approach, a comprehensive investigation was conducted on the environmental impact of LIDs throughout their entire life cycle. Given the suitability of bioretention cells for the study site and their general performance-based attributes that make them ideal choices for treating various pollutants under different spatial conditions, this paper extensively examined their environmental footprints. The life cycle of bioretention cells, comprising eight configurations with varying media amendments, was analyzed using the standard life cycle impact assessment procedure (IS 14,040). This study holds significance as the selection of media type, availability, transportation, and pollutant removal efficiencies directly impact on-site implementation, and each configuration incurs varying levels of environmental impacts that need quantification to meet sustainable and low-impact LID selection requirements. The primary data source for this study was the Ecoinvent database, supplemented by locally sourced data from practitioners. The TRACI 2.1 impact assessment method was employed in OpenLCA software. The results indicated that pumice had the highest environmental impacts, primarily stemming from ozone depletion, smog, and fossil fuel consumption categories due to transportation distance requirements. This Life Cycle Assessment (LCA) study of bioretention cells will be instrumental for practitioners in making environmentally sustainable design choices without compromising system efficiency. Additionally, government agencies can utilize these findings to devise incentives for optimized design providers as it addresses emerging trends in the field of catalysis related to environmental impact evaluation and sustainable design choices for bioretention cell systems. [ABSTRACT FROM AUTHOR]

The magnitude and frequency of extreme rainfall due to climate change is increasing. Increasing rainfall causes serious hydrological problems in cities. Rainfall does not infiltrate the soil, but mostly flows through the sewer pipes into the stream. Most old urban watersheds have combined sewer pipes. When rainfall exceeds the capacity of the combined sewer pipes, sewage mixed with stormwater overflows the sewer pipes and flows directly into the stream. This is called Combined Sewer Overflows (CSOs). CSOs enter the stream with non-point source pollutants accumulated on the surface and pollute the stream. CSOs are one of the major water quality problems in older urban watersheds. This can be solved by replacing the combined sewer pipes with separated sewer pipes, but in reality it requires astronomical costs. As an alternative, the Low Impact Development (LID) technique has recently been introduced. In this study, we analyzed the effects of climate change on CSOs in urban watersheds and applied LID techniques to offset the effects. The LID facility was applied with the most commonly used Bio-Retention cells. HIGHLIGHTS Applicability of bio-retention to offset the negative effects of climate change on urban streams are investigated using EPA SWMM.; Run-off, TP load, and CSOs in urban watershed show high potential for increases by climate change.; The bio-retention cell is useful for offsetting the negative effects of climate change.;

Personal Computer Stormwater Management Model (PCSWMM) was applied to investigate: (1) hydrological responses in the Myponga catchment as a result of land use changes; and (2) the possibility of adopting Water Sensitive Urban Design (WSUD) technologies (bio-retention cells) to manage resulting floods. Calibrated and validated models predicted the measured data with satisfactory accuracy and reliability. Different urbanization scenarios were tested. When the level of urbanization increased from 10% to 70%, mean discharge increased from 45% to 322%. Frequency of flood at 2-year Average Recurrence Interval (ARI) increased from 1 to 44 and frequency of floods at 100-year ARI increased from none to 8. At 70% urbanisation, trialled bio-retention facilities used as WSUD measures almost completely ameliorated 2-year ARI floods by reducing the frequency of such events from 44 to 2. Floods at smaller ARIs (2, 5, 10 and 20 years) were effectively managed by WSUD measures while floods at 50- and 100-year ARIs remained unchanged. The overall results improve understanding of the severity of the impacts of land use changes on the hydrology of a catchment and the ability of bio-retention cells to alleviate the risk of small to medium floods in the Myponga catchment. [ABSTRACT FROM AUTHOR]

Personal Computer Stormwater Management Model (PCSWMM) was applied to investigate: (1) hydrological responses in the Myponga catchment as a result of land use changes; and (2) the possibility of adopting Water Sensitive Urban Design (WSUD) technologies (bio-retention cells) to manage resulting floods. Calibrated and validated models predicted the measured data with satisfactory accuracy and reliability. Different urbanization scenarios were tested. When the level of urbanization increased from 10% to 70%, mean discharge increased from 45% to 322%. Frequency of flood at 2-year Average Recurrence Interval (ARI) increased from 1 to 44 and frequency of floods at 100-year ARI increased from none to 8. At 70% urbanisation, trialled bio-retention facilities used as WSUD measures almost completely ameliorated 2-year ARI floods by reducing the frequency of such events from 44 to 2. Floods at smaller ARIs (2, 5, 10 and 20 years) were effectively managed by WSUD measures while floods at 50- and 100-year ARIs remained unchanged. The overall results improve understanding of the severity of the impacts of land use changes on the hydrology of a catchment and the ability of bio-retention cells to alleviate the risk of small to medium floods in the Myponga catchment.