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京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21743号 / 工博第4560号 / 新制||工||1711(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 田中 茂信, 准教授 田中 賢治, 教授 中北 英一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Stormwater runoff is a major environmental concern, particularly in urban environments. Trends in managing stormwater have evolved (and continue to evolve) from a quantity only approach into a sustainable approach, which integrates quantity, quality, the environment, and aesthetics. Best management practices (BMPs) and Low Impact Development (LID) are two well-documented techniques capable of managing to sustainable standards. There are a number of stormwater models available to design professionals today. However, there are few which integrate site-scale BMP/LID analysis in a simplified fashion. The purpose of this study is to determine if there is a demand in the design profession for simplified stormwater modeling tools to help designers make informed decisions about integrating BMP/LID strategies into site plans. A Web-based questionnaire was administered to a group of design professionals to determine their knowledge of BMPs and their technological needs and preferences in meeting stormwater goals and requirements.

Creeks and rivers are often polluted as a result of stormwater runoff that carries various contaminants in to open water bodies, causing adverse environmental and health effects. Low impact development (LID) techniques are currently employed to treat this runoff prior to discharge. Nitrate, however, is not consistently removed by these LID techniques. This study analyzed the ability of several nanoclays to remove nitrate in runoff and determined the feasibility of using them as a soil supplement for LID implementation. Six different nanoclays and HCl-treated clays were compared (pre-modified trimethyl stearyl ammonium nanoclay, pre-modified dimethyl dialkyl amine nanoclay, unmodified hydrophilic bentonite, unmodified halloysite nanoclay, HCl modified hydrophilic bentonite and HCL modified kaolin) to the control clay, unmodified kaolin, for their ability to adsorb nitrate solution by batch adsorption experiments. The findings determined that the pre-modified trimethyl stearyl ammonium nanoclay was the most effective adsorbent, decreasing the nitrate concentration up to 86% for a nitrate to clay ratio of 6.25 mg: 1 g under normal pH (5-6) and temperature (25⁰C) conditions. The HCl acid modification did not prove to provide significant additional benefits to the clays. Column studies were also conducted on the most successful clay, pre-modified trimethyl stearyl ammonium nanoclay, to assess the breakthrough point when 0.1% w/w and 1% w/w of the nanoclay were added to Nevada Sand. The results showed a projected breakthrough pore volume of 17 when the larger fraction was added to the sand, and a corresponding hydraulic conductivity of 12.6 in/hr, which is 35% slower than the un-amended Nevada Sand. Such a high hydraulic conductivity indicated that future work can test larger fractions of clay to sand mixtures to achieve a higher number of pore volumes before the soil reaches its breakthrough point. Future studies can also further explore both batch and column experiments to assess the feasibility of implementing soil amendments to a filtration system by changing the experimental parameters, such as base soil material, types of nanoclays used, and the nanoclay to nitrate ratios. Additionally, synthetic stormwater from runoff should be used as the influent instead of a nitrate-only solution to reflect more realistic scenarios for a potential real-world application.

Developments that have been taking place on Cal Poly campus over the years have altered the natural hydrology of the area. Stormwater management practices could help reduce the impacts of these developments. Computer models can help to design effective and economical stormwater management solutions at a watershed scale. As such, the objective of this study was to develop a stormwater management model for Cal Poly campus. The model was developed based on the utility data obtained from the university and other watershed data available from open sources. Field surveys were conducted to address some anomalies in the utility data, and streamflow monitoring was performed. The model was calibrated using the streamflow data measured during this study. The calibration effort significantly improved the prediction accuracy of the model. The calibrated model was then used to analyze the hydrologic performance of implementing LID systems for two projects that Cal Poly plans to build. Permeable Pavements (PPs) and Bioretention Cells (BRCs) were the LID types examined. The LIDs were evaluated based on peak flow and runoff volume reductions they would achieve. The potential reductions were compared for current conditions and the proposed project if LIDs were implemented, and for inflows to the LIDs and outflows from the LIDs. The results indicate that implementing a PP system for the proposed student apartment at the current H-1 and R-1 parking lots and a BRC system for the proposed engineering project facilities at the current H-2 parking lots will significantly reduce peak flow and runoff volume. Overall, the developed model will help the university with the traditional stormwater management practices such as flood control and to identify effective LID practices for future developments. Limitations of the current model and recommendations on how to improve the model are also discussed.

Diclofenac (DCF) and other emerging contaminants have been found in environments worldwide. These contaminants may enter the environment due to the application of treated wastewater, biosolids and direct excrement related to veterinary application. Leakage from the soils toward the groundwater is largely controlled by sorption and microbial degradation. Most studies on the environmental fate of DCF have focused on degradation during wastewater treatment processes. However, little is known about their behavior in soil. In this study, the combined effect of adsorption and degradation of diclofenac has been investigated in four (4) 24 ft3 agricultural soil-filled beds designed to mimic natural vegetated soil environments, enhanced via controlled wetting and drying cycles. Contour bund installation on slopes of 5, 10, 15 and 20° were mimicked in the beds. Results showed that the soil environment was a strong inhibitor to the leaching of DCF through the soil. Saturating slopes via contour bund application however can lead to landslides that may impact structures and human life. A feasible contour bund installation site was investigated and found that 20° slopes under saturated conditions resulted in an unsafe factor of safety and is not encouraged as a solution for stormwater management. The effect of contour bund application on slopes under 15° at the installation site can potentially increase removal of emerging contaminants, thereby protecting groundwater resources without endangering life or property.

Climate change and urbanization causes the increasing challenges of flooding in urban watersheds. Even the rivers identified as non-vulnerable are causing catastrophic damage due to heavy flooding. So, several satellite and radar-based precipitation data are considered to study the watersheds with no gauge station or need recent precipitation data. Weather Radar (NEXRAD)arch, the accuracy of satellite-based precipitation data, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Climate Data Record (PERSIANN-CDR), and radar-based precipitation data, Next Generation Weather Radar (NEXRAD), is evaluated in rainfall-runoff simulation considering Hydrological Engineering Centre-Hydrologic Modeling System (HEC-HMS) and Personal Computer Storm Water Management Model (PCSWMM), respectively.The primary research proposes a framework for modeling the rainfall-runoff process using PERSIANN-CDR and a floodplain map in an ungauged urban watershed. The one-dimensional Hydrologic Engineering Centre-River Analysis System (HEC-RAS) model generates a flood inundation map for the pertinent flooding occurrences from the acquired peak hydrograph, providing a quantifiable display of the inundation extent percentage. The second research uses the PCSWMMs to show the extent of flooding. It also employs the compromise programming method (CPM) to rank the most critical sub-catchments based on three parameters: slope, surface area, and impervious area. Three low-impact development (LID) strategies over the watershed determine the best flood management option. Therefore, the overall study presents a comprehensive framework for flood management in urban watersheds that integrates satellite precipitation data, hydrologic modeling, and LID strategies. The framework can provide an accurate flood-prone zone and help prioritize critical sub-catchments for flood management options. The study proposes using HEC-HMS and PCSWMM models to simulate and analyze interactions between rainfall, runoff, and the extent of the flood zone. Furthermore, LID can be applied to reduce flooding in urban watersheds. Overall, the framework can be helpful for policymakers and system managers to build the watershed's resilience during catastrophic flooding events caused by climate change and urbanization.

In the recent century, a process of urbanization has increased globally. Previously rural or natural land have been converted into impervious surfaces to make way for housing, industries, and roads. This anthropogenic process has resulted in an increased amount of surface runoff from precipitation, so-called stormwater. Stormwater can accumulate a range of pollutants when it flows over the impervious surfaces of our cities. These pollutants can have a negative impact on the lakes and streams that receive the stormwater from the urban environments. To reduce the environmental problems associated with the content of stormwater, various techniques have been developed for stormwater treatment, with the aim of reducing the pollutant load in the runoff before it enters the receiving waterbody. One such technology is stormwater biofiltration, also known as bioretention. Stormwater biofilters were developed in the USA in the early 90's and they utilize the natural water remediation properties of plant-soil systems. They are generally characterized by a vegetated submerged filter bed with an underlying drainage layer. They have shown to be an effective method for stormwater pollutant removal. The treatment processes take place both in the vegetation and in filter material. As th ematerial choices and design of the biofilters can vary, so can its treatment performance. Stormwater biofilters have grown in popularity in the last decades since their development and numerous studies have been conducted to evaluate the systems’ treatment efficiency. However, knowledge gaps still exist regarding their implementation in colder climates and the suitability of different configurations and materials. This study examines the removal performance of total and dissolved heavy metals (Cd (cadmium),Cu (copper), Pb (lead) and Zn (zinc)), phosphorus, nitrogen and total suspended solids (TSS) in three stormwater biofilters in a Swedish climate, located in central Malmö. The current biofilters are designed with different configurations of their filter media and are built with 1) sand-basedfilter material 2) sand-based filter material with a submerged zone and 3) filter media consisting of 50% sand-based material in combination with 50% pumice. The results showed that the treatment capacity of the biofilters with a filter media of only sand (biofilter S) and with sand as well as a submerged zone (biofilter S_SZ) was similar for all pollutants. The reduction of total levels of metals (> 85 %) and TSS (>90 %) was consistently high and similar to levels achieved in previous studies for both temperate and colder climates. The removal of dissolved metals was lower in comparison to the removal of the total metal fractions, but the dissolved fractions were still generally reduced in the effluent. A positive removal of total phosphorus and total nitrogen was overall displayed in the effluent from the two biofilters; however,leaching was shown for the dissolved fractions. For nitrogen (N) species, the concentrations in the runoff were generally below the detection limit for the analysis making it difficult to establish probable removal percentages. For the biofilter S_P, which contained a mix of sand and pumice, the removal capacity was lowerfor all parameters compared to the other designs. Overall, the pollutant removal performances are regarded to be satisfactory for biofilters S andS_SZ and their implementation suitable for the given site. However, further investigations should be performed during warmer seasons, especially regarding the removal of nutrients.

Implementing optimal Low Impact Development (LID) practices has grown in popularity as a means of mitigating the adverse effects of urbanization and climate change. As such incorporating aspects of resilience for optimal LID design has become paramount. This study focuses on identifying the current LID optimization strategies and associated research gaps as well as assessing whether a quantitative approach to measure LID resilience exists. To do so, a systematic and bibliometric literature review on LIDs optimization and resilience is first conducted, based on which resilience, climate change, and uncertainty are recognised as hotspot keywords. The review also showed that no LID resilience quantification technique was available. Based on the latter outcome and to facilitate LID’s optimal design in future, this research proposes a new resilience quantification approach of LID by developing set of equations using Analytical Probabilistic Approach (APA) and continuous simulation approach using SWMM. The equations consider LID’s functionality and assess resilience using three indices: robustness, rapidity and serviceability. A new overall resilience index (the product of robustness and serviceability) and reliability index (the product of volumetric, occurrence, and temporal reliability) are proposed using different area ratios between contributing catchment and LID area to assure a resilient and safe LID system. LID costing tool of the Sustainable Technologies Evaluation Program (STEP) is subsequently utilized to estimate the capital cost of LID. Finally, a user-oriented design guideline is proposed for a cost-effective, resilient, and reliable LID system. Although this study adopts bioretention (BR) as a demonstration of the approach utility, the developed approach is applicable to any form of LID practices. / Thesis / Master of Applied Science (MASc) / There is a critical need to develop and implement optimal low-impact development (LID) practices in the field of stormwater management to mitigate the adverse effects of urbanization and climate change. This thesis is focused on developing quantitative resilient measurement approach of LID designs. A comprehensive literature review is first carried out, focusing on identifying various optimization methodologies, relevant gaps, and resilience assessment techniques. Subsequently, a novel resilience evaluation approach is developed, using bioretention (BR). By constructing a new reliability index, the entire BR system's reliability can also be assessed. Finally, a cost-effective, resilient and reliable design guideline for BR system is proposed. Although bioretention (BR) is used as an example in this study, the developed approach opens the gate to quantify the resilience of all types of LID practices.