京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21377号 / 農博第2301号 / 新制||農||1069(附属図書館) / 学位論文||H30||N5150(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 奥本 裕, 教授 白岩 立彦, 教授 稲村 達也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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The objective of this thesis was to develop guidance for an anchored geotextile Rapidly Deployable Armoring System for the landward side of earthen levees to mitigate the effects of storm surge and overtopping waves. A case study of the Backwater Levee protection placed during the 2011 Mississippi River flood by the US Army Corps of Engineers was performed to prove construction feasibility. Full scale anchor testing was performed for 0.3 and 0.6 m rod shaped anchors to determine their load deflection behavior. Anchor test data and shear stress profiles based on flume testing presented in literature were used in conjunction with surface to surface contact interactions to develop a single-layer elastic membrane finite element model (SLEMM) of an RDAS to provide design guidance. The SLEMM appears to perform the finite element formulations correctly, but does not produce physically meaningful results. Further improvements to the model are needed for useable design.

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An investigation to assess the anthropogenic pollutant loads, transport and impact on shallow groundwater in one of Kampala’s peri-urban areas (Bwaise III Parish) was undertaken. Bwaise III is a densely populated informal settlement with a high water table (<1.5 m) and inadequate basic social services infrastructure (e.g, sanitation, safe water supply, roads, etc). Field surveys were undertaken to identify, locate and quantify various pollutant sources. Information on the usability and operational aspects of the excreta and solid waste management systems was obtained from consultations with the residents. Water from installed monitoring wells and one operational protected spring and wastewater (sullage) characteristics (quality, discharges for drains and spring, water levels for the wells) as well as soil characteristics (soil stratigraphy, physical and chemical) were determined through field and laboratory measurements. Laboratory batch experiments were undertaken to estimate phosphorus sorption potential of the soils. The results reveal that excreta disposal systems, solid waste and sullage are the major contributors to shallow groundwater contamination. High contaminant loads from these sources accumulate within the area resulting in widespread contamination. The water table responds rapidly to short rains (48hr) due to the pervious and shallow (<1 m) vadose zone, which consists of mostly organic fill material. Rapid water quality deterioration (increased thermotolerant coliforms, organic content in the form of total kjedahl nitrogen, phosphorus) following rains potentially follows from leaching, desorption and macropore flow. Spatial variation of the water quality in the area is largely related to anthropogenic activities within the vicinity of the well sources. Animal rearing, solid waste dumps and latrines are seen to result in increased localised microbial and organic content during the rains. The spring discharge with high nitrate levels does not respond to short rains suggesting that this source is fed by regional baseflow. The corresponding high microbial contamination in this case is a result of observed poor maintenance of the protection structure leading to direct ingress of contaminated surface runoff. Natural attenuation of contaminants is very limited. Estimated bacteria die-off rates are very low, about 0.01hr-1, suggesting a high risk for microbial contamination. The soils still have potential to retain additional phosphorus, whose sorption is largely a function of iron, available phosphorus and moisture content of the soils. This is also seen with the model results in which the phosphorus contaminant plume sticks to the surface irrespective of the rainfall infiltration rates. Simulation results show that continuous heavy intense rains (> 0.25mm/min) result in rapid flooding occurring within 1hr to 2 days. With lower rains, the water table does not rise to the surface, and no flooding takes place. Protection of the shallow groundwater in the area requires socio-technical measures targeting reduction of pollutant loads within the area as well as a wider spring catchment. Re-protection of the spring, coupled with awareness creation, should be immediately addressed so as to reduce microbial contamination. Community participation in solidwaste management should be encouraged. Resource recovery systems such as composting of the mostly organic waste and use of ecological sanitation toilet systems should be piloted in the area. Successful operation of the systems however depends on continuous sensitisation of the communities. / QC 20101207

Mapping is an enabler for further actions. With the map of an area available, it is possible to plan ahead. Maps of landmasses and heavily used deep waters have been produced and are in use but many shallow waters have been largely unmapped. This thesis proposes and examines two methods of control to produce depth maps of shallow waters using multiple autonomous surface vehicles. Assumptions about the environment are kept to a minimum and agents are expected to explore and map inside a given polygonal boundary. Gaussian process regression is used to guide the agents to areas with large uncertainty. A group of autonomous surface vehicles are used for experimental evaluation. Existing works in this area are compared with the method proposed in this thesis to evaluate map quality and time needed to create the map. Results show that one of the proposed methods is best suited for fast and raw map generation while the other strikes a good balance between accuracy and speed. / Att ha tillgång till en karta över ett område är en förutsättning för många olika aktiviteter, och därför har det skapats allt mer exakta kartor över de flesta landområden. För hav och sjöar har man skapat mer ungefärliga djupkartor för att undvika grundstötningar för sjöfart. Grundare områden har däremot ofta undvikits av stora djupmätningsfartyg, och är därför i hög grad okarterade.I denna rapport föreslås och analyseras en metod för att kartera djupet i grunda områden med hjälp av en grupp autonoma ytfarkoster. Givet en polygon inom vilken man vill ha botten karterad skall gruppen autonomt söka av området med få ytterligare antaganden. Gaussiska processer används för att styra farkosterna mot områden med stora mätosäkerheter, och algoritmen utvärderas i riktiga experiment.Resultaten jämförs med befintliga metoders prestanda, med avseende på kartkvalitet och tid för kartering. Resultaten visar att en av de föreslagna metoderna är snabb men mindre noggrann, medan den andra ger en bättre avvägning mellan kvalitet och uppdragstid.

Yes / A set of shallow-water equations (SWEs) based on a k-epsilon Reynold stress model is established to simulate the turbulent flows over a complex roughness bed. The fundamental equations are discretized by the second-order finite-difference method (FDM), in which spatial and temporal discretization are conducted by staggered-grid and leap-frog schemes, respectively. The turbulent model in this study stems from the standard k-epsilon model, but is enhanced by replacing the conventional vertical production with a more rigorous and precise generation derived from the energy spectrum and turbulence scales. To verify its effectiveness, the model is applied to compute the turbulence in complex flow surroundings (including a rough bed) in an abrupt bend and in a natural waterway. The comparison of the model results against experimental data and other numerical results shows the robustness and accuracy of the present model in describing hydrodynamic characteristics, especially turbulence features on the complex roughness bottom. / National Key Research and Development Program of China (Grant No: 2016YFE0122500, 2013CB036401 and 2013CB036402), China Postdoctoral Science Foundation (Grant No: 2016M591184) and Programme of Introducing Talents of Discipline to Universities (Grant No: BC2018038) / Research Development Fund Publication Prize Award winner, June 2019.

No / Nazarbayev University Seed Grant, entitled “Environmental assessment of sediment pollution impact on hydropower plants”.

Here the nature of gas phase processes and their implications for flow and transport were examined using a pilot-scale, 2-dimensional, laboratory tank instrumented for direct, in situ trapped gas measurements. Experimental conditions mimicked an unconfined, homogeneous sand aquifer with horizontal flow. Key areas of investigation included i) trapped gas dissolution following a water table fluctuation; and ii) gas phase dynamics within a hydrocarbon plume experiencing dissolved gas production via biodegradation. In the first experiment, dissolution occurred as a diffuse, wedge-shaped front propagating down-gradient in the tank over time, with enhanced dissolution at depth. Front advancement at the deepest monitoring point was 4.1 - 5.7x faster. This dynamic, depth-dependent pattern was mainly attributed to increased dissolved gas solubility. An estimated 12% increase in quasi-saturated hydraulic conductivity (Kqs) also contributed to greater dissolution at depth. Overall, the dissolution front near the water table advanced 1 m down-gradient in 344 days, suggesting that gas trapped shallowly will likely persist for significant periods of time. The utility of total dissolved gas pressure sensors for simple in-well measurements to detect trapped gas and monitor its dissolution were also demonstrated. During the second experiment, biodegradation occurred under variable redox conditions, ranging from denitrification to methanogenesis. Significant in situ increases in trapped gas were observed within the tank over 330 days. Maximum gas saturations never exceeded 27% of pore volume even during continued dissolved gas production, indicating ebullition upon reaching a gas phase mobilization threshold. Consequently, associated reductions in Kqs were restricted to a factor of 2 or less, but still appeared to alter the groundwater flow field. While trapped gas increases within the biodegradation plume were expected, declines in gas saturations were also observed. Thus, the overall pattern of trapped gas growth exhibited high spatial and temporal variability. Influencing factors included changes in hydrocarbon inputs and microbial controls on redox zonation, in addition to ebullition and changes in groundwater flow; emphasizing that gas phase growth in contaminant plumes will be highly complex and dynamic in the natural systems. Given the impacts on hydraulic conductivity, and the fate and transport of volatile compounds, an improved understanding of quasi-saturated conditions will be beneficial for various groundwater applications, from recharge and paleoclimate studies to site characterizations and remediation strategies. / Dissertation / Doctor of Philosophy (PhD)