Doctor of Philosophy

dissertationGreen Stormwater Infrastructure (GSWI) has emerged as the next-generation stormwater management solution for urban areas and can provide greater flexibility in treatment options, design type, and site locations compared to traditional stormwater management alternatives. While methodologies for simulating GSWI functionality at the individual site level are well established, the complexity of representing GSWI collectively throughout a watershed remains problematic. One reason is the lack of literature comparing methods that represent GSWI networks within urban watershed models. This research addresses this need by evaluating GSWI up-scaling methods and the associated impacts on estimated benefits from varying spatial distribution and subcatchment aggregation. The first component of this research focuses on GSWI up-scaling methods and the impacts to the hydrologic response estimates. Comparisons are drawn from two GSWI models built to meet performance criteria metrics, such as drawdown time and runoff capture volume. One model applies a GSWI design-specific up-scaling approach, while the other model represents the GSWI network as a nonspecific collective unit. Results from an assessment of the hydrologic response output between the models show comparable estimates within 5% for peak discharge, average flow rate, and volume. Therefore, representing GSWI as nonspecific collectives can comparably estimate watershed-scale benefits to those estimated using representations with design-specific details. The second component compares various GSWI spatial distribution and aggregation modeling scenarios and identifies the impacts of each on hydrologic response estimates. Spatial targeting of GSWI is compared to output from uniformly distributed GSWI in all subcatchments. Statistical assessments using t-test methods indicate that spatial targeting does not significantly impact estimates for volume, peak flow rate, or average flow rate estimates. Increasingly aggregated GSWI subcatchments had varied hydrologic response estimates of volume, peak flow rate, and average flow rate for urban areas, though not varied enough to be statistically significant for the Philadelphia model until the subcatchments were aggregated to a single subcatchment. However, the impact at the event level was obvious for peak discharge. Thus, for watershed areas with smaller subcatchment sizes, the greatest impact is to the peak flow rates. For SLC model scenarios, aggregating GSWI subcatchments significantly influenced all flow

TWINLATIN: Twinning European and Latin-American river basins for research enabling sustainable water resources management. Combined Report D3.1 Hydrological modelling report and D3.2 Evaluation report

Water use has almost tripled over the past 50 years and in some regions the water demand already exceeds supply (Vorosmarty et al., 2000). The world is facing a “global water crisis”; in many countries, current levels of water use are unsustainable, with systems vulnerable to collapse from even small changes in water availability. The need for a scientifically-based assessment of the potential impacts on water resources of future changes, as a basis for society to adapt to such changes, is strong for most parts of the world. Although the focus of such assessments has tended to be climate change, socio-economic changes can have as significant an impact on water availability across the four main use sectors i.e. domestic, agricultural, industrial (including energy) and environmental. Withdrawal and consumption of water is expected to continue to grow substantially over the next 20-50 years (Cosgrove & Rijsberman, 2002), and consequent changes in availability may drastically affect society and economies. One of the most needed improvements in Latin American river basin management is a higher level of detail in hydrological modelling and erosion risk assessment, as a basis for identification and analysis of mitigation actions, as well as for analysis of global change scenarios. Flow measurements are too costly to be realised at more than a few locations, which means that modelled data are required for the rest of the basin. Hence, TWINLATIN Work Package 3 “Hydrological modelling and extremes” was formulated to provide methods and tools to be used by other WPs, in particular WP6 on “Pollution pressure and impact analysis” and WP8 on “Change effects and vulnerability assessment”. With an emphasis on high and low flows and their impacts, WP3 was originally called “Hydrological modelling, flooding, erosion, water scarcity and water abstraction”. However, at the TWINLATIN kick-off meeting it was agreed that some of these issues resided more appropriately in WP6 and WP8, and so WP3 was renamed to focus on hydrological modelling and hydrological extremes. The specific objectives of WP3 as set out in the Description of Work are

The AtollGame Experience: from Knowledge Engineering to a Computer-Assisted Role Playing Game

This paper presents the methodology developed to collect, understand and merge viewpoints coming from different stakeholders in order to build a shared and formal representation of the studied system dealing with groundwater management in the low-lying atoll of Tarawa (Republic of Kiribati). The methodology relies on three successive stages. First, a Global Targeted Appraisal focuses on social group leaders in order to collect different standpoints and their articulated mental models. These collective models are partly validated through Individual Activities Surveys focusing on behavioural patterns of individual islanders. Then, these models are merged into a single conceptual one using qualitative analysis software. This conceptual model is further simplified in order to create a computer-assisted role-playing game.Knowledge Elicitation, Associative Network, Ontology, Water Management, Pacific, Tarawa

Green roof retrofitting: a study into the structural implications associated with green roof retrofits.

Masters Degree. University of KwaZulu-Natal, Durban.The realities of climate change have fast become apparent. It is for this reason that vast quantities of research explored potential mitigation methods to alleviate the strain placed on the environment and the planet by climate change. Structural engineers and the greater engineering community utilise green building practices in an effort to reduce carbon emissions and hence, lower the carbon footprint of a structure. One such practice has been the introduction of green roofs. This study looks at the potential of retrofitting structures with green roofs. It investigates various construction materials and their influence on the potential of retrofitting structures with green roofs. In addition, this thesis investigates the influence of considerations given during structural design such as a structure’s span and the utilisation of different section sizes, in an attempt to provide a general assessment into the practicality of a green roof retrofit. This study has shown that there is a significant potential in retrofitting existing structures with green roofs. In addition, the results of the study have shown that concrete structures are more likely to have a higher potential to be retrofitted. The potential to be retrofitted with a green roof depends on the carrying capacity that in turn depends on a range of factors. However, the primary factor in the magnitude of the carrying capacity is essentially the choice of element decided upon by the structural designer. This study has proved that green roofs have the potential to reduce the temperature of the substructure to a greater degree when compared to other roof types. It has further proved that green roofs possess the potential to significantly reduce storm water run-off in comparison to other roof types. However, this study has highlighted that there is significant basis for further investigation into structural implications associated with green roofs and other relevant area

Capturing the role of the co-play of land use and rainfall on water and sediment flux dynamics across different spatiotemporal scales in intensively managed landscapes

Anthropogenic activities in intensively managed landscapes (IMLs) have significantly modified material travel times and delivery, and have led to more pronounced event-based dynamics compared to undisturbed conditions. Understanding and mitigating human impacts requires the use of both field-based observations and physically-based numerical models to tease out causal relationships and feedbacks between the relevant processes across the cascade of scales, from the plot to the watershed. Unfortunately, there are no event-based numerical models capable of adequately simulating sediment fluxes across scales in IMLs, thus hampering our ability to understand and mitigate anthropogenic impacts.The goal of this study was to develop a conceptual modeling framework for IMLs that considered all the connections and interactions between terrestrial and in-stream sources on an event basis, and to use the framework to identify a characteristic scale unit (CSU) representative of sediment flux laws within the drainage network. The CSU was considered to be a scale at which local-scale variability in landscape properties ceased to have an effect on mean trends in sediment fluxes and, thus, an appropriate scale for simulating/monitoring sediment fluxes for watershed management purposes.The framework was developed and tested in the South Amana sub-watershed (SASW), IA. An upland erosion model was coupled with an instream sediment transport model to simulate material fluxes along different pathways in SASW. A sediment fingerprinting model was also utilized to constrain the predicted contributions of terrestrial and instream sources. Modeling advances made included the incorporation of a surface roughness evolution threshold, space/time variant flow resistance representations of landscape attributes, and the stochastic representation of material origins, travel times, and delivery to the watershed outlet. The developed model was validated via an extensive field campaign performed at scales ranging from the plot to the sub-watershed.The study results revealed thresholds of influence of landscape roughness attributes, and highlighted important intra-seasonal trends in source contributions driven by the co-play of land use and rainfall. A CSU for sediment fluxes and the factors affecting it were identified. Future studies must examine the CSU as dictated by the interplay between event-based and seasonal dynamics, and the implications for watershed management

Modeling water resources management at the basin level: review and future directions

Water quality / Water resources development / Agricultural production / River basin development / Mathematical models / Simulation models / Water allocation / Policy / Economic aspects / Hydrology / Reservoir operation / Groundwater management / Drainage / Conjunctive use / Surface water / GIS / Decision support systems / Optimization methods / Water supply

Building and Using a Hydrology Experiment for Place-Based Learning With Native American Students

Geoscience has a known diversity problem, specifically a participation gap of ethnic minority representation, and it is especially severe regarding Native American representation. To address this participation gap, an identity gap needs to be addressed first. Native students need to visualize themselves as geoscientists before they can commit to geoscience programs and careers. This project uses a hands-on, place-based learning activity as an opportunity for Native students to better see themselves as geoscientists. A portable rainfall simulator was constructed, calibrated, and refined for use in teaching concepts about rainfall, runoff, and erosion. It was employed in place-based learning exercises with Native students from the Four Corners region of the southwestern United States. Students who volunteered to complete surveys and participate in a group interview provided results indicating they could indeed see themselves as scientists better after the exercise

Assessment of trends in rainfall-runoff events in a mountain basin: analysis of the influence of initial conditions by means of a hydrological model and GIS

openDespite the expectation that increases in rainfall with climatic change will result in increases in pluvial flooding, there is more historical evidence for decreases in flood magnitude. The small basin of La Vizza, in the Eastern Italian Alps, provides a clear example for this type of trend divergence. In this basin, flood magnitudes are decreasing, despite increasing rainfall extremes. In this thesis we investigate how changes in soil moisture and snow water equivalent play a role in controlling the above divergence. Using catchment average precipitation and temperature, and a continuous hydrological model able to specify soil moisture and snow water equivalent at the start of each rainfall-runoff events, we aim to better understand the relative role of the two drivers in controlling the trends in runoff events (both volumes and peaks). With this overarching objective, the thesis has the following specific objectives: i) Quantify the diverging trends in annual maxima of rainfall and runoff events for the study basin; ii) Quantifying the snow cover area and snow water equivalent by means of the TOPMELT model and validating it by using MODIS satellite images; iii) Quantify the trends for event-generating precipitation, antecedent soil moisture, and antecedent snow water equivalent and assess their role in controlling the trend in runoff events. The monotonic trends will be assessed using the non-parametric Mann-Kendall test and the trend slopes will be determined by Sen’s slope method. The findings of this research will have significant implications for understanding the role of the underlaying hydrological factors such as soil moisture and snow water equivalent controlling the trends in rainfall-runoff events in other similar mountain basin.Despite the expectation that increases in rainfall with climatic change will result in increases in pluvial flooding, there is more historical evidence for decreases in flood magnitude. The small basin of La Vizza, in the Eastern Italian Alps, provides a clear example for this type of trend divergence. In this basin, flood magnitudes are decreasing, despite increasing rainfall extremes. In this thesis we investigate how changes in soil moisture and snow water equivalent play a role in controlling the above divergence. Using catchment average precipitation and temperature, and a continuous hydrological model able to specify soil moisture and snow water equivalent at the start of each rainfall-runoff events, we aim to better understand the relative role of the two drivers in controlling the trends in runoff events (both volumes and peaks). With this overarching objective, the thesis has the following specific objectives: i) Quantify the diverging trends in annual maxima of rainfall and runoff events for the study basin; ii) Quantifying the snow cover area and snow water equivalent by means of the TOPMELT model and validating it by using MODIS satellite images; iii) Quantify the trends for event-generating precipitation, antecedent soil moisture, and antecedent snow water equivalent and assess their role in controlling the trend in runoff events. The monotonic trends will be assessed using the non-parametric Mann-Kendall test and the trend slopes will be determined by Sen’s slope method. The findings of this research will have significant implications for understanding the role of the underlaying hydrological factors such as soil moisture and snow water equivalent controlling the trends in rainfall-runoff events in other similar mountain basin

Exploring the physical controls of regional patterns of flow duration curves – Part 1: Insights from statistical analyses

The flow duration curve (FDC) is a classical method used to graphically represent the relationship between the frequency and magnitude of streamflow. In this sense it represents a compact signature of temporal runoff variability that can also be used to diagnose catchment rainfall-runoff responses, including similarity and differences between catchments. This paper is aimed at extracting regional patterns of the FDCs from observed daily flow data and elucidating the physical controls underlying these patterns, as a way to aid towards their regionalization and predictions in ungauged basins. The FDCs of total runoff (TFDC) using multi-decadal streamflow records for 197 catchments across the continental United States are separated into the FDCs of two runoff components, i.e., fast flow (FFDC) and slow flow (SFDC). In order to compactly display these regional patterns, the 3-parameter mixed gamma distribution is employed to characterize the shapes of the normalized FDCs (i.e., TFDC, FFDC and SFDC) over the entire data record. This is repeated to also characterize the between-year variability of "annual" FDCs for 8 representative catchments chosen across a climate gradient. Results show that the mixed gamma distribution can adequately capture the shapes of the FDCs and their variation between catchments and also between years. Comparison between the between-catchment and between-year variability of the FDCs revealed significant space-time symmetry. Possible relationships between the parameters of the fitted mixed gamma distribution and catchment climatic and physiographic characteristics are explored in order to decipher and point to the underlying physical controls. The baseflow index (a surrogate for the collective impact of geology, soils, topography and vegetation, as well as climate) is found to be the dominant control on the shapes of the normalized TFDC and SFDC, whereas the product of maximum daily precipitation and the fraction of non-rainy days was found to control the shape of the FFDC. These relationships, arising from the separation of total runoff into its two components, provide a potential physical basis for regionalization of FDCs, as well as providing a conceptual framework for developing deeper process-based understanding of the FDCs

An evaluation of dryland watershed development projects in India:

This study addresses three main research questions: 1) What projects are most successful in promoting the objectives of raising agricultural productivity, improving natural resource management and reducing poverty? 2) What approaches enable them to succeed? 3) What nonproject factors also contribute to achieving these objectives? The major hypotheses are that participatory approaches that devote more attention to social organization yield superior project impact, and that favorable economic conditions and good infrastructure also support better natural resource management and higher productivity.Natural resources India Management., Poverty India., Agricultural productivity Economic aspects India.,