The Dallas-Fort Worth International (DFW) Airport is located in a densely urbanized area with one of the fastest-growing populations in the U.S.A. The airport property includes a large tract of "protected" riparian forest that is unique to the urban surroundings. This dissertation explores variables that influence the benthic macroinvertebrate community structure found in urbanized prairie streams that were initially assessed by the University of North Texas (UNT) Benthic Ecology Lab during four, non-consecutive biomonitoring studies (2004, 2005, 2008, and 2014) funded by the DFW Airport. Additionally, land use analysis was performed using 5-meter resolution satellite imagery and eCognition to characterize the imperviousness of the study area watersheds at multiple scales. Overall, flow conditions and imperviousness at the watershed scale explained the most variability in the benthic stream community. Chironomidae taxa made up 20-50% of stream communities and outperformed all other taxa groups in discriminating between sites of similar flows and urban impairments. This finding highlights the need for genus level identifications of the chironomid family, especially as the dominant taxa in urban prairie streams. Over the course of these biomonitoring survey events, normal flow conditions and flows associated with supra-seasonal drought were experienced. Prevailing drought conditions of 2014 did not negatively influence stream communities, allowing this study to capture the long-term natural (temporal) variability of urban prairie stream communities. Such long-term studies are imperative for discerning between stream impairment versus natural variation, especially as droughts become more frequent and severe.

<p>Regardless of the design approach, the success or failure of stream restoration projects, especially in small urban streams is dependent on the accurate estimation of the channel-forming discharge. Among the different types of channel-forming discharges, effective discharge (Qe) is the only one that incorporates sediment transport mechanics in its estimation process. This thesis primarily focuses on Qe' paying special attention to the different Qe estimation techniques and the different parameters involved in the quantification of Qe.</p> <p>Of the two existing methods of determining Qe' the analytical approach is dependent on the goodness of fit between the frequency distribution pattern of the flow series and the assumed probability distribution function (pdf) and also the sediment rating curve. Frequency distribution pattern of daily streamflow data are conventionally approximated by lognormal pdfs. However, the flow characteristics of urban streams often have a definite percentage of zero flows throughout the year resulting in a low mean and high variance. That is why the conventional lognormal pdf often results in a poor fit which affects the analytical estimation of discharge such as Qe and half discharge (Q1/2) from the pdf. Therefore, mixed exponential and gamma distributions were introduced as a part of this research which improved the overall fit and provided a more accurate way of determining Qe and QI/2.</p> <p>Qe is dependent on a large number of variables (hydrological and sedimentological). Global sensitivity analysis of Qe using results from continuous hydrological modeling revealed that this channel-forming discharge is highly sensitive primarily to the sediment and then to the hydrological characteristics. The results also revealed that only when the exponent of the sediment rating curve is within a certain range can Q e and discharges corresponding to different recurrence intervals (Q t) be used analogously.</p> <p>The detennination technique of discharge indices such as Qe and Q1I2 are data and analysis intensive. As a result, in the case of degraded streams with little or no streamflow data their applicability becomes restricted. As a part of this research, the analytical probabilistic approach was applied to eradicate the problem associated with lack of data. But before developing the analytical probabilistic approach for the estimation of Qe and Ql/2 ' the existing probabilistic method of detennining peak discharge was applied in a practical design problem. Encouraged by the results, the analytical probabilistic approach was applied for detennining the probability of exceedence of streamflows. The advantage of the derived analytical probabilistic flow duration relationship is that it allows the construction of flow duration curves directly from watershed hydrological and climatological data, which are readily available as compared to streamflow data at daily or even smaller time steps, especially for small urban streams. The derived analytical probabilistic flow duration relationship sets up the foundation for detennining different discharge indices.</p> / Doctor of Philosophy (PhD)

No description available.

No description available.

Exotic species alter the streamside plant community by changing the resources available to the stream food web, causing cascading changes throughout the entire aquatic ecosystem. To better understand the impacts of exotic litter species on stream communities, investigations were made at global and local levels. A meta-analysis was performed to understand which environmental and litter quality factors impact native and exotic litter decay rates on the global scale. It was found that exotic species are likely to decay faster than native species at larger mesh sizes, and in warm temperature environments because high quality exotic leaves have a lower C:N ratio than native leaves. An urban litter decay experiment in Victoria, B.C. streams contrasting Alnus rubra, Salix sitchensis, Hedera sp., Rubus armeniacus and plastic trash found that trash decays more slowly than leaf litter, but leaf species all decay at the same rate, and stream invertebrates colonize all litter types equally. Significant differences in litter decay rates and invertebrate community alpha and Shannon diversities were also observed across the four different streams. The more that is learned about the impacts of exotic leaf litter, the better we are able to respond to keep streams as healthy and as biodiverse as possible. / Graduate / 2017-08-10 / 0329 / 0793 / kimkenn@uvic.ca

No description available.