<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)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/14219 |
| Date | 09 1900 |
| Creators | Quader, Asif |
| Contributors | Guo, Yiping, Civil Engineering |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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