River regulation imposes direct changes on flow and sediment delivery, producing a suite of downstream responses in channel morphology. On the Peace River in northern British Columbia and Alberta, the W.A.C. Bennett hydroelectric dam has reduced peak flows while leaving sediment load effectively unchanged. My research aims to identify systematic, regulation-induced patterns of channel gradation in the mainstem Peace and its tributaries below the dam. The significance of regulation within the natural variability of basin hydrology is assessed by comparing actual regulated river flows to simulated flows based on reservoir level fluctuations. Mainstem bed elevation changes are assessed from repeatedly surveyed cross-sections and specific gauge records, supplemented by analysis of channel planform change. Results show degradation to be minimal, due to the naturally armoured gravel bed and elimination of competent flows. The predominant pattern in the upper regulated reaches is one of aggradation below tributary confluences and other sediment sources. In the long term, the Peace River may be raising its proximal bed to compensate for a loss of sediment transport capacity since regulation. Backchannel abandonment and other planform changes appear to be occurring more slowly, and may be less important to river slope adjustment. Data from the lower river are few and inconclusive. Tributary gradation was investigated by means of air photo, field surveys and dendrochronology of young floodplains. These methods reveal a range of responses to regulation, including degradation, aggradation and no apparent change. Degradation due to reduced tributary base level appears to attenuate downstream as the Peace River flood is restored by unregulated tributary flows, though this trend is complicated by other factors such as tributary sediment supply, flood timing between tributary and mainstem, and ice activity. Aggradation due to tributary fan growth may mitigate degradation; it is a less prominent response, though it appears to predominate in the lower Smoky River. Regulation is a secondary effect in the tributaries, and its influence on gradation has been limited. On the mainstem, however, it is a primary change, and the resulting channel gradation will take a long time to complete. / Arts, Faculty of / Geography, Department of / Graduate

The Chilliwack River flows through the Cascade Mountains until reaching a narrow gorge near Vedder Crossing where it flows onto the Fraser Lowlands and eventually meets the Fraser River. Below Vedder Crossing, the river is actively building an alluvial fan by depositing its sediment load of gravel and sand. This deposition has resulted in frequent channel shifts over the fan surface with the most recent migration occurring around 1894 when the river shifted down Vedder Creek. Over the last century the Vedder River has been undergoing very complex changes in response to changes in the incidence of severe floods, changes in sediment supply and interference from river training. Extensive channelization works carried out in the 1960's induced temporary degradation over part of the channel which was accompanied by rapid aggradation in the reach immediately downstream. This rapid channel adjustment ceased in less than 10 years. In 1975 a flood having a return period of about 10 years deposited 260,000 cubic yards of sediment onto the fan which increased the mean bedlevel by nearly 1 foot. By comparison, the average annual deposition rate was estimated to be 72,000 cubic yards per year. Based on bedload transport calculations, approximately 700,000 cubic yards of sediment could be deposited by a 50 year rainstorm flood. In order to provide long term flood control, either the upstream sediment supply will have to be reduced or dredging will have to be carried out on the lower river. It is not feasible to eliminate aggradation by transporting the incoming bedload through the system and into the Fraser River. Some strategies are considered which, by controlled dredging and training would maintain the channel permanently in its present position. More severe floods would be contained by set-back dikes. It is thought that, with care, these measures could be consistent with salmon habitat requirements. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Thesis (M.Sc. (Zoology)) -- University of Limpopo, 2019 / Freshwater ecosystems in South Africa are losing their quality and quantity over time due to pollution mainly from mining, agriculture, industries, deforestation, sewage systems, construction of dams, channel modification and over extraction of water. The Dwars River, a tributary of the Olifants River, is of no exception, as recent studies indicated an increase in nutrient input possibly from agriculture. The Dwars River is an important source of water for nearby communities (Ga-Mampuru). The aim of the study was to assess water and sediment quality of the Dwars River using macroinvertebrates as bioindicators of pollution. Water and macroinvertebrates sampling were done seasonally from July 2017 to May 2018. The water quality results indicated that non-toxic constituents such as salinity and EC (Electrical Conductivity) were above permissible limits stipulated by the DWAF (1996) guidelines. More sensitive taxa were found upstream, despite high concentrations of some nutrients and metals in the water column. The high abundance and distribution of macroinvertebrates observed upstream was confirmed by the Canonical Correspondence Analysis (CCA), South African Scoring System (SASS5) and Average Score Per Taxon (ASPT) results during the study. Site 1 was dominated by the most sensitive taxa and this could be due to high dissolved oxygen content and increased heterogeneity of the area. Site 4 was dominated by the most tolerant taxa, according to the CCA, SASS score and ASPT results. This could possibly be due to the nutrients and heavy metals washed from upstream, which get adsorbed by the sediment. The results for species abundance, diversity and richness indicated that Ephemeroptera was the most abundant, while Diptera was the most diverse. Ephemeropterans are known to be indicators of good water quality. Site 1 had the highest number of families and orders while site 4 had the least families and orders. Ephemeroptera, Plecoptera and Tricoptera (EPT) taxa richness and Shannon diversity (H’) index values are high upstream and decrease downstream. Overall, the SASS5 indices, CCA and physicochemical results indicated that the water quality in the Dwars River is deteriorating in most impacted sites / National Research Foundation (NRF) and VLIR

>Magister Scientiae - MSc / The ecology of spring fed rivers has been under-studied in South Africa. As a result, little is known or documented on the effects of seasonal variation of flows on the species diversity, distribution and abundance of aquatic macroinvertebrates in rivers dominated by spring discharges in, South Africa. In order to expand our understanding of the structure and functioning of spring fed rivers, the study determined and compared the current ecological state of the spring fed Liesbeek River tributary and the non-spring fed Disa River focusing on discharge, water quality and macroinvertebrates.

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