Document Type

Thesis

Degree Name

Master of Environmental Studies (MES)

Department

Geography & Environmental Studies

Faculty/School

Faculty of Arts

First Advisor

Michael English

Advisor Role

Thesis Supervisor

Abstract

The Slave River Delta, 61˚15'N, 113˚30'W, is located at the mouth of the Slave River in the southeast arm of Canada's Great Slave Lake. Although the delta itself lies some 1600 km downstream from the W.A.C. Bennett Dam at Hudson's Hope, British Columbia, the mean annual discharge and sediment load of the Slave River have decreased by 16% and 33% respectively since regulation. Such alterations in the Slave River flow regime have significant implications for the growth of the River Delta since the transfer of sediment to the delta front is one of the most important factors in the landform’s continued development. Using data gathered from field research, historical sources, aerial photography, and two Geographical Information Systems, temporal variations in the distribution of flow throughout the Slave River Delta between 1946 and 1994 were identified along with changes in the extent of subaerial landforms. It is estimated that summer flows through Old Steamboat Channel and Middle Channel decreased by approximately 90% and 94% respectively over the 48 year period while discharge in Resdelta Channel has increased by close to 35%. Observations indicate that this shift has been accompanied by increases in channel length and bar formation in Old Steamboat Channel and Middle Channel. This suggests that energy gradients may be decreasing in the distributaries and may lead to their eventual abandonment. According to the available data, completion of the W.A.C. Bennett Dam in 1968 appears to have had some impact on the loss of approximately 652 ha within the delta between 1966 and 1977; however, deltaic growth since regulation has increased by almost three times that of the pre-impoundment period. Examination of depositional environments within the Slave River Delta indicates that most of the growth during the post-impoundment period has occurred within the outer delta region in the quiet sheltered environments of Nagle Bay and Jackfish Bay. Additional growth has been observed in the central portions of the delta as well. Analysis of suspended sediment concentration ([SS]) and discharge in distributary channels indicates a relatively strong relationship during the summer and autumn seasons; however, the relationships is complicated during the spring by the influence of breakup. The relationship between discharge and [SS] is dependent upon the distribution of flow throughout the delta. Within two channel bifurcations of the main body of the Slave River, [SS] versus discharge is generally characterised by the classic power relationship defined by Leopold and Maddock (1953), although there is some indication that the system may be sediment limited during peak flows in the summer. Beyond two bifurcations, discharge and [SS] tends to be inversely related and channels within these classifications are generally characterized by deposition.

Convocation Year

1997

Convocation Season

Spring

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