Master of Arts (MA)
Geography & Environmental Studies
Faculty of Arts
Highland Creek can be defined as a flashy stream on the basis of the basin and channel hydrology and hydraulics. The extremes between the low and high-flow stage are dependent on the hydro-geomorphological features of the urban environment. The peculiarities of the urban landscape, serve to differentiate Highland Creek from naturally flashy channels.
The sedimentary structures were grouped into coarse and fine facies. The deposition of material apparently occurs under progressively decreasing energy levels, during falling flow stage.
Bedform and sedimentary structure associations, and their evolution are dependent on the dynamics of the flashy channel. That is, the development of bedforms and associated features should be examined in view of the magntidue or intensity of interaction between the bed material and the flow. Small-scale bedforms may not fully develop, if the bed configuration does not achieve a balanced state with the flow conditions, especially under rapidly varied flow conditions. The evolution of bedform associations, and the recognition of such phenomena are readily identified with falling-flow stage. The small-scale bedforms are not preserved in the alluvium, with the exception of bed armour. Parting lineations on ripples, ripples on channel bars, and channel bars on the channel form are recognized at low flow, although they are not preserved during subsequent events. On the macroforms, as for example, point bars and riffle bars, are likely to be preserved because of their low sensitivity to short-term flow dynamics.
The analysis of paleocurrent directions suggested that the small-scale bed features and sedimentary structures were largely inefficient for modelling general flow directions. Sample vector resultants deviate significantly from the trends displayed by the channel and the valley. The hierarchical ranking of the paleocurrent indicators was subdivided into two distinct groupings: a) a ranking of grand vector resultants with respect to the valley direction; and b) statistical ranking as derived from the comparison of concentration parameters (K) about the grant vector resultants of the sample groupings. The channel orientation is the best general paleocurrent indicator, since the vector resultant parallels the trend of the valley. Gravel fabrics and imbricates were combined to form the second order paleocurrent indicators. The grand resultants of the fabrics and the imbricates deviate by 17° from the parallel-to-flow direction of the valley and the channel. The small-scale sedimentary structures and bedforms are relatively inefficient paleocurrent indicators, since grand vector resultants deviate by 40° from the direction of the channel and the valley, as demonstrated by cross-strata and ripple orientations.
Bellamy, Kevin, "Sedimentary Structures and Paleocurrents in a Flashy Channel" (1979). Theses and Dissertations (Comprehensive). 1492.