Ian A. Campbell

Spatial scale dependence of sediment dynamics in a semi-arid badland drainage basin

Abstract Problems of spatial scale transference are of key interest in drainage basin research. The objective of this study was to investigate the spatial scale dependence of sediment dynamics in semi-arid badland drainage basins. Simulated rainfall experiments indicated that on microscale plots runoff generation and sediment entrainment occurred when total rainfall exceeded 0.5 to 6 mm on pediment surfaces, 1.5 to 4 mm on sandstone surfaces, and 8 to 25 mm on shale surfaces. The sediment concentration/discharge relationship for two mesoscale basins displayed a change from clockwise to counterclockwise hysteresis when total rainfall exceeded the threshold rainfall for the initiation of flow in deep tunnel systems. The initiation of tunnel flow causes counterclockwise hysteresis due to a delayed increase in sediment concentrations during a runoff event. This contrasts with the clockwise hysteresis caused by flushing in the early stages of runoff for smaller rainstorms. Comparison of micro- and mesoscale sediment dynamics indicates that microscale thresholds are not by necessity in evidence at the mesoscale. In addition, at the mesoscale elements exist which are non-existent at the microscale, e.g. a deep tunnel system. The behaviour of the mesoscale basin is dominated by these elements rather than by the microscale components it contains.

Glaciotectonism and landsliding in Little Sandhill Creek, Alberta

Abstract Slope failure and gully erosion along Little Sandhill Creek, a tributary of the Red Deer River, Alberta, Canada, has exposed large stratigraphic sections in which the effects of glaciotectonism and landsliding are clearly revealed. Six main units are identified ranging from a deposit of coarse fluvial sands, through various glacial diamictons and gravels and sands, to postglacial fluvial and lacustrine (pond) and aeolian sediments. Incision by Little Sandhill Creek since late Wisconsinan deglaciation ca. 12,500 B.P., resulted in periodic landslides culminating in the main slope failure which occurred post ca. 5400 B.P. The slide was reactivated by irrigation water return flow from the adjacent prairie surface.

Solute release and sediment entrainment on microcatchments in the Dinosaur Park badlands, Alberta, Canada

Abstract This paper first considers the uptake of solutes and entrainment of sediments in runoff generated by simulated rainstorms on different badland surfaces, then, properties of the regolith materials related to solute uptake are described and studied in a number of simple laboratory experiments. Field and laboratory results are in close agreement. Runoff, solute and sediment uptake are profoundly influenced by the large amounts of sodium montmorillonite present in the regolith. Shale surfaces, although responding late to rainfall, release increasing amounts of sediment and solutes (sodium and sulphate) as they swell and increase in erodibility. On other surfaces low rates of rainfall acceptance are caused by the secretion of montmorillonite gels, and there is a gradual decrease in solute and sediment concentration as accumulated salts are flushed from the surface. The effect of the chemistry of the simulated rainfall on the experimental results is examined. It is considered possible to characterize the pattern of solute and sediment uptake on the different badland surfaces and to apply this information to the identification of runoff sources in mesoscale drainage basins and to the routing of storm runoff.

Glacial and postglacial stratigraphy of Dinosaur Provincial Park and surrounding plains, southern Alberta, Canada

Abstract Thirty-one stratigraphic logs from the Dinosaur Provincial Park area reveal seven major lithofacies associations (LFAs). LFA 1 is a preglacial fluvial deposit recording deposition on a sandy braided floodplain. This LFA fines upwards to LFA 2, a glacilacustrine deposit, which records the first advance of Laurentide glacier ice into the region. Erosional contacts between LFAs 1 and 2 and bedrock suggest that large expanses of badlands may have existed prior to glaciation. LFA 3 is a grey till which, together with glacitectonized bedrock, records ice movement from the northeast. LFA 4 represents supraglacially derived diamictons and outwash. Its oxidized colour indicates either a considerable period of subaerial weathering or groundwater activity and the deposit is tentatively assigned an interstadial or interglacial age. A second glaciation is recorded by LFA 5 (heterogeneous diamicton) and LFA 6 (homogeneous diamicton). LFA 5 records a period of subglacial molding and then cavity filling by fluvial and debris flow deposits. LFA 6 records lodgement and melt-out of the same glacier ice after it had glacitectonically thrust large rafts of older LFAs. The sequence of molding-cavity fill-tectonism-melt out represents large scale decoupling of the glacier from its bed and later surges, creating extensive deformation of the substrate. Melt-out was interrupted in some places by remobilization caused by surges which continued throughout ice retreat. LFAs 7a-7e record deposition in glacilacustrine, fluvial, pond and aeolian environments after deglaciation. Some previously reported and new radiocarbon dates on regional and local surface drainage are discussed with reference to fluvial incision and Holocene climate. All LFAs are tentatively correlated with stratigraphic sequences reported from adjacent areas of southern Alberta and former regional glaciodynamics are assessed.

Sediment entrainment and transport during local rainstorms in the Steveville Badlands, Alberta

Summary Patterns of runoff generation and sediment yield in a small badland drainage basin show that localized rainstorms of short duration transport substantial amounts of sedimentinto the Red Deer River. Experimental plot studies indicate that the threshold precipitation necessary to initiate runoff varies greatly with lithology. Despite lithologic differences, spatial variation in rainfall and highly complex topography, good correlation was noted between sediment yields assessed by different methods. Although great annual and seasonal variations in sediment yield occur, the overall pattern of freesion rates is remarkably consistent.

Runoff chemistry as an indicator of runoff sources and routing in semi-arid, badland drainage basins

Abstract The temporal variations of runoff chemistry during a storm event reflect the dynamics of runoff and solute sources. This study concerns the use of runoff chemistry to investigate runoff generation and routing in semi-arid, badland basins drained by ephemeral streams. Discharge, sediment concentration, and electrical conductivity (EC) were measured at the outlets of a 20.2 hectare and a 7.9 hectare basin. Runoff samples were analysed for sodium, potassium, calcium, magnesium, aluminium, and sulphate. EC values ranged from 255 to 800 μS cm −1 . During the initial phase of flow, EC values dropped sharply owing to the flushing effect. The EC reached a minimum around the time of peak flow, and slowly increased during the falling stage owing to the dissolution of suspended sediment and, during large storms, the influx of solute-rich water from tunnel systems and shale surfaces. Sodium was the dominant cation, and variations of sodium concentration were similar to those of EC. The concentrations of the remaining cations showed little variation throughout a storm event. Cation composition was controlled by the displacement of sodium from the exchange sites by divalent cations. Sulphate concentration was strongly correlated with EC, and showed the same pattern of variation throughout a runoff event. Nevertheless, for a similar EC, sulphate concentrations were proportionally lower in runoff from sandstone and pediment surfaces, and proportionally higher in tunnel flow, runoff from shales, and during initial flushing. The SO 4 -EC relationship hence proved to be a sensitive indicator of the start of tunnel flow and runoff generation on the shales, even though each variable had little value when used separately.

Holocene Alluvial Chronology of One Tree Creek, Southern Alberta, Canada

Abstract An alluvial chronology for the One Tree Creek basin, a southern tributary of the Red Deer River in southern Alberta, is reconstructed using terrace and palaeochannel remnants and associated radiocarbon dated bones. Prior to the development of One Tree Creek as a northeastward flowing tributary, the prairie surface was scoured by proglacial floodwaters decanting from Glacial Lake Bassano/Patricia in the west. Radiocarbon dates on bones from the bedload gravels in palaeochannels provide a morphochronology of Holocene stream incision. Tentative average incision rates for the middle and upper reaches are calculated at 0.34–0.38 cm a‐1 since 2.8 ka BP and 0.80 – 1.60 cm and 0.81 – 0.96 cm a‐1 for the two periods of 1870 to 1230 BP and 1230 BP to modern respectively. Terraces and palaeochannels dating to the period of highest incision (1870 BP to modern) include numerous reworked bones dating to earlier periods, indicating that fluvial downcutting triggered slope instability and terrace reworking. Although the lower bedrock reaches of the creek may have incised down to the present level of the Red Deer River during early postglacial time, the middle and upper reaches were rapidly incised into Quaternary sediments during the late Holocene when climatic conditions were more humid.