HR: 0800h
AN: H11C-0659    [Abstracts]
TI: Spatial and Temporal Variability in Flood Conveyancing in a Semi-Arid Australian Catchment: Implications for Floodplain Deposition.
AU: Purvis-Smith, D
EM: D.Purvis-Smith@adfa.edu.au
AF: School of PEMS, University of New South Wales, Northcott Drive, Canberra, ACT 2600, Australia
AU: * Croke, J C
EM: J.Croke@adfa.edu.au
AF: School of PEMS, University of New South Wales, Northcott Drive, Canberra, ACT 2600, Australia
AU: Thompson, C J
EM: C.Thompson@adfa.edu.au
AF: School of PEMS, University of New South Wales, Northcott Drive, Canberra, ACT 2600, Australia
AB: This study investigates the effect of spatial and temporal variability in flood generation and conveyance at a constricted tributary junction within a semi-arid catchment in north-eastern Queensland Australia. Flood discharge and rainfall records indicate that floods with a 5y recurrence interval occurred regularly in the period from 1972 to 1984. The floodplain inundation and flow velocities of several of these events are modelled using a one-dimensional flow routing model, HEC-RAS. For flood events dominated by one of the main tributaries, the Medway Creek catchment alone, floodplain inundation in the constriction occurred during a 1.5y equivalent event. In contrast, a 5y flood discharge is required to inundate the floodplain prior to the zone of valley narrowing. This is due to the abundance of secondary channels which increase the total channel capacity. 137Cs measurements of floodplain sediments indicated deposition rates of ~0.5 cm a year on average since peak fallout (~1964). 137Cs measurements also show that floodplain erosion (¡Ý 6 cm since fallout) has occurred within the zone of valley narrowing. It appears that the affect of flow concentration through this feature in the past has been local channel scouring thereby increasing channel capacity. Differences in elevation between the two major tributaries appears critical to the currently enhanced rate of floodplain deposition within the constriction reach, because it is more frequently inundated by slow-moving back-water flows from the Nogoa River.
DE: 1804 Catchment
DE: 1820 Floodplain dynamics
DE: 1821 Floods
DE: 1825 Geomorphology: fluvial (1625)
DE: 1861 Sedimentation (4863)
SC: Hydrology [H]
MN: 2007 Fall Meeting