Oral Presentation 9th Australian Stream Management Conference 2018

Establishing the feasible fine sediment trapping efficiency of floodplains: a case study in Southeastern Queensland (#85)

Jonathan Garber 1 2 , Ian Rutherfurd 1 , Jon Olley 2 , Joanne Burton 3
  1. University of Melbourne, Carlton, VICTORIA, Australia
  2. Australian Rivers Institute, Griffith University, Nathan, Queensland, Australia
  3. Department of Environment and Science, State Government of Queensland, Brisbane, Queensland, Australia

River floodplains are perceived as effective sinks of fine sediment. This idea is attractive to managers as river corridors can be used to filter out fine sediment pollution from degraded catchments. More specifically, managers hope that revegetating riparian areas will increase that trapping rate. This paper explores how effective a floodplain can be at reducing the total sediment yield from the catchment.

We postulate that there are theoretical bounds on how much fine sediment a floodplain can trap, as only a proportion of the total discharge and suspended sediment load reaches the floodplain, and only a fraction of that is deposited. Therefore the floodplain trapping efficiencies can be predicted as a function of river corridor morphologies, hydraulics, Hydrologic data, and suspended sediment transport data

We attempt to estimate the feasible range of floodplain trapping efficiencies using numerical models at the cross section, reach, and catchment scaled taken from the literature. With these models we will try and optimize the trapping efficiency of a simulated channel by varying the discharge frequency distribution, the floodplain geometry (area, height) floodplain roughness, and suspended sediment rating. We will compare our predicted range of estimates to our own data, and data reported in the literature to validate the model. Finally, we apply our methodology to forecast the reduction of fine sediment yields in South-eastern Queensland river corridors due to floodplain trapping