Chiverrell,

Cooper, JR

Feeney,

Hooke,

Smith, H

Feeney

Chiverrell

Hooke

University of Liverpool Repository

Geophysical Research AbstractsVol. 19, EGU2017-6592, 2017EGU General Assembly 2017© Author(s) 2017. CC Attribution 3.0 License.Evaluation of CAESAR-Lisflood as a tool for modelling river channelchange and floodplain sediment residence times.Christopher Feeney, Hugh Smith, Richard Chiverrell, Janet Hooke, and James CooperUniversity of Liverpool, School of Environmental Sciences, Geography and Planning, United Kingdom(c.j.feeney@liverpool.ac.uk)Sediment residence time represents the duration of particle storage, from initial deposition to remobilisation, withinreservoirs such as floodplains. Residence time influences rates of downstream redistribution of sediment and as-sociated contaminants and is a useful indicator of landform stability and hence, preservation potential of alluvialarchives of environmental change. River channel change controls residence times, reworking sediments via lateralmigration, avulsion and incision through floodplain deposits. As reworking progresses, the floodplain age distribu-tion is ‘updated’, reflecting the time since ‘older’ sediments were removed and replaced with ‘younger’ ones. Therelationship between ages and the spatial extents they occupy can be used to estimate the average floodplain sedi-ment residence times. While dating techniques, historic maps and remote sensing can reconstruct age distributionsfrom historic reworking, modelling provides advantages, including: i) capturing detailed river channel changes andresulting floodplain ages over longer timescales and higher resolutions than from historic mapping, and ii) con-trol over inputs to simulate hypothetical scenarios to investigate the effects of different environmental drivers onresidence times. CAESAR-Lisflood is a landform evolution model capable of simulating variable channel width,divergent flow, and both braided and meandering planforms. However, the model’s ability to accurately simulatechannel changes requires evaluation if it is to be useful for quantitative evaluation of floodplain sediment resi-dence times. This study aims to simulate recent historic river channel changes along ten 1 km reaches in northernEngland. Simulation periods were defined by available overlapping historic map and mean daily flow datasets,ranging 27-39 years. LiDAR-derived 2 m DEMs were modified to smooth out present-day channels and burn inhistoric channel locations. To reduce run times, DEMs were resampled to coarser resolutions based on the size ofthe channel and historic rate of lateral channel migration. Separate pre-defined coarse and finer channel bed andfloodplain grain size distributions were used, respectively, in combination with constructed reach DEMs for modelsimulations. Calibration was performed by modifying selected parameters to obtain best fits between observedand modelled channel planforms. Initial simulations suggest the model can broadly reproduce observed planformchange and is comparable in terms of channel sinuosities and the mean radius of curvature. As such, CAESAR-Lisflood may provide a useful tool for evaluating floodplain sediment residence times under environmental changescenarios.

Evaluation of CAESAR-Lisﬂood as a tool for modelling river channel change and ﬂoodplain sediment residence times

Evaluation of CAESAR-Lisﬂood as a tool for modelling river channel change and ﬂoodplain sediment residence times

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