An analysis of the effect of river bank slope and unsaturated flow in the bank storage process

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Doble, Rebecca; Brunner, Philip; McCallum, James; Cook, Peter


2012-01-30


Journal Article


Ground Water


50


1


77-86


Understanding the underlying mechanics of bank storage and return flow is important for quantifying the contributions of event water and groundwater in sustaining streamflow during dry periods. Analytical models have been widely used to estimate the impacts of bank storage, but are often based on assumptions of conditions that are rarely found in the field, such as vertical river banks and saturated flow. Numerical simulations of bank storage and return flow in river-aquifer cross sections with vertical and straight but sloping banks were undertaken using a fully–coupled, surface–subsurface flow model. Sloping river banks were found to increase the peak bank storage flux and storage volume (98% increase in peak flux and 40% increase in storage for a bank slope of 3.4°), and delay the timing of bank return flow (2.3 times longer for 50% of bank storage volume to return to the river for a bank slope of 3.4°). Furthermore, the explicit consideration of unsaturated flow caused the bank return flow to depart significantly from the analytical solution for vertical banks, but had less of an effect for rivers with sloping banks. Results suggested that conventional analytical approximations cannot adequately be used to quantify bank storage when realistic geometry is considered. Similarly, there are some conditions in which it is important to include an unsaturated zone to accurately model bank storage and return flow in rivers with vertical banks. Bank storage and return flow were also modelled for more realistic scenarios, with idealised cross sections and river hydrograph from the Fitzroy River, Western Australia to indicate the importance of accurately modelling sloping river banks at a field scale. Results showed that following a single wet season flood event, it may take over five years for 50% of the bank storage volume to return to the river.


Wiley-Blackwell


bank storage; baseflow; HydroGeoSphere


Hydrogeology


https://doi.org/10.1111/j.1745-6584.2011.00821.x


Link to Publisher's Version


© 2011, The Author(s). Ground Water © 2011, National Ground Water Association


EP104348


Journal article - Refereed


English


Doble, Rebecca; Brunner, Philip; McCallum, James; Cook, Peter. An analysis of the effect of river bank slope and unsaturated flow in the bank storage process. Ground Water. 2012; 50(1):77-86. https://doi.org/10.1111/j.1745-6584.2011.00821.x



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