Modelling the compound flood hydrodynamics under mesh convergence and
future storm surge events in Brisbane River Estuary, Australia
Abstract
Floods are the most common and destructive disasters around the globe,
which becomes more challenging in coastal areas due to higher population
density and catchment area relative to floods in an inland area. For
effective coastal flood management to reduce flood adverse impacts it is
necessary to investigate the flooding processes and their join
interaction in a coastal area. This paper selected the Brisbane River
Estuary, Australia as an example and the MIKE 21 model is applied to
investigate the effects of mesh resolution on the flood discharge and to
explores compound flooding by computing variances in coastal flood
assessments resulting from a separation of tidal and riverine processes.
The statistical results showed that the Nash-Sutcliffe coefficient, E of
water level are varied from 0.84 to 0.95 and the model simulated the
2011 flood extent results agreed with 90% accuracy with the observed
flood extent. Five mesh resolutions cases were analyzed and the result
found that the finer mesh resolution Case 5 was more appropriate for
calculating the peak discharge with 2.7% with estimated discharge.
Compound flood event simulation results emphasized that not considering
the interaction of various flooding drivers caused 0.62 m and 0.12 m
reduction in the flood levels at Jindalee and Brisbane city gauges, and
uncertainties in flood extent. Simulated results of flood at Brisbane
city gauge, showed that 2011 and 2013 floods with storm surge scenario 4
demonstrate, the increase in flood level to be 12% and 34%
respectively. The results recommend flooding assessment by using mesh
convergence with joint probability of compound flood under future storm
surge for planning and management of coastal projects.