9.6 Overbank flood return to river channel
Flooding did occur throughout the Adelaide region during the 2010–11 year, however this volume could not be quantified in a way that is complete, neutral and free from material error.
The majority of flooding occurred in the north of the Adelaide region during the 2010–11 year. The following figure shows the extent of the 100-year flood peak average recurrence intervals (ARI) calculated in a composite of flood hazard mapping studies. The composite study area covers only 6.2% of the Adelaide region. The studies are mostly concentrated in built up areas with a risk of flooding from both watercourses and stormwater.
Map of 100-year flood peak average recurrence intervals in the Adelaide region
Data source: South Australian Department for Water – a composite of flood hazard layers derived from various flood hazard studies.
The volume of overbank flood return to river channel is expected to be significant. However, its influence on the surface water balance is not expected to be material. This is because the volume of flood waters returning to the river channel is likely to be a substantial portion of the volume of flood waters that left the river channel (line item 17.5), which could also not be quantified.