17.5 Overbank flood spilling
Only limited minor flooding (see definition in the Australian Water Information Dictionary) occurred in the Adelaide region during the 2011–12 year. The corresponding volume could not be quantified in a way that is complete, neutral and free from material error.
The following figure shows the extent of the 100-year average recurrence intervals flood peak 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 average recurrence intervals (ARI) flood peak in the Adelaide region
Data source: South Australian Department of Environment, Water and Natural Resources (DEWNR) – 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 not significant and its influence on the surface water balance not material.