Attachment 4 - Stormwater Managment Plan

SQIDEP Evaluation                                                   SPEL Basin, Sippy Downs


Cherry Picking of Storm Events
SQIDEP v1.3 does not explicitly require that sequential storm events be monitored and
reported. None the less, the Independent Evaluators have checked for evidence of cherry
picking.

We have reviewed all storms that were excluded from the data set. Dr Drapper included in
his Detailed Report a summary of the rainfall and storms that occurred during the monitoring
period. This table is extracted and shown below:




Figure 5 Reported rainfall and monitoring records.

The chart shows that there were 6 recorded storm events, intense events with an average
depth of about 50mm which failed to capture more than 80% of the hydrograph and were
therefore discarded. There are also a number of events where either the inlet or outlet
sample was not obtained presumably due to mechanical or some kind of equipment failure
or simply because no outflow occurred. These are credible events and are considered
typical of any monitoring dataset noting that flow and quality monitoring equipment is
notoriously unreliable.

Analysis of the spread of reported events also indicates some events where performance
was high and equally some events where performance was not great. A “cherry picked”
dataset would, by definition, only include events with good performance. The duration of the
monitoring period, which is considered relatively short at 13 months, is indicative of a study
which did not wait for high performing events to occur.

At the request of the Evaluators, Dr Drapper also provided data logs for storm events which
were excluded and these demonstrated that there was a failure of equipment to record for
example the first 100mm of rainfall. It is noted this is not a fully independent data analysis
however it adds to the body of evidence to demonstrate cherry picking was not undertaken.
                                                                                            27