2015-04-28 Planning and Organisation Committee Agenda

PLANNING & ORGANISATION COMMITTEE MEETING AGENDA     28 APRIL 2015


                                                   Attachment 1




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PLANNING & ORGANISATION COMMITTEE MEETING AGENDA                                                         28 APRIL 2015

                                                                                                      Attachment 1

                                                                         PO Box 120 Coolum Beach Qld 4573
                  Hydrology & Water                                      Tel 07 5448 2839 Mob 0405 194 639
                                                    .                    Email [email protected]
                       Management Consulting                             Web www. hydrologyandwater.com.au
                                                                         ABN 25 153 466 981 ACN 153 466 981

              27"" March 2015                                                      Our Reference: J00193Lt1

              Rebecca Britton
              Noosa Council
              [email protected]

                                Cyclone Marcia Hydrologic Data Collection and Analysis
              Dear Rebecca,
              Hydrology and Water Management Consulting Pty Ltd (HWMC) has completed hydrologic data
              collection and analysis of the flood event associated with ex-tropical cyclone Marcia and we provide
              this letter to summarise the results.

              1.       RAINFALL INTENSITIES
              The low pressure system associated with ex tropical cyclone Maria resulted in moderate
              precipitation throughout much of the Noosa LGA, with greatest intensities being recorded in the
              hinterland areas. Analysis of rainfall intensities recorded at gauges throughout the Noosa LGA has
              been carried out and plotted against design rainfall intensity data produced by the Bureau of
              Meteorology using the latest 2013 IFD data. The approximate location of these rainfall gauges is
              provided in attachment A for reference and it is noted that this attachment also shows the location of
              flood height alert gauges in the region. The rainfall IFD plots are provided in attachment B of this
              letter and a summary of the findings at key locations is provided below:
                      Cooroy Alert Gauge
              The peak intensity averaged over a 24 hour duration recorded at the Cooroy Alert gauge was
              slightly less than a 20% Annual Exceedance Probability (AEP) design rainfall intensity. Over a 48
              hour duration, the peak average intensity was slightly less than a 10% AEP event.   Intensities
              recorded over durations ranging from between approximately 1 hour and 36 hours generally fall
              between the 10% and 20% AEP design intensities (in old terminology this would be similar to
              between 10 year and 5 year Average Recurrence Interval intensities).
                     Tewantin Alert Gauge
              Peak average intensities recorded over durations of up to 6 hours were less than the 50% AEP
              intensities at Tewantin. For durations of 6 hours or longer, the peak average intensities recorded
              were slightly greater than the 50% AEP event.
                      Black Mountain Alert Gauge
              Peak average intensities recorded over a 1 hour duration were between a 10% and 5% AEP design
              intensity. Over a 24 hour duration, the peak average intensity recorded was slightly less than a 20%
              AEP event.   Over a 48 hour duration, the peak average intensity recorded was approximately
              equivalent to a 10% AEP event.
                      Pomona Alert Gauge
              Peak average intensities recorded at the Pomona Alert gauge where generally in the range of
              between a 10% AEP and a 20% AEP event.
                      Cooran Alert Gauge
              Peak average intensities recorded at the Cooran Alert gauge over a 6 hour duration where
              equivalent to between a 5% and 2% AEP event. For most other durations, the intensities ranged
              between the 5% and the 20% AEP event.

                                         eee reer erence eee                                           ee

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