20220089 Jirrima Cr SWMP

 CONCLUSION
This Stormwater Management Report has outlined how the stormwater run-off from the site is to be managed to
comply with the relevant requirements to minimise any adverse impacts to the downstream environment.

     •    The lawful point of discharge test for the proposed development is achieved as the development proposes
          to discharge run-off to the existing drainage feature downstream of the site to which it currently drains.
          Assessment of the impacts arising from the development have found the overall flow depth and volumes are
          not considered to not result in risk or damage or impact use of the adjacent properties thereby achieving
          lawful discharge conditions.

     •    The proposal will result in an additional dwelling situated within a largely pervious catchment. The pollutant
          generation and peak flow increase from the new development will be a relatively minor increase which is
          considered to be suitably mitigated through discharge through the large areas of vegetated buffer prior to
          capture within the waterway. No stormwater treatment nor attenuation is proposed for the additional
          dwelling.

     •    Any future dwelling will be required to provide a minimum 3kl of rainwater reuse capacity in accordance
          with the Sustainable Building Design Code.

     •    Council flood data was obtained for Jirrima Crescent which found the road is immune to storms up to the
          50% AEP event. The road remains trafficable for the 10% and 1% AEP storm events. These parameters will
          govern the required immunity of the proposed culvert crossing to the new lot.

     •    The site and its upstream and downstream catchments have been modelled in TUFLOW under the 2100
          climate change conditions and in accordance with QUDM and ARR methodologies. The analysis found that
          the crossing would achieve the required immunity levels through provision of 4 1500mmx750mm culverts
          to be located at the existing low points of the current driveway access to the rear of site. Although some
          increase occurs to peak depths in the adjacent properties, the increase is contained within the riparian buffer
          zone and typically coincides with the areas of biodiversity significance overlay, therefore the increase is
          unlikely to result in damage to infrastructure nor impact the use of the adjacent lots.

     •    During construction, erosion and sediment control measures in accordance with best practice standards are
          to be implemented to minimise potential contaminants impacting the downstream receiving environment.
          An erosion and sediment control plan shall be developed by the contractor prior to any works commencing
          on the proposed development.

     •    The proposed crossing therefore provides adequate serviceability to the proposed lot and generally
          achieves the outcomes of Noosa Council regarding stormwater management objectives.




Project number 20220089                                                                                  Page 18 of 23
File 20220089 Jirrima Cr SWMP.docx, 2023-05-09 Revision 0


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