Appendix D - Engineering Report.pdf

5.3      Stormwater Quantity Management


Refer to Engineering Drawings C6070/20/P06 for details of stormwater catchments and
existing/proposed stormwater infrastructure.


Walsh Consulting Engineers have reviewed the requirement for providing detention for the
proposed development and have concluded that the development site may be exempt from
providing on-site detention on the following grounds;


      1. The subject site is located within the lower one-third of a major regional catchment.
         Stormwater detention is less likely to be required at the bottom one-third of the
         catchment (Brisbane City Council Stormwater Guidelines). Detaining stormwater flows at
         the lower reaches of a watercourse may result in increased likelihood that peak discharge
         from the site will coincide with peak discharge from major upstream external catchments.
      2. Stormwater runoff from the subject site is directed to a tidal waterway, where flooding is
         governed by tidal surge. Providing on-site detention for the site would be redundant.
      3. Existing stormwater drainage infrastructure within the site is privately owned and
         maintained. The existing infrastructure generally has capacity to convey development site
         stormwater. Upgrades to the internal drainage network will be undertaken as required.
      4. The increase in flows from the development will not cause adverse impacts or actionable
         nuisance to surrounding properties.
      5. Significant capture of stormwater runoff is achieved in existing constructed waterbodies.
         Harvested rainwater is utilised for irrigation of the Noosa Springs Golf Course. The existing
         constructed waterbodies provide frequent flow management and reductions to total
         volume of runoff from the development site.
      6. Proposed rainwater harvesting and reuse tanks will provide additional frequent flow
         management and reductions to total volume of runoff from the development site.