Ensuring no offsite or onsite flooding impact
The project must demonstrate that the design and delivery of the new community will not impact neighbouring communities. This is the responsibility of Stockland as the proponent and Council, which is defined in legislation.
The new waterbody will provide flood immunity in the same way as the nearby Twin Waters canals. These canals have kept the Twin Waters community safe from many high rainfall events since the 1990s.
Detailed modelling has been undertaken based on the design of the new community. Many potential scenarios were modelled including significant rainfall events. These extreme events were also combined with climate change, predicted sea level rise, and maximum high tides. The site has flood immunity for rainfall events such as 1:100 year events plus climate change predictions.
The modelling demonstrates the site can be developed with no adverse flooding impacts to nearby communities. The modelling demonstrates there will be some improvements to existing flooding in Pacific Paradise and Twin Waters, during high rainfall events.
Properties on De Vere Road, Pacific Paradise are also protected through new stormwater infrastructure that will drain underground to the new lake.
Independent, expert peer review: Specialist hydrology studies and an independent peer review verify that the site is suitable for residential development. Flood immunity is achieved through the creation of a large on-site lake and enhanced stormwater infrastructure.
Flooding resilience is achieved through filling and raising the developable area, combined with the creation of large onsite lake system (19ha including walkable waterfront). The large lake can contain, secure and slowly discharge large volumes of in-flowing stormwater during high rainfall. The lake will be maintained at a lower level than the developable area to be able to receive and gradually discharge high-volume stormwater.
The land for development will be ‘profiled’ to create an inwards, internal gradient. The slope will carry water inwards within the site along with stormwater systems and towards the new lake. Water will not flow towards the existing Twin Waters community or external homes. Water will also be directed towards the mature onsite vegetation to maintain its health and sustain this impressive natural feature.
The lake will not be tidal and will be maintained at a constant level. The lake will be designed to gradually discharge water through an underground pipe to the Maroochy River. The design and capacity of the lake allows for predicted climate change scenarios.
Efficient water movement during high rainfall events
The onsite lake will improve the movement of water during high rainfall events, as the waterway will securely contain and safely discharge excess water into the Maroochy River. The lake provides a more efficient flow path than the existing developed site, with the result that the development will have no adverse impact on flood levels external to the site. The containment and discharge of excess water within the Stockland Twin Waters site will improve flood immunity at Pacific Paradise.