Key points
- Lot amalgamation and re-orientation sought to mitigate natural hazard risk.
- Redefining lot boundaries can avoid the intolerable flood risk areas within the lots.
Prior to 2008, 2 adjoining lots in Newport in the Northern Beaches local government area were affected by regular flooding of the creek that ran through the northern-most lot.
The adjoining properties in Newport were oriented in an east-west alignment, as shown in the PMF extent Newport Beach flood study (PDF, 416 KB) and 1% AEP extent Newport Beach flood study (PDF, 856 KB), which is orientated with north at the top of page.
The 1% annual exceedance probability and the probable maximum flood extent maps from 2002 (PMF extent Newport Beach flood study (PDF, 416 KB) and 1% AEP extent Newport Beach flood study (PDF, 856 KB) show that the northern-most lot is significantly affected. The dwelling present on the northern lot was below the 1% annual exceedance probability flood level and the dwelling on the southern lot was not flood-affected.
A development application was submitted to the former Pittwater Council to adjust the lot boundaries to a north-south alignment. This would allow new residential dwellings on both lots as shown in Figure 2, also with north orientated to the top of page.
The new dwellings were completed in 2008 to better accommodate floodwaters from the creek. Their habitable floor levels were set to the flood planning level and deck areas across the remaining flood prone portions of the lots allow for flood conveyance of rare flood events.
The creek was also rehabilitated as part of the lot reorientation to achieve a better urban stream outcome. This case study shows how redefining lot boundaries can increase resilience against flood events, with buildings sited off the area experiencing the greatest impacts of the hazard.
