The Woy Woy Peninsula (the Peninsula) urban area is bounded by Brisbane Water to the north and east, Broken Bay to the south, and Brisbane Water National Park to the West.
Terrain and Land Ocupation
The Peninsula (18.5 km ) including the Kahibah Creek Catchment is generally a flat sand-plain, where ground levels typically vary between RL 4m to 6m (AHD). The remaining study area backs onto the National Park and Blackwall Mountain and is typically of higher elevation with rocky outcrops.
The majority of the catchment is characterised by predominantly low-medium density urban development.
Many areas on the Peninsula are not serviced by piped drainage systems, kerb and gutter infrastructure nor have effective overland flow paths. As a result, overland flow is prone to gather in local sags in the street network. Where these sags are unrelieved, or the capacity of the stormwater pits is insufficient, stormwater runoff will pond until it reaches a level where it can flow overland, infiltrate or evaporate.
In many areas of the catchment the presence of a high groundwater table can significantly affect the local drainage capacity, preventing infiltration of rainfall and
creating significant areas of ponded water. During very wet periods the water table can rise such that flood inundation in local areas remains for several weeks. Therefore, the interaction between surface and groundwater flows is an important element of the flood behaviour in the Woy Woy Peninsula.