Council on standby as lake creeps up
WOOLGOOLGA Lake has reached the height where it requires daily monitoring.
Coffs Harbour City Council monitors daily height using an automated alarm system which begins to send advice messages to relevant staff once it reaches 1.2 metres.
The council is currently in this phase as the lake has reached 1.3 metres.
As council's Director of Sustainable Infrastructure Mick Raby explains, the lake is classified as an Intermittently Opening and Closing Lake or Lagoon (ICOLL).
Best practice in managing such a dynamic natural system is to let ICOLLs be ICOLLS - minimum interference.
The council collaborates with various authorities including DPI Fisheries and Marine Parks to manage the lake and the rationale is that ICOLLs provide the best, and in some cases only, breeding grounds for a whole range of fish and marine life forms.
Woolgoolga Lake is of added importance because of its direct connection with the Solitary Islands Marine Park.
With housing and other development around the lake management of the system is a complicated matter with the Sunset Caravan Park one such example.
The lake can begin to cause issues for the park when it reaches a height of around 1.7 metres.
The council and the key external agencies have a negotiated agreement that council may intervene and trim the height of the beach at the entrance to a minimum level of 1.6 metres but only if the lake is at 1.3 metres or higher and only if a rainfall event of 100mm in 12 hours is predicted.
The council's history demonstrates that a 100mm rainfall in 12 hours in the catchment results in an increase of 300mm in the height of the lake.
"We will intervene to ensure the height of the beach at the lake entrance is reduced to 1.6 metres if significant rainfall is predicted, ensuring the lake will break out before any inundation of low lying surrounding areas occurs. The beach height is currently 1.58 metres," Mr Raby said.
Woolgoolga, and all other ICOLLs, are prone to fill via two natural mechanisms.
Water can come from inland via heavy rainfall in the catchment and it can become blocked by the beach.
Storm surges can also bring water into the lake from the ocean.