Karragarra Island is characterised as having predominantly low and high bushfire risk with a small section of very high bushfire risk in the south westof the island where there is limited residential development. The bushland vegetation is not considered significant enough to allow a fire to develop to a point where it is likely to become uncontrollable. Karragarra Island has a Rural Fire Brigade capacity located centrally on The Esplanade that is capable of responding to bushfires.
Flood Prone, Storm Tide
Flood prone, storm tide and drainage constrained land mapping has identified that a 100 ARI (average recurrent interval) storm surge event may have the potential to cut Karragarra Island in two, inundating the fire station and surrounding homes. There is also potential that the ferry terminal may be impacted however the internal areas of the island would experience limited affects from storm surge.
Landslide hazard mapping identifies the majority of Karragarra Island has low to no landslide risk, with limited areas of high to very high risk primarily along the southern and western boundaries of the island. There is limited residential development in these areas that is regulated under the Redland Planning Scheme to comply with the requirements of the Landslide Hazard Overlay which aims to mitigate against the risk of landslide.
Critical infrastructure on the islands at the time of a disaster event includes utilities such as power, water, sewerage and telecommunications, and water transportation including ferry and barge services. Impacts of a disaster on these services may have far reaching long term affects for island communities.
The sewer network operated by Redland City Council covers Coochiemudlo Island, and parts of Dunwich and Point Lookout on North Stradbroke Island. Those parts of Dunwich and Point Lookout and Amity Point not serviced by the sewer network utilise septic systems, as does all of SMBI.
Many of the newer homes, businesses and the primary schools on Russell and Macleay Islands use modern sewerage treatment systems that require power to operate. Therefore during extended periods of power outage the toilets are unable to be utilised or risk failure if used. This limits the number of community buildings that can be used as evacuation centres during a disaster event.
The most serious affect of a failing sewerage system is the potential for highly infectious diseases to occur including dysentery and hepatitis. Mosquitoes and flies that spread a number of other illnesses can breed in areas where liquid waste reaches the surface. There are also risks to the natural environment including the health of waterways and Moreton Bay.
Water can be supplied to Russell Island via either North Stradbroke Island or the mainland. From Russell Island, the supply is then piped via Karragarra Island to Lamb Island and then onto Macleay Island. The water supply for Coochiemudlo Island is also piped directly from the mainland. The mainland water supply is connected to the SEQ water grid and therefore the risk of the water supply failing is extremely low. However the islands of Karragarra, Lamb, Macleay and Coochiemudlo only have one connecting pipeline. When one of these pipeline fails there will be a loss of supply and emergency supply measures will be put in place.
The North Stradbroke Island townships of Dunwich, Amity Point and Point Lookout source their water supplies directly from the bore fields located on North Stradbroke Island and again the risk of the water supply failing is extremely low.
The electricity supply provided by Energex to the SMBI group and North Stradbroke Island comes via Russell Island. The supply originates on the mainland north of Cabbage Tree Point and crosses the Western Boating Channel, connecting to the southern end of Russell Island at Rocky Point, then continues north through the centre of Russell Island before branching off to service North Stradbroke Island and Karragarra Island. The electricity supply from Karragarra Island then connects to Macleay Island which in turn is connected to Lamb Island.
This sequence of connections highlights the importance of Russell Island to the electricity supply for SMBI and North Stradbroke Island. A new substation has been built on Russell Island to assist in ensuring the power supply to Russell Island is more robust and with less power fluctuations. Energex has also installed number of transformer connection points on Macleay Island which enables Energex to use generators to supply power to Macleay, Karragarra and Lamb Islands in the event of a major power failure; however this would be a reduced supply.
The main line that crosses to the southern end of Russell Island is strung on concrete poles high above the ground in a relatively inaccessible area of moderate to high bushfire risk. If the line was impacted by bushfire, Energex would restore the line as quickly as possible given the population on SMBI and North Stradbroke Island.
The electricity supply to Coochiemudlo Island comes via an underwater line from the Victoria Point reserve at the end of Colburn Street and connects to the western tip of the island near the golf club. The line runs underground until it meets the established road network and as such has limited impact from bushfire, tidal surge or flood hazards.
Landline access to North Stradbroke Island and SMBI is via a microwave link from the mainland to exchanges on the islands. The exchanges on North Stradbroke Island are located at each of the three townships of Dunwich, Amity Point and Point Lookout and for SMBI the exchanges are located on Russell and Macleay Islands. Coochiemudlo Island is connected via a submarine cable that runs from the Victoria Point exchange to the island.
The exchanges on North Stradbroke Island and SMBI require electricity to operate and all have battery back-up systems that operate for a limited period of time. During extended periods of power outage Telstra have generators they can be deployed from the mainland to provide additional capacity. Telstra also have other resources such as a mobile exchange, mobile satellite coverage and mobile base station that can be deployed if required.
There is no mobile phone towers located on SMBI or Coochiemudlo Island; coverage is from towers on the mainland and North Stradbroke Island. Mobile phone towers on North Stradbroke Island are located in each of the three townships which provide good coverage over these areas. The Amity Point tower also has a radio link to Karingal on the southern end of Moreton Island. There are mobile coverage black spots in the southern part of North Stradbroke Island and some parts of SMBI.
Other telecommunication issues that will impact the community during periods of power outage include cordless landline phones and access to the internet both of which require power to operate. With advancing technology, more people are utilising smart phones to access the Internet, which utilises the mobile phone network placing more pressure on the capacity of the network.
North Stradbroke Island, Coochiemudlo Island and SMBI are all accessible via vehicle barge and passenger ferry, departing from Toondah Harbour, Victoria Point and Weinam Creek Marina respectively. Along with the barge and ferry service to SMBI, Bay Island Transit (BIT) also operates the QAS boat, called Kitty Kat from the Weinam Creek Marina. The QAS boat is available 24/7 and an arrangement is already in place to transport Energex staff to SMBI in an emergency, if Kitty Kat is not required for patient transport.
The passenger ferries are designed to operate in rough seas and therefore the size of the waves in the bay or the strength of the wind is unlikely to stop the ferries from running – high winds are more of an issue for the vehicle barges. However, the safety of passengers as they board and depart from the passenger ferries and visibility during heavy fog or torrential rain does determine whether the passenger ferries will operate. The passenger ferries are able to land directly onto the island’s foreshores if the jetty or pontoons were damaged or destroyed. The main safety consideration in doing this is the loading and unloading of passengers.