It's not possible to ensure that all rivers, drainage channels and pipes can cope with all flood levels. This would be far too expensive. We have to prioritize our investment in stormwater and floodplain management based on risk and the potential cost of flood damage.
For urban stormwater flooding, risk is managed by designing a 2-stage system:
1) The Minor flood system is the underground pipe system.
2) The Major flood system is used when the underground pipes can't cope. Flows are then handled by a surface system of roadways, paths, drainage reserves and easements. These flow to a trunk drainage system for safe disposal.
The way we calculate flood risk is very complicated. Flood heights are basically measured by their relation to sea level. Floods are also measured by how often they are likely to occur - Annual Recurrence Interval (ARI) and Annual Exceedence Probability (AEP). This likelihood allows us to estimate the damage costs.
Our Flood Management Policy uses the 1% AEP / 100 year ARI flood frequency as the design flood standard for planning and general risk management purposes.
The policy also sets the minimum habitable floor level required for a particular location. This is the 1% AEP flood height, plus an extra 0.50m.
NSW State Emergency Service
The NSW SES is the primary response agency for flood emergency. For further information on how to prepare for flooding, visit the FloodSafe website - www.floodsafe.com.au
It's predicted that "global warming" will potentially worsen the severity of flooding and coastal erosion though a combination of rising sea levels and more severe storms. Peak flood flows and depths will increase.
In the Great Lakes region for example, we have adopted as policy the Sea Level Rise Benchmarks (NSW Government, 2009) of 0.50m by 2060 and 0.90m by 2100. These estimates may change with further scientific advice. A review of Council sea level benchmarks is expected. This will lead to a revision of Council's floodplain mapping and management.
Written information relating to flooding on a specific property can be purchased from Council by applying for a Flood Level Certificate:
This certificate shows the availability and standard of available flooding information for a particular property. If available, the certificate will give an estimated flood level. It can only give information that Council has available, and doesn't take into account Council's planning controls or policies.
Prior to making an application for the Flood Levels Certificate please contact Council to confirm that the information is available for the property in question. A fee is required to be paid at the time of application. Please allow approximately five working days for processing.
MidCoast Council, along with NSW Office of Environment and Heritage conducts flood studies for all lakes and rivers in the region.
There are 4 stages in floodplain management:
1) Flood Study - Determines the actual flood behaviour and the extent of the flood problem.
2) Floodplain Risk Management Study - Evaluates various management options for the floodplain, considering existing and proposed developments.
3) Floodplain Risk Management Plan - Confirms the management measures and costs before acceptance by Council.
4) Plan Implementation - Involves project planning to put the floodplain management solutions in place, whilst making sure they are compatible with existing Local Environmental Plans.
Gloucester and Avon Rivers Flood Study
Gloucester Shire Council prepared a flood study for the Gloucester and Avon rivers. This flood study was undertaken as part of the Gloucester Water Study Project.
A flood study is a comprehensive technical investigation of flood behaviour. Flood levels, extents and velocities will be examined within the study area for a range of design events, up to and including the Probable Maximum Flood.
The study will help improve council’s planning and management of the catchment, such as setting flood levels for development and improving flood emergency responses. The NSW State Emergency Service also use the data from flood studies to develop Local Flood Plans that are used in the event of an emergency.
The study area for the flood study includes the Gloucester River, from the confluence of the Barrington River to the crossing at Stanton’s Lane; and the Avon River, from its confluence with the Gloucester River to the upper reaches of the catchment west of Stratford.
Floodplain Risk Management Committee
A Floodplain Risk Management Committee was formed to oversee the implementation of the flood study. The Committee was made up of Councillors, Council staff, representatives from State Government agencies including the State Emergency Service and the Office of Environment and Heritage as well as local community members.
Great Lakes Region Flood Management Studies and Plans
Most flood studies, risk management studies and plans are available for download using the links below. They are also available for viewing at Council's Forster Office. Copies may also be purchased by contacting Council on (02) 6591 7222. In circumstances where more detailed flood study interpretation is required it may be necessary to consult a registered surveyor and/or suitably qualified engineer.
Because of the large file size of these documents, some have been broken into more manageable downloadable segments.
Group 1: Wallis Lake
Group 2: Port Stephens and Lower Myall
Group 3: Wallamba River and Nabiac
Group 4: Bulahdelah and Upper Myall
Group 5: Smiths Lake
Group 7: Karuah River
Manning Valley Region Flood Studies and Plans
In November 2016 an updated flood study for the Manning River catchment was adopted. It aims to assist us to better understand, plan and manage the risk of flooding in our region.
The Manning River catchment has a history of major flooding, including the significant events of 1978 and 1990 and more recently smaller events in 2011 and 2012.
In order to appropriately plan for future flood events and reduce the potential impacts of flooding on our community, an updated Manning River Flood Study was conducted during 2015 by specialists BMT WBM, with the valuable input of locals who shared their experiences of flooding in the area.
The Review and Update Manning River Flood Study replaces the previous study which was completed 25 years earlier. With the assistance of new-age technology, and taking into account increased rainfall due to climate change and sea level rise predictions, it provides a comprehensive overview of our floodplains extending from downstream of Wingham, across to the coast. Areas of focus include Tinonee, Taree, Cundletown, Harrington, Manning Point and adjacent rural and semi-rural areas.
Flood studies have also been completed for both Wingham (2011) and Lansdowne (2015). The reports can be viewed by clicking the links below.
Stormwater is the rainwater that flows over land or through pipes. Council is responsible for the major stormwater drainage facilities in the Great Lakes area, including stormwater pipes and culverts, concrete and earth open drains, detention basins, gross pollutant traps and constructed wetlands. Land owners are responsible for stormwater facilities that service their own property.
Councils are encouraged by State Government to implement a program of major improvements to stormwater management. They are funded by a stormwater levy. This is in addition to funds already allocated in the budget for stormwater projects. Works include upgrading stormwater systems, gross pollutant trap and constructed wetland maintenance, stormwater reuse and harvesting programs, and community education.
Land within a town or village, both residential and business is eligible to be charged the stormwater levy. Vacant land, land exempt from rates, non-urban land and Crown land are all exempt.
We are responsible for the cleaning of these drainage systems. If you know of a blocked or overgrown drain, you can report it here. Please note that in some instances, the reeds that grow in drains and wetlands help keep the lakes clean. They slow down the flow of the water allowing sediments to drop out and nutrients to be absorbed. These reeds will not be removed.
If you have a problem with stormwater run-off on your road or running off the street onto your property you can contact our customer service team or report it here.
Problems caused by surface or underground water drainage from one property to another are civil matters and must generally be resolved between neighbours.