Council's Role in Flood Management

Before the event

The City of Newcastle's role is to investigate the risk of flooding and to prepare for future floods through land use planning, development control and flood mitigation works. It is not possible to predict when, where, or how big the next flood will be. However, we can estimate the likelihood of different sizes of floods and their consequences so we can plan ahead.

The City of Newcastle (CN) is working on solutions to manage flooding with grant assistance from the government to implement actions adopted in our Flood Management Plans.

During the event

The State Emergency Service (SES) is the lead emergency management agency during floods.

CN's role during a flood is to assist emergency management departments such as SES, Rural Fire Service and NSW Police.

After the event

CN leads the clean-up tasks after a flood event and coordinates repairs to damaged public assets such as roads, parks, trees and drainage. CN also applies for funding from the government to cover public asset damages.

What the City of Newcastle is doing to reduce flood risk

A number of actions were recommended in the Floodplain Risk Management Plans adopted by the elected Council for the Newcastle City Wide and Wallsend Commercial Area. Implementation of the recommendations has been an ongoing process. The underlying fact for Newcastle is that urban development on the floodplain has been undertaken since European settlement. Once development has occurred in a location and a particular use of land is established it is difficult and expensive to change or move those uses to reclaim the floodplain.

This means that urban land uses in the floodplain is likely to stay and the elimination of all flood risk is practically impossible. However there are measures, such as planning controls, that can be applied to reduce flood risk in the long term as redevelopment takes place. There are no easy solutions and the most effective means of reducing risk is to apply a range of measures such as flood education, planning controls, emergency management, on-site detention and drainage improvements.

Specific Implementation Actions

Flash Flood Alert Service

Wallsend Commercial Area FRMP Implementation Study

City of Newcastle undertook a succession of studies following the June 2007 event in accordance with NSW Floodplain Development Manual. The result was adoption the Floodplain Risk Management Plan in 2009, which included the recommendation for a range of actions to the total value of $44M. The works included substantial widening of the Ironbark Creek channel through the commercial area and upgrading the Minmi Road bridge to improve the passage of flood water.

The total cost to implement the FRMP was considered to be prohibitive and would not easily attract funding. An Implementation Study was then needed to investigate more cost effective options. SMEC Consultants were appointed in 2013 to undertake the Implementation Study. The Study used the FRMP actions as a starting point to develop more cost-effective solutions. As a result four targeted actions have been identified and assessed in detail using a cost benefit analysis. The Study recommended removal of the Tyrrell and Boscawen Street road bridges and replacing those with pedestrian bridges. In addition modification of the Nelson Street road bridge was recommended as the most cost effective solutions to reduce flood risk.

The draft report was presented at a Councillor workshop and the ordinary meeting of Council in April 2014 and public exhibition was held in May 2015. Feedback from the public exhibition and subsequent meeting of Council on the 25th August indicated that the recommendation of the report was too disruptive to traffic and commercial businesses of the town. As an alternative to the report recommendation the replacement of all three road bridges is being investigated and implemented.

Morgan Selwyn Street Floodway

The Morgan – Selwyn Street floodway in Merewether has been identified as a priority high hazard flood precinct in the City Wide Floodplain Risk Management Plan. City of Newcastle worked with the Water Research Laboratory (WRL) of the School of Civil and Environmental Engineering at UNSW Australia assess a Voluntary Purchase (VP) scheme for the Morgan-Selwyn floodway. VP involves the purchasing of private property that are subject to significant flood risk where no other feasible options of physically reducing the flood risk are available. Physical and numerical models of the Morgan-Selwyn floodway were built to quantify local flood behaviour in terms of flood levels, velocity distributions and flood hazard for a range of different voluntary purchase scenarios. The confidence in the results of the modelling is high when a combination of physical and numerical models are used because there are two models at hand to realistically test various scenarios and verify results.

It was found that during flood events greater than the 10% AEP a significant volume of overland flow is conveyed down Morgan/Selwyn Streets because it is in excess of the drainage network capacity. The overland flow has the potential to impact a number of private properties along the floodway. Numerous scenarios were tested through removal of the buildings in the floodway in an effort to retard overland flows. In conclusion 11 properties would require purchase using public funds to reduce the flood risk to manageable levels. The funds required to purchase 11 properties are excessive and as a result the VP scheme is not feasible. Considering that no feasible flood mitigation options have been found to physically reduce the flood risk at this location City of Newcastle is implementing emergency management measures such as the Flash Flood Alert Service, Flood Signage and Flood Education.

Flood Education Campaign

The City of Newcastle has prepared a flood education campaign with assistance from Headjam to increase flood risk awareness of residents.

The campaign focus is for residents to know their flood risk at their home, work, school and immediate surroundings. The campaign intends on achieving this through placement of digital ads on a range of websites with emotive imagery that shall encourage residents to click on the ads and be directed to our Know Your Flood Risk webpage. The page includes an interactive map that requires residents to enter their home address and investigate the flood risk map in their location.

Low Lying Areas - Phase 1 - Sea & Groundwater Monitoring

On 25 July 2017, the elected Council adopted a strategic position paper (the Paper) to protect the low lying areas from future flood risks associated with climate change. The Paper includes a list of actions (phase 1 -6) that are triggered if increments of sea level rise are recorded. Phase 1 was triggered upon adoption of the Paper and requires sea and groundwater level monitoring.

In relation to sea levels, City of Newcastle has worked with the Department of Planning, Industry and Environment (DPIE) to establish a benchmark and methodology for the measurement of mean sea level rise. The Paper has set the benchmark based on mean sea level at time of its adoption.

City of Newcastle and DPIE have since investigated the behaviour of sea levels. DPIE has recommended using the Fort Denison tide gauge in Sydney for the monitoring because, not only is this the longest publicly available record in the southern hemisphere, but more importantly the site holds data of the highest accuracy in NSW. There is not reported to be any difference in sea level rise between Sydney and Newcastle.

When analysing the data from 1990 to 2017 it was found that the mean sea level has risen by approximately 3cm or 0.032m. This indicates sea levels are rising slowly, and it indicates that there is at least 10 to 25 years until the 0.1m trigger (Phase 2) is reached. Phase 2 requires installation of improved flood gates and drainage outlets, high powered pumps, and the design of the levee for construction in Phase 3 (0.2m sea level rise).

In relation to groundwater, wells have been installed in March 2018 and a long term groundwater monitoring program will commence to better understand groundwater behaviour in the study area.