By Elmira Jamei & Ashok Sharma from Victoria University
Amidst the growing concerns over climate change, sea level rise, and the surge in urban density, the risk of flooding in urban areas near coastlines is on the rise. A lack of green space and green infrastructure in the western suburbs of Melbourne makes our region especially prone. In response to this pressing issue, it is imperative for local councils, government agencies, water authorities, and emergency services to join forces and devise a strategic plan to mitigate flood risks in the west.
Historically, Victoria is renowned for being among the most bushfire-prone regions worldwide, akin to areas like California and Greece. With its temperate climate, Victoria faces dry summers and receives less rainfall compared to northern regions, escalating its fire risks.
Unlike the heavy rainfall commonly seen in northern states, Victoria tends to experience lighter drizzle. (Melbourne’s average annual rainfall is 520 millimeters compared to Sydney 1175mm, Brisbane 1149mm)
But in September, Victoria typically experiences above-average rainfall and cooler temperatures, saturating the ground in many areas. The colder conditions reduce water evaporation, increasing the likelihood of widespread flooding in the state.
The heavy rainfall and flooding in October 2022 across Greater Melbourne, was unprecedented in terms of intensity, especially in the western suburbs. Numerous areas recorded their highest total October rainfall on record, or in at least 20 years.
With the projected 1.4-meter rise in sea levels by the year 2100, the risk of flooding will increase significantly during extreme rainfall events.
According to detailed modelling recently released by the Victorian government, more than 4.7 square kilometres of inner-Melbourne and parts of Port Phillip Bay could face the threat of rising sea levels and storm tides due to climate change in the coming decades. The analysis also suggests that a quarter of the Port Phillip council area, might experience inundation under the same scenario. In Geelong for example, approximately 47 square kilometres, or 4% of the total council area, could be at risk of inundation due to a 1.4-meter sea level rise.
It’s recommended that these areas implement early measures to mitigate the risk of inundation and establish monitoring programs for informed decision-making. Periodic modelling with updated parameters will be necessary to provide better information on sea level rise.
Flooding is an inherent aspect of Melbourne’s weather cycle and urban life, yet it can significantly impact our daily routines. The sea level rise and increased rainfall due to climate change will significantly impact the carrying capacity of stormwater systems resulting in increased local flooding events. This issue is particularly pronounced in Melbourne’s western suburbs, where there is a scarcity of green infrastructure and an excess of gray infrastructure, including buildings, roads, and pavements, which leads to reduced water retention capacity and escalates the vulnerability to flooding.
What’s needed is Water Sensitive Urban Design (WSUD) which helps retain stormwater and reduce flooding to some extent. Examples of WSUD approaches include rain gardens, bioretention systems, rainwater tanks, pervious pavement, constructed wetlands and sedimentation basins.
These approaches can be retrofitted into existing developments and incorporated into new developments, mitigating the risks to individuals, properties, and infrastructure. Overall, higher flood resilience in urban areas can be achieved with the planning and implementation of integrated urban water management systems and water sensitive urban design approaches.
As sea levels continue to rise, the effects extend beyond the coastline, impacting groundwater levels in coastal areas and posing significant challenges for buried infrastructure. To mitigate these risks and safeguard local facilities, proactive measures must be taken. Here are key aspects to address the impacts of sea level rise in coastal areas:
Strategic Land Use Planning: Implementing land use planning strategies and establishing building and renovation criteria that minimize flood risks.
Infrastructure Development: Constructing, maintaining, or upgrading drainage systems with Water Sensitive Urban Design (WSUD) approaches, flood management infrastructure, and multifunctional assets.
Public Awareness and Education: Providing comprehensive flood information and education to the public to enhance awareness and preparedness.
Assessment of Sea Level Rise Effects: Undertaking a comprehensive assessment of sea level rise effects on coastal lands and infrastructure for risk assessment, understanding challenges in implementation, and developing necessary action plans and policies. Adaptation measures should be tailored based on geographic locations, soil conditions, topography, and existing policies.
Life Cycle Cost Analysis: Conducting life cycle cost analysis to select the most effective and sustainable measures for specific areas, considering environmental and social factors.
Collaborative Planning: Local councils and state governments should collaborate in planning strategies to mitigate impacts due to sea level rise, ensuring a coordinated and cohesive approach.
Without appropriate planning sea level rises will have catastrophic impacts on coastal communities around the globe, detrimentally impacting infrastructure, urban flooding, and increased saltwater contamination of local water sources. Coastal suburbs in the western suburbs of Melbourne are not immune to this risk.
