FAQs

As part of this study, we need to gather community knowledge, location information and ideas to best inform effective mitigation solutions for the township.

Understanding how flooding impacts the landscape, properties, roads and the local environment is important to knowing how best to approach the problem.

We're hoping you can help us in determining: 

• how flood waters behave in the area 
• how it impacts the landscape and where
• what type/size of water infrastructure is needed to protect people, the landscape and the natural environment 
• where opportunities exist to capture excess flood waters and for further uses – water conservation and keeping the town green (street trees, parks, reserves, sports ovals)
• where opportunities exist to capture stormwater runoff and clean it in landscape features, such as wetlands before it reaches our creeks, rivers and bay
• where opportunities exist to bring natural spaces back to the town with habitat for flora and fauna that can be enjoyed by all

Council and Melbourne Water have shared responsibility for managing stormwater in Longwarry. In Longwarry which falls within the Koo Wee Rup Flood Protection District, Melbourne Water are responsible for all the larger catchments (>60ha), as well some less than 60ha (primarily all the main drains). Council is responsible for the remaining smaller catchments.

Longwarry township has several small creeks that feed into the Bunyip River and a number of Melbourne Water constructed open channels that provide drainage services to the area, namely Cook Drain, Mackey, Johnson Extension, Johnson, Corduroy, Toys and Martin drains.

At the drop-in sessions, you will get to meet the project team members (from Council and Alluvium), ask questions and share your experiences. 

You will also have the opportunity to view and make comments on hard copies of the following:

• Study Area Map (SAM) – designed to capture your local knowledge and insights on the project area
• Flood Maps – areas known to be flood-affected– designed to capture your local observations
• Environmental Values Maps – areas of environmental value that need protection – others you know about and why / what is notable about this location (e.g. species of plants/animals, key habitats etc.)
• Cultural Values Maps – areas of cultural and heritage value that need highlighting and protection

• Other special features and values to be protected (or improved, where possible) – anything we missed.

These local insights will better inform our work on the geomorphology, environmental and cultural heritage investigations for the study area.  This knowledge will also help inform our design responses for stormwater-related infrastructure solutions to existing challenges and planning for future growth and climate change. Asset locations will ensure existing environmental/social values are protected and/or enhanced through blue-green design thinking that integrates people, place and water safely within the landscape.

Help us build the story of Longwarry by placing a dot and adding comments (sticky notes) where you are aware of local area values, special places, significant concerns, quality habitat niches, breeding populations, cultural heritage, flooding issues, poor water quality in waterways, wetlands, etc. 

A catchment is an area where rainfall is collected by the natural landscape and is either absorbed into soils where it is: 

• naturally filtered and replenishes underground storages (e.g. aquifers, bores, groundwater supplies)
• taken up by plants/vegetation for survival and growth
• evaporated off surfaces
• carried below the surface to the nearest waterway where it maintains natural flows in creeks/rivers, or it may run off the surface to the waterways.

Example: Cup your hands together and fill them with water. You now have a “catchment”. Where water seeps between your fingers, it’s similar to soils taking up rainfall. Where your hands come together represents the lowest point in the landscape where water naturally collects and empties into a common point (e.g. a river, a creek, a gully or a bay).  

When there are multiple points of emptying into the low area of the landscape this tells us there are sub-catchments within the larger catchment.  When rainwater falls, and cannot be absorbed by the catchment soils, it runs off as stormwater and drains differently across the landscape and empties at different points. 

Each sub-catchment is its own drainage basin that sits within the larger catchment, and each needs to be considered, both separately, and as part of a connected whole.

Stormwater is rainwater that falls on hard surfaces (where it can’t be absorbed) and runs off towards the nearest low point in the landscape. This runoff occurs when there is insufficient soil area for rainwater to filter into the ground, or is surplus after filling up dams, basins, ponds, wetlands, tanks etc, so it runs off the surface to the nearest drainage pit, drainage pipe, creek, gully, river or bay to empty.

In our urbanised areas where we have houses/shops/warehouses/factory roofs, roads, paths, paved areas, courtyards, carparks etc, stormwater runoff can be both “too much” for our natural creeks, rivers and bays; and can be too much for our drainage pits and pipes (stormwater infrastructure) to cope and causes flooding. This urban stormwater runoff can also be of poor quality as it takes all the urban pollutants and litter we generate in our cities and towns with it (including septic tank leaks and discharges in un-sewered areas).  

Stormwater runoff from urban areas can alter river flows, change an area’s flooding patterns (which affects flora and fauna survival); and increase flow velocities (speed) in waterways causing potential bank erosion/collapse which results in turbidity (cloudiness of water caused by sediments preventing light penetration to aquatic plants) and sedimentation of the waterway (reducing its capacity to hold more water and/or burying fish, water bugs or frogs eggs). Damage caused by stormwater runoff can also lead to issues of useability of a piece of land (or a home through flooding impacts).

A flood occurs when there is too much water that falls in a rain event for an area of land or stormwater pipes to cope with, causing areas to become inundated (submerged) when normally would be dry. Flooding occurs for several reasons such as:

• the topography of an area (low-lying lands) 
• proximity to a river or creek (or bay in the case of tidal flooding)
• limited natural ground surfaces (soils and vegetation to absorb rainfall)
• the intensity and duration of a rainfall event (storm intensities are increasing with climate change and becoming more frequent)
• the limited capacity of the local stormwater drainage system (pits, pipes, retarding basins etc) to cope with the volume of rainfall (particularly if it falls in a shorter space of time = more intense storms)
• the limited capacity of local waterways to cope with extra volumes of water
• the time it takes for a waterway to recede and be able to receive more water from urban areas, to allow pits and pipes (the drainage system) to also empty into the waterway, allowing the infrastructure to receive more hard-surface runoff.  

Floods are a natural process of the water cycle and our rivers, creeks and estuaries have evolved over the longest time to cope with and also benefit from these irregular flood patterns. Many of our Australian plants and animal species are adapted to patterns of dry periods and intense rain periods and rely on these patterns for their ultimate survival. However, flood impacts and frequency have been further affected by human activities (e.g. building cities and towns, building larger dwellings and fewer gardens/green spaces).  

Even with a stormwater drainage network in place, flooding can still occur in big rain events because:

1. the storm is bigger than the design capacity of the pipe network and 
2. the pipes can’t empty if the creeks are full, so they back up and spill out (surcharge) in our streetscapes.  

Until the creek empties its floodwaters, the pipe network cannot empty, so storm duration and intensity play a big part in flood severity.

This is where water-sensitive or water-smart approaches and integrated water management (IWM) play a significant role in resolving these issues in our urban landscapes.

You have probably heard mention of the “100-year storm” (or 1 in 100-year storm).  A storm of this nature results in a large rainfall total that falls within a given period (lots of rain in a shorter timeframe than the landscape or infrastructure is designed to manage.

 This does not mean this size storm only occurs every 100 years, it means it has a 1% chance of occurring in any given year. To avoid confusion this has now changed to the 1% AEP (Annual Exceedance Probability).

For many of us, we have noticed how climate change has led to an increased frequency of high-intensity storms. Many areas have experienced multiple intense storm events over the last 10 years.

While stormwater drainage pipe networks are designed to best practice Australian Standards to protect urban areas from flooding impacts, in these large storms the whole landscape plays a role, not just the pits and underground pipes network. 

That means our roads, paths, open space parks and reserves, and our front and backyards are all part of the stormwater drainage network in big events. They help to hold these large flood volumes and convey them into the pits, pipes and waterways. 

As the flood flows decrease in creeks/rivers, they can receive more flows from the piped network, allowing these to empty. To protect urban areas from this large quantity of water (rainfall and runoff), retarding basins, wetlands and stormwater harvesting schemes (e.g. storage lakes and large tanks) are designed into our urban areas to provide flood protection.

Creeks, rivers and bays are affected by stormwater runoff from our urban (and agricultural) areas – by the quantity (too much runoff) and the quality of stormwater (carrying urban pollutants from our streets to our waterways (natural environments).  

When it rains, all the hard surfaces (roofs and roads) that have built up sediments (e.g. mud, dirt, soil), gravel screenings, organic materials (e.g. food waste, livestock/animal droppings, fertilisers, etc), litter or chemicals (e.g. pesticides, herbicides, heavy metals, petrol, oils and greases, etc) – all get washed into our waterways, ponds, wetlands and bays when stormwater is not absorbed into soils and filtered naturally. 

These are being replicated through blue-green designs, now commonly known as water-sensitive urban design – where natural systems are designed and constructed to do what nature once did.

The habitat in these areas can be impacted by what’s in the stormwater runoff. 

Vegetation can be affected by pollutants and die back, or struggle to grow, affecting species diversity and reducing wildlife options for habitat and food supply. The loss of vegetation, particularly trees can then impact our human comfort levels when urban heat in an urbanised area starts to rise when canopy trees (shade cover) are lost. 

This then leads to challenges of Urban Heat Island (UHI) impacts and increased community vulnerability during heat waves. This can be addressed through greening and cooling.

Sediment, mud or dirt from construction works, exposed and eroding soils (no grass cover or vegetation to hold soils together), or stockpiles of garden supply deliveries (left uncovered) get washed into the stormwater system and end up in our natural waterways and water bodies.  

These sediments can:

• cover aquatic plants and reduce access to sunlight for growth
• cause abrasion to fish gills and loss (as they cycle water through their gills for oxygen)
• bury habitat pockets, fish eggs and good water bug life. A loss of good water bugs means a loss of a primary (basic) food source for most creatures such as fish, frogs, turtles, birds and platypi and will negatively impact wildlife populations and diversity.  

Organic litter can increase nutrient concentrations in water bodies and cause a spike in toxic blue-green algal blooms. It can kill off native plant species that do not cope with rich organics. 

As natives die off, we lose food supplies and habitat for local wildlife. As the good vegetation goes, the weeds move in and can encourage undesirable critters to move in also who then compete with local wildlife. It also degrades local amenity. 

Some chemicals in stormwater can kill plants and animals immediately or cause long-term impacts on the local environment (some areas never recover). 

Everything is connected. 

Stormwater treatment systems come in a variety of blue-green design options, that can be selected to best suit a location and the challenges. 

These options range from wetlands to rain gardens, biofiltration systems to sand filters, swales, sediment basins and gross pollutant (litter) traps to combined (multi-functional) systems. 

Each type of system has different levels of effectiveness in cleaning stormwater of its various urban pollutants. Some systems also provide some flood protection functions (not just treatment).  

Blue-green or water-sensitive urban design options for stormwater treatment:

• Filter or clean urban stormwater runoff to remove harmful pollutants before they reach our creeks/ rivers / natural environments where they can do further damage.
• Can provide some flood storage benefits by holding back excess rainfall until the storm passes and creeks, pits and pipes can cope with more flow.
• Reduce the speed and amount of stormwater that runs off to waterways, protecting their natural ecological balance and species survival.
• Can be used to filter stormwater for storage and use, such as irrigation (conserving our limited drinking water supplies). 

Choosing the right treatment system for the location is important for the job it needs to do (its water function) – e.g. flood protection, stormwater treatment, stormwater harvesting, biodiversity enhancement, vegetation survival, etc. 

Equally, the right stormwater treatment system can significantly improve an urban landscape in terms of amenity, community access and enjoyment, social inclusion and connection, urban cooling and passive greening, and if done well, can encourage higher visitor use to the site. 

A constructed treatment wetland, for instance, can provide multi-functional benefits from flood storage to water quality treatment to harvesting and irrigation reuse, while also providing quality aquatic habitats and experiences for communities. 

Wetlands are often called the kidneys of the catchment. Once called wastelands or swamps (and were typically filled in/covered over) these systems used to provide natural filtering in the landscape - just like our kidneys they remove pollutants and protect downstream environments (our creeks, rivers, bays, and beaches).  

Over the last 30+ years, organisations have been returning these “wet-landscapes” to urban areas as ‘constructed wetlands’ that are designed to mimic nature’s natural filtering processes.

Constructed wetlands are often a series of deep and shallow pools, densely planted with a specific selection of aquatic plants that can withstand the harshness of urban runoff, using the organics in the water to grow and thrive and removing these from the water. 

Stormwater pipes are diverted to these wetlands, where the flows are slowed down to allow the system enough time to filter (clean) out pollutants through a combination of the shape and structure of the wetland itself, and the biological processes (plants, good algae/microorganisms etc) within the system. 

These biological processes trap sediments to the wetland floor, extract nutrients from the water to support plant growth and detoxify chemicals before the water then moves on to the creek.

A well-designed wetland can also provide flood protection, new aquatic habitats for safe breeding and wildlife protection, visual amenity, cooling and greening of local neighbourhoods, and an area for communities to visit, meet with others, recreate - observe and interact with nature, and simply enjoy.

Blue-green designed infrastructure is simply an approach to urban stormwater which is managed by designing assets that provide flood resilience, protect the health of local waterways from the impacts of urban pollutants, enhance local landscapes and open spaces, improve town greening and create cooler, greener areas by keeping water safely in the landscape. This is also referred to as Water Sensitive Urban Design.

Simply, it’s about designing water infrastructure to better blend into the landscape or mimic nature and create destinations (not just infrastructure) that can be enjoyed by communities, while still performing critical water management functions. 

By designing smarter, we can safely hold water within the landscape it falls in, where it can provide urban greening and cooling benefits, improve soil moisture, provide new habitats for plants and animals; as well as provide a source of water to keep streetscapes, parks and reserves healthy and green. 

This is critical for human comfort as urban centres absorb and generate heat during the day, and then expel this higher heat from all hard surfaces during the night (preventing natural evening cooling) - this is known as the Urban Heat Island effect.

Members of the community most vulnerable to heat extremes are typically the elderly, the ailing (sick), pregnant, and the very young. From 1996 to 2010 Victoria experienced the millennium drought (13 years). In January 2009, the two weeks before the Black Saturday (7 Feb) bushfires, the Victorian heatwave extremes resulted in ‘excess deaths’ (Chief Health Officer) with 374 Victorian lives lost due to heat-related stress (not bushfire).

By creating blue-green water infrastructure and blue-green “corridors” in urban landscapes we can provide communities the ability to move comfortably and safely from one point to another via green/cool avenues (not just roads) to recreate and enjoy the neighbourhood, as well as providing corridors for wildlife to move safely and freely from one point to the next in search of food, shelter or breeding partners.

By keeping water within the landscape it also means we are not increasing urban runoff discharges to our natural rivers and creeks, which can also lead to flooding impacts further downstream. 

We also take the pressure off these natural environments and prevent their degradation from poor quality runoff, high volumes, faster flows, bank and bed erosion, habitat and species losses etc. Further, we are also maintaining a cooler urban environment by using this runoff to promote vegetation survival and tree canopy cover, which in turn provides human thermal benefits and protects community health and wellbeing.

Integrated Water Management (IWM) is a collaborative approach to the way we plan for and manage all elements of the water cycle wisely and building our climate resilience (adapting the change). 

The water cycle in this context includes rainwater, potable (drinking) water, flood waters, wastewater (blackwater/sewage, greywater), recycled water and stormwater. IWM also includes managing and protecting the health of our waterways and bays; seeking alternate water supply options that are fit for purpose (e.g. harvested stormwater for irrigation, potable water for drinking, tank water for laundry/gardening); and creating urban landscapes that use water wisely, and are safe, green and cool.

All authorities with some responsibility for managing aspects of the urban water cycle work collaboratively as part of geographically based IWM forums across Victoria, as part of the Victorian IWM Framework (2017). 

Baw Baw Shire (and Longwarry) falls under the Westernport IWM Strategic Directions Statement (SDS). 

Climate resilience is the capacity of social, economic, and ecological systems to cope with, adapt to, and recover from climate-related shocks and stresses. It is a way to plan and act to prevent or mitigate the impacts of climate change while also addressing the root causes (e.g. emissions). 

In the case of water management, this means having a diverse range of water sources to choose from that are safe, secure and affordable to use.  The majority of everything we do from water for consumption, cleaning, bathing, toilet flushing, laundry and irrigation is from our limited drinking (potable) water supplies.  

Alternate water is about using the right type of water for the right job or task, often referred to as “fit for purpose”. In a climate of water unpredictability, this builds our resilience over time to extremes, using the right water at the right time while still ensuring that public health and the environment are protected.

For instance, rather than using valuable drinking water to flush toilets or wash our clothing, or water the garden we could be using rainwater from our rooftops (and stopping this extra water from entering stormwater pipes and impacting our natural rivers and creeks).  

Instead of using drinking water to water our parks, reserves, street trees and sports fields we could be using harvested stormwater from our drainage pipes, treating it through a wetland (and UV treatment) before pumping it to sportsgrounds to keep turf alive and green for year-round sporting club use.  

Irrigated lands also provide improved natural cooling effects to local neighbourhoods.

Use of alternate water supplies must be managed to meet public health requirements, environmental standards and community expectations. It can provide:

• Conservation of limited drinking water supply
• Cost savings in drinking water use
• Reductions in the amount of stormwater / treated wastewater (effluent) that is discharged to our bays, creeks and rivers
• Opportunities to create greener, more liveable urban landscapes, especially in periods of climate change, heat extremes and periods of drought.