CASE STUDY: Integrated Water Cycle Management

CASE STUDY: Integrated Water Cycle Management Water, Wetlands, and Wattanobi Woollybutts

Media release, Prime Minister’s Office, 2006, August 23

Harvesting Stormwater to protect the Porters Creek Wetland

… Australian Government funding of $2.6 million toward a $16 million investment will help protect a significant wetland area in NSW from stormwater that will flow from urban development in the catchment.

… The Porters Creek Wetland Stormwater Harvesting project will enable stormwater to be collected, treated and reused to maintain the natural cycles… The Porters Creek Wetland is widely recognised for its diversity of habitats and its contribution to the environmental flows of the Wyong River…

Porters Creek Wetland Foliage of woollybutt From Watanobbi Knoll looking out after significant rainfall. Eucalyptus longifolia. over the Porters Creek catchment. (source: Wetland Web CD) (source: Wetland Web CD) (source: Wetland Web CD)

PORTERS CREEK WETLAND UNDER THREAT

Porters Creek Wetland is the largest remaining freshwater wetland on the NSW Central Coast. Water flowing in from its upper catchment is filtered by the swamp forest communities of the wetland before flowing into the Wyong River and Tuggerah Lake.

In recent times, Porters Creek Wetland has come under pressure from urban development. As suitable land in the Sydney region has become less available, the Central Coast has been identified as one of the few areas able to provide land for new housing and employment. Over the next 30 years, the population of Warnervale/Wyong is likely to more than double to an ultimate population of about 50,000.

How will Porters Creek Wetland survive this onslaught? The answer lies in careful catchment management. Surprisingly, this will have the added benefit of additional supplies of fresh water harvested from otherwise damaging stormwater runoff. CASE STUDY: Integrated Water Cycle Management

CASE STUDY

This Study explores how best to manage the Porters Creek Wetland and its catchment to:

. withstand the potential impacts of expanded urban development . continue its protection of the down stream catchment areas . provide for new opportunities (e.g. water harvesting, relaxation, education)

We briefly survey the characteristics of the wetland, outline the principles of Integrated Water Cycle Management (IWCM) and Water Sensitive Urban Design (WSUD), and analyse how these principles might best be applied to the case of sustainable development in the Porters Creek Wetland catchment. CASE STUDY: Integrated Water Cycle Management

1. Porters Creek Wetland

What is Porters Creek Wetland?

 Porters Creek Wetland is a freshwater swamp forest, five square kilometres in area, located east of the F3 Freeway between Watanobbi and Warnervale, in Wyong Shire.  In wet weather, the basin quickly fills up with water. In dry weather it slowly dries out. Millions of plants and animals that can cope with the wet and the dry times live in this basin and form the wetland which provides habitat for: . more than one hundred fish, amphibian, reptile, bird and mammal species; . almost two hundred plant species, including nine species of paperbarks; . a number of endangered plant and animal species; &

. at least one endangered plant community – the tall paperbark forest

Map of vegetation communities in Porters Creek Wetland showing the direction of water flows

Community Types Always Wet

Wet only when it rains

Location of the Porters Creek Wetland in its Catchment (source: Wetland Web CD) CASE STUDY: Integrated Water Cycle Management

2. Wetland Wonders ACTIVITY: The Table below lists the main vegetation communities of Porters Creek Wetland. The first column lists five ecosystems from wettest to driest, but the other columns contain scrambled information about their communities. Your task is to unscramble the information and match it to the appropriate environment. (See Appendix 1 for a blank template of the Table.)

Surface Community Description of the community with images of typical water type community members conditions (scrambled) (scrambled) 1.Always The Low Woollybutt and Prickly Paperbark Woodland grows wet Paperbark in places that are more often dry than wet, are Forest sometimes damp and rarely flooded. It has many woollybutt gum trees and needle-leaf prickly paperbarks. Needle-leaf prickly paperbarks provide safe nesting places for small birds and animals.

2. Almost The Tall paperbark forest grows in areas that are often wet always Sedgelands but sometimes dry. The two main trees in these wet forests are the Laced Paperbark and the swamp mahogany. The winter flowers of the swamp mahogany are an important food source for many insects, birds and possums. 3. More Woollybutt Red gum and grass tree woodland grows in places wet and Prickly that are dry as often as they are wet. Beneath the than Paperbark many red gum and scribbly gum trees and dry Woodland paperbarks, there are grass trees, banksias and tea trees. The plants provide homes and food for honeyeaters and endangered squirrel gliders. Its dimpled ground provides shelter and breeding pools for the endangered Wallum froglet. 4.Sometimes The Tall Sedgelands are places with very few trees but lots of wet, Paperbark sedges, reeds, rushes and the endangered water sometimes Forest blades. They are found in the wettest parts of the dry wetland. Animals found in the sedgelands include the large and noisy purple swamp hen, the tiny Porters Creek yabbie, the rare Wallum froglet, the southern emu-wren and the mouse-like dusky antechinus. 5. More The Red Low paperbark forest grows in places that are mostly dry Gum and wet, but not as wet as sedgeland. The main tree is a than Grass Tree short skinny paperbark called Melaleuca ericifolia. It wet Woodland can survive long periods of flooding. Low paperbark forest provides nesting and feeding places for many small insect and nectar feeding birds as well as the brown bandicoot, swamp rat and many frogs. (source: Wetland Web CD) TESTABLE HYPOTHESIS: Increased storm water runoff into Porters Creek Wetland would alter the relative proportions of its five vegetation communities; e.g. Sedgeland is likely to increase and the Woodland communities decrease in area. OPEN-ENDED QUESTION: Think about what sources of evidence there might be for major changes in the Porters Creek Wetland since pre-European times. Suggest methods for CASE STUDY: Integrated Water Cycle Management researching whether increases in stormwater have affected the Porters Creek Wetland and whether the proportions of the five communities have changed during the past 250 years. CASE STUDY: Integrated Water Cycle Management

3. The Catchment for the Porters Creek Wetland

What is the Porters Creek Catchment?

Porters Creek Catchment is the area of land that supplies water to Porters Creek Wetland. It stretches from Buttonderry in the northwest to Woongarah and Kanwal in the east and Wyong River in the south. It has three main floodplains that bring water to the wetland from:  the east - the Warnervale catchment (18 km2)  the north - the Buttonderry Creek - Mountain Road catchment (15 km2)  the north-west - the Jilliby, Hue Hue Creek and Warnervale Business Park (10km2)

(source: Wetland Web CD) CASE STUDY: Integrated Water Cycle Management

The Catchment continued … ACTIVITY: Based on the description of the Porters Creek Wetland catchment area on the previous page and the supporting information in Appendix 2 at the back of this document, answer the following questions:

1. List four values of wetlands. 2. What percentage of the wetlands in Wyong Shire has been lost? 3. What is a catchment? 4. What is the total area of the three main catchment areas that feed into the Porters Creek Wetland? 5. How can human activities in the catchment affect the health of the wetland?

Wetland in Flood

 The flooding of Porters Creek Wetland has been a common sight since the days of settlement. Photos 1 and 2, below, taken fifty years apart, show the view across the floodwaters towards Watanobbi Knoll.  Photos 3 and 4 are from the Knoll in the opposite direction, with and without floodwaters.  The cycle of wetting and drying is important for the health of the wetland plant communities each of which is maintained by a specific moisture regime. Droughts are just as important as floods and it is possible for some plant communities to be too wet for too long.  There is concern that urban development in the catchment may increase the amount of flooding into the wetland. This can happen as bush and farmland is replaced by suburbs which have greater stormwater runoff.

1. 1950s flood 2. 2002 flood

3. 2006 wet 4. 2006 dry (source: Wetland Web CD)

OPEN-ENDED QUESTION: 1. Do the photos suggest that there was more or less wetland vegetation on the floodplain in 1950, 2002, and 2006? 2. What effect is the replacement of bush and farmland by suburbs in the catchment areas likely to have on the potential amount of stormwater flowing into Porters Creek Wetland? Why? What effect is this likely to have on the various plant communities of the Wetland? What steps do you think could be taken to minimise this impact? CASE STUDY: Integrated Water Cycle Management

4. What killed the Watanobbi Woollybutts?

Woollybutt dieback

 The problem: On the northern edge of the suburb of Watanobbi in Wyong Shire, there is a patch of the Woollybutt woodland. During the 1990s many of the woollybutt and paperbark trees in the woodland died and weeds invaded the ground beneath them. The largest patch of dieback and weeds occurred at the end of the Fishburn Crescent stormwater drain, which delivers stormwater from 30 hectares of streets and house.  Possible causes: Although it seemed reasonable to suspect that stormwater was in someway involved in the death of the trees, it was possible that something entirely different had killed the woollybutts. Possible causes included fungal attack, insect attack, prolonged drought, pollution or changes in soil chemistry. Without detailed investigation it would have been unwise just to assume that stormwater was the primary cause.  The need to investigate: By discovering the precise cause of the dieback, it would be possible to repair the damage at Fishburn and prevent the same thing happening elsewhere. By eliminating false explanations, we could avoid bad or ineffective solutions.

Curb and guttering Woollybutt dieback Fishburn drain, 2003 (source: Wetland Web CD)

ACTIVITY: Your task is to design an Investigation Plan that could be used to diagnose one possible cause of the Woollybutt dieback. Some steps to include in your Investigation Plan might be:  collect possible explanations (e.g. reports of tree dieback from the internet);  select one to investigate in depth and write down your hypothesis;  suggest the specific types of data you might need to collect (from field surveys, experiments and/or questioning local residents) to test your hypothesis:  outline the investigation procedure you would need to follow to gather this data (factors to consider are equipment , personnel (including any expertise required), techniques (e.g. transects, experimental treatments, controls, safety issues). CASE STUDY: Integrated Water Cycle Management

5. Impacts of stormwater (Before you begin this section you might like to read the general information about the impacts of stormwater contained in Appendix 3).

ACTIVITY: Analysis of phosphorus levels. . The following graph shows the level of phosphorus found during water quality sampling at eleven locations in 1998. . The sites were surveyed on seven different occasions but the data from only three samplings are summarised here. . Site 1 is the junction of Porters Creek and Wyong River, site 2 is at the southern outlet of the Wetland, site 3 is near Fishburn Drain, Sites 4 and 5 are upstream of the railway. . All sites are shown on the Porters Creek catchment map on Page 4.

Total Phosphorus Concentration

0.8 0.7 ) L

/ 0.6 g Survey1

m 0.5 (

P 0.4 Survey2 T 0.3 n Survey3 a

e 0.2 M 0.1 0 1 2 3 4 5 Sites

(source: Wetland Web CD)

1. Find sites 1, 2, 3, 4 and 5 on the Porters Creek catchment map (page 4).

2. Stormwater from Fishburn drain at Watanobbi flows into the wetland through site 3. It then filters through a kilometre of wetland before leaving at site 2. Compare the total phosphorus from sites 2 and 3. Can you suggest why the levels of these nutrients are different at the two sites?

3. In what way does Porters Creek wetland help protect Tuggerah lake? CASE STUDY: Integrated Water Cycle Management

6. Stormwater is suspected in the dieback of Watanobbi Woollybutt

Reasons for suspecting stormwater

 In the time before the suburb was built, most rain falling on the hillside at Watanobbi soaked into the bush and soil, was used by plants, evaporated back into the atmosphere, or seeped slowly over the ground into the wetland. Building the suburb changed the water cycle of this land.  The stormwater system of Watanobbi today is designed to keep the streets as dry as possible and prevent flooding. It does this by collecting water from every house, footpath and street and carrying it through pipes to large outlets on the edge of the wetland. This has caused serious water-logging in some places and increased dryness in other places. It has also brought an increased supply of nutrients.  Reasons for believing that the stormwater outlet had something to do with the tree dieback near Fishburn drain included: o the greatest number of dead trees were close to the stormwater outlet; o the ground under these trees was permanently waterlogged o many plants stopped growing when they were water-logged for long periods o similar tree dieback has occurred below other stormwater outlets o fresh leaves sprouted on some of the surviving trees during the drought, when the ground in the dieback area dried out.

Sydney Red Gum with Land fill causes water to The Sydney Red Gum nine land fill around the roots pond at the base of tree months later (source: Wetland Web CD)

ACTIVITY: Water Sensitive Urban Design

If we assume that stormwater runoff from the Fishburn drain was in fact the cause of the observed Woollybutt dieback, then suggest two possible measures that could have been taken to reduce the impact of excessive storm water on the Wetland around the Fishburn drain outlet. Explain how these measures would achieve their effect. (Before carrying out this task, take the time to read Appendix 4, which briefly outlines the concept of Water Sensitive Urban Design (WSUD)). CASE STUDY: Integrated Water Cycle Management

7. The response to the Woollybutt dieback

Water Sensitive Urban Design Definition 1. WSUD means designing and building towns and suburbs so that they use rainwater efficiently and allow rainwater to flow in much the same way as the original bushland. Definition 2. WSUD is the design of urban areas so that they: . use water in an ecologically sustainable way . mimic the absorption and flow of rainwater in the natural landscape . deliver clean water to the natural streams, wetlands, lakes and estuaries.

Example - the Fishburn Drain Project

 As a result of research into the causes of the tree dieback and other vegetation changes in the vicinity of the Fishburn Crescent stormwater drain, decisions were taken by Wyong Shire to improve the stormwater outlet to reduce its impact on the Porters Creek wetland.  A Gross Pollutant Trap (GPT) was designed to slow down the out flow of the stormwater during periods of heavy runoff, to trap sediments and to disperse the filtered outflow widely rather than narrowly into a channel  The narrow, deep, bare-earth drain was replaced with a wide, shallow, vegetated swale which spread the outflow broadly over a wider area to prevent the ponding of water in the Woollybutt woodland that had previously occurred at the end of the channel.

Constructed GPT Outlet from the GPT The swale ready to be planted (source: Wyong Shire Council) ACTIVITY: The effectiveness of the Fishburn Drain Project. Examine the photos above and consider the steps carried out to improve the Fishburn stormwater outlet.

1. What do you think would be the principle effect of these measures on the wetting and drying cycle of the Woollybutt woodland community?

2. What effect, if any, do you think these measures might have on the nutrient (e.g. phosphorus) outflow into the Woodland?

3. What kind of plant species do you think would have been used to vegetate the swale? Would this be expected to have any effect on the flow of nutrients like phosphorus and nitrogen into the Woodland?

4. What other measures do you think might have been taken in the Watanobbi urban areas to reduce the negative impacts of outflows from the Fishburn Crescent stormwater outlet? CASE STUDY: Integrated Water Cycle Management

8. Water Extraction from Porters Creek in response to Drought

THE CONTEXT: Australia is the driest inhabited continent on Earth (only Antarctica has less annual precipitation than Australia). Since the mid 1990s the severe drought conditions that have affected many parts of the Australia land mass including most of NSW, have heightened awareness of the vulnerability of our water supplies, rural and urban, to climate variability. ACTIVITY: Examine the table of data below showing the total amount of water held in all storage areas of the Central Coast water supply (expressed as % of the maximum storage capacity) at specified dates between January 2001 and July 2007.

Total water storage (%) Date 2001 2002 2003 2004 2005 2006 2007 Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Storage 42 47 44 45 39 37 33 27 25 25 22 16 13 22 %

Your task is to express this data in a graphical form to better display the changes in water storage that have taken place over the seven year period. Use the grid below to assist you in drawing a line graph of the data.

50 45 40 Water 35 storage 30 (% of 25 total capacity) 20 15 10 5 0 01 01 02 02 03 03 04 04 05 05 06 06 07 07 Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Dates between January 2001 and July2007

WATER EXTRACTION: By January 2007, the total water storage within Gosford and Wyong Shires of NSW had fallen to 13% of capacity. To guarantee household water supplies, the Gosford/Wyong Councils’ Water Authority acted to implement a wide range of measures to cut water consumption and to search out new sources of supply. One of their initiatives was to begin a program of fresh water extraction from Porters Creek. During 2006, a temporary weir was constructed in the wetland, at a point just before it enters Wyong River. A pump was installed and used to extract fresh water to boost town water supply by between 1.5 to three million litres a day. The plan was for the weir to be in place for two years and then to be removed.

Porters Creek enters Wyong River Porters Creek Pump Station (source: Wyong Shire Council) CASE STUDY: Integrated Water Cycle Management

9. Integrated Water Cycle Management for Porters Creek Catchment Though designed as a temporary measure, the necessity to pump from Porters Creek prompts a reappraisal of the resource value of the Porters Creek Wetland. A fresh approach to the management and use of water within whole catchments is necessary if we wish to avoid decline not only of our natural environment but also our own quality of life. This approach is Integrated Water Cycle Management (IWCM).

Throughout the world, clean potable water is a precious resource and ICWM has an important role to play in its sustainable use into the future.

Good quality wetland water resource Poor quality wetland water resource (source: Wyong Shire Council) What is “Integrated Water Cycle Management”? . Integrated Water Cycle Management (IWCM) is a planning method that water management authorities can use to achieve an optimal balance of benefits for the community and natural environment from available fresh water resources. . It involves the integration of the four components of the water management system - (1) supply of potable water (2) sewerage (3) stormwater (4) grey water - so that water is used to best effect within a catchment, state and national context. . It recognises that a whole system approach to management of all components of the urban water system can lead to better, more sustainable development. . It aims to maintain as far as possible the pre-development conditions by managing and reusing increase flows that result from development.

ACTIVITY: Modelling the effects of WSUD and IWCM Consider the eastern (Warnervale) component of the Porters Creek catchment. Its area is about 18 hectares and the total annual runoff was probably about 30,000 megalitres per year (ML/yr) before any urban development occurred. Your task is to complete the last column of the following Table that records the expected impact on runoff achieved by Waters Sensitive Urban Design (WSUD) methods and stormwater harvesting (one of the Integrated Water Cycle Management methods).

Stormwater runoff Estimated multiplicative annual runoff factor (ML/yr) Pre-development R 30, 000 (before any urbanisation) Development uncontrolled 3.5 x R (rampant urbanisation) Development + WSUD 3.0 x R (e.g. on site tanks, precinct constructed wetlands, swales) Development + WSUD + IWCM 1.2 x R (e.g. site and precinct measures plus stormwater harvesting)

QUESTION: Based on the above estimates how much (usable) stormwater would be harvested in one year using IWCM? CASE STUDY: Integrated Water Cycle Management

10. Proposed Development in the Porters Creek Catchment

The Department of Infrastructure Planning and Natural Resources anticipates that the population of the Warnervale/Wyong District will increase by 29,000 in the next 30 years. Within the Porters Creek catchment a further 2000 hectares is targeted for employment generation (commercial and industrial), urban development and a town centre at Warnervale to meet the State’s regional growth demands.

Planned developments in the Porters Creek Wetland Catchment (Source: Ecological Engineering)

A major threat to the Porters Creek Wetland posed by these developments is the increased runoff generated from the decreased “water absorption” of the development areas because of the increase in impervious areas (i.e. roads, driveways, paving, roofs etc.). This results in a significant increase in low to medium flows after rainfall. Unless checked, additional flows will impact on water quality and the natural wetting and drying cycle of Porters Creek Wetland and its tributaries.

For this reason, future land releases in Wyong Shire will be guided by the principles of Integrated Water Cycle Management (IWCM) and Water Sensitive Urban Design (WSUD) to ensure that development minimise any impact on Porter’s Creek Wetland and similar hydrologically sensitive ecosystems. ‘Any development should aim to promote sustainable and integrated management of land and water resources for the benefit of both present and future generations’.

Stormwater harvesting and reuse is a key aspect of these guidelines. CASE STUDY: Integrated Water Cycle Management

11. The Proposed Porters Creek Stormwater Harvesting Project

Plans to Harvest Stormwater in the Porters Creek Wetland Catchment

 Planning for the Porters Creek Stormwater Harvesting Project is well underway.  Modelling undertaken to date indicates that the medium to low flows from rainfall events can be transferred out of the stormwater system, thereby maintaining the more natural drying cycles of the wetland and reducing the distribution and frequency of flooding in the wetland.  The Stormwater Harvesting and Reuse Project proposes a regional stormwater storage system located at a disused brick pit site. Stormwater infrastructure from future and existing developments can be connected to this regional storage system.  A transfer pipe system will convey treated stormwater from the Warnervale Town Centre area to the regional storage and then on to additional treatment wetlands below Porters Creek Wetland. The transfer pipeline will eventually discharge treated water into the Wyong River weir pool. Discharge will be managed to specifically meet (or help to meet) the downstream environmental flow requirements of the river, developed under the Water Sharing Plan. This will allow similar quantities to be extracted upstream in the weir pool for transfer to the potable water supply that are additional to allocations developed under the Water Sharing Plan.  A projected average annual stormwater yield under a full development scenario is around 7 gigalitres (based on a piped catchment of 1750 ha of developed area with some 400 ha located in the adjacent Spring and Wallarah Creek catchment). This will allow an expected 5.4 gigalitres of additional extractions with system optimisation.

(Source: Ecological Engineering)

ACTIVITY: List three potential benefits from the Porters Creek Stormwater Harvesting Project. CASE STUDY: Integrated Water Cycle Management

12. The Future of Porters Creek Wetland Porters Creek Wetland is about: the BIG

woodland canopy in flower flooded paperbarks with azolla

swamp mahogany and fern red and scribbly gums dryland paperbarks, grass and undergrowth sedges (source: Wetland Web CD) and the SMALL

tree paperbark snake inflorescence

banksia

orchid bracket fungus

mushroom fungus antechinus

ranunculus green tree white–cheeked frog honeyeater

(source: wetland Web CD) How we manage such places will determine the kind of future we build for ourselves. A future like this? Or a future like this? CASE STUDY: Integrated Water Cycle Management

APPENDIX 1: Blank template for the Wetland Wonders activity (on Page 3).

Surface Community Description of the community with images of typical water type community members conditions 1.Always wet

2. Almost always wet

3. More wet than dry

4.Sometimes wet, sometimes dry

5. More dry than wet CASE STUDY: Integrated Water Cycle Management

APPENDIX 2: The Value of Wetlands and the Threats to Porters Creek Wetland (extracted from Info Sheet 5-2 of the Porters Creek Wetland CD-ROM available to Schools through Gosford and Wyong Councils ).

The Value of Wetlands

A wetland is a habitat with plants adapted to waterlogged soils. These wet soils may occur permanently, seasonally, ephemerally or tidally. Vegetation in wetlands may be dominated by sedges, rushes, reeds, herbs, shrubs or trees.

Wetlands are among the world’s most productive ecosystems and contribute greatly to the health of downstream river systems and estuaries. Wetlands filter nutrients and sediments from runoff. They reduce downstream flooding by retaining flood waters for a period of time. They are also habitat for many plants and animals (playing a particularly important role in fish and bird breeding).

For many years wetlands were not valued and were filled-in for other uses. Many that remained were degraded by draining, clearing, grazing and by activities in the surrounding catchments which changed water flows and reduced water quality. It is estimated that over half of Wyong Shire’s wetlands have been lost since European settlement.

Attitudes towards Wyong’s wetlands changed during the 1990s. During this time Wyong Council mapped the significant local wetlands and created special conservation zoning, called 7(g), to protect them. In addition the NSW government gave 29 of Wyong’s wetlands protection under the Coastal Wetlands State Environmental Planning Policy 14 (SEPP14).

Pristine wetland (source: Wyong Council) Degraded wetland CASE STUDY: Integrated Water Cycle Management Threats to Porters Creek Wetland

Porters Creek Wetland has had a long history of human impact. Major impacts on the wetland over the last century have been: clearing, cattle grazing increased burning and the construction of drainage channels, the Main Northern Railway and the Sydney Newcastle Freeway. Invasive weeds and feral animals have been introduced to the wetland and are now a serious threat to the native species. Today, urban development is further reducing the natural bushland of the catchment and increasing the flow of stormwater into the wetland. Due to concern about these threats, Wyong Council has developed a Management Plan for the wetland and is introducing improved stormwater treatment and ‘water sensitive urban design’ in Warnervale catchment. CASE STUDY: Integrated Water Cycle Management APPENDIX 3: Storm water impacts (extracted from Info Sheet 5-3 of the Porters Creek Wetland CD-ROM available to Schools through Gosford and Wyong Councils).

Stormwater Impacts

Stormwater is rain water running off urban and agricultural catchments. The Stormwater System of Wyong Shire is the network of drains and pipes that collects rainwater runoff from all the towns, suburbs and industrial areas of Wyong Shire and transports it to wetlands, streams, lakes and the ocean. The stormwater system reduces flooding in our towns and suburbs and helps them dry out more quickly after rain.

The Stormwater System has several possible kinds of environmental impact:

1. It reduces the amount of rain that soaks into the ground throughout the Shire. It does this by collecting rain that falls on roofs, paths, roads and carparks. This means that there is less ground water to feed our bushland, wetlands and creeks during dry periods. Unless they are very carefully designed, additions to our stormwater system can reduce the availability of water in bushland areas.

2. It increases the amount of rain that is flushed into natural streams and wetlands. This changes the environments of those places and can cause some plants and animals to die because of erosion, sedimentation and too much wetting. Unless they are very carefully designed, additions to our stormwater system can overload and degrade natural streams and wetlands.

3. It increases the amount of pollution that is flushed into natural waterways. As stormwater flows off buildings, carparks, roads and factory yards, it collects many types of pollution (see pollution list below). Since the stormwater system is designed to move water quickly, it also works like a pollution expressway. Even harmless things such as leaves from trees, can become pollution when large amounts of them are dumped at the end of a drain. The stormwater system is separate from the Sewerage System and so stormwater is not treated at Sewerage Treatment Plants. Although some drains have gross pollution traps or other ways of filtering stormwater, unless they are carefully designed, additions to our stormwater system can increase the pollution into our wetlands, streams and lakes waterways.

4. It uses rainwater inefficiently by rapidly flushing it away into creeks, the lakes and the sea. Wyong Shire Council is working to reduce all of these potential stormwater impacts by improving stormwater treatment in our major drains and by introducing Water Sensitive Urban Design in the new urban areas.

Gosford City and Wyong Shire Councils currently collect and reuse more than 50 million litres of stormwater a year. CASE STUDY: Integrated Water Cycle Management APPENDIX 4: Water Sensitive Urban Design (extracted from Info Sheet 5-5 of the Porters Creek Wetland CD-ROM available to Schools through Gosford and Wyong Councils).

This Info Sheet looks at possible solutions to these problems, using “Water Sensitive Urban Design” (WSUD).

What is Water Sensitive Urban Design?

Water Sensitive Urban Design begins by recognising that rainwater is a valuable resource, not a waste product. If you design urban areas so that they use rainwater more efficiently and in much the same way as the original bushland, then you are using WSUD. Of course your new designs will only work if the people who live and work in the new suburbs do the right thing. This means that Water Sensitive Urban Design not only needs clever new design ideas, it also needs people who understand and manage it.

Techniques of Water Sensitive Urban Design

WSUD uses many different techniques such as rainwater tanks, porous paving, grass swales and constructed wetlands to capture, clean and recycle rainwater.

Porous paving House tanks Pebble swale

Some steps to follow in doing Water Sensitive Urban Design?

Step 1: Map the existing environment and investigate how rainwater flows through it.

Step 2: Draw a simple diagram that describes how rainwater behaves in your sub-catchment (stormwater engineers would make a mathematical model for this step).

Step 3: List the rainwater and stormwater objectives of your design

Step 4: List the developer’s objectives for your sub-catchment (i.e. how big is the subdivision and where is it will be placed, how many houses wanted, how many shops and car parks)

Step 5: Select the methods and devices you think will achieve your rainwater and stormwater objectives, e.g. rain tanks, gardens, absorption trenches, swales (stormwater engineers would use their model to select the best mix of these things).

Step 6: Create your water sensitive design for the subdivision.

Of course, in the real world, you also have to find investors to provide finance, a construction company to build it and home buyers to purchase it when it is finished. And only then will you be able to test it to see if it is really water sensitive.