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Reducing the frequency of urban run-off Little Stringybark Creek Project

This Project is supported by:

Presenter: Leigh Holmes Stormwater Victoria Annual Conference 23/06/2010

Contents

1. Introduction 2. The Project Area 3. Project Research 4. Stormwater Fund 5. Implementation Experience · Hereford Road RB · Pembroke Secondary College

Introduction

· The Little Stringybark Creek is located within the undulating hills of Mount Evelyn in Melbourne's East. The Little Stringybark Creek is experiencing severe erosion and degradation due urban stormwater that runs off houses and roads of Mt Evelyn at a much more frequent rate than its pre-urbanised days. The Little Stringybark Creek Project is a research program co-ordinated by the University of Melbourne and Monash University It is putting into practice new approaches to stormwater management, that focus on improving the health of creeks and rivers. Working with local government, water authorities and residents, the project will test the design and implementation of real, on-ground solutions. Most importantly, the project will test how stormwater management can be improved in established suburbs, like Mt Evelyn. This is a world-first demonstration of restoring an urban creek by fixing up its biggest problem first: urban stormwater runoff.

· · ·

·

The Project Area

Project Research

·

Research conducted over the last 6 years has found that stormwater runoff is the primary degrading influence on stream eco-systems in the eastern suburbs and fringes of Melbourne. Urban stormwater drainage systems within the Little Stringybark Creek catchment have been found to be causing the degradation of the Creek. Research has also shown that impervious areas like roofs and roads have much less effect on streams if they don't drain directly to a stream via stormwater infrastructure. On average stormwater runoff drains straight into the Little Stringybark Creek 121 days a year (post development). If runoff could be kept on a property or development for all but the biggest storms (12 or fewer days a year, like before Mt Evelyn was developed), then the impact due to urbanisation on the creek will be greatly reduced.

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·

Stormwater Fund

· ·

Stormwater Fund is an incentive program offered as part of the Little Stringybark Creek Project. The first round of incentives was offered to landowners in 2007/2008 who install rainwater tanks and rain-gardens that retain, use and treat stormwater on their property. In 2010, funding will again be provided to private land owners All proposed works in the creek's catchment are assessed for the benefit they provide to the creek. This is done via the Environmental Benefit (EB) Calculator. This calculator not only aids the design work, but also provides a cost benefit analysis of the proposed works. This fund is also used to assess the EB of streetscape projects within the catchment area.

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· ·

Implementation Experience

Collaboration - Little Stringybark Creek Project · Shire of Yarra Ranges · Research · Melbourne Water

Two Case Studies: · Hereford Road Basin · Morrison Reserve/Pembroke Secondary College

Hereford Road ­ Existing Basin

Hereford Road ­ Proposed Infiltration Basin

Hereford Road Basin ­ Issues

Existing Soil Profile · Clayey Silt - Silty Clay · Permeability tests undertaken at different depths (0 ­ 1.3 metre) · Ranged from 1 mm/hr to 20mm/hr

Drainage / Retarding Basin Objectives Operations and Maintenance Community Acceptance

Hereford Road Basin ­ Typical Section

100mm below finished surface

Monitoring tubes

Existing pit 90mm riser with perforated end cap 400mm sandy loam 100mm coarse sand 100mm gravel 400mm scoria Existing soil

Hereford Road Basin ­ Working With Stakeholders

Hereford Road Basin ­ Benefits

Waterway Health · Reduction in surface runoff days from 120 to about 15 Robust Design that Optimises Operational Needs Resilient Landscape · Available subsurface water storage for drawdown by plants in dry periods

Morrison Reserve / Pembroke Secondary College

Catchment Size Approx 10ha

Morrison house

Sports grounds

Pembroke Secondary College Car park

Netball courts

Mount Evelyn Special Development School

Morrison Reserve / Pembroke Secondary College

Key Drivers · Maximise system yield · Reduce the frequency of run off (12 days or less) · Unrestricted Irrigation operations · Easily maintainable system

Morrison Reserve / Pembroke Secondary College Rainfall Data

Croydon Station Pembroke Secondary College Site

Data: 1996 - 2006

Morrison Reserve / Pembroke Secondary College Stormwater Inflows

1 Year = 0.075 m3/s 3month = 0.030m3/s 5mm/hr = 0.005m3/s Morrison house 1 Year = 0.135 m3/s 3month = 0.05m3/s 5mm/hr = 0.02m3/s Sports grounds

Pembroke Secondary College Car park

Netball courts

Mount Evelyn Special Development School

Morrison Reserve / Pembroke Secondary College Irrigation Demand

The irrigation calculations determined that an annual average demand of 3.225ML/hectare/year

Irrigation Zone Football Oval Football oval + Athletics area Football oval + Athletics area + Soccer Pitch Irrigation Area (ha) 1.058 2.626 3.211 Irrigation Demand (kL/year) 3,413 8,470 10,358

Once the turf is converted to warm season grasses it is expected that the irrigation demand will decrease to approximately 2.5ML/hectare/year. monthly irrigation distribution

Monthly Irrigation Demand

25%

% of Total Annual Irrigation Demand

20%

15%

10%

5%

0%

a nu Ja ry ry ua br Fe M ch ar ril Ap M ay ne Ju ly Ju A t us ug S m te ep r be er ob ct O m ve No r be em ec D r be

Month

Morrison Reserve / Pembroke Secondary College Pre-treatment Options

Pre Treatment Options Enviss

Permapave Permapave Drainage Layer Slotted Pipe

Morrison Reserve / Pembroke Secondary College

Surface Runoff Days

140 120

100

80

60

40

20

target

0

Existing

Stormwater Harvesting

Stormwater Harvesting + Infiltration

Morrison Reserve / Pembroke Secondary College Layout Plan

280m2 Infiltration Basin 20m2 Pre-treatment Enviss or Permapave 500kL Tank 5m2 Pre-treatment Enviss or Permapave 20m2 Pre-treatment Enviss or Permapave

Morrison Reserve / Pembroke Secondary College Tank Size & Reliability

Irrigate Football Oval(3413kL/Year)

100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0 500 1000 1500 2000 2500 80% 70% 60% 50% 40% 30% 20% 10% 0% 0 500 1000 1500 2000 2500

Irrigate Football Oval & Atheletics Field (8470kL/Year)

Irrigate Football Oval, Athletics Field & Soccer Pitch (10360kL/Year)

70% 60% 50% 40% 30% 20% 10% 0% 0 500 1000 1500 2000 2500

Morrison Reserve / Pembroke Secondary College Tank Size & Reliability

80% 70% 60% 50% 40% 30% 20% 10% 0% 0 500 1000 1500 2000 2500 Tank Reliability (8470kL/Year) High Flow Bypass = 0.1m3/s Tank Reliability (8470kL/Year) High Flow Bypass = 0.02m3/s

Equates to approx 500kL/Yr

Morrison Reserve / Pembroke Secondary College

Benefits · Waterway health (reduction in surface runoff days from 120 to about 12) · An alternative water source for school / community sports fields · A more sustainable source of water than groundwater · Information and education tool within the school environment · Partnership For Further Information http://www.urbanstreams.unimelb.edu.au/

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