Urban Water Security Research Alliance Can Stormwater Harvesting - - PowerPoint PPT Presentation

Can Stormwater Harvesting Restore Pre-Development Flows in urban catchments in South East Queensland? Stephanie Ashbolt

Stormwater Harvesting and Ecohydrology

Science Forum, 19-20 June 2012

Urban Water Security Research Alliance

CONTENTS

• Introduction – the problem
• Aim of this work
• Method – data, simulation modelling
• Results – simulation analysis
• Conclusions – how results relate to project

aims

INTRODUCTION: THE PROBLEM

Urbanisation or development of a catchment increases impervious surfaces, leading to:

• Increased surface runoff
• Reduced infiltration to

groundwater Which means:

• Increase in frequency,

magnitude and duration

• f flow events
• Increased erosion,

changes to creek morphology

THE SOLUTION? Flow Frequency Management Objectives

Designed to mitigate increase in frequency and magnitude of flow in urban developments. From the proposed development, capture and manage:

– The first 10mm of runoff (per day) from impervious surfaces where the total impervious surface is 0 to 40% – The first 15mm of runoff (per day) from impervious surfaces where the total impervious surface is greater than 40%

In other words, capture a volume equal to:

– Impervious area (m2) x target design runoff capture depth (mm/day) x 1000

Manage captured stormwater using one or more of:

– Stormwater evaporation – Stormwater reuse (including rainwater collection and use) – Infiltration to native soils or a bioretention system – Flow diversion

AIM 1 Assess the effect of urbanisation on the flow regime 2 Assess the effect of Flow Frequency Management Objectives in restoring predevelopment flows, for a range of urbanisation extents Use calibrated and validated catchment models

DATA COLLECTION AND ESTIMATION

• Rainfall: 0.2mm instantaneous tipping

bucket rain gauge

• Stream level: 6 minute pressure transducer
• Rating curves: cross-section

measurement, flow rate vs height (current meter, acoustic doppler current profiler), Hydstra software

• Impervious area: automated analysis of

aerial photos

UPPER YAUN CREEK

Area: 362ha TIA: 3% ToC: 1.9 hours Slope: 6.8%

SCRUBBY CREEK

Area: 144 ha TIA: 0% ToC: 1.1 hours Slope: 2.9%

TINGALPA CREEK

Area: 2785 ha TIA: 1% ToC: 8.25 hours Slope: 0.9%

SIMULATION MODEL: SWMM

Calibration: 18 months streamflow and rainfall data Hourly timestep Shuffled complex evolution algorithm (Matlab) Performance metric: Nash Suttcliffe Criterion of Efficiency

SIMULATION MODELLING SCENARIOS Various degrees of urbanisation:

• Predevelopment (0% impervious)
• Existing
• 5, 10, 15, 20, 40, 50, 60, 70% impervious

Above with runoff capture according to FFMOs

capture volume = %IA*catchment area*10/15mm

RESULTS: YAUN CREEK URBANISATION

5 10 15 1e-03 1e-02 1e-01 1e+00 1e+01

Runoff at catchment outlet

Percent time hourly runoff is exceeded (%) Hourly runoff (m^3/s) 0 % existing (3%) 5 % 20 % 40 % 50 % 70 %

RESULTS: YAUN CREEK FLOW CAPTURE

5 10 15 1e-03 1e-02 1e-01 1e+00 1e+01

Runoff at catchment outlet

Percent time hourly runoff is exceeded (%) Hourly runoff (m^3/s) 0 % 5 % 5% with capture 20 % 20% with capture 40 % 40% with capture 70 % 70% with capture

RESULTS YAUN CREEK 90TH PERCENTILE FLOW

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0% impervious 5% impervious 5% impervious with runoff capture 20% impervious 20% impervious with runoff capture 40% impervious 40% impervious with runoff capture 50% impervious 50% impervious with runoff capture 70% impervious 70% impervious with runoff capture 90th percentile hourly flow (m3/s)

RESULTS YAUN CREEK HIGH FLOW SPELLS

1 2 3 4 5 6 0% impervious 5% impervious 5% impervious with runoff capture 20% impervious 20% impervious with runoff capture 40% impervious 40% impervious with runoff capture 50% impervious 50% impervious with runoff capture 70% impervious 70% impervious with runoff capture High flow spell duration (% of record) Mean of high flow spell (m3/s)

RESULTS: SCRUBBY CREEK URBANISATION

5 10 15 1e-03 1e-02 1e-01 1e+00 1e+01

Runoff at catchment outlet

Percent time hourly runoff is exceeded (%) Hourly runoff (m^3/s) 0 % 5 % 20 % 40 % 50 % 70 %

RESULTS: SCRUBBY CREEK FLOW CAPTURE

5 10 15 1e-03 1e-02 1e-01 1e+00 1e+01

Runoff at catchment outlet

Percent time hourly runoff is exceeded (%) Hourly runoff (m^3/s) 0 % 5 % 5% with capture 20 % 20% with capture 40 % 40% with capture 70 % 70% with capture

RESULTS SCRUBBY CREEK 90TH PERCENTILE FLOW

0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014 0.0016 0.0018 0.002 90th percentile of hourly flow (m3/s)

RESULTS SCRUBBY CREEK HIGH FLOW SPELLS

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 High flow spell duration (% of record) Mean of high flow spell (m3/s)

RESULTS: TINGALPA CREEK URBANISATION

10 20 30 40 50 60 0.01 0.05 0.10 0.50 1.00 5.00 10.00

Runoff at catchment outlet

Percent time hourly runoff is exceeded (%) Hourly runoff (m^3/s) 0 % existing (1%) 5 % 20 % 40 % 50 % 70 %

RESULTS TINGALPA CREEK FLOW CAPTURE

10 20 30 40 0.01 0.05 0.10 0.50 1.00 5.00 10.00

Runoff at catchment outlet

Percent time hourly runoff is exceeded (%) Hourly runoff (m^3/s) 0 % 5 % 5% with capture 20 % 20% with capture 40 % 40% with capture 70 % 70% with capture

RESULTS: TINGALPA CREEK MEAN and 90TH PERCENTILE FLOW

0.1 0.2 0.3 0.4 0.5 0.6 0.7 Average of mean hourly flow per day (m3/s) Top 90th percentile of daily flow (m3/s)

RESULTS TINGALPA CREEK HIGH FLOW SPELLS

1 2 3 4 5 6 7 8 9 10 High flow spell duration (% of record) Mean of high flow spell (m3/s)

CONCLUSIONS

Generally: There is an increase in flow magnitude, frequency and duration with urbanisation. Flow capture according to FMMOs is able to reduce this impact towards a lower effective urbanisation. However: Flow frequency management objectives do not return to predevelopment for these catchments.

ACKNOWLEDGEMENTS

Co-authors:

Santosh Aryal Kevin Petrone Brian McIntosh Shiroma Maheepala

With help from:

Richard Gardiner Rezaul Chowdhury

Urban Water Security Research Alliance THANK YOU www.urbanwateralliance.org.au