A risk based framework for managing stormwater inputs to estuaries, using ecological condition triggers Jocelyn Dela-Cruz, Anthony Pik, Paul Wearne, Tony Weber, Peter Scanes and Tim Pritchard

No state wide planning policy on WSUD Councils have set their own policies and stormwater management targets 44 Councils 13 Policies Butler, R. (2015)

http://www.marine.nsw.gov.au/

6 District Plans: http://www.planning.nsw.gov.au/Plans-for-Your-Area/Sydney/Sydney-Districts

8 Regional Plans: http://www.planning.nsw.gov.au/Plans-for-Your-Area/Regional-Plans

Lake Illawarra exceed trigger value 5.3 8.1 2.1 3.9 4.3 3.8 2.5 2.4 2.2 1.4 4.4 3.9 9.6 2.5 3.5 2.1 4.3 2.4 3.8 exceed trigger value Data from WCC (2015)

http://www. illawarramercury. com http://www.illawarramercury.com.au/story/636045/threat-to-lake-illawarra-never-greater/

Stormwater water quality targets (Landcom) How do we accommodate urban development while protecting the community’s values and uses of the lake? Stormwater water quality targets (Landcom) 40-45% reduction in TN load post development 55-65% reduction in TP load post development 80-85% reductions in TSS load post development Neutral or Beneficial Effect (NorBE) works in theory ‘no net increase’ in practice

Risk-based Framework for Considering Waterway Health Outcomes in Land Use Planning Decisions Risk Evaluation Risk Analysis Establish Context, and Identify Risks Land use scenario Risk assessment Effects Based Assessment Waterway Objectives Communication and Consultation Monitoring and Review Strategic Impact Assessment Are the risks acceptable? NO YES Risk treatment Land use settings Detailed design and implementation plans

determine sustainable load Effects Based Assessment Landcom, no net increase Catchment Model Photos: D. Wiecek, OEH determine sustainable load determine impact Hydrodynamic/Hydraulic Model Ecological Response Model (meeting objectives) Littleboy et al., 2009; Proceedings of the 18th World IMACS/MODSIM Congress Sanderson and Coade, 2010; Environmental Modelling and Software 25(6), 724-736

no controls no net increase Chl a (µg/L) current Landcom trigger SUSTAINABLE LOAD TN (kg/y)

e.g. urban residential (15 dwellings/ha) Forest (Greenfield) Rural Agricultural (Brownfield) Re-development (from 10 d/ha) TN stormwater load reduction Landcom 0 100 200 300 400 500 Net Present Value of Basin ($k/ha)

Landcom (improvement) sustainable load no net increase (runoff) no net increase (improvement) TN (kg/ha/y) Greenfield Landcom (runoff) Landcom (improvement) TN (kg/ha/y) Re-development

Benefit Map maintain or improve improve maintain

Infrastructure planning and offsets: e.g. WSUD capability high low

Planning of Green-Blue Grid, co-benefits River Styles - Recovery Potential

TN (kg/ha/y) water clarity Micro-algae flushing

River Styles - Fragility Proximity Environmental Assets Macrophytes (EECS) Protected wetlands Key Fish Habitats Shorebird Habitats

RISK = X LIKELIHOOD (TN per hectare, flushing, fragility, river order) CONSEQUENCE (micro-algae, water clarity, aquatic assets) RISK = X

ACTION 5.4.1 – protect sensitive estuaries and coastal lakes This work has led to: ACTION 5.4.1 – protect sensitive estuaries and coastal lakes ACTION 5.4.2 – implement a risk-based decision framework for managing water quality and waterway health in Lake Illawarra ACTION 5.4.3 – implement a risk-based decision framework for managing water quality and health for all estuaries and lakes where development is planned, with priority given to sensitive estuaries and lakes http://www.planning.nsw.gov.au/Plans-for-Your-Area/Regional-Plans/Illawarra-Shoalhaven

TAKE HOME MESSAGE Not all waterways are the same, use an effects based assessment Not all development scenarios are the same, waterway health improvements are more attainable under Brownfield and Re-development scenarios Stormwater management should be commensurate with level of risk, not a one-size-fits-all approach