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Conjola Community Association Community Consultative Body for the Conjola District

This presentation discusses the shortcomings of the current interim entrance management policy for Lake Conjola and proposes immediate amendments. It suggests implementing a "Managed Entrance" policy based on scientific findings and utilizing the M2 DST to improve the management of the lake's entrance. The presentation also explores the possibility of outsourcing the management of the policy and investigates alternative funding sources.

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Conjola Community Association Community Consultative Body for the Conjola District

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  1. Conjola Community Association Community Consultative Body for the Conjola District Lake Conjola Entrance Management Review Meeting and Workshop • 6 February 2019

  2. Presentation Agenda Preamble Background Facts Shortcomings of Current Interim Entrance Management Policy Proposed Immediate Policy Amendments Replacement Policy of a “Managed Entrance” for Lake Conjola

  3. Preamble • Current Policy is not based on scientific findings for Conjola • Current Policy has led to increased lake closures, flooding, excessive sand volumes, loss of amenity with no ecological gains

  4. Preamble (cont’d) • Conjola and Bendalong Communities respectfully request the “Managed Entrance” option as recommended by PBP 1999 become the Lake Conjola Entrance Management Policy • Utilise the “M2” DST  “Regime State”

  5. Background Facts • The Lake is a modified/urbanised wave dominated barrier estuary • Not classified as an ICOLL in 1985, 2005, 2010 - but was in 2013 with no reported change in characteristics • Historically open 85% of the time • Entrance subject to flood, tide, waves, wind-blown sand  Nett Annual Surplus of sand = 10,000m3

  6. Background Facts Source: Patterson Britton & Partners LC Entrance Study May 1999

  7. Background Facts “Regime State”  Hydraulic Efficiency of Tidal Flows through continually scoured northern entrance opening

  8. Background Facts Managed Entrance option utilises northern natural bedrock Continual scour for ebb flows  reduction in closures Higher lake water does not achieve additional scour due to bedrock Additional scour achieved through wider, deeper ebb flow

  9. Background Facts Recorded Lake Closures... 1916 - 1998 there have been nine (9) closures: GHD 2013 Report and SMH editorial 13th March 1936 that Lake Conjola had been open 20 years 1916 – 1936 (Source: Trove), 1994-1998 : Four (4) failed openings to the south, last of which resulted in erosion of ancient sand dune

  10. Background Facts 1999 emergency dredging implemented “Managed Entrance”  remained open for 12 years Council ignored results and resumed failed management practice

  11. Background Facts 2011 – 2019  9 flood events : 8 low level, 1 significant in 2015 Aug 2015... 2.10m flood removed 100K/m3 yet closed in 4 mths 2016... navigation channel removed 16k/m3  open 23 mths Proactive “M2” DST in place since 2003, largely ignored Mar 2011 Aug 2015

  12. Shortcomings of the Current IEMP Council’s selective option  “Emergency Opening” rather than “Planned Opening”, has resulted in .....

  13. Shortcomings of the Current IEMP M2 13

  14. Planned Opening Option (IEMP App C) dfd

  15. Immediate Policy Amendments Commit to ‘Planned Opening’ at northern entrance Reduce trigger levels for ‘Planned Opening’ to 0.75m AHD, with channel works to commence at 0.65m AHD Apply same trigger levels to ‘Emergency Opening’ Agree 0.65m AHD (92% > MHW 0.34m AHD) is implied Emergency Adopt existing ‘M2’ DST into Policy ........

  16. Immediate Policy Amendments Source : Simplified Science – The DST for Lake Conjola Entrance Mgt, McLean, et al, 2003

  17. Replacement Policy Agree on interpretation of PBP 1999 ‘Managed Entrance’ Refine technical framework for ‘Managed Entrance’ + adopt M2 Surplus sand used as replenishment of Conjola and/or Bendalong CZMP4 and/or Mollymook CZMP5 Agree state funding sources underpinned by HH nett profits Memorandum of Understanding  Conjola/Bendalong/SCC Outsource Management of Policy Investigate PPP as alternative to Item 6

  18. Conjola Community Association • Lake Conjola Entrance Management Review • Questions?...

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