COLLAROY-NARRABEEN COASTAL IMAGING SYSTEM REPORT 3 ANALYSIS OF SHORELINE VARIABILITYAND EROSION/ACCRETION TRENDS: JULY 2006 - JUNE 2007 by M J Blacka, D J Anderson and I L Turner Technical Report 2007/30 August 2007 THE UNIVERSITY OF NEW SOUTH WALES SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING WATER RESEARCH LABORATORY COLLAROY-NARRABEEN COASTAL IMAGING SYSTEM REPORT 3 ANALYSIS OF SHORELINE VARIABILITY AND EROSION/ACCRETION TRENDS: JULY 2006 – JUNE 2007 WRL Technical Report 2007/30 August 2007 by M J Blacka, D J Anderson and I L Turner Water Research Laboratory School of Civil and Environmental Engineering Technical Report No 2007/30 University of New South Wales ABN 57 195 873 179 Report Status Final King Street Date of Issue August 2007 Manly Vale NSW 2093 Australia Telephone: +61 (2) 9949 4488 WRL Project No. 02092.03 Facsimile: +61 (2) 9949 4188 Project Manager Doug Anderson Title Collaroy-Narrabeen Coastal Imaging System - Report 3: Analysis of Shoreline Variability and Erosion/Accretion Trends: July 2006 – June 2007 Author(s) Matthew J Blacka, Doug J Anderson and Ian L Turner Client Name Warringah Council Client Address Civic Centre, 725 Pittwater Road, Dee Why NSW 2099 Client Contact Daylan Cameron – Catchment Management Team Client Reference The work reported herein was carried out by the Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, acting on behalf of the client. Information published in this report is available for general release only by permission of the Director, Water Research Laboratory, and the client. WRL TECHNICAL REPORT 2007/30 CONTENTS 1. INTRODUCTION 1-1 1.1 General 1-1 1.2 Maintenance, Upgrades and Operational Issues 1-2 1.3 Report Outline 1-2 2. BACKGROUND 2-1 2.1 Environmental Setting 2-1 2.2 Study Area 2-1 3. OVERVIEW OF COASTAL IMAGING, IMAGE TYPES AND IMAGE PROCESSING METHODS 3-1 3.1 What is Coastal Imaging? 3-1 3.2 The Difference between Coastal Imaging and a 'Surfcam' 3-1 3.3 The ARGUS Coastal Imaging System 3-2 3.4 Installation at Collaroy-Narrabeen 3-2 3.5 Image Types 3-3 3.5.1 Snap-Shot 'snap' Images 3-3 3.5.2 Time-Exposure 'timex' Images 3-3 3.5.3 Variance 'var' Images 3-4 3.5.4 Day Time-Exposure 'daytimex' Images 3-4 3.6 Basic Image Processing – Merge and Rectification 3-4 3.7 Shoreline Detection and Analysis 3-5 3.7.1 Pixel Intensity Clustering 3-5 3.7.2 Standardised Procedure for Shoreline Mapping 3-6 4. COASTAL IMAGING WEB SITE 4-1 4.1 Coastal Imaging Home Page 4-1 4.2 Image Archive 4-1 4.3 On-Line ‘Beach Analysis System’ 4-2 5. MORPHODYNAMIC DESCRIPTION OF COLLAROY-NARRABEEN: JULY 2006 – JUNE 2007 5-1 5.1 A Morphodynamic Classification of Beaches 5-1 5.2 Morphodynamic Interpretation of Daily Images 5-2 5.2.1 July 2006 5-3 5.2.2 August 2006 5-3 5.2.3 September 2006 5-4 5.2.4 October 2006 5-4 5.2.5 November 2006 5-4 5.2.6 December 2006 5-5 5.2.7 January 2007 5-5 5.2.8 February 2007 5-6 5.2.9 March 2007 5-7 5.2.10 April 2007 5-7 5.2.11 May 2007 5-7 5.2.12 June 2007 5-8 5.3 Visual Assessment of Net Beach Width Changes (July 2006 – June 2007) 5-9 5.4 Visual Assessment of Total Beach Width Changes (July 2004 – June 2007) 5-10 - i - WRL TECHNICAL REPORT 2007/30 6. QUANTITATIVE ANALYSIS OF SHORELINE CHANGES: JULY 2006 – JUNE 2007 6-1 6.1 Weekly Shorelines 6-1 6.2 Shoreline Variability – Mean, Maximum, Minimum, Standard Deviation 6-2 6.3 Time-Series of Beach Widths at Control Transects (Precinct 3) 6-3 6.4 Weekly Shorelines (July 2006 – June 2007) Relative to Mean Shoreline Position of Previous Twelve-Month Monitoring Period 6-3 7. QUANTITATIVE ANALYSIS OF TOTAL SHORELINE CHANGES: JULY 2004 – JUNE 2007 7-1 7.1 Weekly Shorelines and Shoreline Variability: July 2004 – June 2007 7-1 7.2 On-Line Beach Width Analysis 7-3 8. ANALYSIS OF EROSION-ACCRETION TRENDS 8-1 8.1 Methodology 8-1 8.2 Monthly Beachface Bathymetric Mapping 8-1 8.3 Monthly Erosion-Accretion Trends 8-2 8.4 Annual Net Erosion-Accretion Trends 8-5 8.5 Total Erosion-Accretion Trends: July 2004 – June 2007 8-6 9. SUMMARY AND CONCLUSIONS 9-1 9.1 Qualitative Visual Assessment 9-1 9.2 Shoreline Variability and Beach Width Analysis 9-3 9.3 Erosion/Accretion Trends 9-4 10. ACKNOWLEDGEMENTS 10-1 11. REFERENCES 11-1 APPENDIX A – WEEK-TO-A-PAGE: JULY 2006-JUNE 2007 APPENDIX B – MONTHLY WAVE CLIMATE SUMMARIES: JULY 2006–JUNE 2007 - ii - WRL TECHNICAL REPORT 2007/30 LIST OF FIGURES 2.1 Locality 2.2 Collaroy - Narrabeen Embayment, NSW 2.3 Precinct 3 3.1 Schematic of an ARGUS Coastal Imaging System 3.2 Location of Coastal Imaging System – Flight Deck Building 3.3 Cameras Mounted at an Elevation of Approximately 50 m 3.4 Snap-Shot, Time-Exposure and Variance Image Types (30/06/07) 3.5 Pan and Plan View Images: Five-Camera Merge/Rectification 3.6 Identification of ‘Shoreline’ Feature from Colour Images 3.7 Standardised Shoreline Mapping Procedure 4.1 Coastal Imaging Web Site – Home Page 4.2 Coastal Imaging System Web Site – Image Archive 4.3 On-Line Beach Analysis System – ‘Week-to-a-Page’ 4.4 On-Line Beach Analysis System – ‘Beach Width Analysis’ 5.1 Morphodynamic Beach State Model (after Wright and Short, 1983) 5.2 Snap Images from Camera 1 (South): 01/07/06 and 30/06/07 5.3 Snap Images from Camera 5 (North): 01/07/06 and 30/06/07 5.4 Annual Beach Changes C1 (South) and C5 (North): July 2004 – June 2007 6.1 Weekly Shorelines: July 2006 – June 2007 6.2 Weekly Beach Width: July 2006 – June 2007 6.3 Statistical Summary of Beach Width Changes: July 2006 – June 2007 6.4 Time-Series of Beach Width: July 2006 – June 2007 6.5 Weekly Beach Width July 2006 – June 2007 Relative to Prior Twelve-Month Mean Shoreline Position 7.1 Weekly Beach Width: July 2004 – June 2007 7.2 Time-Series of Beach Width: July 2004 – June 2007 7.3 On-Line Beach Width Analysis to June 2007 8.1 Definition Sketch - Intertidal Bathymetry from Hourly Waterlines 8.2 Beachface Mapping – June, July 2006 8.3 Beachface Mapping – August, September 2006 8.4 Beachface Mapping – October, November 2006 8.5 Beachface Mapping – December 2006, January 2007 8.6 Beachface Mapping – February, March 2007 8.7 Beachface Mapping – April, May 2007 8.8 Beachface Mapping – June 2007 8.9 Monthly Erosion/Accretion: June - September 2006 8.10 Monthly Erosion/Accretion: September – December 2006 8.11 Monthly Erosion/Accretion: December 2006 – March 2007 8.12 Monthly Erosion/Accretion: March – June 2007 8.13 Erosion/Accretion per Twelve Month Monitoring Period - iii - WRL TECHNICAL REPORT 2007/30 LIST OF FIGURES CONTINUED 8.14 Cumulative Beachface Erosion/Accretion, July 2004 to June 2007 8.15 Total Net Erosion/Accretion to June 2007 - iv - WRL TECHNICAL REPORT 2007/30 1-1. 1. INTRODUCTION This report was prepared by the Water Research Laboratory (WRL) of the University of New South Wales for Warringah Council. It is the third in a series of annual data summary reports, to describe, quantify and analyse the regional-scale coastline variability and erosion/accretion trends observed at Collaroy-Narrabeen Beaches. This annual summary supplements the more extensive on-line and ‘real-time’ monitoring program information that is available to Council and the community via the world-wide web (refer Section 4). It is intended that the growing database described herein, of qualitative and quantitative coastal monitoring information, will inform and enhance the current and future management of the Collaroy-Narrabeen embayment. 1.1 General In July of 2004, an ARGUS coastal imaging system was installed at the Collaroy- Narrabeen site for an initial period of three years. This leading-edge technology was selected by Warringah Council to provide regional-scale, continuous and long-term monitoring of this ‘high value’ coastal embayment. It is the ability to provide quantitative as well as qualitative information that distinguishes the ARGUS coastal imaging system from conventional 'webcam' or 'surfcam' technology. Collaroy-Narrabeen is the first coastal management site in New South Wales that utilises coastal imaging technology and associated digital image techniques to monitor regional- scale coastal response to natural and engineered coastal impacts. Coastal imaging stations have been operating at coastal management sites in Australia since the first site was installed at the northern Gold Coast in 1999, and at the present time there are a total of 8 stations operated by WRL throughout Queensland and New South Wales (Turner et al. 2006). Electronic copies of this and previous monitoring report(s) are made available for public viewing and download in PDF format at: Æ www.wrl.unsw.edu.au/coastalimaging/public/narrabn (link: monitoring reports) The purpose of this third annual data summary report is to present a summary of the results of shoreline change analysis and erosion/accretion analysis for the twelve-month monitoring period July 2006 – June 2007, and to assess the net changes that have occurred WRL TECHNICAL REPORT 2007/30 1-2. within the Collaroy-Narrabeen embayment since the commencement of the monitoring program 36 months ago in July 2004. 1.2 Maintenance, Upgrades and Operational Issues During the period July 2006 to June 2007, the ARGUS station operated successfully without the need for significant maintenance or upgrades.