Westcoast District Coastal set-back lines

1. Westcoast District Coastal set-back lines

2. Presentation Overview • West Coast District project overview • ICM Background • Default coastal zone • Purpose of coastal set-back determination • Determination of risk – open coasts • Determination of risk – estuaries • Next steps • Questions asked of participants

3. Westcoast Set-back Lines Project - overview • Royal HaskoningDHV core project team: • Tandi Breetzke, Gerard van Weele, Dr Andrew Mather & Petrie Swart • 8 steps • Inception, preliminary work & stakeholder notification  • Modelling to determine Coastal Processes / Hazard line  • Stakeholder engagement now • Draft Set-back line(s) & coastal protection zone determination • Stakeholder engagement • Draft Final report • Stakeholder review • Final report

4. Background • Vulnerability of Coastal Ecosystems / coastal zone • Impacts associated with dynamic processes (Both erosion and accretion) • Global climate change – no longer debated & the coast is bearing the brunt • In response - Integrated Coastal Management – Green Paper – White Paper – ICM Act – specific management tools: • Coastal Committees • Coastal Management Programmes • Estuary Management Plans • Set-back/management lines • Proactive rather than reactive response to issues

5. Default coastal zone ICM Act Parameters CPZ includes: • Littoral active zone • Protected area • Wetlands / lagoon etc. • Land below HWM • Land flooded during 1:50 flood or storm • 100m / 1km from HWM FOR NOTING: Existing requirement for EIA: • 100m from HWM • Specified areas e.g. sea, estuary or littoral zone

6. Default coastal zone

7. Set-back Lines – ICM Act, No 24 of 2008 “An MEC must… • establish or change coastal set-back lines— • to protect coastal public property, private property & public safety; (ii) to protect the coastal protection zone; (iii) to preserve the aesthetic values of the coastal zone; or (iv) for any other reason consistent with the objectives of this Act; & (b) prohibit or restrict the building, erection, alteration or extension of structures that are wholly or partially seaward of that coastal set-back line.”

8. Set-back Lines – for noting • ICM Act Coastal set-back lines are proposed to be re-named as Coastal Management Lines to avoid confusion with the EIA Regulations Development Setback Lines • Western Cape set-back methodology developed and extensively presented, tested and reviewed: • Initially at Milnerton and Langebaan • Then in the Overberg District • Different methodology applied by the City of Cape Town • Lessons learnt / direction provided by the implementation all of these studies will be applied in determining the West Coast coastal set-back / management lines

9. Set-back lines - For noting • Lidar imagery used – excellent topographic data and aerial photos • KMZ files prepared for viewing via Google Earth (access via websites) • Technical report detailing process also available on website • GIS viewer developed to allow easy access to data / images / draft lines • Relevant environmental information was abstracted from the WCD CMP, IDPs and websites and reflected spatially • Risk is depicted in the short, medium and long term

10. Determination of the Physical Processes / Hazard Line(s) (Open coasts) 1 • Scientific • Process based • No scope for subjective assessments 2 3

11. Off-shore Wave Statistics • Technical modeling process using: • Wave Direction • Wind Speed • Significant Wave Height • Peak wave Direction and period • Interesting points to note: • When determining Significant Wave Height 36 individual storm events were identified • 50% of these storms have occurred in the last five years (less than a third of the total record period) • The largest storm on record occurred in Aug 2012

12. 4 Determination of the Physical Processes / Hazard Line(s) (Open coasts) 5 • Scientific • Process based • No scope for subjective assessments 6 7 8

13. Determination of the Physical Processes / Hazard Line(s) (Open coasts) • Scientific • Process based • No scope for subjective assessments

14. Transform Off-shore to In-shore Wave Statistics • Technical modeling process • Use the Delft SWAN (Simulating WAvesNearshore) model (http://www.swan.tudelft.nl) to transform offshore waves • Take account of bathymetric (sea bottom) changes • Determine the in-shore wave statistics

15. Determination of the Physical Processes / Hazard Line(s) (Open coasts) • Scientific • Process based • No scope for subjective assessments

16. Wave run up modeling • Near-shore waves modeled as run up the beach

17. Determination of the Physical Processes / Hazard Line(s) (Open coasts) • Scientific • Process based • No scope for subjective assessments

18. Sea Level Rise (Bruuns Rule) & Storm Beach Retreat • Using Bruun’s Rule predicted sea level rise reflected as low (200mm), medium (500mm) & high risk (1000mm) • Storm beach retreat - determined by measuring shoreline before and after storm events, however this was not possible so a conservative allowance of 20m has been provided for.

19. Determination of the Physical Processes / Hazard Line(s) (Open coasts) • Scientific • Process based • No scope for subjective assessments

20. Long term beach retreat • Determine the long term erosion based on a detailed analysis of historical shoreline positions from available aerial photography for sandy shorelines only. • Stable coastlines and accreting coastlines will be assumed to require no retreat.

21. Examples - Strandfontein

22. Examples –Elandsbaai (Railway Line) • [graphic to be added by Andrew all lines for railway line]

23. Examples – Yzerfontein (Sandy shoreline)

24. Examples – Yzerfontein (Rocky shoreline)

25. Determination of the Physical Processes / hazard Line(s) (ESTUARIES) • Scientific if floodlines used • Vegetation assessment to inform process

26. Hazard line determination for estuaries • Use the existing 1:50 or 1:100 floodlines to determine hazard edge • In the event of no suitable 1:50 and 1:100 yr floodlines then map the +5m and +10m above mean sea level contours. • +5m is typically the height floodwater will rise to in a closed estuarine system. • +10m allows a buffer for future SLR as well as estuarine vegetation regeneration areas.

27. Examples - Langebaan

28. Examples – Paradise Beach

29. Example –Berg River

30. Way forward • Assess the environmental, heritage & access layers to determine any additional set back allowances. • Assess the economic issues to determine any additional or reduction in set-back allowances to accommodate economic nodes/activities • Determine the extent of set-back / management line in the study area. • Add authority perspective to determine the CPZ boundary

31. Questions asked • Are you happy with the anticipated storm erosion estimate? • What are the environmental issues that should be considered? • Where are the environmentally sensitive areas? • Where are the wind-blown sand corridors? • How should authorities respond to this determination of risk? • What controls could be included for urban areas seaward of the physical processes / hazard line?

32. www.rhdhv.com/pages/services/environmental/current-projects.phpwww.rhdhv.com/pages/services/environmental/current-projects.php Or www.eadp.westerncape.gov.za/calendar/month (click on calendar, click on these w/s to find documents)