Sand extraction in the Belgian part of the North Sea: European context and lessons from 10 years of EMS control and bathymetric monitoring

Transcription

1 Sand extraction in the Belgian part of the North Sea: European context and lessons from years of EMS control and bathymetric monitoring M. Roche, K. Degrendele, L. De Mol, P. Schotte & H. Vandenreyken R. Van den Branden, G. De Schepper & L. Naudts

2 EU COUNTRIES and EEZ OSPAR, ICES and EMSAGG members/represented

3 Extraction Activities from to 4 Construction / Industrial aggregates Source: ICES WGEXT Reports to 4

4 Extraction Activities from to 4 Beach Replenishment Source: ICES WGEXT Reports to 4

5 Extraction Activities from to 4 Construction Fill / Land Reclamation Source: ICES WGEXT Reports to 4

6 Extraction Activities from to 4 Total extracted Source: ICES WGEXT Reports to 4

7 Extraction Activities from to 4 Total extracted Coastline length Source: ICES WGEXT Reports to 4 EEA coastline

8 The Belgian part of the North Sea: Very restricted area (~ 345 km²) under high pressure Navigation Fisheries Wind farms Electric cables Pipes Telecommunication cables Natural reserves Dumping areas Military exercise areas Danger areas Sand extraction

9 Sand extraction Belgian part of the North Sea Shared extraction sectors sectors 6 m³ / y for building industry 6 m³ / y for beach replenishment Legislation - Dura lex, sed lex: 5m Reference surface Maximum extraction level Control: Extracted volumes Impact on the marine environment

10 Sand reserve: estimation Extraction area 77 to 4 Extraction area 4 Surface inside m isobath = Useful area X 5m = Legal vertical limit km 5 km m³ Usefullegalreserve m³

11 Sand reserve: evolution 6 m 3 77 to 4 useful legal sand reserve reduction of m³ : Reduction of extraction area = 6 m 3 = 84 % Extraction itself = 5 6 m 3 = 6 % Reduction of extraction area Useful Legal reserve Extraction (cumulative volume) Reserve decline is mainly due to external contingencies

12 Sand reserve evolution Model of extraction impact Sandbank bathymetry Monitoring both variables is required? Extraction

13 Sand reserve evolution Model of extraction impact? Sandbank bathymetry Extraction: Register EMS? Sandbank bathymetry: Multibeam echosounder Extraction

14 Seabed Monitoring = a legal obligation! National regulation: Law Continental shelf 3/6/6 Supra national EU regulation: EU Marine Strategy Framework Directive MSFD 8/56/EEC Coastal waters, including their seabed and subsoil, are an integral part of the marine environment, and as such should also be covered by this Directive

15 Monitoring the Extraction: Register Logbook on board The captain has to fill in all relevant information for each extraction Dredging vessel Vessel name Master name Loading data Date -Start time EMS trip number Concession code Loading place - sandbank Unloading data Location Volume (m³) Master's signature Fees related to extracted volume are based on the register!

16 Monitoring the Extraction Method of control in different EU countries Source: ICES WGEXT Reports to 4 Various communications

17 Sand extraction BPNS EMS The Belgian EMS NEW EMS representative EMS dataset Mobile network Approval test Sealed EMS Installation GPS Date Time Position Speed Seal & Unseal Read Modem & SIM Memory card EMS Activity of the pump Dredging pump(s) Shore station OD Nature OD Nature Report Travel number Concession code Extracted volume Activity override Display Feedback Captain Activity Alarm Keyboard

18 Volume calculation using EMS data Volume calculation for any area and time interval 3-3 Extracted volume m³ / ha Assumptions: Fixed loading capacity / ship Start dredging: ship empty End dredging: ship fully loaded

19 Multibeam echosounder (MBES) = Most effective tool for monitoring the sandbank bathymetry 84 RV Belgica Singlebeam EM MBES khz 8 EM3 dual MBES 3 khz Port view Starboard view Time Time Regular Quality control IHO S44 Special Order accuracy (= 3 cm / m)

20 MBES High resolution cartography Sand extraction control zones and sectors Reference models Zone sensu 77 EM surveys -4 Exploration Zone EM EM3D 4 surveys 5 surveys 4-6 Zone sensu 77 EM 4 surveys -3 Zeebrugge Zone 3 sensu 4 EM 5 surveys 6-8 Current sectors Oostende (since 4) km Nieuwpoort

21 Zone Reference surface (time = -3) Monitoring the sandbanks with MBES Reference surface 3. Regular quality control IHO S44 special order km

22 On highly dredged areas: High resolution and full coverage Local and time consuming Monitoring areas km

23 Fast Global but fragmented Monitoring along DECCA lines: km

24 Fast Global but fragmented Monitoring along DECCA lines: km

25 Fast Global but fragmented Monitoring along DECCA lines: Bathymetry DECCA lines reference model m m - m - m

26 Monitoring areas and DECCA MBES Time Series BRMA BRMC HBMB KBMA ODMA TBMAB DECCA BRMB HBMA HBMC KBMB R Z Z Z4 5 km

27 Correlation EMS volumes versus MBES data Extracted volume (m³/ha) from the EMS data MBES data Bathymetry (m) DECCA -reference model 3 Crossing data from same time interval and area: FOR DECCA DATA: EMS VOLUME INTERVALS (³ m³/ha) MEAN BATHYMETRIC DIFFERENCE DEDUCED FROM EMS MEAN BATHYMETRIC DIFFERENCE BASED ON MBES MEASUREMENTS

28 Extracted volume (m³/ha) from the EMS data Correlation EMS volumes versus MBES data MBES data Bathymetry (m) DECCA -ref model 3 MONITORING area ref model 3 Crossing data from same time interval and area: FOR DECCA DATA: EMS VOLUME INTERVALS (³ m³/ha) FOR MONITORING AREA DATA: ALL SURVEY AREA MEAN BATHYMETRIC DIFFERENCE DEDUCED FROM EMS MEAN BATHYMETRIC DIFFERENCE DEDUCED FROM EMS MEAN BATHYMETRIC DIFFERENCE BASED ON MBES MEASUREMENTS MEAN BATHYMETRIC DIFFERENCE BASED ON MBES MEASUREMENTS

29 Sandbank bathymetry, -,5 -, -,5 Sand reserve evolution Model of extraction impact? DECCA Z 3 DECCA Z 3 -, DECCA Z4 3 MBES -,5-3, -3,5-4,? BRMC to 3 BRMA 7 to 3 ODMA 8 to 3-4,5-5,, -,5 -, -,5 -, -,5 EMS -3, -3,5-4, -4,5-5, Extraction

30 Sand reserve evolution Final model of extraction impact

31 Sand reserve evolution and impact of extraction Model validation By mean approach certainly valid and significant! But mandatory to:. Analyze the spatial variability. Investigate seabed evolution around the exploited areas 3. Quantify errors on EMS data and improve EMS positioning XY EMS = XY GPS antenna distance (dredging head -GPS antenna) heading XY Dredging head = real position Dredging head dimension

32 Sand reserve evolution and impact of extraction Optimal reference surface for sand extraction in the BPNS Ongoing Project (start in 3, final phase expected in 6): Reference surface based on geological-seismic surfaces + samples Combine optimal exploitation and preservation of the sandbanks Zone 4 Sector 4a Depth (m) Seafloor Reference level (-5 m) Top Eemian Top Paleogene Accross distance (m)

33 Sand reserve evolution and impact of extraction Optimal reference surface for sand extraction in the BPNS Ongoing Project (start in 3, final phase expected in 6): Reference surface based on geological-seismic surfaces + samples Combine optimal exploitation and preservation of the sandbanks New reference surface Depth (m) Seafloor Reference level (-5 m) Top Eemian Top Paleogene Accross distance (m) TILES project

34 Thank you for your attention! Follow us for the latest news! NL: FR: NL: Dienst Continentaal Plat FR: Service Plateau Continental