FLANDERS HYDRAULICS RESEARCH Sea level rise and its

FLANDERS HYDRAULICS RESEARCH Sea level rise and its danger for the Belgian coast ir. Toon Verwaest ODINAFRICA course – 13 november 2006 – Oostende FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH 1. What is Flanders Hydraulics Research? 2. Definition(s) sea level rise 3. Measurements sea level rise 4. Coastal defence from the perspective of sea level rise 5. The coastal landscape from the perspective of sea level rise FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH What is Flanders Hydraulics Research? • service of the Flemish administration (ministry Mobility and Public Works) • internal consulting • knowledge area is “water” (ship maneuvring in undeep water, coastal defence, ports, navigable waterways, sluices…) • physical models, numerical models, measuring networks in situ, databanks, laboratory experiments FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Definition(s) sea level rise ØReference level on land : “relative sea level” (3 different reference levels) ØRelative sea level movements (ca. 10 different phisical processes, taking place on very different timescales and spatial scales) • time scale < 1 year • time scale > 1 year “mean sea level” FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Bewegingen relatieve zeespiegel op tijdsschaal < 1 jaar FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Bewegingen relatieve zeespiegel op tijdsschaal > 1 jaar FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Measurements of relative sea level rise 1. Relative to the top of quay walls in harbours : maregraphs (100 year data set) 2. Relative to the top of pleistocene subsoil : quartair-geology (10. 000 jaar data set) FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH 18 cm / eeuw FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH 7 cm / eeuw 70 cm / eeuw FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Coastal defence from the perspective of sea level rise • Scenarios of relative sea level rise in 21 st century : from only 10 cm to almost 100 cm • …and the next centuries of the 3 rd millenium : ~ 10 m in the year 3000 → Increase floodable land (the coastal lowlying areas) → Increase failure probability of the coastal defence FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Increase floodable land : FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Increase failure probability of coastal defence : ca. 0, 5 m higher sea level translates into a factor 10 increase in failure probability ! [ this is because the failure probability of a coastal defence is determined (in large part) by the storm surge level] … in addition, there are expactations that the storm climate in the North Sea will worsen : more (frequent) extreme winds FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH COASTAL DEFENCE POLICY = GROW WITH THE SEA using SAND NOURISHMENTS • To protect 1 km of coast ~ for every 10 cm sea level rise 100. 000 m 3 sand • flexibel technique (<-> hard coastal defences such as sea dike structures) • maximum societal benefits : + recreational beach + ecology + landscape • Work with nature : sedimentation of natural sand transport • Important increase of finances for coastal defence (~ factor 3 in 2050 !) • “seaward solution” FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH The coastal landscape from the perspective of sea level rise 21 st century : v Damages of the coastal defence caused by storm surge (erosion of dunes, damages to buildings on the coastal defence…) v “seaward solution” with sand nourishments (to grow with the sea) 3 rd millenium : v managed retreat = change the functions of the land near the coastline (~ a different spatial planning) = “landward solution” (<-> “seaward solution”) FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH SAND NOURISHMENT, example : De Haan FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH SAND NOURISHMENT, example : Oostende FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH MANAGED RETREAT, example : UK : nature areas in stead of farmland FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH MANAGED RETREAT, example : COMCOAST european project FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Other type of MANAGED RETREAT : Controled flooding areas alongside rivers, Thereby also decreasing the water level in the river FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS

Sea level rise and its danger for the Belgian coast – ir. Toon Verwaest – 13 november 2006 FLANDERS HYDRAULICS RESEARCH Other type of MANAGED RETREAT: Projects to create nature areas (not triggered by a coastal defence problem) Sea inlet “slufter” (~1 ha) Increasing the “Zwin” salt marches near borderwith France (~100 ha) near border with The Netherlands FLEMISH ADMINISTRATION - DEPARTEMENT OF MOBILITY AND PUBLIC WORKS