Coastal safety- case studies in Flanders

Transcription

1 Coastal safety- case studies in Flanders Duinkerke, June 12th 2018 ir. Daphné Thoon MDK-Coastal Division

2 Content 1. Introduction 2. Coastal Safety Masterplan - status 3. Management of the sandy coast 4. Case studie Ostende- Mariakerke and Raversijde 5. Case studie seawall Middelkerke

3 1.Introduction

4

5 A low-lying Low lying hinterland hinterland More than 85% of the polders beneath +5m TAW (average storm) 5

6 Harbors Urban areas Dunes

7 A man-made coast line: beaches and sea walls

8 Harbor areas: quaywalls, locks & weirs

9 Non urban areas: beaches and dunes

10 Storm 1953

11 2. Coastal Safety Masterplan

12 Safety assessment and risk calculations: Norm: No victims due to a 1000-year storm surge event: Limited overtopping: 1l/m/s No breaching of dunes and seawalls No erosion that threatens protected buildings

13 Safety Assessment Weak links (1000 year ARI): 1/3d coastline + harbors Mostly at locations with sea walls and quay walls

14 2007: start voorbereiding Masterplan Kustveiligheid

15 Coastal Safety Master Plan Aim: protect the Flemish coastline and the hinterland against the impact of a 1000 year ARI storm surge and prevent large scale floodings by taking into account climate changes till 2050 estimated sea level rise in 2050: 30cm Coastal Safety Master Plan

16 Types of measures Soft measures Hard measures

17 Soft measures Beach nourishments Dune nourishments

18 Hard measures Sea walls and quay walls: storm walls or elevation Reinforcement of locks and weirs Storm surge barrier Stilling wave basin

19 Coastal Safety Master Plan study Master Plan started in 2007 Master Plan and proposed measures approved by the Flemish government in 2011 estimated cost: 300 millions works started in 2011;

20 Anno 2011: measures to be executed Storm wall/ storm surge barrier Stilling wave basin Beach nourishment Dune nourishment 11/06/

21 Anno 2018: Measures to be exectuted Storm wall/ storm surge barrier Stilling wave basin Beach nourishment Dune noruishment 11/06/

22 3. Management of the sandy coast

23 Coastal Safety Masterplan: Management Sandy flood measures: management is required Dynamic environment: natural sand transport + maintenance is needed after heavy storm surges

24 Coastal Safety Masterplan: Management Sandy flood measures: Topographic and bathymetric measurements: 2 times/year 6 yearly detailed safety assessment: 2015 Safety assessments after every heavy storm surge

25 Results safety assessment of 2015

26 Safety assessment conclusions No breaching of dunes and seawalls Weak zones remain weaker but are much better Nourished zones that don t comply to the standard: the norm is just exceeded, so maintenance is needed

27 4. Case studie Ostende Mariakerke & Raversijde

28 Ostende Mariakerke & Raversijde

29 Design of flood measures: 3 goals 1. Reinforcement of the coastal defence 2. Reduce sand blowing on the sea wall and coastal road 3. Create added value to inhabitants and tourists Cooperation of MDK en City of Oostende Design is almost finished

30 1.Beach nourishment and storm walls

31 2.Reduce excessive eolian transport

32 Dune creation for reducing eolian transport

33 3. Added value

34 5. Case studie Seawall reinforcement of Middelkerke

35 Middelkerke

36 Design of flood measures: 4 goals 1. More protection 2. More experience 3. More sun 4. More green Cooperation of MDK en Town of Middelkerke

37 1.More protection: combination of soft and hard measures

38 2.More experience

39 3.More sun

40 4.More green

41 Questions