HSRR02 SEPTEMBER 2010 FLOODRISKASSESSMENTINUNEMBANKED AREASINTHENETHERLANDS

Transcription

1 William Veerbeek FLOOD RESILIENCE GROUP WE Department Unesco-IHE Westvest 7 P.O. Box DA Delft Netherlands T: +31(0) M: +31(0) w.veerbeek@floodresiliencegroup.org SEPTEMBER 2010 Page 1

2 RESEARCH OBJECTIVES Assess potential flood hazard and impact for the unembanked areas in the Rijnmond-Drechtsteden region; Include climate change scenarios; Apply a high level of detail; Include regional adaptation option: Closable but Open. Climate Change scenarios Flood extent & depth Flood impact Urban area Closable Open Rijnmond Flow velocities Flood impact Port area Page 2

3 RIJNMOND-DRECHTSTEDEN: CHARACTERISTICS Located along the Meuse & Merwede (Waal) rivers; 30,000 housing units, 64,000 inhabitants; Port of Rotterdam; High level of differentiation (physical, functional, historical, etc.); Unembanked area, often high level of elevation (sedimentation & man-made). Veerbeek et al, 2010 Page 3

4 1. FLOOD HAZARD Page 4

5 FLOOD MODEL: METHODOLOGY Inundation depths derived from 1D-Hydraulic model HSRR03b (Stijnen & Slootjes, 2010), for current, G and Veerman 2100 scenarios & Closable but Open; 5x5m DEM resolution; GIS extrapolation of observed water stages; Flood velocities through existing hydraulic models and measurements; Failure rate of Maeslant & Hartel storm surge barrier; Range of return periods: 10, 50, 100, 1000, 2000, 4000, years. DEM of the Rijnmond-Drechtsteden area Lansen et al, 2010 Climate Change Rhine Discharge Meuse Discharge Sea level rise [m] Storm duration [h] Scenario at Lobith [m 3 /s] at Borgharen [m 3 /s] Current Conditions (2010) 16,000 3, KNMI 06 G+ (2050) 18,000 4, VEERMAN (2100) 18,000 4, Page 5

6 OBSERVED FLOOD EXTENT (CURRENT CONDITIONS) Many natural floodplains are flooded for low return periods (e.g. 10y) Urban areas are generally flooded only during extreme events Newer port areas (Rotterdam & Dordrecht) are relatively safe Based on Huizinga et al, 2010 Return Period Page 6

7 OBSERVED FLOOD EXTENT (CURRENT CONDITIONS) Within urban areas observed flood extent differs significantly Treshold effects and gradual flooding Based on Huizinga et al, 2010 Return Period Noordereiland/Piekstraat Rotterdam Inundation for low return periods Main streets flooded during extreme events Page 7

8 OBSERVED FLOOD EXTENT Climate change scenarios increase flood extent significantly; Closable but Open option does not lead to reduction; Failure rate Maeslant/Hartel storm surge barier is critical. Flood extent for the range of return periods Flooded area (ha) _lockable/open 2100_lockable/open Return period (years) Page 8

9 OBSERVED INUNDATION DEPTHS Significant variations in inundation depths also outside natural floodplains; For medium return periods (e.g. 100y): Generally low inundation depths in highly populated areas; Some exceptions (e.g. Noordereiland/Piekstraat area) Based on Huizinga et al, 2010 Depth [cm] Noordereiland/Piekstraat Rotterdam EP = 1/100, Current conditions Significant flood depths observable within residential areas Locally more than 1m of inundation Page 9

10 FLOW VELOCITIES High flow velocities only at the Western end of the river mouth (North-Sea); Flow velocities on quays expected to range between 0.1 and 0.25 m/s; Further inland even lower (high hydraulic roughness due to built-up areas); Climate change scenarios will not increase velocities significantly; Conclusion: Low probability of structural damages and casualties/injuries. 2 Calculated flow velocities main channel: low flow conditions combined with a severe storm surge MAASSLUIS STADSHAVENS VAN BRIENENOORDBRUG flow velocity (m/s) :00 00:00 12:00 00:00 12:00 00: STADSWERVEN time (hours) Asselmans, 2010 Page 10

11 2. FLOOD IMPACT Page 11

12 (URBAN) FLOOD DAMAGE MODEL: METHODOLOGY Estimate DIRECT flood damages; High level of detail: individual housing units, infrastructure and public space; Derive damage composition; Perform analysis on spatiotemporal distribution of damages; Refinement from existing flood damage model used in UFM-Dordrecht (Veerbeek et al, 2009); Introduction of specific housing characteristics through Google Streetview; Adapt model to 5x5m cells; Model is synthetic; damage curves developed icw building/insurance sector. Page 12

13 (URBAN) FLOOD DAMAGE MODEL: AGGREGATE DAMAGES Hardly any noticeable threshold effects; Small trend change for G and Veerman 2100 at 1000-year return period; EAD: Increase for G+ (2050) 75%, Veerman (2100) 147% 100 fold increase: Current 1000-year level becomes 10-year level (Veerman 2100) 175 Expected aggregate flood damages for RPs 150 Expected aggregate flood damages for water stages expected Damage [m ] expected Damage [m ] y = 4E-08x water stage [cm +NAP] return period [Y] Current 2050 G Veerman 2050 Closable but open 2100 Closable but open Page 13

14 (URBAN) FLOOD DAMAGE MODEL: DAMAGE COMPOSITION Infrastructure/public space: currently 20% of EAD; Climate change scenarios hardly change this ratio. Housing: Damage to furnishing about 50%. Damage compostion (housing) for the Veerman 2100 scenario Cleaning & drying, 11% 60 What flood damage reduction level can be achieved with an effective early warning strategy? Contents Damage, 48% Floor & w all, 11% Doors & w indow 4% expected Damage [m ] Kitchen, 8% return period [Y] Cleaning & drying Floor & wall Doors & windows Installations, 19% Kitchen Installations Contents Damage Page 14

15 (URBAN) FLOOD DAMAGE MODEL: AGE BUILDING STOCK Distribution of flooded buildings over the age of the building stock (10, 50, 100y); Dramatic increase of flooded monumental buildings (e.g. Dordrecht) Damage distribtuion over the age of the building stock Current Conditions # flooded housing units Construction period # flooded housing units G+ Scenario Construction period Veerman Scenario Is increasing flood risk a threat to our cultural heritage? # flooded housing units Construction period Page 15

16 (URBAN) FLOOD DAMAGE MODEL: ABSOLUTE VS RELATIVE DMGS Relative dmgs: expected dmg over the total building stock per municipality; Substantial differences between municipalities: rate, behavior; absolute, relative; Influence of climate change scenarios changes distribution; Avg. EAD Rotterdam: 4 (current) to 29 (2100 Veerman); Avg. EAD Bergambacht: 614 (current) to 660 (2100 Veerman). Expected damages for the Veerman 2100 scenario: absolute (left) and relative (right) Do these figures indicate possible responses (structural / non-structural)? expected Damage [m ] expected Damage [k ] Rotterdam Dordrecht Nederlek Bergambacht return period [my] return period [my] Bergambacht Dordrecht Nederlek Rotterdam Rotterdam Dordrecht Nederlek Bergambacht Page 16

17 (URBAN) FLOOD DAMAGE MODEL: DAMAGE HOTSPOTS 50% flood damages located in 15% of the damage clusters: highly concentrated; Importance of individual clusters changes for higher return periods (threshold effects) Page 17

18 (PORT) FLOOD DAMAGE ASSESSMENT: METHODOLOGY No standard application of stage-damage curves possible; Existing risk assessment framework is extremely complex; Potentially high level of indirect tangible and intangible damages; Focus on: Infrastructure, utility-lifeline (electricity, gas, etc.); Assessment of additional flood risk i.r.t. existing risk profile for chemical plants. Page 18

19 (PORT) FLOOD DAMAGE ASSESSMENT: EXPERT SESSION Expert judgment to develop a qualitative assessment of flood impact Qualitative assessment of vulnerability: General harbour facilities Effect of flooding Probability of Casualties damage given a flooding event Societal Environment Economical disruption damage Berthing facilities Quay wall Jetties Terminal Terrain Roads and railways Underground facilities Electricity Communication Cables Pipe lines General facilities Lighting buildings Safety installations Vehicles Washout due to water run-off Corrosion Failure of berthing function Roads and terrain not accessible Washout due to water run-off Rupture of pipe lines Failure and damage of electricity and ICT Failure and damage of communication Washing away of loose standing objects Lighting failure Safety onsite cannot be guaranteed Damage to buildings Qualitative assessment of vulnerability: Liquid bulk Effect of flooding Facilities Cable trays are on ground level => spills + release of toxic goods + interruption of processes. Instability of construction of installation, for instance distillation columns built on footings Process installations Rupture / damage of (empty) pipelines Pipelines Corrosion of (salt) water in installations Cooling installation Power failure => uncontrollable processes Probability of Casualties damage given a flooding event Societal Environment Economical disruption damage Storage of goods Oil LNG LPG Toxic gasses: H2F Vegetable oil Rupture of (oil) tanks due to high water pressures LNG cooled storaged=> during power failure uncontrolled boil-off (Controlled) shut-down installations during flood threat Release toxic material from storage Gas supply fo electricity / hinterland interrupted Page 19

20 (PORT) FLOOD DAMAGE ASSESSMENT: CHEMICAL INSTALLATIONS Main question: What is the additional risk of 1m of inundation? BowTie model to assess the chain of consequences during hazard exposure; Use of scenarios: Assess consequences of 1m inundation; Compare a worst case scenarios with and without flooding; BowTie-Model: Propagation of consequences Outcomes (example) flooding Events and circumstances Failure trees, hazards Undesireable event Additional scenarios flooding Worst Case Scenario No Flooding Worst Case Scenario Including Flooding Casualties None/Limited None/Limited Affected persons (health effects) 1000 (~10 health effects) (~100 health effects) Economic damage m EUR (plant, down m EUR (plant, down time, claims) time, claims) Environmental damage Minor Significant Cultural damage None None Page 20

21 (PORT) FLOOD DAMAGE ASSESSMENT: OUTCOMES Wet bulk and infrastructure are sensitive to flood risk: societal disruption: Electricity supply (business interruption); Roads, tunnels and pipes: supply chain disruption; ICT services. Casualties and health: Limited number of casualties; Flood could increase health impacts: Flood water as a distributor; Additional impact of flood risk is limited; EP in the order of 1/1000,000. Pitfalls: Cumulative risk: multiple plants are flooded because of even terrain; Risk chemical plants depends largely on weather conditions (e.g. wind). Page 21

22 3. CONCLUSIONS Page 22

23 CONCLUSIONS Current vulnerability is limited: High level of risk differentiation between areas; Especially historical housing stock protected; Yet, area is vulnerable to extreme events Limited additional risk to Rotterdam port area. Yet, potential for societal disruption during extreme event Climate change: Considerable increase of flood impact, especially in urban areas; Shift in flood damages: historic areas (e.g. Dordrecht). Further study: Coupling local adaptation measures to different risk profiles; Assessment of structural/non structural measures (e.g. insurance); Methodological improvement: damage curves (functional, typological, etc.) Indirect damages assessment port area: ripple effects Page 23

24 CONCLUSIONS More information at: WATERVEILIGHEID BUITENDIJKS SYNTHESE FLOOD RISK IN UNEMBANKED AREAS SYNTHESIS Page 24