This document summarizes challenges and strategies for retrofitting existing buildings in Rotterdam and New York City to increase flood resilience. In 3 sentences: Existing buildings are vulnerable to flooding but retrofitting flood protections takes decades; Options include dry-proofing, elevating structures, or filling basements, with effectiveness depending on building type and site conditions; Long adaptation timelines mean both building-level changes and district-wide strategies are needed to balance resilience and time constraints of climate change impacts.

1. Adapting the existing
Retrofitting buildings for flood risk
Rotterdam and New York
Presentation CAMINO Conference
Antwerp, March 24 2015
Peter van Veelen
Urban planner City of Rotterdam
PhD researcher TU Delft Urbanism

2. The existing is vulnerable
Manhattan
Jersey City
Brooklyn
Jersey Coast
Bridgeport
Long Island

3. Challenge: Retrofit flood
resilience into existing
building stock
• What adaptive measures and policies are effective?
• How can we incorporate adaptation into processes of
urban development and management?
• What pathways to resilience provide flexibility and
efficiency in the long run?

7. Flood risk NoordereilandFlood risk

8. Vulnerability of sewer system

9. Vulnerability of urban infrastructure

10. Basement appartment elevated first floor elevated social housing
Building typology

11. Current policy: living with water
Pictures: DSA Rotterdam

12. 3,00 m + NAP
25/50 year flood
10 year flood in 2050
Annual flood 2100
3,45 m + NAP (4000
year flood)
1000 year flood in
2050 or 500 year flood
in 2100
foto: DSA Rotterdam
Dry proofing

13. Source: Deltares
Sea level riseyears from now
Effectiveness of
measures
Develop adaptation pathways based on combinations of measures

14. Develop adaptation pathways based on combinations of measures
Possible adaptation pathway Noordereiland:
Dry-proofing buildings 20-40 yrs.
Elevated boulevard 35 – 75 yrs.
or: temporary flood defences >100 y.
Source: Deltares

15. Using urban dynamics
Social housing
Annual building stock refurbishing rates: 3%-5% (20-35 year cycle)
Average investment : € 23.000
Annual redevelopment rate: 1% (100 year cycle)
Source: annual reports of social housing corporation (www.aedes.nl)
Privately owned buildings
Planned maintenance cycle: 20 year cycle
Large-scale renovation cycle 30-40 year cycle
Adaptation the existing housing stock requires at least 20 – 40 year

16. New York - Red Hook
Picture: Vin Crosbie

17. Demountable flood wall flood resilient architecture elevating houses
Current policy: building level adaptation

18. Flood risk

19. Less than 30 % of the building stock has a
first floor above the required flood
elevation level
Historical waterfront Elevated Residential buildings
Building typology

21. Wet proofing existing building

22. Filling in all below grade levels
Wet flood proofing
all below BFE levels
Relocate all mechanical systems
Relocation of lost floor area
Within the zoning envelope

23. type Compensation Adaptation
options
NFIP
premium
reduction
# buildings
Wood frame
detached
Elevate building full 6 (1%)
Brick stone
and first floor
above BFE
Plot is overbuilt or
no space available
in building envelope
Wet proof
mechanical
equipment
partial 93 (18%)
Space available in
building envelope
fill all below grade
spaces and wet
proof all below BFE
uses
full 61 (11%)
Brick stone
and first floor
below BFE
Plot overbuilt or no
room in building
envelope
Wet proof
mechanical
equipment
Almost
none
158 (30%)
Space available in
building envelope
fill all below grade
spaces and wet
proof all below BFE
uses
full 208 (40%)
More than 50 % of the buildings can be brought up to full flood resilience requirements
Only 50% of these building plots have opportunity to compensate the loss of space

24. Using urban dynamics
Brooklyn:
Annual renovation rate: 0.4% (250 year cycle)
Annual redevelopment rate: 0.35% (285 year cycle)
District 6 (including Red Hook):
Annual renovation rate: 2% (50 year cycle)
Annual redevelopment rate: 0.2% (500 year cycle)
Source: NYU Furman Center, 2014
Adaptation the existing housing stock requires at least 50 years

25. There is little potential to build resilience from household redevelopment or
renovation within an acceptable timeframe (Sea level rise exceed the speed of
retrofitting).
Need to develop new complementary policies and regulative instruments that
support easy-to-implement building-level resilience.
District-wide solutions are effective to reduce overall flood damages and
disruption but also need a considerable amount of planning and implementation
time. Building level adaptation may be effective “to buy time”.
Conclusions

26. Thanks
pc.vanveelen@rotterdam.nl
p.c.vanveelen@tudelft.nl