What can we learn from experiences of existing barriers

Experiences to date provide some information potentially relevant to protecting New York harbor.

Would storm surge barriers be cost effective?

Table 9.1 lists comparative costs for two representative European barriers plus a hypothetical East River tidal gate designed for water pollution control. Given that water damage resulting from a major hurricane event colliding with New York City has been estimated in the many hundreds of billions of dollars, it is obvious from the table that barriers would be very cost effective, even for one major storm event alone.1

How high would the barriers and seawalls need to be? How long would they be designed to last?

The Dutch have taken the view that their extensive barrier/seawall defenses must be able to withstand a 1000-year storm and have a useful working lifetime of

Table 9.1 Comparative barrier costs in 2006 US$, updated using the US Bureau of Reclamation Construction Cost Trends Composite Trend

Barrier

Dates

Cost

Exchange rate then

$ Cost then

Cost index*

2006 cost

Eastern Scheldt

1979-1986

3 billion

3.32 guilders/$

$900 million

299/1 59

$1.7 billion

guilders

Thames River

1973-1984

600 million £

$1.328/£

$800 million

299/1 53

$1.6 billion

East River

1993

$1 billion

-

$1 billion

299/190

$1.6 billion

TOTAL

$5.0 billion

Source: Delta Barrier Symposium, 1982; Abrahams and Matlin, 1994.

Source: Delta Barrier Symposium, 1982; Abrahams and Matlin, 1994.

200 years. It is our position that such a high standard is also appropriate for Metropolitan New York. In determining the height for the barrier, wave heights, which can add several meters to the total rise, and a safety factor must be added to the storm surge height. Based on estimates for storm surge height from the SLOSH model (see Table 9.2), we have adopted a 15 m barrier as our working height for worst-case scenarios.

Table 9.2 SLOSH-estimated storm surges in meters (feet in parentheses) associated with a direct hit of hurricanes of various intensities

Location

Category 1

Category 2

Category 3

Category 4

Fort Hamilton, Brooklyn

2.8 (9)

4.6 (15)

6.4(21)

8.3 (27)

Willets Point, Queens

13.0 (6)

3.5 (11)

5.6 (18)

7.0 (23)

Amboy, New Jersey

3.3 (11)

6.0 (19)

7.3 (24)

8.2 (27)

Source: US Army Corps of Engineers et al, 1995.

Source: US Army Corps of Engineers et al, 1995.

Are storm surge barriers reliable and fail-safe?

They have to be. Obviously storm surge barriers would need to be 100 per cent reliable; otherwise catastrophic flooding could result. The misery of the New Orleans experience highlights the need for a substantially greater vision of what coastal storm surge protection of low-lying urban areas demands in an era of climate change. Once again, the Dutch experience is worth examining. They possess a bold vision and enduring courage to have built their nation below sea level and are clearly committed to its protection as a central issue of national security. The US has the engineering and oceanographic expertise to design and build storm surge barriers that will function efficiently over a design life of 200 years. It can be done, but the challenge needs to be approached with a much more substantial political and financial commitment than has typically been evident, and with an order of magnitude stronger design features than the city of New Orleans ever possessed.

What are the downsides of an engineering solution? Are we only delaying the inevitable catastrophe?

The downside of an engineering solution to rising sea level and increased threats of severe storms is the fear that the barriers will eventually fail and that the final catastrophe will be far worse than if we decided as of today to:

• modify building codes to prohibit unwise and unsafe shoreline development;

• harden local infrastructure as necessary;

• begin planning for the eventual retreat of the city from the coastline (K. Jacob, personal communication).

Was this article helpful?

0 0

Post a comment