Setting Timeframes for Implementation

When should these strategies be implemented?

After community leaders and stakeholders have determined which people and places to protect and identified possible strategies for protecting them, they should consider the timeframe for implementing these strategies. Because sea levels are rising in most places, strategies that are effective today may not provide adequate protection from tides, waves, and surges in 25, 50, or 100 years. Moreover, many strategies degrade over time, requiring frequent maintenance to retain even current levels of protection: beaches may require to be nourished yearly to replace sand that has eroded away, and levees may need to be reinforced and heightened periodically to combat erosion and subsidence.

For these reasons, cost-benefit analysis for protection strategies often considers their entire projected lifetime. This includes not only present day benefits and construction or implementation costs, but also future maintenance costs and changes in benefits as sea level rises. Because costs and benefits of coastal protection strategies will change over time, strategies with the best ratio of benefits to costs in the near term may not be the best choice for long-term protection. For example, researchers have found that for New York City, a hybrid strategy that combines elevating vulnerable structures with targeted protections to critical infrastructure and limited use of levees and beach nourishment to be the most cost-effective option for protecting against sea level rise-enhanced storm surge through mid-century. However, after mid-century, the researchers found that it may become more cost effective to build sea walls to protect potions of New York Bay.

Mandatory Reading

To learn more about research comparing the costs and benefits of different strategies for protecting New York City from storm surge and sea level rise, read the following Scientific American article:

The Scientific American article discusses several possible strategies for protecting New York City. These strategies could include a sea wall across the Verrazano Narrows like the one shown in the above video rendering.

Activate Your Learning

After reading the article, answer the following questions.

Question 1 - Multiple Choice

According to the article, which of the following were not included in the cost-benefit analysis?

A. Psychological factors
B. Maintenance costs
C. Political factors
D. A and B
E. A and C

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Question 2 - Multiple Choice

According to the article, which of the following were included in the most cost effective, "hybrid" approach?

A. Infrastructure improvements
B. Small flood barriers
C. Large sea walls and floodgates
D. A and B
E. A and C

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• Adaptive Management
• Society and Policy Making from an Integrated Earth Systems Perspective
• Learning Check Point