http://blog.iem.com/">IEM Blog: Building a More Safe, Secure and Resilient World

Author: Steve Stage, Atmospheric Physicist/Dispersion Modeler

Whenever a hurricane threatens a coastal area and flooding is possible, residents immediately ask:

• Will I be injured if I stay?
• Will my home be damaged?

It’s not always easy for residents to get information to help them answer these questions. In this post, I will walk you through how to get this information for Hurricane Sandy using Kings Point, New York, as an example. You can use this method to get similar information for your own location.

Hurricane Sandy is a Category 1 storm, with the potential to cause some wind damage. However, because this is a very large storm making landfall during high tide during a full moon, flooding is expected to be the source of the most damage from this storm and is therefore the focus of this blog post.

A good source for predicted flooding is the National Hurricane Center. You can click on the link for Storm Surge Exceedance and zoom in to see your area. As an example, the plot below shows the predicted height of water above the normal tide level. This plot shows that much of the coastline in the vicinity of New York City could get storm surges of 11 to 15 feet due to Hurricane Sandy.

Stevens Institute of Technology has produced graphs of water levels for Hurricane Sandy that show how tides and winds gang up to cause flooding. You can click on the icon closest to your location and select Show Time Series Plot to see a graph of potential flooding in your area.

In the graph below, which is for Kings Point, NY, the blue line shows that during a full moon, the high tide in this area is 8 feet. The green and purple lines, forecast by computer models, show that the winds from Hurricane Sandy are expected to add 4 to 5 feet of water in this area, bringing the total water level to as high as 13 feet. The red dots are the actual, observed water levels, which were running 2 to 4 feet above the predictions at the time of this graph and suggest that the water may reach as high as 14 to 15 feet.

If you have a home near Kings Point, NY, at an elevation of 10 feet, this means that you could have 5 feet of water in your house, which poses a very real threat to both the structure and your life if you stay. But how much of a threat?

Using the scale below, developed in 1985 by IEM President and CEO Madhu Beriwal, you can see that at 5 feet of water, a typical home will lose over 50% of its value and commercial structures will lose nearly 30% of their value. Historically, about 1 in 45,000 people who stay in an area with 5 feet of flooding will die.

Using the resources listed above, as well as the Beriwal Scale™, residents in other areas affected by Hurricane Sandy can determine predicted flooding at their locations and estimate potential damages and risk of fatality.