If The World Was Perfect, It Wouldn’t Be: Hazard Mitigation Planning in the Big City

Photo by: eguchishintaro/Flickr

An ad hanging in the stairwell in New York asks, “Why should you worry about a hurricane? It’s not like you live on an island.” Well, when you say it like that…

There always seems to be a sentiment amongst many people in the city that a hurricane is just some rain and wind. And it is. In the same way that lava is just hot rocks. The extreme nature is the concern. Also, the fact that we are surrounded by water, with a coastline where wind can funnel said water very efficiently into places like downtown Manhattan. It’s called the New York Bight—which is a kind of funny name, I know, but it is what it is—and it makes storm surge a big problem. Luckily, the city thinks ahead, and has all of its agencies create plans for all kinds of hazards that affect the city, so that we can all brag about being big, bad New Yorkers who will go right back to work when the wind dies down. There is a 500 page Natural Hazard Mitigation Plan (HMP) available on the Office of Emergency Management (OEM) website that details many of those. It’s what I’m working on now.

I felt that, because it’s hurricane season, it seemed fitting that I start my update of the plan in the coastal storms section. Did you know that six tropical storms have affected the city in some manner—mostly flooding—since 2009? Bill, Danny, Earl, Nicole, Irene and Sandy. Some were weaker than others, but it makes the HMP totally worthwhile. It built in a risk assessment for every hazard so each agency could prioritize their projects and procedures depending on the scenario.

For tropical storms and storm surge, OEM used the Sea, Lake, and Overland Surges from Hurricanes or SLOSH model. If you’re going to force an acronym, “slosh” is the kind of word you should be using. Acronyms aside, the model is made using a set of physics equations involving relationships between variables like basin shape, wind speed and storm track and then run several thousand times. The output is called Maximum Envelopes of Water (MEOW) and Maximum of MEOWs (MOM). (Okay, not all of NOAA’s acronyms are great.) Those outputs are helpful to determine the vulnerability of an area, and combined with elevation and factors like saturation levels, they can be used when designating flood zones.

So, a lot of thought, research, a couple thousand model runs and months—years, even—of planning go into designing just storm surge plans. The bottom line is that when the city starts ramping up for a storm, OEM and the other agencies are doing what they know they need to do to keep people safe from that bit of rain and wind.