About Amerisurv| Contact    
Magazine | Newsletter    
Flickr Photos | Advertise    
HomeNewsNewsletterAmerisurv DirectoryJobsStoreAuthorsHistoryArchivesBlogVideosEvents
 
advertisement


Subscriptions
Sponsored By

Software Reviews
Continuing Series
     RTN
An RTN expert provides everything you need to know about network-corrected real-time GNSS observations.
Click Here to begin the series,
or view the Article PDF's Here
76-PageFlip Compilation
of the entire series
Test Yourself

Got Answers?
Test your knowledge with NCEES-level questions.
  Start HERE
Meet the Authors
Check out our fine lineup of writers. Each an expert in his or her field.
Wow Factor
Sponsored By


Product Reviews
Partner Sites

machinecontrolonline 


lbszone.com

GISuser.com

GeoJobs.biz

GeoLearn

 

Spatial Media LLC properties

Associates

ASPRS

newsnow 

Home arrow Archives   The American Surveyor     

Vantage Point: Ankle Deep, Knee Deep, or Higher? Print E-mail
Written by Wendy Lathrop, PS, CFM   
Saturday, 02 August 2014

A 136Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

Hurricane Amanda and Tropical Storm Boris have already sloshed and wind-blasted their way through Central America. Amanda arrived a week before the official June 1 start of hurricane season, with Boris close behind. It's time to assess our storm surge prediction tools. While such storms generally cause most of their damage along our sea coasts, inland areas experience significant flooding from storm surge. What we all want to know is how much water might we expect? Which neighborhoods will be inundated first, and which roads will be impassable for evacuation or rescue?

If we can predict the direction of a storm and where it is likely to make landfall, we improve our opportunity to prepare for flooding events more realistically in relation to human safety and our built environment. Along large bodies of water such as the Great Lakes, the Atlantic and Pacific Oceans, and the Gulf of Mexico, additional height of water from air pressure changes and winds pushing water inland is called storm surge. But storm surge is not confined to those lands immediately along the waterfront. Through a model called Sea, Lake, and Overland Surges from Hurricanes (SLOSH), the National Oceanic and Atmospheric Administration (NOAA) calculates maximum potential impact and coastal inundation risk assessment based on storm intensity, path, and estimated storm size information from its National Hurricane Center (NHC).

The first difficulty is accurately predicting the storm's track and timing of its landfall. A slight shift can mean a different area will be impacted more severely, and a delayed or expedited arrival coincident with high tide can mean a whole lot more water is pushed inland than had been anticipated. A change in storm intensity affects air pressure, sucking water into low-pressure areas, while a variation in storm size influences how much area will be affected. This is not an easy set of variables to play with, so a series of many SLOSH runs creates a Probabilistic Storm Surge (P-Surge) estimate. Based on SLOSHbased simulations of impacts of each model run and relying on statistical analysis of past advisories' accuracy, P-Surge estimates are posted on the NHC website within half an hour of NHC's storm advisory.

Coastal areas are divided into SLOSH basins for computational purposes, and account for susceptibility related to dense population, low topography, and ports. Each basin is modeled to determine Maximum Envelope of Water (MEOW) by calculating SLOSH runs both left and right of the main storm track. By accounting for various uncertainties in storm forecasting, thousands of SLOSH runs yield MEOWs for worst-case scenarios to aid in evacuation planning. An analysis of all MEOWs for a basin will yield MOMs (Maximum of MEOW runs). Obviously in this short space, this generalized description omits many details of the variables and approaches. For instance, SLOSH does not account for rain flooding, normal river flow, or the impact of waves on top of storm surge. However, for fast model runs and its ability to resolve flows through particular situations, it is an invaluable tool.

But aside from all the math, we want to know the effect of storms on humans and our built and natural environments more directly. SLOSH Storm surge heights are referenced to a vertical datum, with all basins in the contiguous United States updated to NAVD88. Not everyone understands elevation, however, and so NHC forecasts storm surge as height above ground level. This year, NHC released an experimental Potential Storm Surge Flooding Map to help identify the areas where storm surge could cause inundation and what to what depth those areas could expect inundation. NHC calls this a "reasonable worst-case scenario for any given location", with the maps representing inundation levels with a 10% probability of being exceeded. The fourcolor coding system represents inundation levels up to 3 feet above ground, greater than 3 feet, greater than 6 feet, and greater than 9 feet above ground.

NHC anticipates releasing initial inundation mapping on its website when it issues its first hurricane or tropical storm watch (advising of a possible storm event) or warning (requiring immediate action as arrival of the storm is imminent) and will be updated every six hours, within about a half hour after running P-Surge. No GIS data from this model will be made available during the experimental phase of P-Surge while NHC seeks feedback and suggestions for improvements, need for modifications, and whether it should be integrated into NHC's regular operations.

The National Research Council's 2009 publication "Mapping the Zone: Improving Flood Map Accuracy" devoted a full chapter to the importance of appropriately communicating flood risk. The vast majority of the public understands an estimated level of inundation better than projected water surface elevation. While limited in scope of analysis, as many quick emergency forecast tools are, this new technology may be able provide a broadly understood straightforward advisory that more of the public will heed.

Wendy Lathrop is licensed as a Professional Land Surveyor in NJ, PA, DE, and MD, and has been involved since 1974 in surveying projects ranging from construction to boundary to environmental land use disputes. She is a Professional Planner in NJ, and a Certified Floodplain Manager through ASFPM.

A 136Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
< Prev   Next >

Marc Cheves, PS 
Editorial: A Great Year to be a Surveyor
Some magazines have what are called "theme" issues. That is, most of the content is focused on one particular subject. In my 22+ years of survey magazine publishing, my philosophy has always been to have a little bit of everything in each issue, thereby eliminating the possibility that ....
Read the Article
Jason E. Foose, PS 
Decided Guidance: Case Examinations: Halverson v. Deerwood Village
Whew! We really beat the snot out of Bryant v. Blevins and practical locations. Well this month we're back on new case that hit the Minnesota Supreme Court's docket in 1982. We've got the familiar gymnastics of jurisprudence featuring an extraordinary array of flying rope stretchers ...
Read the Article
Michel Philips 
Extreme Environment Surveying
A Franco-Chilean team of cave divers used the Nautiz X8 rugged handheld for marine cave surveying, gathering data to classify the inaccessible northern half of Madre de Dios for UNESCO World Heritage. The team of cave divers used the Nautiz X8 ....
Read the Article
Erik Dahlberg 
The Original Green Engineers
Sometimes, it's best just to leave things as you found them. That's the lesson shared by Dr. Richard Miksad and his students at the University of Virginia. As a result of studies covering nearly a decade, Miksad's teams have developed detailed ....
Read the Article
Dave Lindell, PS 
Test Yourself 49: No Dimensions
In square A-C-D-B with side S, C-E is tangent to the semicircle Q1 with diameter B-D. Q2 is the inscribed circle of A-C-E. The tangent to Q1 and Q2 meets the sides of the square at F and H and intersects C-E at t G. Q3 is the inscribed circle of C-G-H. What is the ratio of the radii of circles ....
Read the Article
Jerry Penry, PS 
Discovery on Grizzly Peak
When First Lieutenant Montgomery M. Macomb arrived in Carson City, Nevada, from Washington D.C., on July 28, 1878, his assigned survey crew from the 4th Artillery was waiting and ready for the new field season. At age 25, Macomb was the leader ....
Read the Article
Wendy Lathrop, PS, CFM 
Vantage Point: Fighting City Hall Over Land
Once upon a time (1989 to be exact) in a place not so far away from where I live, a man (Francis Galdo) bought a home across the street from a vacant parcel owned by the City of Philadelphia. That parcel, along with others, had been acquired by condemnation back in 1974 subsequent to a 1956 ....
Read the Article
Patrick C. Garner, PS 
Book Review: Boundary Retracement: Processes and Procedures
When I was in my mid-twenties and learning the honorable profession of land surveying, I was lucky to be guided by a mentor who would grab a book off his office shelf and say, "Every surveyor should have a copy of this!" The first example he waved at me was Davis, Foote and Kelly's Surveying ....
Read the Article

deliciousrssnewsletterlinkedinfacebooktwitter

Amerisurv Exclusive Online-only Article ticker
Featured Amerisurv Events
List Your Event Here
please
contact Amerisurv


Google
 
AMERISURV TOP NEWS

Trimble Intros
TSC7 Controller

GOT NEWS? Send To
press [at] amerisurv.com
Online Internet Content

Sponsor


News Feeds

 
Subscribe to Amerisurv news & updates via RSS or get our Feedburn
xml feed

Need Help? See this RSS Tutorial

Historic Maps
Careers

post a job
Reach our audience of Professional land surveyors and Geo-Technology professionals with your GeoJobs career ad. Feel free to contact us if you need additional information.

 

Social Bookmarks

Amerisurv on Facebook 

Amerisurv LinkedIn Group 

Amerisurv Flickr Photos 

Amerisurv videos on YouTube 

twitter

 




The American Surveyor © All rights reserved / Privacy Statement
Spatial Media LLC
7820B Wormans Mill Road, #236
Frederick MD 21701
301-620-0784
301-695-1538 - fax