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

Sponsored By

Software Reviews
Continuing Series
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







Spatial Media LLC properties




Home arrow Archives   The American Surveyor     

Vantage Point: Fire and Rain Print E-mail
Written by Wendy Lathrop, LS, CFM   
Friday, 25 October 2013

A 529Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

The current fires raging near Yosemite are bringing back vivid memories of driving alongside flames bordering a Nebraska highway late one night. My friends and I had taken a few weeks off from our summer jobs just before our next college semester would start, heading west to hit as many national parks as we could. During one friend's turn to drive, the brightness in the night ahead of us grew into a glowing strip of flames and shooting embers perhaps a hundred feet from the road. Apparently a recent train had dropped an ember, and the railroad tracks were ablaze for miles. With no roads to turn off onto, we uneasily decided Larry should floor it to get up ahead of the seemingly calm if extensive fire. Our tuna-boat-sized Chevy Impala wasn't exactly a speed demon, but eventually the relief of night's darkness once again engulfed us as we left the blaze behind.

It wasn't until a few mornings later as we drove on a California road just re-opened hours earlier that we realized the danger we had dodged. The charred and still steaming forest remnants on both sides of the highway signified what could easily have flared up and engulfed us. The lingering heat created a thick fog filled with ash that nearly choked us and obscured the road. But the rain that day signified a greater impact of which we were totally unaware. Today's papers more fully advise the public of the aftereffects of high temperature fires, including flooding, erosion, and sedimentation into water sources.

How can this be? Shouldn't we welcome rain to quench fire and lower ground temperatures as a return to normal? The answer depends upon several factors, including vegetation density and type, soils and geology, and exposure (the direction slopes face).

Under normal circumstances, we rely on vegetation to absorb a good deal of rainfall, or at least slow its downhill trajectory. Just as on stripped construction sites, areas denuded of plants by fire are subject to sheet flow, with runoff carrying sediment in the form of ashes and soil particles. The outcome: erosion and polluted watercourses.

We generally think of steep slopes as areas subject to eroding away under rainfall, but burned sites are especially at risk for mudflows. These are rivers of liquefied soil-turned-mud, flowing over everything in their paths with force and weight greater than floodwater alone. When the ground is saturated, whether from rapid snowmelt or from heavy or prolonged rainfall, conditions are ripe for mudflows.

For a particularly graphic description of how life-threatening this situation can be, read John McPhee's The Control of Nature in which he describes one harrowing example: "...the Genofile family nearly suffocated as a mudflow raced down the slope, smashing in and filling their home to within inches of the ceiling with mud, rocks, and water on its gravity-driven course."

For the dubious, take 45 seconds to watch a video of a 2010 Dunmovin, California debris flow in real time, posted at http://www.theguzzler.blogspot.com/2010/08/dunmovin-mudslide-clean-up-continues.html The flow's speed and force over this relatively flat desert area tells what must have been happening in the steep mountains visible in the background.

Why else are burnt sites so floodprone? Aside from loss of surface vegetation, there is also chemical change occurring in soils subjected to intense heat. Temperatures at ground level can be high enough to release resins, oils, and waxy fats from plants and leaf litter as they vaporize in the inferno. Because soil is an insulator, the temperature just below the surface stays just cool enough for the vaporized materials to infiltrate and re-condense, forming a hydrophobic layer. This impermeable layer keeps water from seeping into the soil more than to a shallow depth, and slow infiltration leads to more surface runoff and erosion. (Clay soils are less likely to be susceptible to this nonwettable condition than sandy or sandy loam soils.) Combining sloped terrain and hydrophobic soils with saturation is a good recipe for creating post-fire landslide conditions.

But how does all this talk about fire affect our lives as design professionals? We should be aware of environmental factors that could be detrimental to our clients' plans and even their safety. Consider location and site conditions: do they create potential for human-induced disasters? Rather than classify all fires and floods as "Acts of God," we should acknowledge most of them as periodic and foreseeable conditions.

Use of fire sets humans apart from other creatures, and our discovery of how to create it rather than waiting for it has shaped our cultures. For millennia we have used it to clear woods for new agricultural areas, light our way through darkness, cook our food, heat our cold bodies, melt ice for water, and soften metal so we can shape it.

But not all fires begin intentionally. Lightning strikes. Downed electrical wires. Sparks from falling rocks. Spontaneous combustion from the heat of wet or green hay baled and stored too soon. Some of these are predictable, some we can safeguard against, some are random. Planning where we live and work and how we build are a large part of the solution.

Fire certainly shaped the way urban Americans live. Wooden structures easily pass flames from one to another, and over time some cities have banned them in favor of more fire-resistant materials to reduce such spread. "Fire atlases" reported which buildings were masonry and which were wood, with annotations about presence of sprinklers and distance to hydrants and other water sources. These allowed insurance companies to set premiums based on calculated risks, as fire can travel both by contact of flames and by radiant heat exposure.

In less densely populated areas, it is not the distance between residences but the distance to forests and other undeveloped vegetated lands that we should be attending to: that is, the wildland/urban interface. This is an aesthetically lovely place, a rural haven amidst nature. But without a fuel break, or removal of vegetation between nature and human development, the same hazards exist as in cities (flames and radiant heat)--perhaps even higher risks if accounting for distance to water and proximity to sheer mass of potential fuel. Add the danger of flames to the increased risk of flooding from charred areas, and the wildland/urban interface becomes an even more hazardous place.

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 529Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

< Prev

 American Surveyor Recent Articles
Thought Leader: Land is Too Important to Be Left to Land Specialists
A while back I was searching the Internet for an old treatise on land titles. A Google query yielded a book published in 1914. The author was Charles Claudius Kagey and the book was titled "Land Survey and Land Titles, a book for boys and girls, a reference volume for property owners, a text ....
Read the Article
Jason E. Foose, PS 
Decided Guidance: Wacker vs. Price - Irony in Sevenfold
This month's case takes us to Phoenix, Arizona in 1950. The Arizona Supreme Court went all guns-a-blazin' in Wacker vs. Price (216 P.2d 707 (Ariz. 1950)). Maybe it's just me, but I'm sensing plenty of irony and have taken license to point it out along the way. I like what the Court did with this case ....
Read the Article
Allen E. Cheves 
Around the Bend - A Visit to Carlson Software
The Ohio River is one of America's greatest, running near 1,000 miles between Pittsburgh and the Mighty Mississippi. Much of the coal and other products that fueled our nation's industrial expansion flowed between the shores of this maritime ....
Read the Article
Lee Lovell, PS 
Surveying & Mapping Economics Part 3 - Customers & Services
This article continues an inquiry into the economic conditions of the Surveying and Mapping industry (NAICS 541370) using data from the U.S. Census Bureau. This time we will look at customers and services. The data comes from the Economic Census conducted every 5 years on American ....
Read the Article
Jerry Penry, PS 
True Elevation: Black Elk Peak
Black Elk Peak, located in the Black Hills region of South Dakota, is the state's highest natural point. It is frequently referred to as the highest summit in the United States east of the Rocky Mountains. Two other peaks, Guadalupe Peak in Texas and ....
Read the Article
Larry Trojak 
Bringing The Goods - Mobile Scanning an Integral Component
When Jim Smith, Jerrad Burns and Charlie Patton left the Memphis division of a major construction company in 2015, they took with them the knowledge of how to get even the most complex jobs done and what equipment could best serve them in making that happen. So when they joined West ....
Read the Article
Lee Lovell, PS 
Test Yourself 41: Integers, Integers, and Integers
ABF is a 5:12:13 triangle, ACF is a 48:55:73 triangle, ADF is a 3:4:5 triangle, and AEF is a 7:24:25 triangle, all with integer sides and inscribed in a semi-circle. What are the lengths of BC, CD, and DE? ....
Read the Article
Wendy Lathrop, PS, CFM 
Vantage Point: Sunset or Sunrise?
While we often think of legislated government programs as static, they do change over time. Such evolution and opportunity for transformation are part of the dialogue in reauthorizing these programs. Every so many years there is a sunset on each government program, and this September is the ....
Read the Article


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


JAVAD Intros
Spoofer Buster

press [at] amerisurv.com
Online Internet Content


News Feeds

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

Need Help? See this RSS Tutorial

Historic Maps

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 



The American Surveyor © All rights reserved / Privacy Statement
Spatial Media LLC
905 W 7th St #331
Frederick MD 21701
301-695-1538 - fax