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Wednesday, 23 September 2009 18:27

Landslide maps one component of steep slope planning

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The Macon County committee charged with proposing regulations for building on steep slopes is still swimming in a sea of ideas but has agreed on one point. It will incorporate landslide hazard maps into a proposed ordinance, though the maps won’t be the end-all, be-all.

“If we based it totally on that, I think we would be leaving out a lot of issues,” said Al Slagle, chairman of the committee and planning board member.

“I think everybody wants to see the risk maps used as a cross-reference,” said Susan Ervin, who serves on the committee and the planning board. “It’s very clear there’s going to be some kind of coordination.”

The high-resolution topographic maps pinpoint exactly where landslides have occurred in the past, where they are likely to occur in the future, and how far they might travel if they occur. The North Carolina Geological Survey will eventually create maps for every mountain county to better identify high-risk areas.

While the maps have been available for curious eyes at Macon County’s GIS office, as well as online, since 2006, they have not been formally integrated into the slope development process so far.

Members of the slope development strategies committee said the maps could come in handy for deciding which sites require technical study before development occurs. Other counties that have tackled similar ordinances have not had the luxury of such maps while making the major decision of which thresholds would trigger regulation.

Macon County currently has no regulations for steep slope construction. Developers and contractors can build on slopes as steep as they like without consulting with engineers or geotechnical experts.

Committee members said the ideal ordinance would not crush development on slopes with an iron fist. Rather, it would allow for safer, better-informed development.

“It’s not that those things can’t be done. It’s got to be done right,” said John Becker, a committee member and local Realtor.

Rick Wooten, senior geologist at the N.C. Geological Survey, said the landslide hazard maps could be helpful in this capacity.

“If you’re building a house, this can tell you the areas where it makes sense to take a close look at the landscape,” Wooten said.

In many cases, the path to improving safety can be as simple as moving a house 20 or 30 feet to one side.

Nevertheless, the landslide hazard maps are only one part of the equation.

“The maps are useful, but it still requires boots on the ground,” said N.C. Rep. Ray Rapp, D-Mars Hill, who has spearheaded a campaign to require minimal slope development ordinances for all counties in Western North Carolina.

While looking at where landslides are likely to strike can be valuable, the committee is considering other criteria, like the slope’s steepness and soil composition, both of which can affect safety.

The committee analyzed similar ordinances in Haywood and Jackson counties, as well as White County in Georgia, before beginning work on one for Macon County.

One idea floating around is to create no regulations for slopes under a 30 percent grade, mandate that the county conduct an in-house study to determine the need for a geotechnical investigation for 30 to 40 percent slopes, and call for an engineer or design professional to study slopes above 40 percent. Falling into unstable territory, as determined by the landslide hazard maps, would also require a technical inspection.

Others on the committee prefer a lower threshold for triggering the regulations. The in-house county oversight would kick on slopes greater than 25 percent, and mandatory engineering would be required on slopes over 35 percent.

 

Making data available

Traditionally, development in Macon County occurred in more accessible, gentle lying areas. But with an increasing number of second homes, as well as innovations in engineering, there has been more and more building on steep slopes and ridges.

“That’s likely to continue, so we would like it to be done in a way that did not endanger the people building those [and] people living in proximity,” said Ervin, who added that the county should not invest in public infrastructure for “unstable” projects.

But when it comes down to it, Ervin admits the committee is evaluating development on a “pretty low percentage of private properties,” since most of the steepest slopes in Macon County lie within the Nantahala National Forest..

“The risks really are quite low,” said Reggie Holland, another committee member and president of the Macon County Home Builder’s Association. “If it happens, the danger is quite high.”

According to Wooten, many of Macon County’s debris flows occurred on the east facing slopes of the Nantahala Mountains.

In case the landslide hazard maps are not incorporated into the ordinance, they would still serve an important function by helping forecast where landslides may occur.

“They’re very useful to have,” said Joshua Pope, GIS coordinator for Macon County. “It’s like predicting weather. It’s not set in stone, but watching The Weather Channel is still useful.”

And as always, they are available to anyone who wants to take a look.

“Aside from regulations, the most important thing is that people have that information,” said Stacy Guffey, committee member and former county planner. “We have this information, we should use it.”

The reason Macon County has this resource in the first place is because it suffered the most severe damage from the 2004 hurricanes in WNC, according to Wooten.

The Hurricane Recovery Act of 2005 required the maps to eventually be created for all counties in WNC.

Each set of landslide hazard maps has taken a year to complete, with three counties finished up so far: Macon, Watauga and Buncombe.

The N.C. Geological Survey is currently working on landslide hazard maps for Jackson and Henderson counties. It will take at least a year to finish the maps for Jackson County, Wooten said.

Pending final approval and funding from Raleigh, the agency will study Haywood County after maps are completed for Henderson and Jackson counties.

 

The cost of regulations

After the landslide at Peeks Creek in 2004 claimed five lives, Macon County became well aware of the dangers of locating development on hazardous areas.

“We don’t want to see another Peeks Creek going on — ever,” said Becker. “Profit shouldn’t go before safety.”

Still, Becker said he would like to see an ordinance that ensures the safety of Macon County residents without imposing too many rules and regulations.

Teresa Murray, president of the Franklin Board of Realtors, said Realtors do have concerns but understand that something needs to be done.

“There’ll be some costs no doubt when it comes into play,” said Murray. “Hopefully, we can have an ordinance that benefits everyone.”

Requiring technical studies to evaluate dangers obviously would tack on to the cost of developing, but Rapp reminded real estate agents that it would be beneficial to sell property on a steep slope five or six times rather than sell it once and have it torn apart by a landslide.

Initially, Rapp hoped Realtors would be required to inform clients about properties that lie in areas prone to landslides.

“I’m willing to compromise on that as long as we require that the structures be built safely,” said Rapp. “If you’re doing it right from the beginning, then it takes the fire out of this issue.”

Rapp said he will continue to push for legislation that mandates those minimum slope development ordinances in Western North Carolina.

“It’s so fundamental. It’s so basic,” said Rapp. “It’s hard for me to fathom why people will be opposed to it, other than we’re talking about serious, big dollars that can be impacted.”

Rapp said the next big challenge is to make sure homeowner’s insurance for landslides is made widely available.

 

What other counties are doing

As Macon County crafts its first set of steep slope building regulations, one issue confronting planners is when the regulations should kick-in. Other counties with steep slope ordinances faced a similar debate: what is the treshhold for triggering oversight?

• Macon County has the benefit of state landslide hazard maps, which will play a role in determining that treshhold. Other counties didn’t have such maps when crafting their ordinance, and instead rely solely on the slope.

• Jackson: Steep slope ordinance applies on slopes with a grade of more than 30 percent.

• Haywood: Steep slope ordinance applies on slopes with a grade of more than 35 percent.

• Swain: No steep slope building regulations.

• Proposed state bill: A state bill that has been percolating in the legislature would require builders to consult an engineer when building on slopes that exceed a threshold of 40 percent.

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