A group of state senators supports putting $2 million toward high-detail laser mapping of South Carolina, and the leader of the effort hopes it will stop flood-prone developments in the future.
Sen. Chip Campsen, R-Isle of Palms, introduced a measure last March to conduct statewide LiDAR mapping at least every five years. The acronym is short for “light detection and ranging.”
The process usually involves flying a plane fitted with a laser that shoots light pulses at the ground. Those pulses are used to measure the distance between the plane and whatever the light hits, thus showing changes in elevation over a large area.
Campsen’s measure passed out of subcommittee on Wednesday, but he’s optimistic it will get through the state’s upper chamber. It would create a statewide resource for local planning agencies, potential homebuyers and private industry, he said.
“This will help avert a Church Creek basin repeat,” Campsen said, referring to a section of suburban Charleston where city consultants have said overbuilding contributed to chronic flooding.
The new data would also help the state develop more accurate flooding models to show where water might go during a serious storm.
The laser mapping isn’t a bulletproof fix to flooding: It won’t show things like inadequate or broken drainage that’s already in place. It only shows height, not whether a house is located on stable ground or eroding beach.
One concern: Even though the mapping would provide more information, there’s no guarantee that towns, cities and counties which set development rules would use it.
The state has used this technology before. The S.C. Department of Natural Resources led an effort to map all of the Palmetto State with LiDAR from 2007 to 2018, but some of that information is now outdated, said Ken Rentiers, the agency’s deputy director.
The existing data is not easy for the average person to use. The department has it available for free currently on its website, but it’s just the elevation readings taken from the flights. It usually takes additional software to generate an image from that information.
Campsen’s bill, S. 690, requires that after doing the mapping, the state “publish the results to the public.”
It does not specify funding, but Campsen said DNR has asked for $2 million to do the mapping and create a public platform to view it.
The measure is co-sponsored by Sens. Tom Davis, R-Beaufort; Sandy Senn, R-Charleston; and Paul Campbell, R-Goose Creek.
The legislation has been a longtime goal for real estate groups in the state. Josh Dix, of the Charleston Trident Association of Realtors, said a public LiDAR database would crease “a more educated home buyer and home seller” by letting consumers look up the elevation of a property themselves.
Nick Kremydas, chief executive officer of the S.C. Association of Realtors, said better mapping could lead to more stable flood insurance premiums over the long term.
Matthew Fountain, director of stormwater projects for the city of Charleston, doesn’t take a position on the state Senate bill. But he said a central collection of LiDAR data could be invaluable as the city moves toward assessing how each construction project would affect a larger basin, which may be thousands of acres.
In the past, planners have looked at projects in a vacuum, setting standards for how intense a downpour a new subdivision or business should be able to drain. These efforts haven’t always considered how new building would affect older neighbors in a serious storm, however.
“Each individual project was probably OK, but it was the cumulative impact of all of those projects together that probably caused all the problems,” Fountain said.