In order for wetlands to be protected in New York State they need to be on an officail map. Approximately 20 percent of the wetlands in Tompkins County are not on the map, and therefore not protected.
“The wetland maps for Tompkins County date from the 1980s,” said Nick Hollingshead. Hollingshead was there to report on the Wetlands Mapping Project for the Cayuga Lake Watershed Network.
He first got started on the project by mapping wetlands in Dryden in 2014. While the old Fish and Wildlife Service maps were created from aerial photographs on film, new technology has made more accurate mapping possible. Hollingshead is using LiDar, a surveying technology (the term “lidar” was actually created as a portmanteau of light and radar) that measures distance by illuminating a target with a laser light and GIS. “For the most part, LiDar made this possible,” said Hollingshead. The imagery was collected in March, “when saturation of the ground is visible.”
Wetlands in New York State, to be protected under DEC law, must be larger than 12.4 acres, Hollingshead explained. However, significant wetlands exist that don’t meet that criteria. The wetlands mapping project’s ultimate goal is to provide accurate data to municipalities in order to support regulatory protection of local wetlands. The Water Resource Council has drafted a local wetlands law, but “better data would be helpful,” said Hollingshead. To this end, the Cayuga Lake Watershed Network and the county have hired Hollingshead to do the mapping project using LiDar.
Hollingshead said that the DEC counts 5,600 acres of wetlands “whereas my data is 15,000, which I believe is closer to the actuality.” The DEC mapped 81 wetlands larger than 12.4 acres; “I mapped 197,” said Hollingshead.
In order to test his accuracy, Hollingshead mapped known wetlands within Cornell’s purview, gaining a 97.5 percent accuracy score.
Question…how is LIDAR able to identify wetlands? I thought the deciding factor was vegetative related?
There appears to be not enough information available. LiDAR can help an analyst with a variety of classification challenges however, by itself, LiDAR can’t tell you whether a soil is hydric, and it can’t tell you how often an area is saturated (wet season/dry season). LiDAR can help with slope, orientation, elevation, flow measurements (water into an area, and water out for instance), solar exposure, and so much more. LiDAR technology development and applications aren’t static like most traditional remote sensing techniques; it’s still a rapidly evolving tool.
Insights through these types of analysis, using LiDAR to point (pun intended) the researcher to potential targets for more precisely delineating wetlands. If I were running a wetlands delineation mapping project, I’d use a LiDAR sensor on a UAV in conjunction with sub-orbital platforms to capture the maximum potential targets for field analysis, sampling and verification.
LiDAR can help with positional accuracy. In order to meet or exceed Federal Geographic Data Committee standards for classification accuracy more data inputs typically are used especially field verification.