USGS project digitizes Louisiana soils

With a home office in Lafayette, La., the U.S. Geological Survey's National Wetlands Research Center recently moved a satellite office to the Louisiana State University campus in Baton Rouge. Why? To help promote the use of geographic information systems (GIS) and remote sensing in agriculture, says USGS geographer Steve Hartley.

Also of key interest to farmers: USGS is digitizing (converting to computer format) soil information throughout Louisiana.

“Any of the precision agriculture tools, such as GIS, that use soils as one of the layers of input must have that information in a digital form,” says Hartley, who spoke at the Precision Agriculture Conference in Monroe, La.

Currently, most of the state's soil data is available in paper format in old soil survey books. Hartley and colleagues are taking the soil survey books and digitizing them so the data can be used in computer modeling that will enable farmers to better manage their acreage. “Right now, we've been tasked to do most of the parishes in the lower part of the state.”

Hartley says farmers may be wondering why the USGS isn't first doing the soils further north where most of the farming needs are. The reason is the Coastal Wetlands Planning, Protection and Restoration Act.

“It has paid for a lot of this work to be done around the coast of Louisiana. Currently, there are six parishes being worked on. Most of the work is complete although there is some in-house verification to check how well we digitized. We're checking labeling and crosschecking soils codes.”

One of the major problems is some of the soil books Hartley and colleagues are working with are 40 or 50 years old. This causes problems with edge matching, incorrect labeling and the like.

“We're having to go back and fix all that.”

How is the USGS getting the soils from paper format to digital?

“We're taking the aerial photos, combined with the original ratios from the books, and transferring the line work to a Mylar overlay. We then scan that into the computer. When we first started this project, the Natural Resource Conservation Service used satellite imagery to transfer the line work onto the Mylars. The problem with that is you can't see the detail we needed between where the land meets the water. And getting that right is critical for wetlands.”

So, USGS went back — using Digital Orthophoto Quarter Quadrangles (DOQQ's) — and was able to get a truer picture of what was happening. They now have a much better product.

Hartley says there is an interest in terracing some soils to prevent erosion and promote growth of sediment deposits. To accomplish that, there's a need to know what soil types are good for terracing.

“You don't want to start a project where the soils won't terrace up. The maps we're generating will let those soil types be known.”

There are other uses. Hartley said there are four types of marshes: fresh, intermediate, brackish and salt.

“If we look at the potential erosion sequence, we can see what marshes will go first if sea levels rise. This shows that contrary to what one would think, the brackish marsh goes first — not the salt marsh. The brackish has the most erosion potential followed by the intermediate then fresh marsh. The salt marsh turns out to be the most stable. So we can use soils to predict where wetland loss will occur.”

The DOQQ's mentioned by Hartley are available free at LSU's website. The address is:

e-mail: [email protected]

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