New 2012: RI NRCS Completes the First Freshwater Subaqueous Soil Survey Data!
A new version of the Soil Survey of Rhode Island (Spatial version 5, June 2012) is now available for download on and for viewing and creating interpretive maps/reports on the Web Soil Survey. The new version features many improvements, new soil map units, fixes to errors, a re-digitizing of Block Island, completion of Phase II of the RI Coastal Zone Soil Survey, and the first ever example of a freshwater subaqueous soil survey. Below are explanations of the changes and improvements to the RI Soil Survey.
Re-digitization of Block Island
When the 1981 analog (published) soil survey was converted to digital format (GIS shape-file) back in the 1990s, the USGS Topographic maps (in NAD 27 projection) were used as the base map for the hydrology features (water bodies, streams, etc.). As a result when the digital polygons are overlaid on Orthophotography projected in NAD 83 there is a spatial shift in the polygons. While this shift occurs throughout RI it is most prominent on Block Island. A work plan action item to correct this shift was completed for the new 2012 soils data. The entire 6,000+ acre Island was re-digitized by geo-referencing the original field sheets to overlay correctly onto Orthophotography and each polygon was digitized using ArcMap. While no on-the-ground soil mapping was conducted (there are plans to conduct field mapping on Block Island in the future) for this update, there were numerous adjustments of the soil polygons to match the imagery and LiDAR contours. In addition, the entire shoreline area (beaches, dunes, bluffs) were digitized using Pictometry to classify the beach map units and adjust the soil polygons to account for shoreline changes. Below is an example of the 2010 SSURGO and the new 2012 version - note how the 2012 version matches the hydrology. It is hoped this new data will provide more accurate soil interpretations for land-use planning.
Fresh Water Subaqueous Soil Survey
Rhode Island is in the forefront of providing soil mapping, interpretive data, bathymetry, and a wide-array of geophysical data for our submerged lands. The 2010 soil survey data featured the first ever SSURGO certified Coastal Zone Soil Survey which included the subaqueous soil mapping of the coastal lagoons in Washington County. In 2011 as the result of a thesis study by the URI Department of Natural Resources Science, a subaqueous soil survey of six fresh water bodies in RI was initiated. The 2012 soil data includes the subaqueous soil mapping of Watchaug Pond, Worden Pond, Tuckertown Pond, Bellville Pond, Bowdish Reservoir, and Smith and Sayles pond. To complete the mapping six new soil series were established and over 110 soil pedons were collected and analyzed in the laboratory.
Each pond was mapped by collecting detailed bathymetry and a geo-physical map of the subsurface using ground-penetrating radar and acoustic methods. Work is on-going to provide soil interpretations for the soil map units for a variety of uses such as invasive species, carbon storage, phosphorus, and the traditional chemical and physical properties of the soil. Plan are to expand the fresh water mapping is future version of the spatial and tabular data.
Phase II of the Rhode Island Coastal Zone Soil Survey
The Phase II area of the RI Coastal Zone Soil Survey includes the area from Point Judith to Greenwich Bay along with Trustom and Cards Pond (from Phase I area). The Phase II soil mapping consists of a re-map of the coastal dunes, marshes, and beaches along with the shallow subtidal soils for the Narrow River, Wickford Harbor, Greenwich Bay, and other selected areas in RI. The Phase III area will take several additional years to complete but will eventually map the entire coastal zone and shallow water soils to 5m depth for the Ocean State (if funded).
Other Spatial Changes
The 2012 SSURGO soils data also includes changes to the soil polygons and special features throughout the state so all users of the soil survey are encouraged to download the new data to make sure you have the "official" SSURGO data. Other changes include;
The removal of over 2,000 soil polygons that were under the 0.5 acre minimum polygons size. These were mostly very small ponds that were digitized from the USGS Topographic maps, they were replaced by special feature point symbols (WAT, IOW, or WET spots) or combined into larger map units. The tiny polygons caused clutter in the map when viewing at small scales and were often in the wrong position. Now only soil map units 0.5 acres or greater are mapped.
Error fixes - numerous areas state-wide were found in the old data that were incorrectly labeled or the polygons were not properly digitized from the field sheets.
Hydrology fixes - several rivers such as the Wood-Pawcatuck were re-digitized to match the imagery and the hydric soils were also adjusted.
Farmland areas where the RI NRCS is working with landowners were checked for accuracy and re-digitized where errors were identified, over 100 farm areas were reviewed and adjusted.
Hydric soils adjustments - the original soil mapping was conducted on low quality black and white aerial photos and as a result the wet areas were often not mapped accurately. Using new high-resolution color imagery, updated NWI mapping, and our recent set of state-wide LiDAR elevation data an effort was made to adjust the hydric soil areas to improve the accuracy. This project will continue with the new soil version scheduled for 2013.
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