Baldwin County Wetland Conservation Plan - Alabama Department ...

Baldwin County Wetland Conservation Plan Final Summary Document
determinations. Accordingly, BCWCP and USACE staff chose the p-value of the BCWCP wetland
validation study to be 0.90 with an error of ±5%. Using the table provided by the USACE, it was
determined that 138 sampling locations would be necessary in order to establish a strong statistical
foundation in comparing the NWI maps to on-the-ground jurisdictional wetlands.
BCWCP staff found several random sampling scripts on the ESRI web page and reviewed
them with the USACE statistician. After review, it was determined that the Simple Random Sampler,
written in Avenue, be used since it offered supporting documentation. A total of 160 sampling
locations were chosen to account for those locations where site access would be limited or
permission to access the property would not be granted. The sampling script was run with the
Baldwin County boundary as the base coverage to generate a point theme with 160 records. The
point coverage was converted to a polygon coverage using each point as the centroid of a square
acre. A site identification field was added to the data table using a numbering script.
The polygon coverage was then overlaid on Baldwin County’s parcel data. A spatial join was
executed, linking the parcel identification number to the sample table. The data were linked to the
Revenue Commission’s database, in which the property owner’s name and address were linked to
the sampling location. The database was then modified to house all of the data that would be
collected in the validation study. BCWCP staff collected additional field data while making the
jurisdictional determination at each sampling location. These data included the date visited and a
determination of HGM class, functional capacity and soil survey type.
Letters were sent to all property owners requesting permission to access the respective
property. A form was created in the relational database for fieldwork purposes to increase the
efficiency of data collection.
3.2.2.1 Fieldwork
Prior to validation study site visits in the field, BCWCP staff prepared maps of the site in
order to aid in the access of the sites. The recently acquired color infrared (CIR) aerial photography
was used extensively in this process. Site visits were coordinated with USACE staff and property
owners. Each property owner was contacted via telephone prior to a site visit. This also gave staff
the time to educate and inform each of the property owners on the significance of wetland
functions.
Field work at each sampling site consisted of the following steps:
1. GPS: Way points of the sampling location were entered into the Trimble GeoExplorer 3.
This instrument was used to navigate to the sampling locations. In areas of dense canopy
cover, aerial photography and pacing methods were used to reach the square acre sampling
location. GPS data points, site ID number and wetland/upland status were collected at the
southeast corner of each square acre. Upon return from the field, these data were
differentially corrected and exported in a shapefile format.
2. Wetland determination: USACE staff conducted routine wetland determinations at each site per
the guidance provided in the 1987 USACE Wetland Delineation Manual. Dominant
vegetation, hydrological indicators and soil color (type) were noted on the field data sheet.
Other notable features such as disturbances or atypical conditions were also noted.
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