Baldwin County Wetland Conservation Plan - Alabama Department ...

Baldwin County Wetland Conservation Plan Final Summary Document
Table 2. Summary of GIS Layers Utilized in BCWCP RFWAM.
Data Layer Source
NWI USFWS
Endangered Species USFWS and ANHP
Fire Locations AFC
Flood Zones FEMA
Wellhead Protection Areas EPA and GSA
Land Use GSA
8 Digit HUC NRCS
11 Digit HUC NRCS
Hydrology USCB TIGER
CIR BCC
True Color Photos BCC
Centerlines BCC
3.2.3.3 Wetland Classification: HGM Classification Development
Conversion of the National Wetlands Inventory (NWI) or Baldwin County Digital
Wetland Layer classification to the HGM classification system was an essential task of the BCWCP,
as the functional assessment models were based on the HGM system. BCWCP staff were contacted
by the EPA grant manager to suggest collaboration between EPA GIS and BCWCP staff in order to
accomplish this task most efficiently. BCWCP staff provided the data necessary to EPA staff in
order to initiate the conversion process. After an initial review of HGM conversions provided to
BCWCP staff, discrepancies were found and time became limited to correct these errors. Therefore,
staff developed a protocol for the HGM classification of polygons.
Riverine wetlands were identified by a geospatial relationship within the hydrology coverage. In
other words, if a wetland polygon intersected the hydrology coverage, it was classified as riverine.
Since many wetland polygons can exist within a riverine system, all polygons touching these riverine
wetland polygons were also classified as riverine. This process was repeated until all polygons within
riverine systems were identified and classified as riverine. Fringe wetlands were identified in a
similar fashion using a coverage of saltwater hydrology. Polygons intersecting or touching saltwater
areas were identified as fringe wetlands. Further, any polygon with the NWI classification of
estuarine (E) was classified as fringe. This initial identification was then refined through spot checks
conducted by local experts familiar with the coastal landscape of Baldwin County. Flat and
depressional wetlands were identified using a visual interpretation of CIR photography that was
taken during a very dry year in Baldwin County. Because polygons with visible standing water in
such a year must have access to groundwater, they were classified as depressional, and polygons
identified as wetlands but with no water present were classified as flat wetlands. Upon completion
of this process, BCWCP staff evaluated the final product and found that the classifications were
largely accurate. As with any remote analysis, there were some errors in classifications. After several
reviews by other professionals affiliated with other government agencies involved, a final
classification was reached (Figure 10).
3.2.3.4 Wetland model development
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