On this page:
Methods of Sub-watershed Mapping
Methods of Wetlands Mapping
State Land Unit Management Planning


The methods used to map watersheds and wetlands in this project were based on those developed for previous Adirondack Park watershed projects (Roy et al. 1996, Roy et al. 1997, Primack et al. 2000, Halasz et al. 2000).

Sub-watershed Mapping
Sub-watersheds of the study area were delineated for major rivers and ponds with unique pond identification numbers assigned by the Adirondack Lake Survey Corporation (ALSC) and the New York State Bureau of Fisheries (BOF). Watersheds were delineated on USGS 1:24000 or 1:25000 topographic maps using conventional methods (USDA 1977). Separate sub-watershed boundary determinations were made by two different people. A third person at the APA reconciled and verified the maps using 1:40000 NAPP or 1978 1:24000 panchromatic air photos and field checking. Final sub-watershed boundaries were transferred to clean USGS topographic maps and digitized, edge-matched, and joined into a seamless coverage. Air photos and topographic maps were used for two independent determinations of flow pattern between sub-watersheds and directional arrows were drawn on paper copies of the boundary maps. Each paper map was used to digitally assign hierarchical flow direction labels to the GIS coverage of sub-watersheds using an ArcInfo AML (Arc Macro Language program) created by Primack (1997) (Appendix 7). The AML assigned each sub-watershed polygon a unique I.D. number in a data field called 'THIS#' in the polygon attribute table. A second field, called 'FLOWTO#', was created that contained the I.D. number of the receiving sub-watershed polygon. In this way, the path of water from one sub-watershed polygon to another could be followed through the entire St. Regis Watershed.

To uncover inconsistencies between flow direction assignments in the two independently produced flow-pattern maps, the polygon attribute tables were relationally joined using the 'THIS#' field. Where the 'FLOWTO#' field from one of the coverages did not match the 'FLOWTO#' field from the other coverage, the correct flow direction was ascertained by overlaying the sub-watershed polygon outlines over GeoTIFF images of 1:24000-scale USGS topographic maps (NYS GIS Clearinghouse 2000a) in a GIS. If evidence of flow direction could not be determined from the topographic maps, 1:40000 NAPP air photos or 1978 1:24000 panchromatic photos were viewed in stereo. In addition, the ALSC Pond database was a useful source that gave outlet information for most of the ponds in question (ALSC 1999). Differences between the two delineation efforts primarily occurred in areas where there was little topographical variation or where the pond outlet was uncertain, especially where the watershed was isolated and internally draining. After the flow direction hierarchy was finalized, regional watersheds were generated from the sub-watershed map using an ArcInfo AML (Appendix 8, Primack 1988) to select all watersheds flowing into a particular watershed and grouping them.

As a final step in the creation of the sub-watersheds coverage, a field was added to the polygon attribute table that contained the 11-digit USDA/SCS watershed codes (USDA/SCS 1980), which allows the data set to be joined with other data sets that use the SCS codes.

Wetlands Mapping
Wetlands were delineated on 1:40000 NAPP aerial photo acetate overlays and labeled based on the National Wetlands Inventory (NWI) classification scheme (Cowardin et al. 1979). The NWI labeling system takes into account the fact that a wetland may be comprised of more than one cover type. Therefore, labels are assigned to the two most abundant cover types in the wetland (each with at least 30% areal coverage) in the fields 'Class1' and 'Class2,' with 'Class1' always being the taller structure (i.e. FOx, as a forested wetland would always be listed before SSx, a scrub-shrub wetland). Class designations were further modified by codes for hydrologic regime or other special conditions ('Regime' and 'Special' fields, respectively). Before transferring the delineations and labels to Mylar overlays on 1:24000 orthophoto base map quadrangles using an IIS Stereo Zoom Transfer Scope they were examined by a second photo interpreter as a first QA/QC check.

Separate mylar overlays of the wetland labels were transferred from the photos onto sheets of mylar with a Kail Reflecting Projector using the 1:24000-scale wetlands overlay as a base. At this time the wetland polygons on the Mylars were compared with the photo delineations as a second QA/QC check.

The wetland polygon mylars were scanned as TIFF images and vectorized using the software R2V (Able Software Co., Lexington, MA). Vector lines for each file were printed and compared with the mylar polygon overlay. Labels were digitized onto the polygon coverage and sections of the full NWI label were entered into separate fields in the polygon attribute table (data fields: System, Class1, Class2, Regime, Special1, Special2, and Special3). Adding labels to the polygon coverage was used as the final QA/QC check because it allowed for missing or extraneous lines or polygons to be discovered and corrected. After the labels were checked against the original NAPP photo overlay labels, the digitized wetlands data files were considered complete (for additional QA/AC measures see Appendix 6).

The wetlands of the Carry Falls Reservoir Quad, which includes area in both the St. Regis and Raquette River watersheds, were not mapped on the same time frame as other quads within the St. Regis watershed due to problems with availability of adequate aerial photography. Both the St. Regis and Raquette portions of the Carry Falls Reservoir Quad have now been mapped, allowing for complete wetland coverage of the entire St. Lawrence watershed.

State Land Unit Management Planning
Approximately 32 percent of the land in the project area is managed by the State, in 14 separate unit management planning regions. Under Governor Pataki's State Land Initiative, the New York State Department of Environmental Conservation (DEC) is currently in the process of drafting Unit Management Plans for each of the State land units in the Adirondack Park; once the plans have been drafted, the Adirondack Park Agency and the DEC work cooperatively to guide the plans through the approval process. This comprehensive planning effort is one of the major foci of State land managers in the Adirondacks at present, and the process of drafting high-quality Unit Management Plans (UMPs) depends upon the availability of good habitat and ecological data. A major aim of this project was to produce data layers that would be of use to the DEC in preparing UMPs for State land units in the St. Lawrence watershed.

Wetland data layers were prepared for three of the State land units in the St. Lawrence watershed currently involved in the UMP process, the St. Regis Canoe Area, the Bog River Flow Management Complex, and the Raquette Boreal Wild Forest. Wetlands maps were provided to the DEC in two formats:

The Raquette Boreal Wild Forest wetland maps aid an effort underway by the Natural Heritage Program to inventory habitats and ecosystems in the area. Summaries of the wetlands data were also supplied to the DEC, and implications for management were discussed.

Continue to next section of St. Lawrence II Report: Resultsand Discussion
Return to table of contents
References Cited