Wetlands were mapped at 1:24,000 (2007) & 1:18,000 (2008) for use as a planning tool in the Matanuska-Susitna Borough. In 2007, wetlands in the Core Area were visited in the field before they were delineated. In 2008, in the Big Lake watershed, a portion of the Little Susitna watershed and the Knik-Fairview area (fig. 1), they were delineated, then field checked. In 2009 an additional area will be mapped following 2008 methods (west of Big Lake south to Point Mackenzie, and east of the Matanuska River in the Butte area).

2007

In 2007, field sheets were printed at 1:12,000 on 81/2" x 11" paper showing National Wetland Inventory (NWI) wetland boundaries (Hall, et al 2001) and Natural Resources Conservation Service (NRCS) soils polygons with greater than 85% hydric soils (NRCS, 1995). The field sheets guided site selection, and 132 polygons were visited during two field trips, for data collection and mapping classification assignment.

At the sites, plant cover, soils, and water chemistry data were collected. Plant cover was collected by estimating total cover by species in 10% categories over homogeneous areas of appoximately 10 square meters. Lareger plots were used where vegetation pattern idicated, such as in forests. Plants covering less than 7% were estimated to the nearest 1%, those less than 0.5% were recorded as "T" and entered as 0.1%. Depth to the water table and saturation was recorded to the nearest cm, as was depth to redoximorphic features, if encountered. Most wetlands are peatlands, and the depth of peat was measured using a 187 cm dutch auger. If the peat was deeper, we recorded the maximum depth reached, which could be a little longer than the auger. A photograph was taken and the mapping unit assigned, with notes on polygon boundary changes, if needed, drawn on the field sheet.

During the second field trip, pH and specific conductance (25 degrees C) were measured in surface water, or a shallow pit using a YSI 63 meter. The meter was calibrated twice daily, and cleaned frequently following YSI procedures (YSI, 1998).

After the field trips, wetland boundaries delineated by NWI using 1996 stereo-paired aerial photographs were transferred with interpretation, onto frosted mlyar overlying 24" x 30" printed transparencies of 2004/2005 USDA NRCS digital ortho-rectified quarter-quads (DOQQs) using a plastic pencil, and stereoscope on a light table. A five pin register bar was used to align the mylar with the DOQQs, which had been printed with labeled tic marks generated in ArcView 9.2. Interpretation involved using NRCS delineated hydric soils with greater than 85% polygon coverage, and recent field experience. The linework was neatly retraced onto a second frosted mylar, then sent to Resource Data Incorporated, in Anchorage for vectorization and export to ArcGIS 9.2 shapefile.

Shapefile polygons were assigned mapping units using recently acquired field data, and NWI and NRCS polygons as guides. The mapping units are described elsewhere (see MatSuwetlandsmetadata.htm, or MUSummary.htm). Two new wetland ecosystems were described. The first represents peatlands found in depressions between Houston and Palmer, in the area of precipitation deficit. High specific conductance and pH values of surface water in these peatlands indicate strong groundwater discharge. To account for the strong shallow groundwater connection, these isolated peatlands were named "Spring Fens". The second new wetland type was named Tide Influenced Drainageway. They occur along Knik arm, and are affected by the highest tides of the 18.6 year tidal cycle.

2008

The wetland shapefile was created and attributed before field visits. The same procedures were used as in 2007, except the stereo-paired photos were flown during the autumn of 2005 at 1:18,000; and the 24" x 30" DOQQ transparencies were printed at 1;18,000. Initial polygon boundaries were delineated using an ultra fine sharpie on Clearlay® taped over the aerial photos. Polygon delineation was guided by NWI and NRCS polygons, as described above, and previous field experience. These lines were then transferred to frosted mylar and digitized as in 2007.

In 2008, field sheets consisted of numbered, newly delineated wetland polygons rather than NRCS and NWI linework. These were used to guide site selection and assist in assigning data to wetland polygons. Four field trips were made in 2008, with 442 polygons visited.

In addition to the data collected in 2007, in 2008 we were able to collect peat depth to about 497 cm, with the use of auger extensions. We also collected 40 water samples for cation analysis. Peat was described in more detail using gross stratigraphic changes and NRCS categories of: sapric, hemic, and fibric. Additionally, full "Wetland Determination Data Forms" produced in the Alaska Regional Supplement (USACoE, 2007) to the 1987 wetland delineation manual (USACoE, 1987) were completed for most sites.

Water samples were collected from the surface at 40 sites, but also from a depth of 50 cm at eight sites. Water was collected into a pre-sterilized and sealed 250ml polycarbonate bottle, then filtered into 30ml polypropylene sample bottles through either a 0.2 micron filter using a syringe, or a 0.45 micron filter using a peristaltic pump, depending on sediment quantity. Surface water was often collected directly into the syringe. A few drops of ultra-pure nitric acid were added in the field and the samples kept cool. Samples were sent to the Heroy Geological Laboratory at Syracuse University for analysis.

pH and specific conductance were measured in the field using a YSI 63 meter. Measurement of samples collected from 50 cm was accomplished by pumping from a shallow piezometer into a 100 ml polypropylene graduated cylinder through a 0.45 micron filter using a peristaltic pump. The YSI 63 was calibrated between each sample and cleaned daily.

The shapefile was edited to reflect field findings. The 2007 and 2008 shapefiles were combined into a single file. Adjoining polygons were edge-matched heads-up in ArcView.

Contact: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Kenai Watershed Forum PO Box 15301 Fritz Creek, AK 99603 907-235-2218 2 April, 2009