Matanuska-Susitna Wetland Mapping

Cook Inlet Wetlands


Areas mapped as Wetland/Upland complex support wetlands mixed with uplands, but at a scale too fine to delineate. Wetlands cover at least 30% of the area. This designation is used to flag marginal areas. Although a majority of the area might qualify as upland, wetlands also occupy a significant portion, and wet conditions are to be expected not far from the surface. Different names indicate the percentage of the area occupied by wetland. For example, WU60 indicates that about 60% of the polygon's area is covered by wetlands. The most common wetland type occurring in wetland/Upland Complex polygons are Discharge Slope wetlands. These wetlands often occur over a mineral soil and are forested with paper birch and sometimes white spruce. They can be difficult to identify, and experts may even disagree about some spots, especially later in the growing season when the seasonally high water table is at its lowest. A large forested area near the headwaters of Wasilla Creek is mapped as WU. When a perplexing site is encountered an attempt is always made to classify it into another category, and reserve WU for the most difficult cases.

A Wetland / Upland Complex near Chignaki Pond, north of Wasilla.


Table 1. Wetland Indicators in Wetland/Upland Complexes.

Map Component

Peat Depth (cm)

Water Table (cm)

Redox features (cm) Saturation (cm) pH Specific Conductance µS/cm Plant Prevalence Index


16 (32) 70 (26) 28 (23)  
2.66 (28)


Numbers in paraentheses indicate number of samples.

Water table depth is a one time measurement. At sites with seasonally variable water tables this measurement reflects both the conditions that year, and the time of year. If no water table was encountered, no value was recorded; use number of samples to aid interpretation. Deeper average water tables idicate higher variability.

pH measured in a shallow pit with a YSI 63 meter calibrated each sample.

Plant Prevalence Index calculated based on Alaska indicator status downloaded from the USDA PLANTS database, which may use different values than the 1988 list.

Table 2. Common soils and plant communities found in Wetland/Upland Complexes.

Map Component







Picea x lutzii / Salix barclayi / Calamagrostis canadensis

Calamagrostis canadensis - Equisetum arvense

Picea x lutzii / Equisetum arvense - Calamagrostis canadensis


Wetland / Upland Complex Map Units:

WU: Wetland at least 30%, but total percentage not estimated

WU40: Wetland component approximately 40%.

WU50: Wetland component approximately 50%.

WU60: Wetland component approximately 60%.

WU70: Wetland component approximately 70%.

Table 3.Summary of Matantuska-Susitna Valley and Cook Inlet Wetland / Upland Complexes (percentages of all wetlands). Wetland / Upland percentages were only estimated in part the MatSu Valley.
Map Unit MatSu N Cook Inlet N Mat Su Hectares Cook Inlet Hectares Mat Su % Polygons Cook Inlet % Polygons MatSu % Area Cook Inlet % Area
WU 14 238 454 7996 0.21 0.99 1.06 4.26
WU40 1   5.2   0.02   0.01  
WU50 2   5.2   0.03   0.01  
WU60 4   62   0.06   0.15  
WU70 2   26   0.03   0.06  


Do I Need a Permit?



1987 Delineation manual

2007 Regional AK Supplement

Methods, metadata

Maps and posters

Mike Gracz
Kenai Watershed Forum 
PO Box 15301
Fritz Creek, AK  99603
13 January, 2010