26 January 2005 16:22
Although the bulk of this technical report details the methods used, a brief section near the end highlights and discusses findings. This report was prepared as a paper document, on file at the City of Homer Planning Department.
Mapping Classification
More than just wetland boundaries are outlined; different types of wetlands are mapped separately. In order to effectively manage wetlands, names locally relevant to the function of each type of wetland were created. Recent research has suggested that names relevant to function are based on two things: the surrounding landscape and hydrology, how water moves across the landscape (Brinson, 1993; Brinson, et.al., 1995, Tiner, 1997).
With this in mind, a mapping classification was developed in 2002. This classification relies on the knowledge we gained while mapping soils and describing plant communities over a 900,000 acre project area on the western Kenai Peninsula during the previous five years. The mapping classification uses a hydro-geomorphic approach tailored to the local landscape. The geomorphic portion of the classification involved subjectively choosing and naming common ecosystems, which were assigned based on dominant landforms. Examples of landforms/ecosystems include: Depression, Relict Glacial Lakebed, Kettle, Headwater Fen, Discharge Slope and Riparian. Ten ecosystems have been named.
The hydro- portion of the hydro-geomorphic classification uses depth to the water table to further categorize Ecosystem names. For example, a small pond connected to a navigable water body is classified as a Kettle Ecosystem wetland with a water table above the surface. It is named K1: “K” for Kettle Ecosystem and “1” indicating a water table above the surface. A woodland Kettle wetland (deeper water table) is named K4. Plant communities often indicate depth to water table.
The mapping classification is open, that is, the number of map units is not set; they are made up of combinations of basic building blocks, the map components. Map components are basic divisions within each ecosystem, and are used in combinations, following specific naming conventions, to devise map unit names. The number of potential map unit names, using the map components and the naming rules, is much greater than the number actually encountered on the landscape, as some component combinations are unlikely.
NAMING CONVENTIONS:
If more than two components are present, but not in sequential order, then a complex is named separately. Complexes are named on a case by case basis, and must represent common wetland units. Three complexes have been named: LBSF, the lakebed strang-flark complex; DWR a relict Glacial Drainageway complex common along underfit streams; and Tr a Tidal ecosystem complex common at the estuaries of smaller streams. (The term ‘complex’ is also used to describe a mixture of two components).
The final computer mapping file of Homer wetland polygons contains hyperlinks for each polygon to its corresponding map unit description. Federal Geospatial Data Committee compliant metadata describe file creation methods and provide contact information. You may download that zipped ArcView 8.x layer file here.
Wetland delineation and photo interpretation
We used techniques learned while mapping soils on Natural Resource Conservation Service’s (NRCS) Western Kenai Soil Survey. Uncorrected stereo-paired 1:12,000 color aerial photography flown in August 2003 was used under a stereoscope, with acetate overlays and an ultra-fine point "Sharpie" marker to delineate initial wetland polygons. Wetland polygons are relatively homogeneous areas that fit into the mapping classification.
Extensive local knowledge from over six years of field mapping experience informed the aerial photo interpretations and linework, done entirely by K. Noyes. A minimum polygon size of about 3/4 of an acre was used, although some smaller polygons were delineated.
After initial polygons were delineated on acetate overlays, the lines were transferred, using a 0.5 mm plastic pencil, onto frosted mylar overlain onto quarter-quad-centered, geo-rectified film positives of the same color aerial photography. The mylar and film positives were both pre-punched, and a 7-hole register bar was used to ensure exact alignment. Once the lines were transferred, they were re-traced onto a second pre-punched frosted mylar sheet, again using plastic pencil and register bar, creating a final, clean product ready for scanning.
The clean linework was shipped to Resource Data Incorporated, in Anchorage Alaska, where it was scanned, vectorized, edge-matched and cleaned up. The result was an ArcView 3.x (ESRI, Redlands, CA) Geographic Information System (GIS) shapefile.
The shapefile was overlain onto the digital version of the aerial photography in ArcView, where the polygons were assigned map units using the classification system outlined above. Map unit assignments were made while consulting stereo-paired aerial photographs from 2000, 1975, and 1951-52 under a stereoscope, and the 1970 soil survey.
Map units were named based on what was interpreted as the pre-settlement condition of a site. This is not typical mapping protocol, but the combination of old aerial photography (1951-1952 and 1975), a detailed soil map completed in 1970, and the limited settlement impact prior to 1970 allowed confident interpretation of the pre-settlement status of almost every wetland. Mapping pre-settlement conditions will allow an accurate assessment of what percentage of which wetlands has been impacted by settlement at any given time.
During the interpretation, two additional map unit suffixes were created to describe wetlands that were affected by humans (-d and -c). A 'd' suffix indicates a wetland in which the pre-disturbance character could be determined, but now had disturbance affecting more than about 50% of its surface. For example, a woodland Kettle ecosystem wetland (K4) that had now been disturbed over more than about 50% of its area was named K4d.
The 16 wetlands where pre-settlement character could not be determined and that were disturbed are named 'DISTURB'. One wetland was named ‘Dd’, a disturbed Depression Ecosystem wetland of unknown pre-settlement type.
The 'c' suffix was used for human-created wetlands. These are 7 small ponds, Beluga Lake and some of its fringe, and the Bridge Creek Reservoir.
During the summer of 2004 we attempted to visit and photograph all polygons to check for naming and delineation accuracy. To aid ground-truthing, field images were prepared by overlaying numbered polygons onto digital imagery (the same 2003 imagery used to delineate the polygons). The field images with numbered polygons were printed on matte photo paper at 1200 dpi at 1:10,000. A corresponding data sheet was prepared to track changes and record photograph numbers.
A map-able wetland unit is one where the vegetation pattern is relatively homogeneous on the ground and discernable on the 1:12,000 scale imagery. Map units are frequently based on general hydrologic character (depth to ground water), which is typically reflected in vegetation type. For example, sedge types frequently occur on areas where groundwater is at or very near the surface, and shrubby peatlands occupy areas of deeper groundwater.
Only wetland polygons were mapped. Delineation did not formally follow US Army Corps of Engineers Wetland Delineation Manual procedures (Environmental Laboratory, 1987), but we mapped with those procedures in mind, and a soil probe to look for redoximorphic features or water table depth where wetland status was uncertain.
Wetland delineation is not always clear-cut, even when adhering to the standards in the Army Corps Manual. Some areas are wetter some years than others, others just barely meet criteria. On any mapping project, marginal areas are always encountered. When we encountered a polygon with a marginal wetland status, we erred in favor of calling the polygon a wetland.
Many wetlands are obviously wetlands, with a deep peat layer and/or a water table at or very near the surface. Marginal sites tend to be forested and often occupy slope break positions. Marginal sites are common around Homer. The map unit descriptions for these marginal types clearly indicate that their wetland status should be examined carefully if an extremely accurate wetland boundary needs to be established.
The 1970 soil survey was relied upon to help us mapped disturbed areas.
During a field visit, if the map unit name was accurate, it was recorded, otherwise it was re-named. A photograph was taken using a digital camera.
If the linework was not accurate, and included more than one unique map-able unit which covered more than 10% of the polygon area, a line was drawn on a field image to split the polygon; if the polygon was contiguous with another polygon of the same map unit, a note was made to join them.
If the polygon was not a wetland a note was made to delete it. If additional wetlands were found they were drawn on the field images. Polygon numbers are tracked to avoid assigning duplicates.
After field visits, all data were entered into an MS access database, and error checked by printing the entered data, checking it against the raw data on the data sheets and re-entering any corrections.
Lines drawn in the field on the printed aerial images were used along with notes on datasheets to correct linework, heads-up in ArcView, and re-number polygons, if needed.
Digital photographs were downloaded and renamed to match polygon numbers, using lower case letter suffixes to identify multiple photographs of the same polygon.
Polygon editing was done in ArcView, using a link to MS Access to locate and manage polygon records. The MS Access database file was edited to incorporate new fields linking polygon number to digital photograph filenames and ecosystem and map unit description files. After those edits, the MS Access database file was exported and the new fields attached to the shapefile (420Kb, zipped).
The photographs and descriptions are stored on a Kenai Peninsula Borough server and are available on the world-wide-web at www.kenaiwetlands.net (and on a CD provided to the City of Homer Planning Department). American Geospatial Data Committee compliant shapefile metadata are available at http://www.kenaiwetlands.net/Homermetadata.htm.
The ecosystem, map unit and plant community descriptions were generated in HTML using our field notes, and data and NRCS soil survey data. The descriptions contain links to plant lists, official soil series descriptions, literature, wetland plant indicator status and other useful information.
A preliminary GIS map has been successfully tested using ESRI's Internet Map Server software, on the Kenai Peninsula Borough's website. There, a user with internet access and a web browser can manipulate a map containing satellite imagery to retrieve parcel ownership information. The wetland layer will be added soon.
A user with ArcView software can download a shape- or layer file that contains URL fields linking each wetland polygon to a picture (for polygons we photographed) or a map unit description.
Integration with Western Kenai Wetlands Mapping
The wetland mapping completed for the City of Homer was incorporated into the wetland map of the Western Kenai Lowlands. Polygons at the City Limits were merged and edited, and since City of Homer linework was at a finer scale, those polygon names and boundaries were used as fully as feasible.
Tidal wetlands were also mapped as part of the Homer Wetlands Delineation Project. They were not included in the final product to the City, because a more detailed map of tidal wetlands was concurrently prepared by the Kachemak Bay Research Reserve.
The tidal wetland polygons generated and filed-checked by Kenai Watershed Forum are still available as part of the larger Kenai Lowland project. That project is available at www.kenaiwetlands.net, and a download of the GIS shapefile is available there (7.4 Mb, zipped).
The mapping classification relies on a plant community classification, which was created outside of the Homer mapping project. Because the Homer classification and map uses this classification, its methods are described below. The plant community data collection also included the collection of environmental data, such as depth of peat and depth to the water table, and the methods of collecting those data are also described below.
Most of the plant cover data were obtained from the Natural Resource Conservation Service (NRCS). Between 1997 and 2004 NRCS collected soils and vegetation data as part of their Western Kenai Soil Survey. Data from 22 Hydro-Geomorphic Modeling (HGM) plots collected in 1997 along the lower Kenai River watershed were also used (Hall, et. al. 2002). The authors collected data from 100 plots to augment soil survey data, while working for the Alaska Natural Heritage Program (NHP) during the summer of 2001; these methods are described below.
Ocular estimates of percent cover by species are recorded using a plot-less reconnaissance method. Because plants cover the ground at different spatial scales, a homogeneous area was sampled with attention to these different scales. For example, tree cover is more appropriately characterized using a larger plot, while forest floor herb cover can be adequately characterized with a smaller plot. These different scales of occurrence are taken into account when the worker chooses an area to represent plant cover. Unlike using a fixed sized plot, where an alder may or may not occur, the sampler can record alder cover over a larger area, and use a smaller area to represent trailing raspberry cover, as long as the entire area is relatively homogeneous.
Plant cover is recorded to the nearest 1% for values between 1 and 7%; values greater than 7% (up to 15%) are recorded as 10%, then values are recorded to the nearest 10% up to 100%. Care is taken to assure that total cover sums to at least 100%; if observation indicates that cover is obviously much greater than 100%, then the sum should reflect the plants in the plot.
Plant stratum and life form are recorded using the categories of: tall, medium, short and dwarf; and herb, grass, shrub and tree, respectively. Tall trees are greater than 40 feet tall and medium trees greater than 15 feet. A stunted tree category is also used for trees obviously suppressed or stunted, otherwise a regeneration category is utilized. Shrubs are tall if greater than 10 feet tall, medium if greater than 3 feet, and low if greater than 8 inches. Other shrubs are recorded as dwarf. Herbs are tall if greater than 2 feet, medium if taller than 4 inches; if shorter, they are dwarf herbs. Only two grass categories are used: tall if greater than 2 feet and medium if less.
These are the same protocols that NRCS biological technicians used when collecting the data we obtained from the Western Kenai Soil Survey. Plant names follow the 2000 version of the PLANTS database (http://plants.usda.gov).
We measured three of four environmental parameters at each site: 1) water table depth, or 2) depth to modern (versus relict) redoximorphic features; 3) pH and 4) depth of the organic horizon. Water table, organic layer, and redox feature depths were all measured to the nearest centimeter using a metal tape. PH was measured using a YSI 63 pH/conductivity meter. The meter was 2 step calibrated (pH 4.04 and 6.86) daily, using the methods outlined in the meter’s manual (YSI, 1998). When measuring pH in the field, the probe was placed directly into water in a hole dug below the water table and the value recorded when the reading stabilized for 30 seconds.
Each site location was marked on an aerial photograph.
Plant communities
The largest portion of data used in this analysis originated with the Natural Resource Conservation Service (NRCS) Western Kenai Soil Survey, on which the primary author of this project was instrumental in implementing plant community data collection techniques. Various widely inclusive criteria were used to filter the entire soil survey dataset for plots that might be considered wetlands. Wetland plots are those that meet the criteria outlined in the Army Corps of Engineers Wetland Delineation Manual (Environmental Laboratory, 1987). Soils with modern redoximorphic features or a water table closer than 31 cm to the surface; organic horizons greater than 20 cm thick; plots in units mapped as aquic suborder soils, and sites subjectively determined to flood “commonly” to “frequently” were retained.
Those data were evaluated for completeness, especially during years where non-botanists/ecologists collected plant data unsupervised. Unreliable and incomplete data were discarded. Reliable and complete data were printed and error checked against raw data, and corrections re-entered into the database.
We used inclusive criteria- i.e. some of the plots we included in the summary analysis do not meet the wetland criteria established in the 1987 manual. Retention of some plots that might not be considered wetlands is useful for bracketing the classification, but can lead to misleading determinations of how well any individual plant community might indicate wetland conditions.
The best example of this pitfall is the Lutz spruce / Oakfern – Bluejoint community. Field observations indicate that this plant community is most frequently found on uplands. However, in this analysis, two of the three samples occupied by that community were found on marginally wet soils (with redoximorphic features within 16 cm of the surface), and all were found within a soils unit mapped as an aquic suborder. A summary indicating that 2/3 of the samples containing this community are wet would be misleading, as the sample itself reflects only the wet end of the continuum the community spans.
Therefore, plant community fidelity to areas considered to be wetlands using the techniques outlined in the 1987 manual is not perfect. Some 'wetland' plant communities will be found on uplands, while some 'upland' communities will occur on jurisdictional wetlands. As we used liberal criteria to avoid missing any communities that sometimes occur on wetlands, most of the errors should be of the first type, i.e. some of the communities described will occur on uplands.
Additional data were obtained from the HGM (Hydro-Geomorphic Modeling) effort conducted in the lower Kenai River watershed in 1997 by an interdisciplinary team funded by the US Environmental Protection Agency (EPA). The HGM data (Hall, et. al., 2002) were evaluated for completeness and reliability, recoded to match the USDA PLANTS database (which NRCS and Heritage Program field crews used) and error checked, with corrections re-entered into the database.
To determine plant community dominants, these three plant cover data sets (NRCS, HGM and NHP) were combined and run through the computer program TWINSPAN (Two Way INdicator SPecies ANalysis; Hill, 1979) as part of the PCORD (McCune and Mefford, 1999) software package. TWINSPAN is a polythetic, divisive matrix algebraic solution that arranges a matrix of items and their attributes, then divides the items into groups based on maximum differences of attribute presence and abundance. It works well when, as in much plant ecological data, many of the matrix values are zeros (i.e. few plants occur in all plots).
TWINSPAN was run several times on varying subsets of the data (e.g. all the plots with spruce (Picea spp.) cover greater than 10% were run together), and iteratively, with outliers removed on successive runs. Once the primary plants responsible for group divisions became stable, the data sheets were sorted into initial divisions defined by their occurrence (all the sitka alder plots, for example).
Data sheets from each initial division were sorted into final groups within each division using our ecological knowledge and indicator plants identified by TWINSPAN. These final groups are defined by the occurrence of co-dominant or sub-dominant plants (all the sitka alder plots with field horsetail (Equisetum arvense) for example); or the tufted bulrush (Tricophorum caespitosum) plots with significant dwarf birch (Betula nana). The final groups became the named plant communities.
Communities are named systematically. The plants in the tallest layers are named first, within a layer the most frequent plants are named first, and the more abundant plants that occur at the same frequency are named first. Plants in different layers are separated by slashes, plants in the same layer by dashes. The layer order proceeds with trees followed by shrubs followed by grasses and sedges followed by herbs. When a tall sedge is significantly more abundant than a dwarf shrub, as in the Tufted bulrush / Sweetgale or Tufted bulrush / Dwarf birch communities, the sedge is named first. One subset of communities with generally low vascular plant cover and high (sphagnum) moss cover is named with sphagnum moss (in the 'ground' layer) first. Common names generally follow the USDA PLANTS database.
Frequency of occurrence and average cover of dominant plants (greater than 10 percent cover) were tallied. Environmental data (depth to water and/or redoximorphic features; pH, and depth of organic horizon) were also summarized using average, minimum and maximum values found at the soils holes dug in each plant community. The descriptions were written using field notes and sketches, the knowledge we gained working in these ecosystems, and the plant and environmental summaries described above.
Dot maps of the sites visited in each plant community were also assembled (from NRCS and NHP aerial photo location marks) and included in each plant community description.
If subsequent field visits indicated new plant communities were needed, we queried the database to find any plots satisfying group membership (e.g. the Sweetgale- Dwarf birch / Water horsetail community was created by summarizing the plots with sweetgale (Myrica gale) and dwarf birch (Betula nana) cover > 10% that also contained water horsetail (Equisetum fluviatle)). Summaries of the other communities were not re-adjusted to reflect any loss of data caused by the creation of new plant communities. This loss probably would not have changed those summaries significantly.
No attempt was made to shoehorn every plot into a final group (plant community). Many plots are unique and form a diverse 'unclassified plots' group.
Ecosystem and Map Unit Descriptions
Ecosystem and map component descriptions were created using plant community summaries, along with field notes and observations, environmental data and photographs.
Each NRCS soils hole was assigned a wetland map unit based on its location in a wetland polygon. The data collected at these holes were used to summarize wetland environmental information (depth to water table, organic layer thickness, and depth to redoximorphic features) for each map component.
Especially important to the ecosystem descriptions are field notes taken at “type localities” where the dominant environmental gradients in each system are well defined. At these localities, plant and map component relationships to these gradients are described and are represented by artist drawings in the descriptions.
Findings
Wetland Occurrence and Frequency
Outside of areas influenced by saltwater tides, 414 wetlands covering 3795.9 acres of the City of Homer and Bridge Creek Watershed were mapped (37.3% of the land area). Three hundred ninety-five of them were visited and photographed.
Wetlands of some types occur more frequently than others (Table 1). Types are classified at two levels: Ecosystems and map units. Each Ecosystem contains several map units; map units are differentiated by vegetation, depth to the water table or physical characteristics.
Full descriptions of each Ecosystem and its associated map units are available on the World Wide Web at www.kenaiwetlands.net. Highlights are summarized below, with the most abundant map units in parentheses following a description of the Ecosystem they occur in.
Table 1. Acres of non-tidal wetlands in the City of Homer and Bridge Creek Watershed by Ecosystem and Map Unit.
For full Ecosystem and Map Unit descriptions, see www.kenaiwetlands.net.
|
Wetland Type |
Acres |
Wetland Type |
Acres |
Wetland Type |
Acres |
Wetland Type |
Acres |
| Discharge Slope | 1983.5 |
Miscellaneous |
591.1 |
Kettle | 404.1 |
Drainageway |
247.9 |
| SLA |
450.8 |
WU |
434.3 | K1c | 168.2 | DW42 | 147.4 |
| SL | 299.6 | DISTURB | 156.8 | K3d | 39.2 | DW3 | 23.5 |
| SLd | 176.0 | K34d | 37.6 | DW2-4 | 21.2 | ||
| SC | 127.3 | Riparian | 272.7 | K3 | 32.7 | DW34 | 13.6 |
| SLS | 86.1 | RB | 195.1 | K2c | 26.3 | DW3-5A | 13.0 |
| SAL | 72.1 | Reb | 41.5 | K34 | 21.7 | DW5A3 | 9.8 |
| SCS | 70.6 | Rt | 15.4 | K43 | 21.5 | DW24 | 8.5 |
| SM | 69.8 | Rel | 8.8 | K2-4d | 19.7 | DW1 | 4.9 |
| SCLd | 69.2 | Rea | 7.8 | K4 | 13.2 | DW5A | 2.4 |
| SLCd | 67.1 | RA | 2.7 | K32 | 8.8 | DW5 | 1.9 |
| SS | 60.9 | Reac | 0.9 | K23 | 6.6 | DW2 | 1.7 |
| SCSd | 58.4 | RBd | 0.3 | K1-3 | 6.5 | ||
| SSC | 58.0 | RAA | 0.2 | K4d | 3.9 | Depression | 76.7 |
| SSL | 49.9 | K1 | 3.7 | D43 | 22.3 | ||
| SLC | 47.7 | Lakebed | 161.9 | K23d | 1.8 | D4d | 13.2 |
| SA | 43.5 | LB6 | 38.8 | K21 | 1.3 | D4 | 11.0 |
| SCAd | 28.6 | LBSF | 33.8 | K2 | 0.3 | D43d | 8.8 |
| SCA | 21.5 | LB1 | 22.1 | D3 | 8.6 | ||
| SCL | 20.7 | LB4 | 15.6 | Headwater Fen | 28.1 | Dd | 3.1 |
| SLM | 20.4 | LB2-6 | 14.5 | H32 | 12.2 | D12 | 2.2 |
| SML | 19.9 | LB36 | 12.7 | H4 | 10.6 | D1-3 | 2.0 |
| SLMd | 18.9 | LB46 | 7.6 | H2-4 | 9.3 | D1c | 1.8 |
| SCd | 17.0 | LB25 | 6.3 | H34 | 6.9 | D32 | 1.0 |
| SMLd | 14.6 | LB64 | 4.9 | H23 | 6.4 | D2 | 0.8 |
| SAC | 9.7 | LB1-3 | 3.0 | H3 | 3.5 | D21 | 0.8 |
| SSA | 1.9 | LB43 | 2.6 | D3d | 0.8 | ||
| SLSd | 1.7 | D1 | 0.3 | ||||
| SAS | 1.6 | TOTAL WETLAND ACRES: 3795.7; 37.3% of the land area excluding Homer Spit. | |||||
Over half of the mapped non- tidal wetlands in the city of Homer and the Bridge Creek Watershed are Discharge Slope Ecosystem wetlands. These areas are primarily found below the bluffs where, due to the slope configuration and composition, precipitation remains at, or groundwater flows to near the surface. These areas are often wooded with Lutz spruce (SL), or covered with tall alders (SA), or bluejoint grass (SC).
Discharge Slopes store a large amount of water, especially after the onset of autumn rains. Based on a limited investigation by Coble Geophysical Services during the summer and fall of 2004 (report attached), if the water stored in these wetlands instead ran off over the course of a month, another stream about the size of Fritz Creek would be needed to accommodate that flow.
Wetland / Upland complex wetlands (WU) could occur in any Ecosystem, but are typically areas where Discharge Slope wetlands occur in a patchy mosaic with intervening areas of upland. The Discharge Slope wetlands within the WU complex are too small to map individually at the scale used.
Wetlands mapped DISTURB can occur in any Ecosystem, and are those whose pre-disturbance character could not be determined. These wetlands have been disturbed for a long time (most of the area mapped as DISTURB is the airport runway), because if the pre-disturbance character of a wetland could be determined from old aerial photography (1951-51; 1975) or soil survey (1970), it was mapped with a 'd' suffix.
Kettle Ecosystem wetlands are mostly surrounded by uplands (usually of glacial origin), but are connected to a navigable water body by other wetlands. The two human-created lakes (K1c), Beluga Lake and the Bridge Creek Reservoir, form most of the area mapped as Kettle wetlands.
Riparian Ecosystem wetlands are streams and their associated wet stream banks. In Homer, most streams are moderate gradient, with riffles dominating a riffle and pool structure (RB). Many have very narrow wetland zones at their margins.
Relict Glacial Drainageway wetlands occur where peatlands now occupy valleys that contained large glacial meltwater streams during the ice ages. The most common are in important moose foraging habitat, the wide, sedge- and bluejoint-dominated margins of Palmer Creek (DW42), the creek flowing into Beluga Lake. Relict Drainageway wetlands are typically peatlands that are very wet year-round.
Around Homer, Relict Glacial Lakebed wetlands are primarily wooded peatlands (LB6). They occur atop a terrace between Palmer Creek and the bay, including the gull and tern nesting habitat along Kachemak Drive. The water table in these wetlands fluctuates more than in Relict Glacial Drainageway peatlands, and they support slower near-surface groundwater flow.
Depression Ecosystem wetlands are scattered throughout town, most are shrubby woodland peatlands (D43), and many have been excavated and built upon. Depressions are surrounded by upland, and after a recent US Supreme Court ruling are currently not under the jurisdiction of the Clean Water Act, although they are important bird habitat and groundwater recharge areas..
Headwater Fens are more important than their limited area might indicate. The are small kettle-like peatlands in headwater basins of streams. Because of their headwater position any impact to them will be felt down the entire stream. Many of them lie at sources to the Bridge Creek Reservoir, Homer's drinking water supply.
Discussion
Now that Homer's wetlands have been classified and mapped, the process of creating a wetland ordinance can begin. Each wetland type provides an array of functions we value. For example, Relict Drainageways and Lakebeds provide important bird nesting and moose foraging habitat. Depressions recharge groundwater. Just below the surface, large quantities of water move slowly though Discharge Slopes into Drainageways, then into Beluga Lake and Slough. Development will create surfaces more impervious to precipitation, forcing flashier run-off events there. Impairment to riparian and in-stream habitat, insect populations, and water and sediment chemistry was found at 4.4-5.8% impervious surface cover in an Anchorage study (Ourso and Franzel, 2003). Finally, although Headwater Fens are small areas, impacts to them will affect a large downstream watershed including Homer’s drinking water supply.
Once a satisfactory assessment of the functions each wetland provides is made, an ordinance can be designed to maintain functions that would be impossible, or too costly to replicate.
Download final Homer area shapefile (420Kb- In ArcView8.x or 9 you'll need to point to the layer's data source, under 'properties', 'source' to view the full legend). Draft Metadata.
Download a QuickGuide to Kenai Wetland Ecosystems and Mapping Units (zipped html, 1.1Mb) or zipped Word 2000 format (799 Kb).
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Introduction and Key to Plant Communities |
| Contact: Mike Gracz Kenai Watershed Forum Homer Field Office Old Town Professional Center 3430 Main Street Suite B1 Homer, AK 99603 907-235-2218 |
26 January 2005 16:22 |
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