This document describes how the grid depicting Willamette River Basin LAND USE and LAND COVER circa 1990 (Version 121599), named EC90 was composed. Separate grid layers were developed first, then merged in a specific order to produce the final grid. Viewed as a vertical stack, the order of assembly is displayed in the table below: the uppermost grids retain their values, blotting out spatially coincident values of lower grids. This implements a precedence of themes which effectively leads to "changes" in the single theme layers. In particular, as the agricultural field layer is low in precedence, the layering leads to an effective decrease in some ag. field crops as compared with the original agricultural layer. For example, 79% of the area covered by agricultural nurseries (as originally defined) remains in nurseries while 11% is replaced by "natural shrub," 3% by "rural non-vegetated unknown," and 1.6% by "forest closed hardwood."
Each of the thematic grid layers are spatially aligned to the Basin DEM. The background and undefined cells are set to NODATA. The composite grid is similarly aligned to the Basin Digital Elevation Model (DEM), and is clipped to the Basin boundary. Its values correspond to the ERC LULC legend comparison.
UGB = Urban Growth Boundary; FSL = USFS Forest Sciences Laboratory, Oregon State University, Corvallis, Oregon; TM = Landsat Thematic Mapper; METRO = Portland Metropolitan area: RLIS = METRO Regional Land Information System; ODOT = Oregon Department of Transportation.
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and Source |
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Construction Script name |
| Major Roads
Source: dot97c |
19-21 | [dot97c, igds-level 50 => legend 19, igds-level 51 => 20, igds-levels 52, 53 => 21]
Level 50 roads are 3 cells wide; level 51 are 2 cells wide; levels 52-53 are 1 cell wide. (Level 50 represents interstate highways; 51 represents principal arterials; 52, minor arterials; 53, major urban collectors) |
roads19-21 | -- |
| Minor local roads within UGBs in counties other than Yamhill and Columbia Source: Taxassessor-collector parcel data |
21 | [taxassessor-collector parcel data]
Roads are described as spaces between taxlot polygons within the tax-assessor-collector data sets; these polygons are gridded with the number of cells representing the roads dependent on the polygonal description. This description is not available for cities in Yamhill and Columbia Counties because of the absence of digital tax-parcel data. |
ugbtaxrds | -- |
| Minor local roads within all UGBs intersecting Yamhill and Columbia Cos.
Source: dot97c |
21 | [dot97c igds-level 12 (local roads) clipped to UGBs]
Features in this layer are 1 cell wide. In the absence of taxlot data for Yamhill and Columbia, an alternate means is needed to represent the local roads within their UGBs. Comparison of dot97c igds-level 12 with the Eugene-Springfield taxlot data shows a good alignment with the taxlot right-of-ways that are roads. Thus, by using these ODOT data, we are confident that the treatment of roads in Yamhill and Columbia Co. UGBs will be consistent with those UGBs for which we do have taxlots and from which we obtain roads directly. |
dot21ugbyc | -- |
| Railroads
Source: dot97c |
18 | [dot97c, igds-level 18 (railroads)]
This is gridded 1 cell wide. When railroads and roads run side-by-side, and in close proximity, the gridded representations often overlay. The railroad layer was selected to lie "beneath" the roads grids so that the roads representation would be continuous. This means that the gridded railroad lines may disappear beneath the gridded roads in places. |
rr18 |
-- |
Channel, non-vegetated: inside mainstem of Willamette River Source: |
29 | [legend 26-28 (high, moderate, low density built) inside the ac1995p feature boundaries(see water below); TM classification byDoug Oetter, FSL].
This was extracted from the TM landcover so that "built" features within the Willamette River would be represented. Islands within the Willamette River (as defined by OSU coverage ac1995p) lie within this grid depiction, so that any "built" categories on those islands are given this legend category (29). "Built" landcover also occurs within the water of this river coverage. It is assumed that most of the occurrences in this category are gravel or channel bars, with some revetments, river-side roads, and, in the METRO area, bridges and piers. |
chan29 | chan29.aml |
| Water
Source: |
32-33 | [TM landcover water (legend 33) + ac1995p code <> 11 (legend 32) + rivreach_2 Strahler order >= 5 (legend 32).]
The TM landcover water was found not to represent rivers and streams adequately; the goal was to have major rivers that were likely to be wider than 15m continuously defined. The AC1995P polygon coverage was used to ensure that the width of the Willamette mainstem would be described adequately. (Islands were excluded from this representation and thus, the vegetation and other categories layered are depicted on these features). From the Rivreach_2 streams coverage, Strahler orders 5 and greater were gridded at 1 cell. Note that there are some inconsistencies between coverage ac1995p and rivreach_2 in the description of the mainstem. Thus, in some areas, a river loop (from rivreach_2) will add to the water area defined by ac1995p. In most places, however, the channel location defined by rivreach_2 is enclosed within ac1995p. The order invoked in creating this grid was TM landcover water (legend 33) over "AC1995p" (legend 32) over "rivreach_2" Strahler 5-7. |
wat3233 | wat3233.aml |
| Rural structures - outside ugbs Source: |
16 | [digitized from USGS 7.5 min. quadrangle maps]
These structures represent rural dwellings and rural structures, derived from scanned images of USGS 7.5 min. quadrangle maps. Note that some of the structures found in feature extraction (and represented in the grid rs16) fall beneath the roads, railroads and water features defined by the above layers. This occurs because of the gridding process and the explicit precedence of themes. |
rs16 | -- |
| Turf grass - inside ugbs Source: |
91 | [turf grass but primarily golf courses, from TM land cover category 91.]
This was separately extracted from the landcover so that it would overlay the urban landuse data obtained from taxlot information (see below). This was done because it was found through comparison of the taxlot information and the "parks" (landcover category 91) that almost all of the occurrences of "91" were of golf fairways. The civic/os category (above) will include public golfcourses but exclude private courses. It was decided that fairways would be considered unbuildable (not vacant) in the urban modelling, and that they should not be described as "commercial" (a common landuse designation given in the tax lot data to private country clubs, etc.) -- such a commercial designation with no employees would bias the commercial lands inventory used in the population distribution. Also, by explicitly designating fairways, this vegetative cover would be available for consideration as habitat within UGBs. By placing this layer above the taxlot data, private fairways will be identifiable. Outside the UGBs, the Turf Grass category will be present in existing conditions only as it is not masked out by any agricultural layers. UGB boundaries may expand to encompass turf grass areas outside of ugbs in the futures. However, this included turf grass is not given a sacrosanct standing-- it is assumed that turf grass outside UGBs in 1990 is primarly an agricultural crop and is only protected from development if it falls within a civic-open space area, see below. |
turf91u | -- |
| Civic and open space
Source: |
11, 24 and >=29 | [Data from taxlots, METRO/RLIS parks, ownerd; landcover from amended+disturbed TM data]
This grid contains the landcover for all parcels defined as civic open space within the WRB, areas that are off-limits to urban and rural development. Such areas are expected to be potential natural reservations within the WRB. These data include the following categories: public schools, buildings, colleges/universities, Federal, state, county and local parks, wildlife refuges, reservations, public and private cemeteries, Nature Conservancy reserves. The federal and state forests are EXCLUDED from this category as these forests are considered to be primarily focused on wood production. Inside the UGBs, the "built" categories are mapped as "urban built unknown" (legend 11); outside the UGBs, the "built" categories are mapped as "rural built unknown" (legend 24); the rest of the landcover within the civic/os area remains as defined by the amalgamation of the other landcover data (as layered below):the "natural veg", the ag. initial conditions (see below), the amended, disturbed, TM landcover data. This layer will have areas that coincide with taxlot defined areas (see "urban land use" below): this grid overrides those definitions. For example, in the taxlot definition, schools are defined as commercial; if these are public schools, civic/os redefines them to whatever the amalgamated landcover depicts. Thus, a school with a building and lots of playing fields will appear as partly "urban non-vegetated unknown" (11) and partly grass or forest etc. |
civic12 | civic12.aml |
| Urban landuse inside UGBs Source: |
1-4, 6, 8 | [from taxlots and census data, with vacant landuse set to nodata; low density 0-4 du/ac = 1, medium low density 4-9 du/ac = 2, med high 9-16 du/ac = 3, high >16 du/acre = 4; 6=commercial, 8=industrial]
For all counties except Yamhill and Columbia, the property class category of the tax assessor parcel data was remapped into residential, commercial, industrial and vacant. The residential parcels were then compared with the US census household density description to convert them to the appropriate hh density. Vacant lands were set to "nodata" so that the underlying landuses would "show through". Also, where parcels have undefined or ambiguous land uses or for land where no parcels are defined, the underlying landuses "show through". Note that UGBs within Yamhill and Columbia counties are not defined within this grid layer. |
ugbtaxblt | -- |
| Remapped built TM data
Source: |
1-4, 7, 11, 24 | [landuse derived from remapping TM landcover categories 26-28 inside UGBs and outside UGBs; census data].
Inside UGBs: built high density landcover was remapped to commercial/industrial = 7; built low and med densities were remapped to residential, and the Census household density grid was then applied to determine the residential density applicable to that residential grid cell. This technique was used primarily for those counties where taxlot data were not available (Yamhill and Columbia Cos.). This remapping is also used to represent the landcover built categories that fall within undefined or ambiguous parcels in UGBs with taxlot data (as described above). For parcels defined as "vacant" by the taxlot data, any "built" landcover is classified as "urban non-vegetated unknown" (11); similarly, for civic and open space areas. Outside UGBs: "built" landcover is mapped as "rural non-vegetated unknown" (24). The landcover built density categories may include fallow land, rock, bare ground, gravel pits, gravel bars, roofs, roads, etc. Here, it is assumed that the rural structure data, the ODOT roads, etc. (as described above) are better descriptors of the land uses we wish to isolate. Everything that is then left over after these land uses blot out the landcover "built" is set to "rural non-vegetated unknown". Note that gravel pits and mines will most likely be in this category (except for any that fall inside the mainstem Willamette River coverage, as described above). |
bltremap | bltremap.aml |
| Conifer, deciduous, and mixed forests, flooded marsh, natural shrub
Source: |
51 - 62, 89, 87 | [data from TM landcover data refined by disturbance layer/FSL and amended landcover]
These data represent vegetation in the amended+disturbed+TM landscape that is retained in place of spatially coincident ag. cover (below). All forest classes, natural shrub, and flooded marsh pixels are selected. "Natural grass" is not retained as its classification is of low confidence. |
vegaboveag | vegaboveag.aml |
| Agricultural lands
Source: |
66-68, 71-73, 83, 85, 90, 92, 93, 95 | [data from John Bolte and Patricia Berger, Bioresources Engineering, OSU]
Agricultural cover crops as described by Bolte & Berger in their 1990 coverage (Version 3a, dated 12/6/99). This is the starting condition used in the agricultural modelling. |
ec90ag | -- |
| Amended TM landcover | 49 | Replacement of landcover data defined by TM analysis (refined by forest disturbance layer, see below) due to low confidence in original classification: orchards within UGBsare reclassified here into the more general "urban tree overstory" | amendtm | amendtm.aml |
| Forest Disturbance
Source: |
56 | [data fromWarren Cohen,et al, FSL]
Areas of forest disturbance from 1972 to 1988 that introduce conifers of age 0-20 years; water, "turf" inside ugbs, and any built categories from TM data have precedence over the disturbed forest category. |
disturb72-88 | -- |
| Landcover TM
Source: |
26-28, 33, 39-40, 42, 51-62, 73-93 | [fromTM landcover data, Doug Oetter, FSL]
Remote-sensed landcover from TM data with classes renumbered to match the master LULC legend. This is the 40-class version which includes conifer forest age classes. |
lc90_4 | -- |