Longitudinal Patterns - Human Systems
A. Holder
D. Hulse
Relationship of Human Presence to River Restoration
Public Land and Potential for Restoration
The presence of people is an important consideration in prioritizing areas for river restoration. The figures on the facing page show the varying
densities of population, rural buildings, and roads per 1 km floodplain slice,
which together provide an impression of the density of human presence
along the historical floodplain of the Willamette River. The amount of public
land per slice is also shown, another consideration in the availability of land
for restoration.
To use the human presence data as factors in prioritizing river restoration, it is important to acknowledge that different areas have different levels
of long-term investment. Certain places may have a lower commitment to
staying developed than others—thus they have a higher “reversibility” of development, and may be more available for restoration. Other areas may have
a lower reversibility, but the potential gain from restoration may merit the
change. There is a wide spectrum of capital investment and land use commitment, so each parcel of land considered for restoration must be individually
evaluated in terms of that spectrum.
These measures of human presence define one part of restoration opportunity mapping. The other part, as described on previous and subsequent
pages, compares these constraints with maps delineating areas of greatest potential ecological response. The ideal locations are those where constraint is
low (low human presence or high reversibility) and potential gain in ecological response is high.
The public land data come from a composite of ownership information,
derived from several sources. The primary source was county taxlot maps,
which provided the bulk of the identification of public lands, as well as the
lot delineations for lands identified as public by other sources. In the Portland Metro area, the RLIS data set (developed by the Metro Data Resource
Center) provided additional detailed information, and filled part of the gap
left by the lack of digital taxlot maps for Columbia County. Other sources
used to identify public lands and cross-check the main sources are ownership
maps developed by the BLM, Mt. Hood National Forest, and Willamette National Forest; the Bio-management digital map developed by Defenders of
Wildlife; and the USGS 1:24,000 topographic maps. Where the various
sources contradicted each other, the most recent and/or most detailed information was used. The final public land map shows state, county, and city
parks, utility land, DEQ easements, state forests and national forests (though
none in the floodplain), wildlife refuges, research natural areas, and schools,
among other miscellaneous public land types.
Two ways of viewing the amount of public land are graphed on the facing page – the percent of each slice in public ownership, and the total area of
publicly owned land per slice. Since the area of public land in each slice varies widely from the north to the south end of the floodplain, the percentage
measure gives a good proportional comparison of floodplain ownership,
while the actual area of publicly owned floodplain is best compared on the
total area graph.
The Data
The 1990 US Census provided the population density data graphed on
the facing page. Since this is a measure of residences only, areas which daily
have a high human presence, but are primarily business or industrial districts
(such as downtown Portland, Fig. 194), show a low density (see page 56 for
an explanation of population density mapping).
The rural building density data are based on the buildings mapped on
the USGS 1:24,000 topographic quadrangle maps. The USGS maps individual buildings outside of city centers only, using a solid fill for denser urban areas (see page 154 for an example USGS 7.5 minute quadrangle map).
As such, the densest parts of cities are not represented on Figure 197.
The road density graph was generated from the 1997 Oregon Department of Transportation roads data, which include all highways, secondary
roads, and railroads, but not alleys or driveways. Because it includes both the
rural and urban parts of the floodplain, this graph may be the best single
gauge on the facing page of the overall density of human presence in the
floodplain. However, a fuller assessment considers the population, rural
building, and road densities together.
Figure 194. High human presence: Industrial district near Fremont Bridge,
Portland. Historical floodplain and 1 km slices shown in blue. Photo: University of Oregon Map Library.
Patterns
An important, if obvious, pattern to recognize is that the vast majority
of the human presence in the floodplain occurs within the UGBs. Most cities
have not yet fully urbanized the periphery of their UGBs, but in general, the
densities of population, buildings, and roads tend to drop off sharply outside
the UGB (Fig. 195). This indicates the effectiveness of this device in concentrating urban activities within, and limiting them outside, it.
The population density appears somewhat weighted to the southern end
of the floodplain, while the building and road densities are more weighted to
the northern end. A possible explanation is that a large portion of Eugene/
Springfield lies in the floodplain, including the outlying residential areas;
thus the slices there encompass more population. But the floodplain is much
narrower toward the north, especially through Portland. The river has traditionally been a center of commerce and industry, and so the narrow floodplain through the urban core tends to have less residential housing, but high
densities of roads and buildings (Fig. 194).
Public land does not follow as predictable a pattern as the three density
graphs. However, most of the UGBs do show notable spikes of public land,
probably due to the larger number of city parks and civic open spaces compared to the surrounding agricultural lands.
Figure 195. A gradient of human presence, at the northern edge of Eugene
(slices 215-16). Residential subdivisions transition abruptly at the Urban
Growth Boundary (shown in yellow) to farms and rural residences, which
transition to undeveloped floodplain forest and the Willamette River. Photo:
University of Oregon Map Library.
Figures 196-200. (Facing page). Measures of
human presence along Willamette River.
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PNW Ecosystem Research Consortium
RIVER RESTORATION
Human Presence
Scale: 1:1000000
Portland Metro
0 mi
1995 Urban Growth Boundaries (UGBs)
10 mi
20 mi
Slices which intersect UGBs
0 km
10 km
20 km
30 km
S
N
Salem/Keizer
Eugene/
Springfield
Albany
Corvallis
4000
People
per square km.
3500
3000
0 to 21
22 to 42
43 to 81
82 to 201
202 to 302
303 to 898
899 to 2000
2001 to 3850
2500
2000
1500
1000
225
220
215
210
205
200
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
95
100
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
5
10
500
0
Figure 196. Population
density per 1 km slice, circa
1990
0
140
Rural Buildings
per square km.
120
100
0.0 to 1.5
1.6 to 5.0
5.1 to 15.0
15.1 to 25.0
25.1 to 35.0
35.1 to 50.0
50.1 to 70.0
70.1 to 145.0
80
60
40
225
220
215
210
205
200
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
100
20
Figure 197. Rural building density
per 1 km slice, circa 1990
0
50
Kilometers of Road
per square km.
0.000
1.160
1.470
1.810
2.315
2.900
4.450
8.580
to
to
to
to
to
to
to
to
40
1.159
1.469
1.809
2.314
2.899
4.449
8.579
46.179
30
20
10
225
220
215
210
205
200
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Figure 198. Road density per 1
km slice, circa 1990
Percent of
Slice in Public
Ownership
0
60%
50%
0.00% to 0.64%
0.65% to 1.93%
1.94% to 3.39%
3.40% to 5.99%
6.00% to 8.79%
8.80% to 14.99%
15.00% to 24.49%
24.50% to 62.30%
40%
30%
20%
225
220
215
210
205
200
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
Figure 199. Public land percentage per 1 km slice, circa 1990
0
10%
0%
250
Total Hectares
of Public Land
200
0.00 to 7.99
8.00 to 20.99
21.00 to 36.99
37.00 to 55.99
56.00 to 83.99
84.00 to 117.99
118.00 to 164.99
165.00 to 256.99
150
100
Portland Metro
Salem/Keizer
Albany Corvallis
225
220
215
210
205
200
195
190
185
180
175
170
165
160
155
150
145
140
135
130
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
Figure 200. Public land total area
per 1 km slice, circa 1990
0
50
0
Eugene/Springfield
Note: 1km/1km2 equals 1.61 mi/1mi2, 1 hectare equals 2.47 acres
Willamette River Basin Atlas
2nd Edition
141