WORKING PAPER NO. 30
COLUMBIA RIVER BASIN PROJECT
For Water Supply and Water Quality Management
LOWER WILLAMETTE BASIN (OREGON)
PRELIMINARY ECONOMIC RECONNAISSANCE
AND ESTIMATE OF GROWTH, 1960-2010
DATE: September 24, 1962
Prepared by BE8
Reviewed by _______
Approved by
DISTRIBUTION
Project Staff
Cooperating Agencies
General
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Region IX
Division of Water Supply and Pollution Control
Room 570 Pittoek Block
Portland 5, Oregon
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This working paper contains preliminary data and information
primarily intended for Internal use by the Columbia River
: i._ » \.
Basin Project staff and cooperating agencies. The material
presented in this paper has not been fully evaluated and
should not be considered as final.
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LOWER WILLAMETTE BASIN (OREGON)
PRELIMINARY ECONOMIC RECONNAISSANCE
AND ESTIMATE OF GROWTH. 1960-2010
Table of Contents
INTRODUCTION 1
Purpose of This Analysis 1
Definition of the Area 1
Study Period 2
Limitations of This Analysis 2
PRESENT ECONOMIC BASE 2
Population 2
Industry 5
ESTIMATED FUTURE GROWTH 8
Factors Influencing Future Growth 8
Future Employment 11
Future Population 15
Prepared by: Economic Studies Group
Water Supply and Pollution Control
Program, Pacific Northwest
September 1962
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LOWER WILLAMETTE BASIN (OREGON)
PRELIMINARY ECONOMIC RECONNAISSANCE
AND ESTIMATE OF GROWTH. 1960-2010
INTRODUCTION
Purpose of This Analysis
This analysis is intended to provide a preliminary estimate of the economic
potentials and anticipated growth of the subject area.
Definition of the Area
The Willamette River Basin divides conveniently into three parts: (1)
the Lower Portion, comprising the Portland Metropolitan Area (Clackamas,
Multnomah, and Washington Counties); (2) the Middle Portion, comprising
Benton, Linn, Marion, Polk, and Yamhill Counties; and (3) the Upper
Portion, comprising Lane County. This report is an analysis of the
economy of the Lower Portion.
Physically, the eastern part of Multnomah County, comprising the area
east of the Sandy River, lies outside the Willamette River Basin, draining
into the Columbia River. However, because basic statistics are
available on a county basis, all of Multnomah County is included in the
study area. Since the portion of Multnomah County east of the Sandy
River comprises less than one-half of one per cent of Multnomah County
population, no significant distortion is involved. With this exception,
the boundaries of the three^county area conform approximately to the
Willamette Basin boundaries.
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Study Period
The study period is the 50-year period 1960-2010, with an interim point
at 1985.
Limitations of This Analysis
Two limitations apply to this study. The first is that it is intended
only as a preliminary estimate of the outlook for the subject area's
growth. Subsequently, in connection with the Columbia River Basin Project
for Water Supply and Water Quality Management, an analysis will be made
on an industry-by-industry basis of the growth potential in the various
sub-basins. At that time, this preliminary estimate will be reviewed,
and revised if necessary.
The second limitation is that this study is intended for use particularly
in assessing future water needs. Emphasis has been placed on the
analysis of those industries which make heqvy demands upon the water
resource. Other industries have been considered only insofar as they
may have a significant effect on future population. For this reason,
this study is not submitted as a detailed industrial forecast.
PRESENT ECONOMIC BASE
Population
V'
Total population in the three counties of the Lower Willamette Baa^n,
as of April 1960, was 728,000. Table I shows how this population was
distributed among six sub-basins pf the. Lower Willamette Basin. The
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C-3
principal "sub-basin," identified as the Willamette Main Stem, has been
divided into four parts in order to help locate this large population
more precisely.
Table I
POPULATION OF LOWER WILLAMETTE RIVER BASIN, BY SUB-BASIN, APRIL 1, 1960
Estimated
Population,
Sub-Basin or Area Thousands
Willamette Main Stem
All of Multnomah County (a) 523
Clackamas County west of Willamette River 23
Clackamas County east of Willamette River and north
of Clackamas River Basin (b) 38
Oregon City and Abernethy and Beaver Creeks drainage 13
Tualatin River
All of Washington County (c) 92
Clackamas River
Portion of Clackamas County (d) 22
Sandy River
Portion of Clackamas County (e) 3
Molalla River
Portion of Clackamas County 10
Pudd inp^liver
Portion of Clackamas County (f) 4
TOTAL, LOWER WILLAMETTE BASIN (3-county area) 728
(a) Includes portion of Multnomah County east of Sandy River, which had a
population of 2,400 in 1960. Most of this population is along the
Columbia River.
(b) Equivalent to census tracts C8 through C18, plus Johnson, Mt. Scott,
and Kellogg Creeks drainage areas.
(c) See previous project review for Washington County.
(d) Includes City of Gladstone and communities of Park Place and Clackamas
Heights.
(e) Includes only the portion of the Sandy River drainage in Clackamas
County. The portion of the Sandy River basin in Multnomah County has been
included in Multnomah County, shown above under "Willamette Main Stem."
(f) Includes only the portion of the Pudding River drainage in the Lower
Willamette Basin. The other portion of the Pudding River drainage is
included in Marion County, in the Middle Willamette Basin.
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04
There were 23 incorporated places in the Lower Willamette Basin in 1960.
These are shown in Table II, arranged according to the same sub-basin
divisions as were used in Table I.
Table II
POPULATION, INCORPORATED PLACES, LOWER WILLAMETTE BASIN, APRIL 1, 1960
By Sub-Basin
Sub-Basin and Incorporated Place Population
======================;=:===:====== ==========
Willamette Main Stem
Multncmah County:
Portland 372,298
Gresham 3,944
Fairview 578
Troutdale 522
Wood Village 822
Clackamas County west of Willamette River:
Oswego 8,906
West Linn 3,933
Clackamas County east of Willamette River and
north of Clackamas River Basin:
Milwaukie 9,099
Oregon City and Abernethy and Beaver Creeks
drainage:
Oregon City 7,996
Tualatin River
Banks 347
Beaverton 5,937
Gaston 320
Cornelius 1,146
Forest Grove 5,628
Hillsboro 8,232
Sherwood 680
Tualatin 359
Clackamas River
Estacada 95,7
Gladstone 3,854
Sandy River
Sandy1 1,147
Molalla River
Canby 2,168
Molalla 1,501
Pudding River
Barlow 85
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Industry
The economy of the Lower Willamette Basin is more diversified than that
of any other part of the state. While lumber and wood products, the
mainstay of the economies of most parts of Oregon, is also the largest
single manufacturing employment category in the Lower Willamette,
employment in that industry represents only 17 per cent of all manufacturing
employment and only three per cent of the total labor force. Food and
kindred is the second most important manufacturing category, in terms
of employment, representing 14 per cent of all manufacturing employment.
The other 69 per cent of manufacturing employment is well diversified
among the other manufacturing categories, as shown in Table III. A
large portion of the area's employment is in service industries, reflecting
the function of Portland as the service center for its region.
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;" table III
EMPLOYMENT, BY INDUSTRY. LOWER WILLAMETTE BASIN, 1950 and 1960 (a)
Source: U. S. Census of Population
Change in
Employment, Employment
_ thousands 1950-1960,
Industry
Total Labor Force
Military
Unemployed
Industry not reported
Classifiable employed civilian l.f.
Agriculture
Forestry and fisheries
Mining
Manufacturing, Total
Lumber, wood products, furn. and fix.
Primary metals
Fabricated metals
Machinery, non-electric
Electrical machinery
Motor vehicles and equip.
Transportation equip, ex. motor veh.
Other durables (c)
Food and kindred
Textiles
Apparel and fabric, textiles
Printing and publishing
Chemicals and allied
Pulp and paper
Other non-durables and mfr. n.e.c. (d)
Construction
R.R. Transportation
Truck transp. and warehousing
Other transportation service
Communications
Utilities ex. communications
Wholesale trade
Retail—Food
Retail--Eating and drinking
Retail—all other
Finance, .Insurance, Real Estate
Business service
Repair service
Personal service (e) .
Professional and related services (f)
Education—government
Education--non-government
Public administration
19;5Q
264.4
.7
19.3
2.9
241.5
13.9
.7
.4
45.8
12.6
3.2
3.1
2.8
.7
.5
.5
2.4
5.9
2.3
1.9
4.6
1.3
3.2
.8
18.5
8.1
4.5
6.1
4.1
4.6
15.1
7.4
9.6
28.4
12.3
3.0
5.1
18.2
15.5
5.5
3.2
11.5
1960
293.7
1.5
14.8
8.9
268.5
8.8
.8
.2
57.7
9.6
3.7
4.0
4.6
4.3
1.2
3.0
3.4
8.3
2.1
2.8
4.6
1.5
3.8
.8
17.2
6.1
5.8
5.9
4.8
4.9
17.6
6.9
9.7
29.2
15.5
3.9
5.0
17.5
22.5
11.1
3.8
13.6
thousands
+29.3
+ .8
- 4.5
+ 6.0
+27.0
- 5.1
+ .1
- .2
+11.9
- 3.0
+ .5
+ .9
+ 1.8
+ 3.6
+ .7
+ 2.5
+ 1.0
+ 2.4
- .2
+ .9
0
+ .2
+ .6
0
- 1.3
- 2.0
+ 1.3
- .2
+ .7
+ .3
+ 2.5
- .5
+ .1
+ .8
+ 3.2
+ .9
- .1
- .7
+ 7.0
+ 5.6
+ .6
+ 2.1
C-6
Distribution
of Employment
per cent (b)
1950
100.0
.3
7.3
1.1
91.3
5.2
.2
.1
17.3
4.8
1.2
1.2
1.0
.3
.2
.2
.9
2.2
.9
.7
1.7
.5
1.2
.3
7.0
3.1
1.7
2.3
1.6
1.8
5.7
2.8
3.6
10.8
4.7
1.1
1.9
6.9
5.9
2.1
1.2
4.3
1960
100.0
.r
5.0
3.1
91. 4
3.0
.3
A.
19.6
3.3
1.3
1.4
1.6
1.4
.4
1.0
1.1
2.8
.7
c
• «*
1.6
.5
1.3
.3
5.9
2.1
2.0
2.0
1.6
1.6
6.0
2.4
3.3
9.9
5.3
1.3
1.7
6.0
7.7
3.8
1.3
4.6
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Notes to Table HI
(a) As of April i, Lower Willamette Basin includes all of Clackamas,
Multnomah, and Washington Counties.
(b) Based on unrounded figures.
(c) Includes cement, pottery, glass, concrete, gypsum, plaster, stone and
their products; professional and photographic equipment; watches and clocks.
(d) Includes petroleum refining; footwear; coal, tobacco, rubber and
leather and their products. Also includes the "manufacturing not elsewhere
classified" category, a small miscellaneous group.
(e) Includes private household workers; hotels, motels and lodging places;
other personal services; and entertainment and recreation.
(f) Includes hospitals, medical, dental, welfare organizations, and other
professional and related services;
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ESTIMATED FUTURE GROWTH
Factors Influencing Future Growth
The Portland Region, defined to include all of Oregon plus five counties
of southwestern Washington, had a population in 1960 of about 1.9 million,
of which about 38 per cent was in the Lower Willamette Basin (Multnomah,
Clackamas, and Washington Counties). This concentration of population is
largely due to Portland's strategic location with reference to transportation
services, both inland and ocean-going. On the basis of that strategic
location, Portland's economy has evolved into the only diversified
manufacturing economy in the Region, as well as the service-industry center
for the Region. Anticipated future growth of the Lower Willamette Basin
is expected to continue to reflect these characteristics.
In line with national trends, it is expected that the ratio of service
industry jobs to manufacturing or "goods" jobs will increase in the future.
Service industry categories whose employment in the Lower Willamette Basin
increased most rapidly during 1950-60 will probably continue to show the
greatest increases in the future. These include truck transportation and
warehousing, wholesale trade, finance-insurance-real estate, professional
services, education, and public administration. An important part of
Portland's large service industry employment grows out of the city's being
the regional headquarters for many aspects of the area's major resource-
based activity, the timber-based industries.
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In manufacturing, continued growth of population is expected to make possible
the establishment of market-oriented plants for the production of goods
formerly brought in from the East. Because such industries are not compelled
to locate close to any particular resource, their selection of a site is
difficult to predict with precision. However, the diversified economy of
the Lower Willamette Basin and the availability there of ample industrial
acreage and a large, experienced labor force suggest that this area will
attract a substantial part of new manufacturing plants coming to the Region.
Seme indication of which manufacturing categories are likely to experience
the greatest relative growth in the future can be deduced from Table IV,
which compares the distribution of the labor force in the Lower Willamette
Basin with the distribution in the United States as a whole. Except for
those industries whose location is oriented towards the site of a fixed
resource, it can be assumed that, as population density grows in the
Portland Region, both absolutely and relatively, the distribution of
employment in the Region and particularly in its most diversified portion,
the Lower Willamette Basin, will become more like that in the nation. On
this basis, the comparative data in Table IV suggest that growth is
particularly likely to occur in the following categories: machinery (both
non-electrical and electrical); other durables, identified in the footnote
to Table IV; textiles; apparel; and chemicals, except for those which are
resource-oriented.
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Table IV
COMPARATIVE DISTRIBUTION OF LABOR FORCE, BY INDUSTRY, APRIL 1960
(Per Cent of Total Labor Force)
Industry
Agriculture
Forestry, fisheries, mining
Manufacturing, Total
Lumber, wood prod., furn. and fixt.
Primary metals
Fabricated metals
Machinery, non-electric
Electric machinery (b)
Other durables (c)
Food and kindred
Textiles ~'i
Apparel and fabricated textiles
Printing and publishing
Chemicals and related
Other non-durables and misc. mfr. (d)
Construction
Services (e)
Total, Employed Civilian Labor Force
Unemployed
Military
Total Labor Force
Lower
Willamette
Basin (a)
3.0
.4
19.6
3.3
1.3
1.4
1.6
M
2.5
2.8
.7
.9
1.6
.5
1.6
5.9
65.6
94.5
5.0
.5
100.0
United
States
6.1
1.0
25.1
1.6
1.8
1.8
2.2
2.1
4.5
«.6
14
1,7
1.7
1:2
2.5
5-5
54.8
92.5
5.0
2,5
iOO.O
(a) Includes all of Clackamas, Multnomah, and Washington Counties.
(b) Includes electronics and oscilloscopes.
(c) Includes motor vehicles and equipment; other transportation
equipment, including shipbuilding; cement, pottery, glass, concrete,
gypsum, plaster, stone and structural clay and their products;
professional and photographic equipment; and watches and clocks.
(d) Includes pulp and paper and their products; petroleum refining;
and petroleum, coal, tobacco, rubber and leather products. Also in
the total shown is the "not elsewhere classified" manufacturing, a
small miscellaneous category.
(e) Includes "industry not reported" category, representing about
three per cent of the labor force.
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Oil
Future Employment
Estimates of future population and industrial growth in the Portland
Metropolitan Area have been made by the Portland City Planning Commission
and the Portland Metropolitan Planning Commission and, for purposes of
this preliminary report, the findings of those studies have been accepted
as general guidelines.—' In Land for Industry, the Portland Metropolitan
Planning Commission gave estimates of changes in employment from 1959 to
1975 for each principal manufacturing category. With certain adjustments,
the annual rates of growth indicated in that study have been applied to
the 1960 U. S. census figures for manufacturing employment and extended
to 1985 and to 2010, yielding the figures for manufacturing employment
shown in Table V. The principal departure from this technique is in
regard to "electrical machinery," which includes electronics and
oscilloscopes. It is felt that the substantial rate of increase (about
7.2 per cent per year) adopted in Land for Industry for the period 1959-
1975 is likely to decline during the 1985-2010 period. For that latter
period, a rate of 3.3 per cent per year has been used. Also, in Table V,
a small addition has been made to "other durables," on the assumption
that the large growth projected in electrical machinery can be expected to
lead to increased production of parts and supplies for the electronics
industry.
\l Economic Prospects. Portland City Planning Commission, an unpublished
staff report made in 1957; Population Prospects. Portland Metropolitan
Planning Commission, July 1960; Land for^ Industry. Portland Metropolitan
Planning Commission, July 1960.
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For purposes of the projection, it is assumed that total employment in
agriculture, forestry, fisheries and mining will, for the group as a
whole, remain in the future about what it is now. It is expected that
the steep decline in agricultural employment will level off in the future,
though agricultural employment will continue to decline as a percentage of
total employment. Some decrease in agricultural employment may be offset
by an increase in "mining," which includes the sand and gravel industry.
On the basis of employment projected for the "goods" industries, described
above, Table V shows the derived employment in service industries, the
projected total labor force, and the total population which may be
supported by that labor force. It is assumed that service industry
employment will increase relative to goods industries employment. This is
a trend which appears to be strongly established in the national economy.
The assumed increase in the servicergoods ratio is already substantially
above that for the U. S. as a whole. The ratio assumed between population
and total labor force is approximately what it was in 1960 and also
conforms closely to the ratio in the nation and in other metropolitan
areas in 1960.
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Table V
ILLUSTRATIVE DISTRIBUTION OF FUTURE EMPLOYMENT, BY INDUSTRY, LOWER WILLAMETTE BASI
Employment, thousands
Industry 1950 1960 1985 2010
Agriculture, forestry, fisheries, mining 15.0 9.8 10.0 10.0
Manufacturing, Total 45.8 57.7 112.4 202.£
Lumber, wood prod., furn. and fixt. 12.6 9.6 11.4 13.t
Primary metals (a) 3.2 3.7 6.5 11.f
Fabricated metals 3.1 4.0 6.9 11.9
Machinery, non-electric 2.8 4.6 8.5 15.8
Electric machinery (incl. electronics) .7 4.3 24.5 54.8
Transportation equipment 1.0 4.2 8.2 16.C
Other durables (b) 2.4 3.4 9.0 20.C
Food and kindred 5.9 8.3 12.7 19.4
Textiles 2.3 2.1 3.6 6.1
Apparel 1.9 2.8 5.2 9.6
Printing and publishing 4.6 4.6 7.6 12.5
Chemicals and allied 1.3 1.5 2.5 4.1
Pulp and paper (c) 3.2 3.8 4.4 5.1
Other non-durables, and misc. mfr. (d) .8 .8 1.4 2.4
Total, "Goods" 60.8 67.5 122.4 212.8
Ratio, Service industries to Goods 297% 298% 310% 320%
Service industries (includ. construction) 180.7 201.0 379.4 681.7
Goods plus Services employment 241.5 268.5 501.8 894.5
Ratio.,, military+unemployed+industry not
reported to total Goods+Services 9.5% 9.4% 10% 10%
Military, Unemployed and Industry not
reported 22.9 25.2 50.2 89.f
TOTAL LABOR FORCE 264.4 293.7 552.0 984.C
Ratio, Population to Total Labor Force 234% 248% 250% 250%
Population 619 728 1,380 2,461
(a) A report of the Bureau of Mines ("Trends and Outlook in the Pacific
Northwest Aluminum Industry," Bureau of Mines information circular 8046,
published 1962) estimates that aluminum production in the Pacific Northwest in
1980 will be about four times what it was in 1959. This rate of growth is more
than double the rate of growth projected for employment in primary metals in
Table V. It should be emphasized that Table V deals in employment only;
substantial increase in productivity in many industries may lead to a much
greater increase in output.
(other notes, next page)
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*
(b) The "Other durables" group includes cement, pottery, glass, concrete,
gypsum, plaster, stone, and structural clay and their products; professional
and photographic equipment and supplies; and watches and clocks.
(c) This group includes not only pulp and paper manufacturing but also allied
products converted from paper, such as envelopes and boxes. It is estimated
that production of pulpjwill increase from about 1,100 tons per day in the
three-county area in I960 to about 1,300 tons per day in 1985 and 1,500 tons
per day in 2010. Due to limitations on the availability of raw material,
it is not expected that much, if any, of this expansion will occur in
Washington County, where there is now a 70 tons-per-day fibreboard plant,
near Forest Grove. Nor is much expansion expected at either West Linn or
Oregon City because of physical limitations of the sites. It does seem likely
from the standpoint of a'vailabilitjy of raw materials and water supply that
fibreboard production may be established in either the Clackamas, Pudding, or
Molalla River basins .• :The national market demand for this type of product
seems favorable, and the economics of the industry seem to favor location
near the raw materiali
(d) The "Other non-dttrables" group includes petroleum refining, footwear,
and products made of, petroleum, coal, tobacco, rubber and leather, Also
in the total shown is the "not elsewhere classified" manufacturing, a small
miscellaneous category.
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Future Population
Two methods were used to arrive at an estimate of Lower Willamette Basin
population in 1985 and 2010. One method was that shown in Table V, where
the estimation of future population is built up from projections of future
employment in the manufacturing and other "goods" industries and from
assumptions concerning the ratios of "service" employment to "goods".
employment and of population to the total labor.force. The other method
was to allocate to the various basins of Oregon the population forecast
for the state in terms of national population trends, assuming that past
trends in relative growth and in resource development in the various
basins of the state would continue. In using the latter method of
estimating, it was assumed that Oregon population would be 3.05 million
in 1985 and 5.26 in 2010. These estimates of future state population are
related to the "Series II" projection of national population,-!-' which
assumes that fertility will remain in the future at the 1955-57 level.
Allocating the estimated future state population by sub-basin yields
the following results for the Lower Willamette Basin's population: 1985,
1,380,000; 2010, 2,460,000. As shown in Table V, the method based on
estimating future employment yields results which are consistent with
those figures, using the ratios assumed in Table V.
It should be emphasized that the arbitrary nature of these estimates
should be fully recognized. They are, however, based upon assumptions
j./ U. S. Census Bureau, Series P-25, No. 251, July 6, 1962.
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which are considered to be "reasonable," and represent a "best guess" on
the basis of data available for a preliminary economic reconnaissance.
An estimate of the distribution of future population among the various
sub-basins of the Lower Willamette Basin must rest upon even more
arbitrary assumptions than the projection for the larger area. However,
an illustrative and hypothetical distribution, which is considered to be
adequate for certain design purposes, is shown in Tables VI and VII.
Table VI shows an illustrative distribution of future Lower Willamette
Basin population among the three counties comprising the basin. Clackamas
and Washington Counties constituted an increasing percentage of three-
county population during the 1950-60 decade, and it is assumed that this
trend will continue. This assumption is consistent with a report by the
Portland Metropolitan Planning Commission (Population Prospects. July I960),
whose population percentage distribution for 1975 is shown in Table VI.
In extending trends beyond 1975, it is assumed here that, as Clackamas
and Washington Counties become more densely populated, their gain in
population relative to Multnqmah County will become less pronounced. As
the population density in Clackamas and Washington County becomes more
like that in Multnomah County, growth rates will tend to be more uniform
J.n the three counties.
On the basis of the percentage distribution of population among the three
counties shown in Table VI, Table VIJ distributes the indicated county
population further, that is, among the various subrbasins as shown in
Table I.
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Table VI
PERCENTAGE DISTRIBUTION OF LOWER WILLAMETTE BASIN POPULATION BY COUNTY
Share of Lower Willamette Basin Population
per cent
County
Clackamas
Multnomah
Washington
TOTAL
1950
14.0
76.1
9.9
100.0
shown
1960
15.5
71.8
12.7
100.0
19.7 5 (a)
18.7
64.4
16.9
100.0
1985
20.2
61.0
18.8
100.0
2010
21.2
58.5
20.3
100.0
in Population Prospects , Portland
Metropolitan Planning Commission, July 1960.
Table VII
ILLUSTRATIVE DISTRIBUTION OF FUTURE POPULATION, LOWER WILLAMETTE BASIN
BY SUB-BASIN
Estimated Population
thousands
!H*>rBasin_or_Area (a) I960 1985 2010
Willamette Main Stem
All of Multnotaah County 523 842 1,438
Clackamas County west of Willamette R. 23 65 124
Clackamas County east of Willamette R.
and north of Clackamas R. Basin 38 107 205
Oregon City and Abernethy and Beaver
Creek drainage 13 32 60
Tualatin River
All of Washington County 92 259 500
Clackamas River
Portion of Clackamas County 22 42 75
Sandy River
Portion of Clackamas County 3 6 10
Molalla River
Portio^ of Clackamas County 10 19 34
"Pudding River
Portion of Clackamas County 4 8 14
TOTAL, LOWER WILLAMETTE BASIN 728 1,380 2,460
(a) For definitions of areas, see footnotes to Table I.
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C-18
As shown in Table VII, Multnomah and Washington Counties are sub-basin
units in themselves, but Clackamas County is divided into seven sub-basins.
Without a more detailed study than can be undertaken for this preliminary
economic analysis, the allocation of Clackamas County population among
these seven sub-basins must be on a rather arbitrary judgmental basis.
The principal assumption has been that the portion of Clackamas County
west of the Willamette River and the portion east of the Willamette River
and north of the Clackamas River Basin will both grow more rapidly than
the rest of the county. It has been assumed that the Oregon City area
would grow at the average rate for the county, and that the other four
portions (Clackamas River, Sandy River, Molalla River, and Pudding River
sub-basins) would all grow less rapidly than the county average. In
Table VII, the growth rate assigned to the two fastest growing portions
was the same as that for Washington County, which is projected to grow
more rapidly than the Clackamas County average. The growth rate assigned
to the four slower growing portions was the same as that for the entire
three-county Lower Willamette Basin. Table VIII shows the rates used
for calculation of population estimates in Table VII.
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Table VIII
HYPOTHETICAL GROWTH RATES FOR SUB-BASINS OF LOWER WILLAMETTE BASIN
Average Annual As Multiple of
Rates, Per Cent 1960 Population
Sub-Basin or Area (a) 1960-85 1985-2010 1985 2010
==:==========:===== ======= ========= ===== ====
Willamette Main Stem
All of Multnotnah County 1.9 2.1 1.6 2.7
Clackamas County west of Willamette R. 4.2 2.7 2.8 5.4
Clackamas County east of Willamette R.
and north of Clackamas R. Basin 4.2 2.7 2.8 5.4
Oregon City and Abernethy and Beaver
Creek drainage 3.7 2.5 2.5 4.6
Tualatin River
All of Washington County 4.2 2.7 2.8 5.4
Clackamas River
Portion of Clackamas County 2.6 2.3 1.9 3.4
Sandy River
Portion of Clackamas County 2.6 2.3 1.9 3.4
Molalla River
Portion of Clackamas County 2.6 2.3 1.9 3.4
Pudding River
Portion of Clackamas County 2.6 2.3 1.9 3.4
TOTAL, LOWER WILLAMETTE BASIN 2.6 2.3 1.9 3.4
(a) For definitions of areas, see footnotes to Table I.
No estimates of future population of individual cities in the Lower
Willamette Basin are given in this report. As project reviews are
required, the outlook for growth in individual cities will be studied.
However, until such detailed economic studies are made fpr specific
cities, it may be adequate, for ce.rtain design purppa.es, to assume that
the cities in each sub-basin (listed in Table II) will grow at about
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the same rate as the sub-basin in which they are located. A first
approximation of cities' populations in 1985 and 2010 may, therefore,
be calculated by applying to their 1960 population the average annual
growth rates or factors for their sub-basin shown in Table VIII.
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