PNW Ecosystem Research Consortium12

Elevation and Elevation Profiles

A

A’

B B’

C C’

W

W’S

N

Elevation Profile Locations

Not to scale

0˚

1˚ - 2˚

3˚ - 4˚

5˚ - 6˚

7˚ - 8˚

9˚ - 10˚

11˚ - 13˚

14˚ - 16˚

17˚ - 20˚

21˚ - 25˚

26˚ - 30˚

31˚ - 65˚

0 - 6%

2 - 4%

5 - 7%

9 - 11%

12 - 14%

16 - 18%

19 - 23%

25 - 29%

31 - 36%

38 - 47%

49 - 58%

60 - 214%

WRB percent slope WRB degrees slope

Figure 13. Willamette River Basin profiles. On the profiles above, el-

evations for cities and towns are derived from published sources, while

those for physical features are derived from the digital elevation model.

Vertical exaggeration is 30:1 for all profiles.

Figure 14. Calculating slope:

In the maps below, topographic slope is determined individually

for each 1/4 acre (30 meter x 30 meter) cell in the digital elevation

model. The slope is computed by reference to cells in a 3x3 matrix sur-

rounding the target cell. With the elevation of edge-touching cells

given twice the weight as that of corner-touching cells, the maximum

rate of change in elevation from the target to its neighbors, and its di-

rection, are calculated. The compass direction of this line is the topo-

graphic aspect of the target cell.

Slope is represented in two forms, percentage and degrees. De-

grees measure the interior angle of a triangle in which the base is the

“run” and the height is the “rise” along the direction of maximum el-

evation change for the cell. Percentage slope multiplies the rise/run ra-

tio by 100. An increasingly vertical line has degrees slope approaching

90, but a percentage slope approaching infinity as the “run” denomina-

tor goes to zero. A 45 degree slope is a 100% slope.

Distance (km)

Ele

vati

on

(m

)

0

500

1000

1500

2000

0 50 100 150 200

C

C'S. Yamhill R.

(37 m)

Willamette R.(23 m)

Molalla R.(108 m)

Clackamas R.(332 m)

Timothy Lake(984 m)

Woodburn(56 m)

0

500

1000

1500

2000

0 50 100 150

B

B'

Veneta(122 m)

Eugene(128 m)

Cougar Res.(518 m)

Horse Cr.(871 m)

0

500

1000

1500

2000

0 50 100 150 200 250 300

A

A'

Beaverton(58 m)

S. Santiam R.(260 m)

HeadwatersMiddle Fork Willamette R.

(1284 m)

Willamette R.(15 m)

McKenzie R.(290 m)

0

500

1000

1500

2000

0 50 100 150 200 250 300 350 400 450

W

W'

Portland(0 m)

Oakridge(345 m)

Lowell(212 m)

Eugene(122 m)

Corvallis(58 m)

Salem(34 m) Oregon City

(0 m)

distances are along channel.Elevations are at river level;

Hypsology

Hypsology is the study of the relative altitude of places. Map 3 on the

facing page is a hypsometric “hill-tint” in which elevation is depicted

through variations in color and brightness. The shading is rendered as if the

image were a topographic relief map illuminated by a source of light at 45

degrees above the map in the northwest corner, 315 degrees azimuth. It dif-

fers from true illumination in that higher features closer to the light source do

not cast shadows on those behind. No vertical exaggeration is applied.

A. Branscomb

Based on U.S. Geological Survey,32 U.S. Forest Service, and U.S. Bureau

of Land Management digital sources contained in an archive managed by the

Oregon Geospatial Data Clearinghouse,33 Map 3 was constructed from a digi-

tal elevation model made by joining approximately 300 individual 7.5 minute

quadrangle digital elevation models. Each of these is a rectangular matrix of

elevation values spaced 98.4 ft apart (30 m). Vertical accuracy varies from

+/- 24.6 ft (7.5 m) to +/- 49.2 ft (15 m) and horizontal accuracy conforms to

U.S. Geological Survey national map accuracy standards, which at this scale

means that 90% of values lie within 39.4 ft (12 m) of actual location.

θ

θ

θ

Percent slope = 58

Degree slope = 45Percent slope = 100

Degree slope = 60Percent Slope = 173

Degrees of slope =

Percent slope = rise/run X 100rise/run = tan θ

θ

Degree slope = 30

Unit Equivalences

Metric English

100 m 500 m1000 m1500 m

50 m

2000 m10 km50 km

100 km300 km500 km

164 ft328 ft

1640 ft3280 ft4921 ft

1.2 mi6.2 mi

31.1 mi62.1 mi

186.4 mi310.7 mi

LANDFORM

Willamette River Basin Atlas

2nd Edition

13

LANDFORMS

43°22’30"

43°30’00"

43°37’30"

43°45’00"

43°52’30"

44°00’00"

44°07’30"

44°15’00"

44°22’30"

44°30’00"

44°37’30"

44°45’00"

44°52’30"

45°00’00"

45°07’30"

45°15’00"

45°22’30"

45°30’00"

45°37’30"

45°45’00"

45°52’30"

43°22’30"

43°30’00"

43°37’30"

43°45’00"

43°52’30"

44°00’00"

44°07’30"

44°15’00"

44°22’30"

44°30’00"

44°37’30"

44°45’00"

44°52’30"

45°15’00"

45°22’30"

45°30’00"

45°37’30"

45°45’00"

45°52’30"123°45’00" 123°37’30" 123°30’00" 123°22’30" 123°15’00" 123°07’30" 122°45’00" 122°37’30" 122°30’00" 122°22’30" 122°15’00" 122°07’30" 122°00’00" 121°52’30" 121°45’00"

123°45’00" 123°37’30" 123°30’00" 123°22’30" 123°15’00" 123°07’30" 123°00’00" 122°52’30" 122°45’00" 122°37’30" 122°30’00" 122°22’30" 122°15’00" 122°07’30" 122°00’00" 121°52’30" 121°45’00"

S

N

0 mi 10 mi 20 mi

0 km 10 km 20 km 30 km

Projection UTM Zone 10

Scale 1:750000

Elevation (feet)

0 - 20

21 - 50

51 - 100

101 - 200

201 - 500

501 - 1000

1001 - 1500

1501 - 2000

2001 - 2500

2501 - 3000

3001 - 3500

3501 - 4000

4001 - 4500

4501 - 5000

5001 - 5500

5501 - 6000

6001 - 6500

6501 +

(meters)

0 - 6

6 - 15

16 - 30

31 - 61

61 - 152

153 - 305

305 - 457

458 - 610

610 - 762

762 - 914

915 - 1067

1067 - 1219

1220 - 1372

1372 - 1524

1524 - 1676

1676 - 1829

1829 - 1981

1982 +

Map 3. Hypsometry34