Changes in long profile, gradient, gradient index, pseudo-hypsometric integral, valley incision, and sinuosity fractal dimension for rivers in western Oregon were studied to determine their usefulness in assessing an hypothesis of differential uplift within the Coast Range. All data were gathered from topographic quadrangles and geologic maps, and so the results of this paper are limited to the description of river forms with only limited interpretations. Rivers were naturally divided into three groups, those in the western Coast Range, the eastern Coast Range, and the Klamath and Cascade Ranges, and differences in river morphometry were generalized. Rivers in the western Coast Range had more divergent characteristics, whereas those in the other groups were more similar within each group. For example, long profiles of western Coast Range rivers had diverse forms, but in the other groups, long profiles were similar within the group. Pseudo-hypsometric integrals had a wide scatter in the western Coast Range, but in the other ranges, the pseudo-hypsometric integral was more narrowly defined. Valley entrenchment and high sinuosity were common in the western Coast Range, and were less visible in the eastern Coast Range. These regional generalizations do not hold for the central Coast Range near 44.5??N where the Yaquina and Marys Rivers are located. In the eastern Coast Range, the Marys River is unique in that it has a convex bulge in its long profile, does not have an increasing valley-floor width to valley height ratio downstream, and has a high sinuosity fractal dimension. In the western Coast Range, the Yaquina River is unique in that it has a smoothly decreasing long profile, has a very low pseudo-hypsometric integral, and does not have a decreasing valley-floor width to valley height ratio downstream. There may be many explanations for these observations, but these observations are also consistent with tectonic interpretations that the central western Coast Range is the locus of synclinal tilting and that the entire Oregon coast is experiencing landward tilting and uplift. ?? 1993.
Additional Publication Details
Geomorphic observations of rivers in the Oregon Coast Range from a regional reconnaissance perspective