Research Abstract
“Development and Analysis of Lithologically
Controlled Regional Curves of Hydraulic Geometry for Appalachian Mountain
Streams, Ridge and Valley Physiographic Province, Pennsylvania”
M.S. Thesis in Geology, Matthew S. Finkenbinder (2008)
Regional
curves of hydraulic geometry are frequently constructed for physiographic
provinces, regions that have similar geologic structure, climate, and
geomorphic history. As a result, the factors controlling channel form are more
alike than would be the case for streams across widespread geographic regions.
However, geology can vary significantly within a physiographic province. The
purpose of this study, therefore, was to determine if regional curves would be
more precise predictors of hydraulic geometry if developed for geologically
similar streams within a physiographic province. A total of 34 reaches on six
ungauged mountain streams in the Ridge and Valley Physiographic Province of
Pennsylvania were used to develop lithologically controlled regional curves for
drainage area versus bankfull cross-sectional area, bankfull width, and
bankfull mean depth. The slope,
y-intercept, and R2 value of the non-carbonate lithologically controlled
regional curves were compared to three distinct regional curves of varying
watershed size and physiography. These comparisons reveal that lithologically
controlled regional curves for bankfull cross-sectional area are consistently statistically
different than the other three curves. The factors that may influence
differences in the regional curves include bedrock geology, geologic structure,
physiography, channel gradient, watershed size, riparian vegetation, and land
use. Comparison of R2 values shows regional curves derived from a larger sample
size and including a majority of larger watersheds (> 75 km2) produce less
variance. An additional regional curve was derived by combining hydraulic
geometry data from the lithologically controlled watersheds and non-carbonate
watersheds initially investigated by Chaplin (2005). Higher R2 values indicate
the combined curves developed with a larger sample size and dominated by larger
watersheds produce less variance compared to the lithologically controlled
curves. Future regional curve
investigators should include ungauged watersheds, increase sample size, and
more fully constrain the variables controlling natural channel dimensions to
assess if more precise hydraulic geometry relationships can be developed within
physiographic provinces.
(South Branch
Little Aughwick Creek,
