Title page for ETD etd-05162008-110931

Type of Document

Master's Thesis

Author

Lowther, Brian Christopher,

Author's Email Address

bclowthe@ncsu.edu

URN

etd-05162008-110931

Title

Stream Channel Geomorphology Relationships for North Carolina Piedmont Reference Reaches

Degree

Master of Science

Graduate Program

Biological and Agricultural Engineering

Advisory Committee

Advisor Name	Title
Dr. Greg Jennings	Committee Member
Dr. James Gregory	Committee Member
Dr. Jean Spooner	Committee Member

Keywords

reference reach
regime equation
regional curves
hydraulic geometry relationships

Date of Defense

2008-05-14

Availability

unrestricted

Abstract

ABSTRACT
LOWTHER, BRIAN CHRISTOPHER. Stream Channel Geomorphology Relationships for North Carolina Piedmont Reference Reaches. (Under the direction of Gregory Jennings).

The purposes of this study were to measure geomorphic parameters of North Carolina Piedmont reference streams and to develop empirical hydraulic geometry relationships to assist stream designers in selecting appropriate design parameters for similar restoration streams. From more than 50 candidate streams, 19 were selected as reference streams for detailed data collection. The reference streams were all well-vegetated with stable streambanks, variable bedforms, and good floodplain connections. The watershed drainage areas ranged from 0.1 to 8.2 square miles. Stream reaches were surveyed to measure stream channel dimension, pattern, and profile parameters. GIS software was used to delineate the watersheds and estimate the impervious area percentage for each reference stream watershed.

Regression was used to develop 23 significant power function relationships for dimension, pattern, and profile parameters as functions of watershed drainage area, estimated bankfull discharge, and other morphology parameters. These regime equations can be used by designers to estimate channel form for similar watershed conditions where a channel is to be reconstructed. Significant relationships were found for bankfull cross-sectional area, width, mean depth, pool area, pool depth, pool width, meander length, meander beltwidth, radius of curvature, and estimated discharge as functions of drainage area. Additional significant relationships were found for pool width, meander length, meander beltwidth, radius of curvature, pool spacing, riffle length, and pool length as functions of width; pool area, max depth, radius of curvature as a function of bankfull cross-sectional area; pool depth as a function of bankfull mean depth; riffle slope as a function of average channel slope.

The additional equations and graphs were created for potential use in stream restoration and to compare to previously developed relationships (Doll et al., 2002; Leopold and Wolman, 1960; Rinaldi and Johnson, 1997b; Williams, 1986). For each relationship, a graph shows the best-fit regression line surrounded by the data points and confidence limits. The graphs illustrate the considerable variability in the field-measured geomorphic data existing in stable streams located in the North Carolina Piedmont region. In addition, regression equations resulting from the data analysis show few relationships are linearly related and fit better to a power function. Due to natural variability found in the reference reaches, comparisons to previously developed relationships found no statistical differences among the equations. Comparisons with current Piedmont regional curves and the results indicate a smaller slope for the range of drainage areas.

The relationships developed in this study can be used in stream assessment to evaluate departure from stability and in preliminary design to evaluate whether potential stream designs will work within site constraints. The application for each regression relationship is limited to use on streams with similar watershed size, hydrology, soils, and land use to reference reaches used in the study. The results of this study show that the developed equations for dimension, pattern, and profile must be utilized carefully with streams due to the probable variability in stable streams. The overall project focuses on reference reach validation, database creation, hydraulic geometry relationships, and instruction on the proper use of the developed relationships.

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