HYDRAULIC GEOMETRY RELATIONSHIPS FOR URBAN STREAMS THROUGHOUT THE PIEDMONT OF NORTH CAROLINA¹

Abstract

Hydraulic geometry relationships, or regional curves, relate bankfull stream channel dimensions to watershed drainage area. Hydraulic geometry relationships for streams throughout North Carolina vary with hydrology, soils, and extent of development within a watershed. An urban curve that is the focus of this study shows the bankfull features of streams in urban and suburban watersheds throughout the North Carolina Piedmont. Seventeen streams were surveyed in watersheds that had greater than 10 percent impervious cover. The watersheds had been developed long enough for the streams to redevelop bankfull features, and they had no major impoundments. The drainage areas for the streams ranged from 0.4 to 110.3 square kilometers. Cross‐sectional and longitudinal surveys were conducted to determine the channel dimension, pattern, and profile of each stream and power functions were fitted to the data. Comparisons were made with regional curves developed previously for the rural Piedmont, and enlargement ratios were produced. These enlargement ratios indicated a substantial increase in the hydraulic geometry for the urban streams in comparison to the rural streams. A comparison of flood frequency indicates a slight decrease in the bankfull discharge return interval for the gaged urban streams as compared to the gaged rural streams. The study data were collected by North Carolina State University (NCSU), the University of North Carolina at Charlotte (UNC), and Charlotte Storm Water Services. Urban regional curves are useful tools for applying natural channel design in developed watersheds. They do not, however, replace the need for field calibration and verification of bankfull stream channel dimensions.

Bankfull Hydraulic Geometry Relationships for the Inner and Outer Bluegrass Regions of Kentucky

“…While both streams have similar bankfull discharges (4.7 m 3 s −1 at Chenoweth Run; 4.7 m 3 s −1 at Goose Creek) and drainage areas (14.2 km 2 at Chenoweth Run; 15.5 km 2 at Goose Creek), the level of imperviousness is quite different (33.9 percent at Chenoweth Run; 11.1 percent at Goose Creek) (Tables 1 and 2). Both Cianfrani et al [55] and Doll et al [56] found that urbanization increased bankfull channel width as compared to rural streams in the Piedmont region of the U.S. Contrary, Annable et al [57] found that urbanization did not result in significant channel enlargement for streams in Ontario, Canada.…”

Can Rapid Assessments Predict the Biotic Condition of Restored Streams?

“…As little as 10% impervious cover has been linked to stream degradation, with the severity increasing as impervious cover increases [21]. Urban cover or impervious cover can result in increased peak discharges [22], channel enlargement [23,24] and associated erosion, a decline in water quality and habitat as well as a decline in macroinvertebrate community metrics [7]. Booth [6] concluded that biological condition was highly variable with low levels of anthropogenic development, but was consistently poor at high levels of impervious cover percentage and associated urban cover.…”

Tools to Estimate Groundwater Levels in the Presence of Changes of Precipitation and Pumping

“…To recognize these impacts a "covariate" also plays an important role in this study. A covariate is a statistical term used to identify an interaction which is not measured but is observed in the record [22] [40] [41]. A covariate may be binary and is often referred to as either a hidden, lurking or dummy variable.…”