Virginia Coastal Program: 2004 Coastal Grant Project Description and Final Summary
Project Task:
85.01
Grantee:
Dept. of Conservation & Recreation/U.S. Geological Survey
Project Title:
Support to Develop Regional Channel Geometry Curves
Project Description as Proposed:
The USGS proposes to collect data that will be used to develop regional curves for the non-tidal coastal plain of Virginia. This is accomplished by identifying relations between drainage area and bankfull discharge, cross-sectional area, width, and average depth for stream riffle sections. Currently, practitioners in Virginia are forced to use regional curves developed for North Carolina and Maryland to help design stream restoration plans. This is part of a larger statewide effort by the USGS and its partners. This project supports many objectives contained in the Virginia Nonpoint Source Pollution Management Program document intended to address stream channel erosion, preservation of natural stream channels, provide technical guidance, and strengthening design standards and specifications for stream restoration. The primary (g) guidance management measures this work is applicable to are channelization & channel modification and streambanks & shoreline erosion. Additionally, many of the Urban Runoff measures will benefit from this project. Stream channels often are disturbed by human activities such as construction or agriculture and require restoration to approximate natural stable conditions to reduce erosion and sedimentation and provide suitable aquatic habitat. Central to the methodology of natural channel design is that of determining bankfull discharge. Bankfull discharge is determined by developing regional regression relationships between drainage area and bankfull channel geometry, which are important tools for designing and restoring stable stream channels. By identifying bankfull characteristics at multiple stream gage locations and stratifying them by hydro-physiographic province “regional curves” can be developed. There are about 15 gauge stations within the coastal zone to be evaluated in this project. Sites will be selected based on geographic distribution, current channel conditions, length of discharge record, and watershed & flow characteristics.
Second Year Overview:
With the majority of field work complete, the focus of this portion of the study will be analysis of data from all sites to develop regression equations representing relationships between drainage area and bankfull channel geometry. Further statistical analysis will be done to investigate the fit of the data to the power functions developed, and to determine if combination of Virginia and Maryland regional curve data is acceptable.
A major focus will be toward developing a reference document for stream restoration efforts around the state. The main product will be a USGS Scientific Investigations Report that will document investigative methods and results including regional curves and statistics for relationships between drainage area and bankfull cross-sectional area, width, average depth, and discharge.
The US Geological Survey will contribute $15,000 in additional funds toward the completion of this study.
Federal Funding:
$29,250.00
Project Contact:
Jennifer Krstolic - jkrstoli@usgs.gov, (804) 261-2635
Project Status:
Project Completed
Final Product Received:
USGS Scientific Investigations Report: Development of Bankfull Regional Curves for Streams of the Rural, Non-Tidal Coastal Plain Physiographic Province, Virginia and Maryland (PDF)
Project Summary Provided by Grantee:
The U.S. Geological Survey (USGS), in cooperation with the Virginia Department of Conservation and Recreation (DCR) Coastal Nonpoint Source Pollution Control Program, developed bankfull regional curves for use in rural, non-tidal coastal areas of Virginia during 2005, 2006, and 2007. To represent the highly correlated relation between bankfull discharge or bankfull-channel geometry with drainage area, empirical regression relations, or regional curves, were developed. These regional curves are one-variable ordinary least-squares regressions relating bankfull discharge, cross-sectional area, width, and mean depth to drainage area in settings that are expected to have homogenous runoff characteristics. Equations describing the regional curves can be used to estimate the discharge and dimensions of the bankfull channel when the drainage area of the watershed is known.
Bankfull geometry and discharge data were collected at six gages and associated stream reaches (sites) in Virginia and two sites on the Delmarva Peninsula of Maryland. Data from these eight sites were combined with data from 12 sites in Maryland for the development of regional curves. All study sites in Virginia and Maryland represent drainages that feed into the Chesapeake Bay. Drainage areas for the 20 sites in the regional curves range from 0.28 mi2 to 113 mi2.
Bankfull cross-sectional area, width, mean depth, and estimated bankfull discharge (the response variables) were regressed against the basin drainage area (the explanatory variable) to show the relation between drainage area and each of the variables. The relatively high R2 value (0.945) for cross-sectional area indicates that it had the strongest relation to drainage area of the parameters measured. The R2 values for the other geometry parameters indicate that 89.0-percent, 87.1-percent, and 79.3-percent of the variability in each regional curve was explained by drainage area for bankfull width, mean depth, and bankfull discharge, respectively. These curves can be useful in field-identification of bankfull features and stage for un-gaged streams in non-urban areas. The bankfull regional curves developed are applicable to rural streams in the non-tidal Coastal Plain areas of Virginia and Maryland.
During the past six months GIS analysis was finalized for basin characteristics. The statistical analysis of the survey data was completed. Figures and tables were developed to display the power functions and related data, and a draft report was sent through the USGS colleague review process. A revised draft report was prepared for editorial review. This draft was submitted as the end product of this grant, although the final printing and distribution will occur after March.
Disclaimer: This project summary provides the federal dollars initially awarded to the grantee. Due to underexpenditure or reprogramming of grant funds, this figure may change. For more information on the allocation of coastal grant funds, please contact Laura McKay, Virginia Coastal Program Manager, at 804.698.4323 or email: Laura.McKay@deq.virginia.gov
A more detailed Scope of Work for this project is available. Please direct your request for a copy to Virginia.Witmer@deq.virginia.gov
