Project Title Regional Curves Number Location Western Virginia/Valley and Ridge Cooperating Agencies Canaan Valley Institute Project Chief Jeff Keaton Period of Project July 2002 -

Valley and Ridge Physiographic Province Highlighted in Brown

Background

Stream channels often are disturbed by human activities such as construction or agriculture. In recent years, scientists and engineers have begun to apply the principles of natural channel design to the construction and restoration of stream channels. Natural channel design involves rebuilding a channel with the appropriate cross section dimensions, slope, and plan view pattern so that it can pass the water and sediment loads supplied to it while maintaining its appropriate form. Stream channels designed to approximate natural stable conditions are more likely to remain in equilibrium over time and therefore reduce erosion and sedimentation, provide suitable aquatic habitat, and offer increased aesthetic and recreational value.

Problem

A concept central to the methodology of natural channel design is that of effective or “bankfull” discharge. Bankfull discharge, which typically has a return interval of between 1 and 2 years, is considered to be the streamflow magnitude that is most effective in moving sediment and thus forms the average structural characteristics of channels. The bankfull channel geometry characteristics of cross-sectional area, width, and average depth have been shown to be highly correlated with both discharge and drainage area. Regionally based relations between drainage area and the resultant bankfull channel geometry are important tools for designing and restoring stable stream channels. Bankfull characteristics used to develop these “regional curves” must be calibrated at stream gage locations and stratified by hydro-physiographic province. Regional curves developed for the hydro-physiographic provinces in Virginia will greatly benefit natural channel design projects in the state.

Objective

Develop bankfull channel geometry relations for the Valley and Ridge province in Virginia, West Virginia, Pennsylvania, and Maryland.

Relevance and Benefits

Properly developed regional curves for a specific hydro-physiographic province are an invaluable tool for stream restoration design. Development of regional curves specifically for physiographic provinces of Virginia will enhance the ability to develop successful natural channel designs based on climatic, geologic, and hydrologic characteristics of specific regions of the state.

Approach

USGS personnel in the four states listed above are collecting stream channel geometry and bed material data at gaging stations throughout the Valley and Ridge. All gaging stations in the province which meet pre-determined criteria for the project are included in the study. Streams at each gage site are surveyed. The survey data collected includes at a minimum two riffle cross sections and a longitudinal profile of the stream. Bed material size is determined through a modified Wolman pebble count. This information will be used to classify the streams based on the Rosgen classification system and to develop regression relations between drainage area and bankfull width, depth, cross-sectional area, and discharge.