

Publications—Scientific Investigations Report 
By Scott A. Olson and Michael C. Brouillette
U.S. Geological Survey Scientific Investigations Report 20065217
The body of the report is available in PDF Format ( 1,703 KB)
A logistic regression equation was developed for estimating the probability of a stream flowing intermittently at unregulated, rural stream sites in Vermont. These determinations can be used for a wide variety of regulatory and planning efforts at the Federal, State, regional, county and town levels, including such applications as assessing fish and wildlife habitats, wetlands classifications, recreational opportunities, watersupply potential, wasteassimilation capacities, and sediment transport. The equation will be used to create a derived product for the Vermont Hydrography Dataset having the streamflow characteristic of “intermittent” or “perennial.” The Vermont Hydrography Dataset is Vermont’s implementation of the National Hydrography Dataset and was created at a scale of 1:5,000 based on statewide digital orthophotos.
The equation was developed by relating fieldverified perennial or intermittent status of a stream site during normal summer lowstreamflow conditions in the summer of 2005 to selected basin characteristics of naturally flowing streams in Vermont. The database used to develop the equation included 682 stream sites with drainage areas ranging from 0.05 to 5.0 square miles. When the 682 sites were observed, 126 were intermittent (had no flow at the time of the observation) and 556 were perennial (had flowing water at the time of the observation).
The results of the logistic regression analysis indicate that the probability of a stream having intermittent flow in Vermont is a function of drainage area, elevation of the site, the ratio of basin relief to basin perimeter, and the areal percentage of well and moderately welldrained soils in the basin. Using a probability cutpoint (a lower probability indicates the site has perennial flow and a higher probability indicates the site has intermittent flow) of 0.5, the logistic regression equation correctly predicted the perennial or intermittent status of 116 test sites 85 percent of the time.
Abstract
Introduction
Description of Study Area
Site Selection
Data Collection
Basin Characteristics Database Development
Logistic Regression Equation
Limitations of the Logistic Regression Equation
Application of the Logistic Regression Equation
Summary and Conclusions
Selected References
2–4. Graphs showing—
2.  Distribution of A, drainage areas. B, elevations. C, channel slopes. D, waterbody areas. E, ratios of basin relief to basin perimeter. F, areas of well or moderately welldrained soils for intermittent and perennial streams observed in Vermont 
3.  Observed frequency of perennial and intermittent streams by drainage area in Vermont. 
4.  Receiver operating characteristic curve for the logistic regression equation for estimating the probability of a stream having intermittent flow in Vermont. 
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For further information, contact:
Keith W. Robinson, Director
U.S. Geological Survey
New Hampshire  Vermont Water Science Center
361 Commerce Way
Pembroke , NH 03275
(603) 2267807
or visit our Web site at: http://nh.water.usgs.gov