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Prepared in cooperation with the Vermont Center for Geographic Information

A Logistic Regression Equation for Estimating the Probability of a Stream in Vermont Having Intermittent Flow

By Scott A. Olson and Michael C. Brouillette

 

U.S. Geological Survey Scientific Investigations Report 2006-5217

 

The body of the report is available in PDF Format ( 1,703 KB)


Abstract

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, water-supply potential, waste-assimilation 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 field-verified perennial or intermittent status of a stream site during normal summer low-streamflow 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 well-drained 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.

TABLE OF CONTENTS

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

 

Figures

 

  1. Map showing location of sites observed for perennial and intermittent streamflow in Vermont

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 well-drained 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.

 

Tables

 

  1. Streamgages monitored during the data collection and their median and 25th and 75th percentiles of August daily flows for ensuring field observations occurred during normal streamflow magnitudes
  2. Basin characteristics developed for testing in the logistic regression analysis
  3. Diagnostics for explanatory variables used in the logistic regression equation for estimating the probability of a stream in Vermont having intermittent flow
  4. Classification table depicting accuracy of the logistic regression equation predicting the perennial or intermittent status of the stream sites held out of the logistic regression analysis for equation verification
  5. Classification table for the logistic regression equation for estimating the probability of a stream in Vermont having intermittent flow, with a probability cutpoint ranging from 0 to 1
  6. Estimated covariance matrix for the logistic regression equation
  7. Ranges of the basin characteristics used in the logistic regression equation

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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

dc_nh@usgs.gov

(603) 226-7807

or visit our Web site at: http://nh.water.usgs.gov

 



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