USGS

Initiation and Frequency of Debris Flows in Grand Canyon, Arizona

U.S. GEOLOGICAL SURVEY
Open-File Report 96—491

 

CONTENTS

Abstract

Introduction

Purpose and Scope

Units and Place Names

Acknowledgments

Setting

Methods

Initiation Mechanisms and Precipitation Recurrence Intervals

Selection of Geomorphically Significant Tributaries

Repeat Photography and Binomial Frequency of Debris Flows

Morphometric, Lithologic, and Climatic Variables

Statistical Procedures

Initiation of debris flows

Importance of Shale

Logistic-Regression Analyses

Eastern Grand Canyon

Western Grand Canyon

Non-Significant Variables

Discussion and Conclusions

References Cited

 

FIGURES

  1. Map showing the Colorado River in Grand Canyon National Park, Arizona
  2. Diagram showing the morphology of a typical debris fan in Grand Canyon
  3. Stratigraphic column showing rocks exposed in Grand Canyon
  4. Replicate photographs showing the debris fan at Ruby Rapid in Grand Canyon
  5. Replicate photographs showing the debris fan at South Canyon in Marble Canyon
  6. Histograms showing the statistical distributions of tributary drainage areas in Grand Canyon
  7. Map of Grand Canyon showing tributaries with debris-flow histories
  8. Photograph showing debris-flow source areas in Monument Creek
  9. Graph showing the failure mechanisms that have initiated debris flows in Grand Canyon
  10. Schematic diagram illustrating the initiation of debris flows by the direct failure of bedrock in Grand Canyon
  11. Photograph showing colluvial wedges overlying Muav Limestone
  12. Schematic diagram illustrating the initiation of debris flows by failure of colluvial wedges during rainfall
  13. Particle-size distribution of a debris-flow deposit
  14. Graph showing the principal component scores of variables used in the logistic-regression analyses for eastern Grand Canyon
  15. Graph showing the relation between drainage area and gradient in western Grand Canyon
  16. Graph showing the principal component scores of variables used in the logistic-regression analyses for western Grand Canyon
  17. Graph showing the relation between drainage area and gradient in eastern Grand Canyon
  18. Map showing the probability of debris flows in tributaries of the Colorado River in Grand Canyon
  19. Histograms of the probability of debris-flow occurrence in eastern and western Grand Canyon

TABLES

  1. Mean annual precipitation and temperatures in the vicinity of Grand Canyon
  2. Drainage-basin variables used in logistic regression
  3. Precipitation associated with selected debris flows in Grand Canyon
  4. Clay mineralogy of source material and debris flows in Grand Canyon
  5. Calibration model for debris-flow probability in tributaries of eastern Grand Canyon
  6. Verification model for debris-flow probability in tributaries of eastern Grand Canyon
  7. Calibration model for debris-flow probability in tributaries of western Grand Canyon
  8. Verification model for debris-flow probability in tributaries of western Grand Canyon

CONVERSION FACTORS

For readers who prefer to use inch-pound units, conversion factors for the terms in this report are listed below:

Multiply By To obtain

millimeter (mm) 0.03937 inch (in.)
meter (m) 3.2818 foot (ft)
square meter (m2) 10.76 square foot (ft2)
kilometer (km) 0.6214 mile (mi)
square kilometer (km2) 0.3861 square mile (mi2)

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)--a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called “Sea Level Datum of 1929.”

 

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