Alluvial fan flooding / Committee on Alluvial Fan Flooding, Water Science and Technology Board, Commission on Geosciences, Environment, and Resources, National Research Council.

Format:

Book

Contributor:

National Research Council (U.S.). Committee on Alluvial Fan Flooding.

Language:

English

Subjects (All):

Alluvial fans.

Floodplain management.

Physical Description:

1 online resource (x, 172 pages) : illustrations, maps

Edition:

1st ed.

Place of Publication:

Washington, D.C. : National Academy Press, 1996.

Language Note:

English

Summary:

Alluvial fans are gently sloping, fan-shaped landforms common at the base of mountain ranges in arid and semiarid regions such as the American West. Floods on alluvial fans, although characterized by relatively shallow depths, strike with little if any warning, can travel at extremely high velocities, and can carry a tremendous amount of sediment and debris. Such flooding presents unique problems to federal and state planners in terms of quantifying flood hazards, predicting the magnitude at which those hazards can be expected at a particular location, and devising reliable mitigation strategies. Alluvial Fan Flooding attempts to improve our capability to determine whether areas are subject to alluvial fan flooding and provides a practical perspective on how to make such a determination. The book presents criteria for determining whether an area is subject to flooding and provides examples of applying the definition and criteria to real situations in Arizona, California, New Mexico, Utah, and elsewhere. The volume also contains recommendations for the Federal Emergency Management Agency, which is primarily responsible for floodplain mapping, and for state and local decisionmakers involved in flood hazard reduction.

Contents:

ALLUVIAL FAN FLOODING

Copyright

Preface

Contents

Summary

1 Introduction

ORIGIN OF THE PROBLEM

The Problem of Delineating Flood Hazards on Alluvial Fans

The Problem of Defining Alluvial Fan Flooding

THE COMMITTEE'S RESPONSE

THE NFIP DEFINITION OF ALLUVIAL FAN FLOODING

IMPLICATIONS OF ALLUVIAL FAN FLOODING AS A DISTINCT TYPE OF FLOODING

IMPLICATIONS OF ALLUVIAL FAN FLOODING FOR FLOODPLAIN MANAGEMENT

THE COMMITTEE'S DEFINITION OF ALLUVIAL FAN FLOODING

REFERENCES

2 Flooding Processes and Environments on Alluvial Fans

FORMATION AND NATURE OF ALLUVIAL FANS

Streamflow Fans

Debris Flow Fans

Composite Fans

Incised Channels on Fans

FLOODING PROCESSES ON ALLUVIAL FANS

Flooding on Streamflow Fans

Flooding on Debris Flow Fans

Flooding on Composite Fans

CHANGE OVER TIME

REPORTS OF FLOODING ON ALLUVIAL FANS

3 Indicators for Characterizing Alluvial Fans and Alluvial Fan Flooding

STAGE 1: RECOGNIZING AND CHARACTERIZING ALLUVIAL FAN LANDFORMS

Determining whether or not a Landform is an Alluvial Fan

Composition

Morphology

Location

Defining the Boundaries of an Alluvial Fan

Toe

Lateral Boundaries

STAGE 2: DEFINING THE NATURE OF THE ALLUVIAL FAN ENVIRONMENT AND IDENTIFYING THE LOCATION OF ACTIVE EROSION AND DEPOSITION

Defining Active

Identifying Areas of Flooding and Deposition on the Active Part of an Alluvial Fan

Preparing a Geomorphic Map of Different Age Fan Surfaces

Morphologic and Weathering Criteria Used to Prepare a Geomorphic Map

Vegetation Criteria Used to Prepare a Geomorphic Map

Types of Alluvial Fan Flooding

Defining Flooding along Stable Channels

Identifying Areas Where Sheetflow Deposition Occurs

Identifying Areas Where Debris Flow Deposition Occurs.

STAGE 3: DEFINING AND CHARACTERIZING AREAS OF 100-YEAR ALLUVIAL FAN FLOODING

AVAILABLE METHODS OF ANALYSIS

SUMMARY

4 Applying the Indicators to Example Fans

HENDERSON CANYON, CALIFORNIA

Recognizing and Characterizing Alluvial Fans

Defining the Lateral Boundaries and Topographic Apex of the Alluvial Fan

Defining the Nature of the Alluvial Fan Environment

Active Fan

Relict Fan

Mountainous Drainage Basin

Storm of August 15-17, 1977

Changes in Flow Path

Characterizing Alluvial Fan Flooding Processes

Defining Areas of Active Alluvial Fan Flood Hazard

Defining Areas of Nonalluvial Fan Flooding Hazard along Stable Channels

Determining the Type of Processes Occurring on the Active Parts of the Alluvial Fan

THOUSAND PALMS WASH, CALIFORNIA

Flood of 1977

Flow Path Changes

Characterizing Alluvial Fan Flooding and Sedimentation Processes

LYTLE CREEK, CALIFORNIA

Past Floods

TORTOLITA MOUNTAINS, ARIZONA

Determining Whether or Not a Landform is an Alluvial Fan

Composition.

Morphology

CAREFREE, ARIZONA

Accounts of Flooding

Storm of June 22, 1972

Storm of October 6, 1993

Flow Path Movement

Defining Areas of Active Alluvial Fan Flooding Hazard

Determining the Types of Processes Occurring on the Active Parts of the Alluvial Fan

Using Soil Maps to Define the Nature of the Fan and the Extent of Flooding

RUDD CREEK, UTAH

Sedimentation Event of 1983

HUMID REGION ALLUVIAL FANS

Defining the Toe, Lateral Boundaries, and Topographic Apex of an Alluvial Fan

Defining the Nature of the Alluvial Fan Environment and Identifying the Loci of Active Sedimentation.

Defining Active

Identifying Areas of Flooding and Deposition for the Time Period Chosen to Represent the Active Part of an Alluvial Fan

Defining and Characterizing Areas of Alluvial Fan Flooding on Active Parts of Alluvial Fans

Defining Areas of Alluvial Fan Flooding Hazard

Identifying Areas where Flow Departs from Confined Channels (i.e., where Flow Paths are Uncertain)

Identifying Areas where Sheetflood Deposition Occurs

Identifying Areas where Debris Flow Deposition Occurs

Identifying Areas where Structures or Obstructions Might Aggravate or Cause Alluvial Fan Flooding

5 Conclusions and Recommendations

CONCLUSIONS

RECOMMENDATIONS

Definition

Supporting Explanation

Appendix A Characteristics and Hazards Reported in Published and Unpublished Accounts of Alluvial Fan Flooding

Appendix B Sources of Data

Appendix C Biographical Sketches of Committee Members

Appendix D Glossary and List of Acronyms

List of Acronyms.

Notes:

Bibliographic Level Mode of Issuance: Monograph

Includes bibliographical references.

ISBN:

9786610191956

9780309185493

0309185491

9781280191954

1280191953

9780309589383

030958938X

9780585028842

0585028842

OCLC:

42329408