FLOOD08020

• County: Statewide
• Basin: Statewide
• Title: Techniques for Estimating the Magnitude and Frequency of Floods in Minnesota
• Date: 1/1/1988
• Prepared For: USDOT
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

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CONTENTS

Page

Abstract. . _ . . . _ . . . . . . . . . . . . . . . . . . . . . . . . _ _ _ . . . _ _ _ _ . . . . _ . . . . . . . _ . . . _ _ _ . . 1
Introduction. . . . . . . . . . . . _. . .. .. . . _. . .. . .. . . . . . . _ _. . .. _ . .. . . . .. . .. . . . .. 1
Background. . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . _ . . . _ . . . . _ . _ . . . . . . . _ 1
Purpose and scope. . . . . . . _ . . . . . . . . _ _ _ _ _ _ . . . . . . . . . . . . . . . . . . . . . . . . . _ 2
Analytical techniques............... _ . . . . . _ . . _ . _ _ . . . _ _ . . . . . . _ _ . _ . . . . . . 2
Flood-frequency analysis of gaging stations_.. ___. .___.__. '___'" 2
Multiple-regression analysis.__.... ______.. ....... ._...... ._. __.. 4

Regional analys is _ _ . . . . . . . . _ . . . . . _ _ _ _ _ . . . _ _ . . . . . . . . . . . . . . . . . . . . . . 6
Basin characteristics investigated...... .____. __.__... ._. ._... ... 8
Estimating flood frequency of unregulated streams...... .__.. ._..... ... 8
Analyses of ungaged sites using generalized relationships. ._..... 8

Examp le 1. _ . _ . _ . . . . . . . . . . . . . _ . . . _ _ . . . . . . . . . . _ . . . _ . . . . . _ _ . . . . 12
Transfer of flood-flow information from a gaged site. ... ._.._. ... 13

Example 2.............. _ . . _ . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . 14
Example 3......................... _ . . . . _ _ . _ . . . . . . . _ . . . . . . . . . 15
Accuracy and limitations of estimating technique.__......... ._..... .._ 16

Summary and conclusions. _ . . _ . . . . . . . . . . _ . . _ . _ . . . . . . . . . . . . . . . . . . . . . . . . . . 18
References cited......... _ . . _ . . . . _ . . . . . . . . . . . . _ _ _ . . . _ _ _ _ . . . . . . . . . . . _ . . 19
Glossary. . _ . . . . . _ _ . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . _ . . _ . . . _ _ . . . . . . . . . . . . 20

Figure 1.
2-4.

Table
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JJ
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2-5.

ILLUSTRATIONS

Graph showing example of flood-frequency plot..... ._.....
Maps showing:
2. Location of gaging stations used to define
regression equations......_...... ...... ._.....
3. Hydrologic regions in Minnesota ................
4. Hydrologic mean annual runoff in Minnesota._. ...

TABLES

1.

Predictive equations, standard errors of the estimate,
and equivalent years of record for all regions...... ...
Basin and flood-flow characteristics for:

2. Region A. . . . _ . . . . . _ . . . . . . . _ . . . _ _ _ _ . . . . . . . . . . _ _ . .
3. Region B.. . . . . . . . . . . _ . _ _ _ _ _ _ . . . . . . . . . . . . . . . . . . . .
4. Region C_.. _... _.. _ _....... _ _ _. _..... _.. _.. _....
5. Region D.. . . . . . . . _ . . . . . . . . . . . . _ _ _ . . . . _ _ . . . . . . _ . .
Ranges of basin characteristics for each of the regions
used in the regression analysis. . . . . _ . . . . _ _ _ . . _ . . . . . . . -

6.

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