FLOOD02650

• County: La Plata
• Stream Name: Animas River
• Basin: San Juan/Dolores
• Title: Hydrology Addendum to FIS La Plata County Unincorporated Areas
• Date: 5/21/2002
• Prepared For: La Plata County
• Prepared By: Montgomery Watson
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE OF CONTENTS

SUBJECT

PAGE

Authorization................. ....... ......... ........ .......... .................. ...... .......................... ............. .......1

Purpose of Study ....................................................................................................................1

Watershed Description...........................................................................................................1
Existing Flood Control Improvements...................................................................................1

H)'irologic Analysis...............................................................................................................2

Unit Hydrograph Computation ..........................................................................................3

Channel Routing ...... ..........................................................................................................3

Frequency Rainfall.............................................................................................................3

Infiltration Rate Calibration...................................................................... ........... ..... .........4

Vallecito Dam Operation ...................................................................................................5
Hydrologic Analysis Results ..............................................................................................5

Hydraulic Analysis .................................................................................................................1 0

Mapping .............................................................................................................................10

Cross Sections......................................................... ............................................. ..... .... .....1 0

Roughness Coefficients ......................................................................... ........ ............ ...., ...1 0

Bridges..............................,............................................................................................... .11

Hydraulic Model ...............,.................................................................... ............................12

Hydraulic Analysis Results............................. ........................................................ .......... .13

Profiles.............................................................................................................................. .14

Flood Plain Maps ....... ........................................................................................................14
Results and Recommendations ..............................................................................................14

References .................................... ... .......................................................................................16

TABLE

PAGE

I USGS Stream Gages ..................................................................................................2

2 Infiltration Rates ............................................................................ ............................4
3 Discharge Frequency Peaks .......................................................................................5
4 Structural Crossing Inventory ...........................................,........................................12

5 Water Surface Elevations...........................................................................................13

FIGURE

PAGE

I Hydrographs at Red Creek.........................:.::............................................................6

2 Hydrographs near Colurnbus.................................................................. ....................7

3 Hydrographs at Bear Creek ........................................................................................8

4 Hydrographs at Bayfield ............................................................................................9