FLOOD10929

• County: Mineral
• Community: Creede
• Stream Name: Upper Willow Creek
• Basin: Rio Grande
• Title: Upper Willow Creek Watershed - FLood Control and Stream Stability Study
• Date: 10/1/2002
• Prepared For: Willow Creek Reclaimation Committee
• Prepared By: Agro Engineering
• Floodplain - Doc Type: Floodplain Report/Masterplan

TABLE OF CONTENTS

E XE C UTIVE SUMMARy........................................................................................................... i

Section 1 - Project Overview ..................................................................................................... 1-1

1.1 Introduction................................................................................................................. . 1-1

1.2 Project Objectives ........................................................................................................1-2

1.3 Proj ect Location........................................................................................................... 1-3

1.4 Overview of Problems................................................................................................. 1-5

1.4.1 Flood Control............................................................................................................. 1-5

Flume Entrance................................................................................................................ 1-6

Mining Museum Area...................................................................................................... 1-6

North Creede . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1- 7

Commodore Mine............................................................................................................ 1-7

Amethyst Mine................................................................................................................. 1-7

1.4.2 Sediment and Debris ..................................................................................................1-7

Section 2 - Analysis of Problems ..............................................................................................2-1

2.1 Development of Topographic Information ..................................................................2-1
2.1.1 Low-Resolution Topography ...............................................................................2-1
2.1.2 High-Resolution Topography.............................................................................. 2-1
2.2 Baseline Floodplain Analysis...................................................................................... 2-9
2.2.1 Past Floodplain Studies........................................................................................ 2-9

2.2.2 Hydro logy ............................................................................................................ 2 - 9

2.2.3 Hydraulic Analysis................................................................................................... 2-13

2.2.3.1 Model Geometry and Setup........................................................................... 2-13

2.2.3.2 HEC- RAS Results.......................................................................................... 2-16

2.2.3.3 Floodplain Delineation................................................................................... 2-17
Upper Willow Creek Above Flume........................................................................... 2-22
Overtopping of Weir at Cross Section 14.................................................................. 2-22

Avulsion at Cross Section 8.5 ....................................................................................2-24

Avulsion at Cross Section 6.1....................................................................................2-24

Windy Gulch Culvert................................................................................................. 2-25

Entrance to Army Corps Flume................................................................................. 2-26

North Creede Culvert................................................................................................. 2-28

West Willow Creek Bridge........................................................................................ 2- 30

We s t Willow C re e k Culvert....................................................................................... 2 - 3 0

Commodore Mine...................................................................................................... 2- 32

Amethyst Mine Culvert.............................................................................................. 2- 36

Culverts between Commodore and Amethyst Mines ................................................2-36

2.3 W a tersh e d Con di ti 0 ns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 - 3 7

2.3.1 Watershed Physical Characteristics................................................................... 2- 37
2.3.2 Watershed Sediment Sources............................................................................. 2- 39
2.3 .3 Watershed Sediment Production PotentiaL........................................................ 2-41

2.4 Sediment Transport.................................................................................................... 2-43

2 .4. 1 S lop e Anal y s is. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 - 43

2.4.3 Sediment Transport............................................................................................ 2-45

2.4.4 Channel Debris................................................................................................... 2- 50