Santa Clara Pueblo: Challenges in the Design and Installation of Debris FlowBarriers in a Post-Wildfire Landscape

Joseph Renner, G.I.T.1; Joseph McElhany1; Bill Niemann, Ph.D., E.I.T., P.G.2; William F. Kane, Ph.D., P.G., P.E.1

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Project Overview

• General characteristics of post-wildfire debris flows

• Project description

• Geologic setting of Santa Clara Canyon

• Barrier design

• Installation & Oversight

General characteristics of post-wildfire debris flows

Click for current wildfires

Rio Arriba Co., NM

Wildfire Activity by County, 1994-2013

Post-wildfire debris flowsUSGS, 2004

Post-Wildfire Debris Flows

According to USGS (2011):

• After a wildfire watersheds can shift from a system dominated by infiltration to one dominated by runoff.

• Decreased infiltration and increased runoff because wildfire:

• destroys rainfall-intercepting canopy,• destroys soil-mantling litter,• destroys “duff,”• overheats soil, making it more water-repellent,• deposits fine ash, blocking soil pores especially, when wetted.

Post-Wildfire Debris Flows (cont.)

According to USGS (2011):

• Enhanced runoff can erode ash, soil, boulders and vegetation.

• Sediment-laden flow can progressively transition to debris flows.

• Debris flows most common 2-3 years after wildfires

USGS, 2002Perry Castaneda Library

at U. of Texas

Project Description

• Santa Clara Canyon is on land owned by Santa Clara Pueblo, a community of people belonging to the Tewa ethnic group of Native Americans. The canyon is sacred to these people.

• Canyon roads and infrastructure were extensively damaged by debris flows following the Los Conchas wildfire in 2011, which burned for five days and destroyed over150,000 acres (244 square miles). At that time the fire was the largest wildfire in New Mexico history.

Fowler, 2011

Los Conchas wildfire, 2011

Fire and debris flow damage, Santa Clara Canyon

Fire and debris flow damage, Santa Clara Canyon

Project Description (cont.)

• FEMA money obtained to repair damages and install fourdebris flow barriers in high-risk tributary canyons.

• Kane GeoTech, Inc. was hired to design the barriers and provideconstruction oversight.

• I was involved as a temporary employee of Kane GeoTech, Inc. as part of a sabbatical from Marshall University.

Design and Construction Oversight

Barrier Installation

Drilling Services

Barrier Manufacturer

Project Partners

Geologic setting of Santa Clara Canyon

Valles Caldera

Bedrock geology

Surficial geology

9-22-14

(USGS, 2011)

Extent of Las Conchas Fire

Barrier Design

Dimensions of debris barriers

Barrier No. Barrier Type Top channel width (ft)

Bottom channel

width (ft)Height (ft)

H.A. 1 GB UX 180-H6 64 24 20

H.A. 4

BERM N3

BERM N4 GB UX 160-H6 77 50 12

Barrier Dimensions

bedrock

bedrock

7/8” braided steel ropes

rock anchors(1.25” wire rope)

bedrock & rock anchors (1.25” wire rope)

rock anchors(1.25” wire rope)

rock anchors(1.25” wire rope)

rock anchors(1.25” wire rope)

4

32

7/8” braided steel rope

2 22 2

Barrier Design

6’ anchors in concrete (1.25” thread bar)

Barrier Design

Geobrugg Rocco Ring Net

Brake rings

Installation & Oversight

10-14-14Air rotary drill

mounted on Spyder Kaiser S2.4

rock anchors(1.25” wire rope)

grouted anchor

grouted anchors

7/8” upslope retaining ropes

Barrier design --support ropes and rock anchors

Barrier design--brake rings

Barrier designGeobrugg Rocco Ring Net

Daily Field Reports (DFR’s)

Debris Flow Barriers

• Effective• Inexpensive

• Ease of construction

Thank you!