Emergency Watershed Protection

Protecting Life + Property While Enhancing the Riparian Ecosystem

North Fork Big Thompson River

 
 
snipNorthfork.JPG

North Fork EWP

 
 

The North Fork project is located at the confluence of the North Fork and main stem of the Big Thompson River near the Town of Drake. Set in a natural opening in the canyon, the North Fork reclaimed historic channel pathways and deposited large quantities of sediment during the 2013 Colorado flood.

Storm Mountain Bridge at the upper project boundary was flanked by flood flows, while the Highway 34 bridge at the downstream end was completely blocked by sediment and debris. 

Additionally, public and private infrastructure built within the river corridor, including campground buildings, private residences, a hotel, and a roadway embankment, were damaged by these natural river processes.

Restoring immediate access was a top priority after the flood, but emergency measures executed without a holistic vision left the reach severely degraded and in need of significant additional investment to repair.

 
Construction near Storm Mountain Bridge, February 2017.

Construction near Storm Mountain Bridge, February 2017.

 

Project Goals

Protect life, property + Infrastructure

Stabilize streambanks to protect against additional damage to existing infrastructure

 

mitigate flood risk

Increase the capacity of the stream channel and floodplain

 

improve water quality

Improve water quality through the reduction of sediment loading caused by bank erosion; establish cover on critically eroding land.

 

enhance ecosystem structure + function

Enhance riparian habitat through revegetation. Improve fish habitat through revegetation, improved water quality, and better in-stream habitat complexity

 

expand recreational opportunities, bolster economic development + enrich tourism 

Create a space that blends into the landscape and feels natural;  develop features that encourage participation with the river. 

 
 
Top: Construction on the North Fork EWP project. Credit: Mike Blazewicz
Below: The confluence of the North Fork and the main stem of the Big Thompson River in Drake, CO during the 2013 flood, September 2013.  Credit: Civil Air Patrol

In this project, natural channel adjustment of the low-flow and bankfull channels is welcome and even encouraged.

Because large flood flows cannot be contained with the channel, an overflow channel was excavated and guidebanks were added to direct flood flows around critical infrastructure.

Engineered in-channel structures are designed using native materials that mimic natural bed forms in order to sustain long-term bed stability while replicating natural elements in the system.  

Whenever possible, plant materials were incorporated into engineered structures (bioengineering), as the combination of rock and roots will add strength to the structures and provide long-term ecological benefits to the stream.

Large wood was reintroduced into the channel and floodplain to provide habitat complexity and direct erosive energy away from vulberable stream banks. 

 

 

3000

Cubic yards of sediment removed

2100

linear feet of River rehabilitation

899

container plants installed

15

large wood structures constructed

November 2013: Looking upstream at the North Fork of the Big Thompson River from the US 34 bridge 2 months after the flood. The flood deposited massive amounts of sediment and debris at the confluence of the two rivers. Water and sediment caused damage the homes, businesses, roadways, and bridges located in the active river corridor. Photo Credit: Bill Spitz.

November 2013: Looking upstream at the North Fork of the Big Thompson River from the US 34 bridge 2 months after the flood. The flood deposited massive amounts of sediment and debris at the confluence of the two rivers. Water and sediment caused damage the homes, businesses, roadways, and bridges located in the active river corridor. Photo Credit: Bill Spitz.

 
March 2017: Looking upstream at the North Fork from the US 34 bridge during construction. The project removed sediment and debris to increase the river corridor’s size and allow areas for future sediment deposition and realigned the channel for improved floodplain access and a better approach to the bridge. Wood and rock structures are intended to provide bank protection and grade control while allowing for natural shifting of the low-flow channel.

March 2017: Looking upstream at the North Fork from the US 34 bridge during construction. The project removed sediment and debris to increase the river corridor’s size and allow areas for future sediment deposition and realigned the channel for improved floodplain access and a better approach to the bridge. Wood and rock structures are intended to provide bank protection and grade control while allowing for natural shifting of the low-flow channel.

 
July 2018: 16 months after the completion of construction activities.

July 2018: 16 months after the completion of construction activities.

 
February 2017: Upper project reach immediately after construction.

February 2017: Upper project reach immediately after construction.

December 2016: Looking upstream at the North Fork from the US 34 bridge after emergency work was completed (December 2016). Efforts undertaken in the months following the flood to quickly protect damaged structures from a large spring runoff resulted in a channelized ditch with riprap on both sides. The emergency repairs may have provided some emotional comfort but offered very little long-term relief and even less ecological benefit.

December 2016: Looking upstream at the North Fork from the US 34 bridge after emergency work was completed (December 2016). Efforts undertaken in the months following the flood to quickly protect damaged structures from a large spring runoff resulted in a channelized ditch with riprap on both sides. The emergency repairs may have provided some emotional comfort but offered very little long-term relief and even less ecological benefit.

 
May 2018: Looking upstream at the North Fork from the US 34 bridge one year after project completion. In this lower reach, the project created riffle/pool sequences and planted the site with native container plants and live stakes. Four riparian seed mixes were installed and have begun to establish over the last two growing seasons.

May 2018: Looking upstream at the North Fork from the US 34 bridge one year after project completion. In this lower reach, the project created riffle/pool sequences and planted the site with native container plants and live stakes. Four riparian seed mixes were installed and have begun to establish over the last two growing seasons.

 
This reach is looking outstanding! Cascades and pools are functioning really well and the campsite seems to be thriving again...Thank you for bringing this project to life and making it successful.
Job well done!
— Joe Juergensen, Project Manager
 

Project Sponsorship + Funding

The project was designed and constructed for Larimer County in partnership with the Big Thompson Watershed Coalition. It was completed as part of the flood recovery activities associated with the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Phase 2 Emergency Watershed Protection (EWP) Program.   Larimer County provided the local match in the form of donated rock material.

Our partners at Muller Engineering Company performed the detailed design services for this project while Watershed Science + Design and Round River Design oversaw the implementation of the project in the field.

 

North Fork EWP

Project location