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Fall Creek Fish Migration Barrier


The San Juan Cutthroat Trout is a rare lineage native to the San Juan National Forest.  They are subject to competition and interbreeding from invasive species such as rainbow trout, which threaten the survival of the lineage in many areas.  In Fall Creek, a tributary of Wolf Creek just south of Wolf Creek Pass, a surviving population of San Juan trout has been discovered in the upstream part of the creek.  The Forest Service intends to build a migration barrier to prevent invasive trout from traveling upstream and protect the existing population and has identified a suitable location to build a small waterfall for the purpose.  The Senior Design team has designed the required migration barrier to remain stable and effective under 100-year flood conditions. 

The Fall Creek fish migration barrier project aims to design a structure within Fall Creek to prevent the passage upstream of certain species of non-native fish. This effort is to protect the San Juan cutthroat trout and prevent cross breeding with other species. Because of natural stressors including aquatic invasive species, they are only found in 11% of their original habitat. The length of Fall Creek upstream of the barrier location is home to San Juan trout and this barrier will allow them to thrive in this section with no competition from other species.

The location where the barrier is to be installed has a relatively straight trapezoidal channel section downstream of the barrier site. The area upstream of the barrier site is two channels that converge. There is a 5-10% downhill slope Southwest. The soil is sandy with large rocks ranging in size. There is no concern for expansive soils. There is a concern pertaining to water seepage and erosion and washouts during large floods. There is no bedrock to tie the foundation to.

Flow data was collected at 7 different points upstream and downstream of the barrier site. There was little flow in the stream due to the time of year data was collected. The highest flow collected in the area was .0315 cubic feet per second.

The bank full flows in Fall Creek are 200-1000 cubic feet per second. The actual flows in the stream are expected to be much less, with the 100-year flow estimated to be 350 cfs. The expected velocities of the stream are less than 30 feet per second. The expected shear force is up to 35 pounds per square foot. 


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Team Members

  • Stephen Peyton
  • Daniel Philippus 
  • Luke Metzer
  • Isabella Montoya
  • Ben Becker
  • Brandon Julian
  • Hannah Shultz

The Client

United States Forest Service

  • Clay Kampf


Project Advisor: Lisa Woodward

Technical Advisor: Alexandra Wayllace, Ph.D., Marte Gutierrez, Ph.D., Kristoph-Dietrich Kinzli,  Ph.D.

Donations Made by: Colorado Trout Unlimited


Elevator Pitch


The San Juan Cutthroat trout are a rare lineage that live in Fall Creek, near Pagosa Springs, CO. There are only about 2,000 known members of the species in existence today. The habitat for these fish lies in the San Juan National Forest.  

The purpose of this project was to build a new barrier structure to keep invasive brook and rainbow trout species from traveling further upstream to interbreed with the San Juan Cutthroat in their native habitat above the existing natural barrier. This is an effort to preserve this endangered fish. The structure was designed in an arch shape to reduce stress on the structure and stands 7 feet above the streambed. The height was chosen from flow modeling of a 100yr event while needing to always maintain a 4-foot effective drop to prevent full grown invasive trout from jumping the barrier. Wingwalls were added upstream of the barrier to channel flow towards the center of structure, and tapered walls were implemented downstream of the barrier structure to maintain bank stabilization.

Design Approach

The design is based around a waterfall, which is intended to maintain a 3 ft effective drop from crest to water surface during a 100-year storm event.  The center of the waterfall is lower than the edges to keep flow towards the center of the stream. Upstream wingwalls are used to funnel water towards the waterfall and prevent high flows from going around the barrier.  Downstream wingwalls are used to minimize bank erosion.  A splash pad is located below the waterfall to avoid undercutting.

In order to have a good design, it is crucial to grade the site to meet the demands of the project. The first design parameter focused on for this project was ensuring that a 7 ft drop from the crest of the waterfall to the top of the creek bed downstream was achieved. After finding a spot near a natural 3 ft drop in the creek, it was determined that this would be the location for the waterfall. Once we had the location, elevations needed to be determined for the up and downstream creek bed that allowed the 7 ft drop while still ensuring that the cut to fill ratio was met. It was determined through engagement with the client that off-site soil would not be used. In grading terms, the amount of cut needed to exceed the amount of fill required for our grading design. Knowing that the client wanted a -1% bed slope going into the structure from upstream, and a -2% bed slope leaving the structure, a profile for the creek was designed. The final step was grading the banks of the creek to ensure that it was hydraulically sound. This was challenging given the steep existing grades for the banks. Constant alterations were made to ensure all demands were made while ensuring a slope no greater than 2:1 occurred for soil stability, except for where the finished ground tied into the existing grades.  A surface view and plan view can be seen in the images below.

Fall Creek is fed by a 3.43 sq-mi catchment area that serves as a tributary to Wolf Creek.  The creek is rainwater fed with the snowpack assumed to contribute to flow in late spring.  The hydrologic model assumes that snow melt is maximized via NOAA snowpack equivalency calculations, and that a 24 hr storm occurs in accordance with the TP-40 Rainfall Frequency Atlas with a type-II storm distribution over that 24 hour period. A series of models were run according to the total rainfall accumulation corresponding to a given frequency.  This project is required to maintain effectiveness during the 100-year storm event, which corresponds to a modelled discharge of 600 cfs with assumed safety factors.  The client has indicated that the discharge is far beyond the expectations for the area, and that 350 cfs is more realistic.  This flow value is in alignment with values from StreamStats, which is produced by USGS. 

In order to determine stresses on the waterfall and necessary waterfall and wingwall heights, the system was modeled using a two-dimensional, unsteady-state HEC-RAS hydraulic model. For initial design, the current geometry was modeled, and then design decisions were validated by running the model with the design geometry.  Boundary conditions were set based on the outputs from the hydrologic analysis above.  Although the most conservative prediction for the 100-year flow was about 600 cfs, on the advice of the client we did final design validation with a design flow of 350 cfs. 

This Fall Creek Fish Migration Barrier design consisted of using three different types of blocks, 5’x5’x8’, 4’x4’x5’, and 3’x3’x3’ using a typical profile as shown above. Based off of block placement there were three main cross sections analyzed, the crest section, the maximum downstream retaining wall section, and the upstream wing wall section.

From here, the structure was analyzed along a 2-D typical profile along the structure. There were five main failure types analyzed for this 2-D profile: bearing capacity failure, moment failure between the block and the foundation, and sliding failure between the block and the foundation, and between the individual blocks. The upstream wing walls and downstream retaining walls were analyzed as typical 2-D sections using Terzaghi’s earth pressure formulas. This method considered analyzing lateral forces such as soil and water pressures against the friction forces caused from the weight of the structure and the soil on top of it for friction. For moment failure, the overturning moments caused by the lateral earth pressures and lateral water pressure were analyzed against the righting moments of the weight of the structure and any lateral pressures on the opposing site of the structure. The factors of safety for this analysis consisted of 1.5 for sliding, 2.5 for moment/overturning, and a maximum bearing capacity of 2000 psf.  Uplift was considered for all cross sections that met water. While the crest was stable in the 2-D typical profile that also included hydraulic shear, another different analysis method was used when analyzing overturning and sliding both between the individual blocks and between the entire structure and potential lateral stresses applied to the ends of the arch. Due to the arch shape of the crest any lateral displacement of said structure would put the arch further into compression if the blocks were placed tightly together enough to hold to structure together when in compression. While the benefits of this arch shape where not accounted for, it was still important to analyze any lateral pressure caused by this arch shape to soil surrounding the outer edges of the crest. This analysis found that any potential stresses applied to soil because of the arch shape were well within the passive earth pressure of the soil. In a more critical condition, it would have been important to analyze the structure using a finite element program/computer analysis to get the exact effects of the placement of the blocks, however it was determined that the design was already conservative and stable enough to withstand the applied loads and therefore did not need a more accurate analysis.

In addition to the basic structural design described above, the site plan includes components to address freeze-thaw and minimize subterranean flow.  Behind the waterfall face, layers of geomembrane are to be extended in order to minimize infiltration and prevent the face from being subjected to freeze-thaw stresses.  In addition, a seepage pipe is optionally included to reroute any subterranean flow around the wall. 

Risk Mitigation

The Rowdy Anglers did analysis on risk mitigation for the Fall Creek Fish Migration Barrier. The analysis focused on technical risk, time risk, and environmental risk.

The first subsection of risk is technical risk.  There are two areas of high risk involved in this subsection.  High risk, for the purposes of this project is anything that would cause immediate failure or disrupt the completion of the project as a whole.  The first critical risk in the technical design are the tie-in points of the structure itself.  Currently, there are two large trees with full roots systems, one on each side of the bank, in the locations where the structure will tie into the bank of Fall Creek.  Initial discussions revolved around using the two trees and anchors for the structure, but since those conversations, a risk analysis has been performed.  If the construction of the barrier caused the root system to lose stability or damaged the root system and endangered the life of either tree, there is a high possibility of one of the trees falling.  If this occurs and either tree falls on the structure it is surely to cause damage and possible failure of the structure.  This therefore is an area of high risk, if the trees are left in place during construction.  The second area of high risk in the technical design is a lack of material sourcing.  Early estimates and consulting have shown that the preferred prefabrication material is not kept in large quantities by local suppliers in the Pagosa Springs, CO area.  This poses a threat to the completion of the project and therefore is worth considering a high-risk objective.

The second area of risk in this analysis is time sensitive risk.  The entirety of this section has been deemed high risk because any if any of these risks manifest themselves, it will cause the delay and or termination of the project before completion.  This is in direct opposition of our project goals and deliverables therefor creating a high risk.  These risks, stated in the above chart, include unforeseen weather in a particular season, administrative shortfalls, and lack of logistical excellence.  These risks, while all having the same effect on the project, have individual reasons ranging from the uncontrollable (weather) to lack of attention to detail by contractor and USFS personnel.

The third area of risk is environmental risk.  After analysis, this area poses 4 critical risks worth denoting in detail. The first is possible chemical seepage from concrete during construction causing pollution to the stream and harm to the native fish species.  This is a high risk, because if flows are not low enough to pump the river around the construction site and the concrete is not given ample time to cure, it will reach the water of Fall Creek.  This however is avoidable given current project guidelines and construction plans.  The second area of high environmental risk is posing health threats to native species in the stream at the time of construction. This is most certainly and assumed risk on behalf of the project.  Fortunately, most of the critical species, The San Juan Cutthroat Trout, are currently living in the San Juan National Forest Fishery.  This will provide population maintenance until the successful construction of the barrier is complete.  The next area of environmental risk is noise pollution during construction.  This is also an assumed risk that largely unavoidable for this project.  The only mitigation that will help with this is limiting the amount of time of construction by ensuring onsite efficiency.  The last area of high risk for the environmental analysis is the water pollution caused by construction.  This is a critical risk given the fact that there is municipal water use a few hundred yards downstream.  This will be mitigated by constructing the barrier in extremely low flows where the water is diverted by a pump around the construction site.

In concluding the risk analysis, a few areas of low risk are worth mentioning.  Specifically, in the technical risk section, there are areas of risk that will require maintenance throughout the life of the structure.  This includes removing large debris and maintaining bank stability once the structure is established.

Design Solution

The design is based around a waterfall, which is intended to maintain a 3 ft effective drop from crest to water surface during a 100-year storm event.  The center of the waterfall is lower than the edges to keep flow towards the center of the stream. Upstream wingwalls are used to funnel water towards the waterfall and prevent high flows from going around the barrier.  Downstream wingwalls are used to minimize bank erosion.  A splash pad is located below the waterfall to avoid undercutting.

Next Steps

While the team was able to achieve their requirements, there were some portions of the work breakdown structure that the team did not complete. This includes an intermediate and final 3D model, initial structural calculations and a RISA structural analysis. The team was able to complete all other topics to the levels required for the project scope. The intermediate and final 3D model where not constructed because they were not deemed necessary for the project. The initial 3D models where important for visualizing the designs in the preliminary design review. However, following the design decision, this visualization was no longer necessary or was satisfied by the AutoCAD/Civil 3D drawings. The initial structural calculations where not performed because they were not needed for the preliminary designs. Once a design was chosen, structural calculations where performed to verify that the selected design could satisfy the loading requirements. Lastly, the RISA Structural Analysis was not performed because the design was conservative enough that this higher level of accuracy was not necessary. The construction schedule can be seen below.


Meet the Team

Stephen Peyton

Role: Communication Lead

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Major: Civil Engineering

Future Plans: I will be interning with the US Army Corps of Engineers – Alaska District.  I hope to return to Colorado in a few years and to work on hydrology or humanitarian projects.  My motivation is to improve the lives of others, and as long as I attain this goal, I consider my work and career successful.

Fun Fact:  I own 35 patterns of plaid.

Daniel Philippus

Role: Scrum Lead

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Major: Civil Engineering

Future Plans: Daniel is staying at Mines to pursue a master’s degree in hydrology, where he intends to emphasize mathematical and computational approaches to hydrologic science and engineering.
Fun Fact: Daniel once did 33 river crossings in a single day when backpacking in New Mexico.


Luke Metzer


Role: Project Manager

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Major: Mechanical Engineering

Future Plans: Luke has accepted a job as a Catholic missionary with Focus and will be serving in full time campus ministry when he graduates. He also has aspirations of attending graduate school to earn an MBA.

Fun Fact: Luke loves drinking coffee on the porch in mornings watching the sunrise.


Isabella Montoya

Role: Safety Lead

Major: Environmental Engineering

Future Plans: I plan on working in the mining industry.

Fun Fact: I am a Colorado native.

Ben Becker

Role: Structural Design Lead

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Major: Civil Engineering

Future Plans: I will return to the Colorado School of Mines next fall for my masters in structural engineering which I will graduate with in December 2021. This summer I have a structural internship with CDM Smith.

Fun Fact: I used to work for and am part of owner of a lumber/firewood company.


Brandon Julian

Role: Technical Lead

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Major: Civil Engineering

Future Plans: I plan on moving to Montrose, Colorado and begin working for Del-Mont Consultants as a Project Engineer.
Fun Fact: I learned how to ride a dirt bike before I learned how to ride a bicycle.


Hannah Shultz

Role: Budget Lead

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Major: Environmental Engineering

Future Plans: I will be graduating in December and I am in pursuit of a future career in site remediation.

Fun Fact: I plan to get a private pilots license after I graduate.