Eleven-Mile Canyon Demonstration Project

Case Study 4

The Eleven-mile Canyon Demonstration Project

Project Overview The Eleven-mile Canyon Demonstration Project is located on the South Platte River in Park County, Colorado (figure 1). This project area is located in a semiarid (less than 15 inches of precipitation per year) portion of the foothills zone of the Rocky Mountains (Pennak 1977). The bedrock underlying this canyon area is comprised primarily of biotite granite that produces highly erodible, unproductive soils. This condition also results in sparse ground cover, contributing to the area’s erosive nature. The landscape is bisected by relatively steep, narrow drainages with abundant erosional stream channels.

Figure 1: Vicinity map of Eleven-mile Canyon. Study reaches are identified by reach numbers. (The inset map identifies the location of the canyon within the Pike National Forest.)

In the late 1800s a railroad was built in the Eleven-mile Canyon, further narrowing the Eleven-mile Canyon floor. Large native trees were removed Eleven-mile Canyon Demonstration Project from the valley floor for use in the nearby metropolitan areas.

In the early 1900s the city of Denver began building reservoirs and associated conduits for water storage in the South Platte River corridor, for use by the increasing population. The releases from these reservoirs have created a hydrograph considerably different than what would be expected under historic conditions (figure 2). The removal of trees, location and maintenance of the road corridor, and modified flow releases from upstream reservoirs has created a stream system considerably altered from pre-European settler conditions.

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Figure 2: Comparison of a hydrograph from a regulated section of the South Platte River downstream of Eleven-mile Canyon to a more natural flow regime in Tarryall Creek, a tributary to the South Platte River.

In 1993, a complete stream-condition inventory determined limiting factors for trout production (Winters, Gallagher, McMartin, 1993). The results showed that the lack of inadequate habitat complexity was the primary limiting factor in portions of the canyon. Low-gradient “glides” were areas particularly associated with relatively homogenous habitat conditions. To remedy the poor habitat conditions, the Pike-San Isabel National Forests and the Colorado Division of Wildlife (CDOW) signed a multiyear cooperative agreement. We identified strategic boulder placement, anchoring large coniferous trees in sections of the stream channel, and reconstructing the stream channel as appropriate for this type of system (Rosgen C-type channel). Construction began in 1996.

We placed structures primarily in glides with fairly uniform current velocities and little heterogeneity in habitat conditions.

Eleven-mile Canyon Demonstration Project From our inventory efforts, we agreed that physical changes in the morphology of the river were necessary for providing better quality habitat availability for various life-stages of brown and rainbow trout. The desired changes included: 1) A decrease in the width-to-depth ratio where appropriate. 2) An increase in residual pool depth in identified pools. 3) An increase in habitat complexity in relatively sterile glide habitats. 4) No loss or improvement to aesthetic values for visitors. 5) An ultimate increase in abundance of adult rainbow and brown trout.

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To determine the effectiveness of the instream channel structures, we attempted to answer these four questions.

1. Do instream channel structures in a regulated mountain river increase aquatic habitat complexity and ultimately adult trout abundance (density and biomass) by increasing habitat complexity and residual depth, and decreasing the width-to-depth ratio of the project area? 2. Do structure orientation and elevation determine the effectiveness (scour success and self-maintenance) of instream channel structures? 3. Which types of structures are most efficient in increasing aquatic habitat complexity, residual pool depth, and fish abundance (density and biomass)? 4. Which structures and placement characteristics result in limited maintenance while providing the desired effects?

Project Methods, Design, and Monitoring In 1993, initial preproject basinwide stream habitat surveys used a modified Hankin-Reeves method (Winters, et al, 1991, rev. 1997). We identified stream reaches according to channel type and valley configuration (Rosgen 1996). Within each reach, we recorded specific stream channel morphological and biological habitat conditions. Also, we took photographs for each habitat unit (e.g., pool, riffle, glide) and other unique or impacted areas, for later comparisons with postproject conditions.

To further quantify the potential influence of modifying various habitat complexity to homogenous glides in the project area, we modeled changes

in stream velocities, substrate, and depth using the physical habitat Eleven-mile Canyon Demonstration Project simulation model (PHABSIM) for different life-stages of brown and rainbow trout developed by Bovee (1982). The purpose of this exercise was to determine whether the PHABSIM model could accurately predict the changes in habitat for different life-stages of brown and rainbow trout. The CDOW developed habitat suitability curves for the South Platte River, and used them to identify potential changes in adult and juvenile life- history stages of both species. We identified a glide in the project area that had conditions of both a typical homogenous habitat in the project area and areas of complexity due to boulders and a large tree within the stream channel. These natural “structures” comprised a relatively small percentage of the larger habitat.

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We carefully placed seven transects within the glide, one at the downstream hydraulic control and six to represent the various conditions within the habitat unit. To apply the PHABSIM model, to represent the glide without structure, we weighted the transect at the hydraulic control and those upstream that weren’t influenced by structure and modeled it for various flows, species, and life-history stages. To elucidate the effect of adding structure to the river, we entered the remaining transects into the model and ran the procedure a second time. We hypothesized that the difference in weighted useable area (WUA) between the modeling effort using the different transects would be realized when various structures were built. Because of modeling limitations, we did not incorporate instream cover, such as overhead seclusion objects, into the model.

The CDOW had been conducting population estimates of salmonids in the demonstration area for several years, using the 2-pass, Seber-LeCren removal methodology (Seber 1982). This method locates two stations in the project reach that do not overlap the structure placement sites. Two stations occur at the structure sites. The CDOW used truck-mounted multiple-array electrofishing gear with each fish weighed and measured for population density and biomass estimates.

The CDOW made maps of specific structure placements. After identifying the specific habitats, the CDOW strategically placed cross- sectional transects. To determine what (if any) changes in stream channel morphology occurred as a result of the project implementation, the DCOW also established permanent benchmarks for reference, and measured both elevation and stream current velocities before project implementation.

We used pre- and post-project monitoring design to determine changes in channel scouring and deposition associated with the structures as

Eleven-mile Canyon Demonstration Project well as with fish population changes. We also determined reference habitat conditions outside of the project area were not warranted for this study. Comparisons between pre- and post-microhabitat conditions at the particular project site became the means by which we would measure the success of the structures. In addition, we regularly documented the effectiveness of each structure to remain functional over time.

Fish sampling took place in the fall. We conducted habitat transects and stream mapping at the low-flow period following runoff, and conducted PHABSIM measurements at three different flow levels to encompass the range of flows in the project area (Bovee 1982).

We measured facet slope of structure boulders—as well as maximum and residual pool depth downstream of each of the boulders that make up the vortex and deflector structures—once in 2003. The purpose of collecting

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this data was to determine whether any measurable benefit existed to angling the slope of the top of individual boulders slightly downstream, to maintain effective scour.

We began this project with the following assumptions: l The monitoring techniques would be sensitive to changes realized by the project. l Funds and personnel would be available when needed. l The South Platte River would exhibit typical dynamic flow regimes during the monitoring efforts. l Changes in stream channel morphology and fish population dynamics could be related to the project. l Consistency in monitoring efforts was paramount. l Stochastic events such as landslides, unusual flooding, drought, or anthropogenic activities would not compromise the success of the project.

Monitoring Results and Interpretation (a) Basinwide Inventories Table 1 presents a subset of the basinwide inventory results conducted prior to project implementation. We designed this type of inventory to identify limiting factors and potential project sites. We speculated that the relatively large size of the river in the study area could make monitoring with this technique too imprecise to quantify changes within the entire reach following project implementation. However, this monitoring did provide some insights on conditions observed. For instance, in a relatively low-gradient stream channel (C types based on Rosgen 1992), we would

expect considerable meandering with abundant lateral pool formation. Eleven-mile Canyon Demonstration Project In steeper step pool sections (B or A types), we would expect smaller plunge or scour pools interspersed with longer riffle sections. Our results indicated just the opposite, with pool habitat being more abundant in B-type channels (26 percent) than in C-type channels (19 percent). Glides accounted for more than twice the percentage of area in the C channel types (45 percent) than in the B channel types (22 percent).

In addition, the percentage of actively eroding streambanks was only slightly higher in the C-channel types (29 percent) than the typically more stable B-channel types (22 percent). Actively eroding streambanks were mostly associated with the adjacent gravel road. We did not use Reach 23, which included both channel types, for this estimate. These results made clear that erosion and subsequent deposition in lower gradient stream habitats has dramatically altered the overall characteristics of the river in

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the study reaches. Our observations within the study area suggested that these results did indeed reflect actual conditions.

Reach Channel Percentage Percentage Percentage Percentage Number Type* Pools** Riffles** Glides** Eroding 23 B3 / C4 18 49 33 30 24 C4 7 29 64 31 25 B2 30 44 26 24 26 C3 15 37 48 24 27 B2 23 55 22 29 28 C3 21 45 34 16 29 B2 25 56 19 17 30 C4 11 33 56 30 31 C4 41 38 21 45 Table 1—Results of the preproject basinwide inventory conducted in the Eleven-mile Canyon demonstration area.

* - Based on Rosgen 1996. **- Based on Winters, et al 1991, revised by Winters & Gallagher 1997.

(b) PHABSIM Modeling The PHABSIM results reflected an obvious bias towards changes only in depth and velocities. The results of the juvenile life-stage of both rainbow and brown trout indicated a major increase in weighted usable area (WUA)

Eleven-mile Canyon Demonstration Project after we included the transects with the influence of the boulders and trees within the stream channel (data currently not available). However, modeling of adult rainbow and brown trout with the same technique resulted in a decrease of WUA when we included the habitat transects in the model (figures 3 and 4).

Both rainbow and brown trout populations have increased considerably following habitat installation at the PHABSIM site, and observations indicate numerous adult trout within the influence zone of the structures. Nevertheless, the PHABSIM resulted in a decrease in both adult rainbow and brown trout WUA. The results of this analysis indicate that this type of modeling may not be appropriate or sensitive enough to elucidate the potential change in the appropriate habitat measure as WUA under these conditions. Electrofishing results indicate that while stream velocities, depth, and substrate may not have changed considerably with

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the introduction of the “with habitat” transects, the cover provided by placement of large trees and boulders has provided adequate cover to attract trout. It would appear that other techniques of monitoring changes in habitat may be more cost effective and sensitive than this PHABSIM.

IF IM Weighted Us able Area (WUA) for Adult B rown T rout (S ummer)

3000

2500

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WUA ( sq. Ft. ) WUA WUA (Sq. Ft.) 500

0 0 50 100 150 200 250 300 350 400 450 500 550 -500 Discha rge

With Habitat Improvements Without Habitat Improvements Figure 3—Results of the PHABSIM modeling exercise for adult brown trout.

IF IM Weighted Us able Area (WUA) for Adult R ainbow T rout (S ummer)

14000

12000

10000

8000 Eleven-mile Canyon Demonstration Project

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Figure 4—Results of theWit hPHABSIM Habitat Impr omodelingvements exerciseWithout Hforab iadulttat Imp rainbowrovements trout.

(c) Transect Results We strategically placed transects to monitor the changes in stream cross- sectional area and contour resulting from the structures in the stream. We established these transects in 1996, immediately before work on the

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structures, and resurveyed them between 1998 and 2000, with a complete resurvey in 2003. Transect monitoring turned out to be of limited value for quantifying the small geomorphic changes resulting from the project. Transect monitoring revealed noticeable changes in channel shape and function at Riverside Site #1, where considerable reshaping of the channel occurred through construction efforts (figure 5). At other sites, where boulders and trees were placed in the stream channel and no extensive excavation occurred, we had to locate transects immediately adjacent to the structure to capture the relatively small areas where bed contour was modified. As a result, several transects placed before structure installation showed little detectable change (figure 6).

R ivers ide S ite 1 - C ros s S ection #4

Elevation 90 Elevation

86 0 20 40 60 80 100 120 S tation on X -S ec (ft)

2003 ELEV 1996 ELEV

Eleven-mile Canyon Demonstration Project Figure 5—Example of a transect demonstrating obvious change in channel characteristics at Riverside Site 1 – Transect #4. [Note the post-project “spike” in elevation resulting from a tree placement on the left (approximately 34 feet), and the increased elevation resulting from a point-bar and side channel constructed on the right ( approximately 65 to 100 feet).

We encountered several problems when using transects for monitoring the structures. Probably the single most difficult aspect of this work was relocating the cross-section pins. We had established transects using 2-foot-long 3/8-inch rebar pins with yellow survey caps stamped with a U.S. Department of Agriculture Forest Service tag. By 2003, more than 50 percent of these pins had disappeared, particularly in the more popular recreation areas such as Eleven-mile Picnic Ground (site 5). Additionally, permanent benchmarks established with cadastral survey markers, were

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disturbed or removed. When we established the transects, we conducted horizontal site surveys, measuring range and bearing from the benchmark to each of the transect pins. This data allowed us to reestablish missing pins, as long as we could find one or two existing pins. However, at the time we established the transects, we had no access to global positioning system equipment—an asset that might have made relocating lost pins considerably easier.

S IT E 4 - C ros s S ection #2

Elevation 94 Elevation

90 -20 0 20 40 60 80 100 S tation on X -S ec (F t)

2003 ELEV 1996 ELEV Figure 6—Example of transect showing little measurable change at site 4 – Transect #2.

(d) Fish Monitoring Figure 2 presents the results of the fish population sampling results for the

two sites corresponding to structure placement (Gerlich 2001 and Spohn Eleven-mile Canyon Demonstration Project 2003). These results show a positive trend in total trout biomass since project initiation in 1996 for the Middle Station and in 1998 for the Habitat Station. While pretreatment sampling information would have been valuable for comparison, the positive trend following treatment indicates that the goal of improving trout populations is being met. In addition, observations during sampling indicated that large adult trout were using the cover that the instream structures provided. Habitat areas exhibiting the homogenous conditions associated without treatment typically resulted in few (if any) adult trout captured. While snorkeling observations would provide a better way of quantifying actual habitat use, the electrofishing results—as well as our visual observationsstrongly suggest an influence from the structures.

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Middle S tation - C ombined B iomas s T rend Analys is

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Lbs / Acre Lbs / Lbs6 /0 Acre

0 1997 1998 1999 2000 2001 2002 2003

Middle Station Linear Regression Habitat S tation - C ombined B iomas s T rend Analys is

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Lbs / Acre Lbs / 8 /0 Acre No Survey 60 Conducted 40 in 2001 20

0 1999 2000 2001 2002 2003

Habitat Station Linear Regression Figure 7—Fish sampling biomass for two habitat modification sites in the Eleven- mile Canyon project area.

(e) Boulder-Facet Measurements

Eleven-mile Canyon Demonstration Project Preliminary analysis of the data indicates that the relative position of the top of the rock to the bankfull stage is the more critical element in maintaining effective scour. However, where the rock placement is sufficiently low (1/2 of bankfull or less), the facet slope of the individual rocks appeared to have some effect on scour and residual pool depth of the habitat immediately downstream. We know of no research of this parameter in the literature that may aid in future construction and monitoring of rock structures.

Photo Points In 1993, while conducting the basinwide stream habitat surveys of the nine reaches in Eleven-mile Canyon, we took extensive photographs of each habitat unit at the downstream boundaries looking upstream, and of the right and left banks of each unit. We used a Nikonos 35-millimeter

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single-lens reflex camera with a 35-millimeter wide-angle lens and Kodak Ektachrome 200 slide film for this work, and stored the slides in archival slide file folders. We intend to digitize these images for electronic storage.

Photo-point monitoring of the individual habitat units may prove to be the most cost effective and repeatable monitoring tool in this project. The photos clearly show bank stability conditions, presence of mid-channel bars, and riparian vegetation communities at the meso-habitat scale. Photo-point locations are relatively easy to relocate using the basinwide stream habitat survey data sheets (Winters et.al. 1993) and a tape for measuring upstream from the beginning of the stream reach.

We need more time to determine which structures and placement characteristics resulted in limited maintenance while providing the desired effects.

Project Monitoring Partnerships and Costs Partners: CDOW- FS – Monitoring Electrofishing sites and Construction ($) ($) Construction cost: 50,000 15,000 IFIM study: 10,000 Monitoring cost: 38,000 25,750 Total cost: 88,000 50,750

Total monitoring cost to date: $ 73,750 Eleven-mile Canyon Demonstration Project Total construction cost: $ 65,000 Total project cost: $138,750

For further information contact: David S. Winters, regional aquatic ecologist, Rocky Mountain Region, USDA Forest Service, 740 Simms Street, Golden, CO 80401

Teresa Wagner, wildlife, fish and aquatics program leader, Ottawa National Forest, USDA Forest Service, E6248 US Hwy 2, Ironwood, MI 49938

J. Peter Gallagher; forest fishery technician; Pikes Peak Ranger District; Pike and San Isabel National Forests, Comanche and Cimarron National Grasslands;

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Lessons Learned l The basinwide inventory approach (Winters and Gallagher 1997) was an important tool for establishing limiting habitats, sources of impacts, and influences to stream habitat structure. However, we do not feel that the approach was sensitive enough to quantify changes at a microhabitat scale in a river of this relatively large size. l The PHABSIM modeling effort was costly and inadequate for determining changes relative to instream habitat for different species and life-history changes. If not applied correctly, the results could be very misleading. l Strategic cross-sectional measurements can be a cost effective and accurate way to quantify changes in streambed elevation. However, repeatability is a concern. Crews need to be highly trained in surveying techniques, and anglers can remove benchmarks and surveying “headpins.” Changes that transect trends show as minimal may actually be important to fish populations. Transect placement is critical. l To account for natural variability, we may need to conduct some fish-population monitoring for several years before and after project implementation. l Although fish sampling and creel surveys are relatively expensive, they are important monitoring tools. Angler’s successes and opinions of the project can be valuable in determining the success of the project. l Photo points are a cost effective and visually beneficial way of communicating success and failure of various restoration techniques. l If goals are to be met, all appropriate parties must agree upon funding and personnel needs before project implementation. Eleven-mile Canyon Demonstration Project We intend to continue monitoring transects and facet slope scour to see if these tools are beneficial over time. Additionally, we would like to digitize our existing collection of photo points and to repeat the photo monitoring done during the 1993 basinwide stream surveys, using digital photographic equipment. CDOW plans to continue monitoring the existing four electrofishing stations for the foreseeable future. Furthermore, the USDA Forest Service is working with the CDOW area fisheries biologist to establish meso-habitat sampling stations at the middle electrofishing station, where the agencies will be adding several more large wood structures in the fall of 2004. These sampling sites will consist of wire grids installed in the river substrate below the trees before tree installation, with wire terminals leading to permanent access points on the bank.

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References Cited Bovee, K. D.1982. A guide to stream habitat analysis using the instream flow incremental methodology. United States Fish and Wildlife Instream Flow Information Paper Number 12. FWS/OBS-82/26. Fort Collins, Colorado: U.S. Department of the Interior, Fish and Wildlife Service.

Earthman, E. M. 2001. Sustainable fishing regulations: a case study of Eleven Mile Canyon. (Master’s thesis, Colorado College, Department of Economics and Business, Colorado Springs, Colorado.)

Gerlich, G. W. 2001. South Platte River – Eleven Mile Canyon fisheries management report. NE Region Technical Report (unnumbered). Denver, CO: Colorado Division of Wildlife. 11pp.

Pennak, R. W. 1977. Trophic variables in rocky mountain trout streams. Archiv fur Hydrobiologie 80:253-285.

Rosgen, Dave. 1996. Applied river morphology. Wildland Hydrology. Pagosa Springs, Colorado.

Seber, G. A. F.; LeCren, E. D. 1967. Estimated population parameters from catches large relative to the population. Journal of Animal Ecology. 36:631-643.

Spohn, J. 2003. [personal communication]. Area fisheries biologist. On file at: Colorado Division of Wildlife, N.E. Region.

Winters, D. S.; Gallagher, J. P. 1993. Basin-wide stream habitat inventory: a cooperative inventory conducted by the USDA Forest Service and the Colorado Division of Wildlife. Unnumbered internal technical report. Pueblo, CO: U.S. Department of Agriculture, Forest Service, Pike-San

Isabel National Forests and Cimarron and Comanche National Grasslands. Eleven-mile Canyon Demonstration Project

Winters, D .S.; Bennett, E. N.; Gallagher, J. P. 1991. Basin-wide stream habitat inventory: a protocol. Pueblo, CO: U.S. Department of Agriculture, Forest Service, Pike and San Isabel National Forests, Cimarron and Comanche National Grasslands. 30p.

Winters, D. S.; Gallagher, J. P. 1997. Basin-wide stream habitat inventory: a protocol for the Pike and San Isabel National Forests and Cimarron and Comanche National Grasslands. Pueblo, CO: U.S. Department of Agriculture, Forest Service, Pike and San Isabel National Forests and Cimarron and Comanche National Grasslands. 42p.

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