Hydraulics Memorandum February 2022.pdf

Tularosa AOP

NM FTFS 233(1)

Hydraulics Memorandum

In Partnership With:

U.S. Forest Service Gila National Forest Catron County, NM

Federal Highway Administration Central Federal Lands Highway Division

February 2022

Signature Sheet

Report prepared by: ____________________________________________________ Aaron Estep, P.E., Hydraulic Engineer

Report reviewed by: ____________________________________________________ Luis Calderón, P.E., C.F.M., Lead Hydraulic Engineer

Approved for distribution by: ____________________________________________________ Luis Calderón, P.E., C.F.M., Lead Hydraulic Engineer

Distribution

Electronic:

N:\NM\233(1)\Hydraulics\9_Final Report Project Management, Justin Henwood Design, Joshua Kaplan Environmental Protection, Lisa Hemesath

Subject: NM FTFS 233(1) Tularosa AOP Date: February 2022

From: Aaron Estep, PE

Hydraulic Engineer

FHWA Central Federal Lands Highway Division

To: Justin Henwood, PE, PMP

Project Manager

FHWA Central Federal Lands Highway Division

This memorandum presents a summary of the previously completed design effort as well as the additional hydraulic analyses performed for the replacement an existing concrete low water crossing in Catron County, NM.

The crossing provides access across the Tularosa River along the National Forest System Road 233 (NFSR 233).

The project location is identified in the figure below. The existing low water crossing has developed a headcut at the downstream extent of the concrete apron creating a migration barrier for fish and amphibians. Specifically, two species that are of interest are the federally threatened Loach minnow (Tiaroga cobitis) and Chiricahua

Leopard frog (Rana chiricahuensis). The project proposes to replace the existing low water crossing, re‐establish aquatic organism passage (AOP), and rehabilitate aquatic habitat and stream channel downstream of the crossing.

THE USDA ENTERPRISE PROGRAM – REPORT SUMMARY

The USDA Enterprise Program was retained by the Forest Service Southwest Region and the Gila National Forest to assist with site assessment and project planning associated with the Tularosa AOP project. The Enterprise Team provided a site assessment summary, stream survey, hydrologic and hydraulic analysis, conceptual designs of the downstream channel rehabilitation, and design recommendations for the proposed low water crossing replacement structure in a report dated February 2020. Below is a summary of the key findings outlined in the report. The full report itself is included with this memorandum as Appendix B.

SITE ASSESSMENT AND SURVEY

As part of the report development, a site assessment was performed in November 2018 and approximately 2,700‐ ft of the Tularosa River was surveyed. The crossing is located within a depositional area with a wider valley bottom. Immediately upstream of the crossing, the channel has a braided pattern that appears to be a relatively recent development as a historic photo (1964) indicates a single thread channel. Flows then accelerates across the concrete low water crossing and apron (approximately 60‐ft in length) and drops 4‐ft off the end of the apron into the channel below. This acceleration of flows has likely led to the incised channel condition immediately downstream of the structure. The incised channel condition continues for approximately 300‐ft downstream of the crossing. Wolman pebble counts indicate that the D50 throughout the project section was “fine sand” with the D84 ranging from “coarse sand” to “small gravel”. In addition to the crossing itself, the channel profile was surveyed approximately 850‐ft downstream and 1,850‐ft upstream of the crossing and 15 cross sections spanning the valley bottom were collected. Channel survey indicates that the majority of the project section (2,000‐ft of the 2,700‐ft surveyed) had a slope of between 0.27% and 0.36%. Above the crossing, the slope of the centerline channel through the deposit fan (approximately 130‐ft) had a slope of 2.33%. Finally, the valley floor has as slope between 0.8% and 1.1%. A surface was developed from the survey information and was used for additional analysis as outlined in this memorandum.

HYDROLOGIC ANALYSIS

To compute flow rates at the low water crossing, the Enterprise Team utilized a stream gage located immediately downstream of the crossing. The crest gage had 52‐years of record (1956‐2016) with a watershed area of 428‐ sqmi. Since the watershed area at the gage was relatively close the watershed area at the crossing (406‐sqmi), the computed peak flows at the gage were used (without area adjustments) to simulate flow at the crossing. The observed flow during the November 2018 site visit was estimated to be 2 to 3‐cfs and as such, 3‐cfs was considered to be a reasonable design flow for AOP at the crossing. Computed peak flows from the report are provided in the table below.

Exceedance Probability

Return Interval (years)

Peak Discharge

(cfs)

Confidence Limits (cfs)

5% 95%

95 1.05 3.0 1.7 27.8

80 1.25 33.1 16.7 73.3

67 1.5 88.9 51.1 139

50 2 214 117 278

20 5 779 426 1119

10 10 1254 807 2570

4 25 1836 1538 7820

2 50 2213 2273 19240

1 100 2528 3159 49230

HYDRAULIC ANALYSIS

Using the surveyed cross sections, a HEC‐RAS 1D model was developed to evaluate approximately 1,700‐ft of the existing surveyed reach. The goals were to assess flow velocity and depth within the identified reference reach at the upstream surveyed extents. For the model, a Manning’s n value of 0.035 (sand bottom) was used in the channel and n values of 0.05 ‐ 0.1 (grassy vs wooded) were used in the overbank. Downstream boundary conditions were set based on an overall stream gradient of 0.7%. The 1.05‐ and 1.25‐year floods were used as the design flows representing near base flow and low stage flooding. Model results, including average depth and velocity and top width of flow, for the reference reach section are included in the table below.

Return Interval (years)

Flow (cfs)

Average Velocity (ft/s)

Average Depth (ft)

Range of Velocity (ft/s)

Range of Depth (ft)

Top Width of Flow (ft)

1.05 3 1.38 0.56 0.37 ‐ 2.68 0.28 ‐ 1.53 7.99 ‐ 8.15

1.25 33 2.59 1.42 1.31 ‐ 5.03 0.36 ‐ 2.92 28.89 ‐ 34.42

CONCEPTUAL DESIGNS AND RECOMMENDATIONS

Several design options were considered including modifications to the existing low water crossing, a new bridge to span the channel, a culverted crossing, and an articulating concrete block low water ford. Due to the high sediment, wood, and debris loads associated with the Tularosa River, it was recommended that the crossing maintain a similar low water crossing type structure. Therefore, the preferred alternative recommended by the

Enterprise Team is an articulated concrete block low water ford along with downstream channel rehabilitation. A conceptual design was developed by the Enterprise Team and includes a series of constructed riffles, pools, and large wood structures to reduce downstream channel incision and improve aquatic habitat. The conceptual design will be incorporated into the plans.

The report also included recommendations for the design of the articulated concrete block low water crossing which has been designed and evaluated in this report. These recommendations were based on flow characteristics associated with known Loach minnow habitat. General design recommendations from the

Enterprise Team are provided below:

A reasonable design flow for AOP is at or slightly above 3‐cfs.

In order to pass adult fish through the crossing, the low‐flow water velocity at the structure should be no greater than 1.9 ft/sec.

The structure should be narrow enough to maintain a depth between 0.3‐ and 0.9‐ft during low flow conditions.

HYDRAULIC DESIGN CRITERIA

The design and analysis of an articulated concrete block low water ford was developed utilizing the design recommendations provided by the Enterprise Team in the previous section and supplemented by the Forest

Service design guidance document entitled “Low‐Water Crossings: Geomorphic, Biological, and Engineering

Considerations” (USFS 2006). Select key design elements for low water crossings were taken from Table 4.1 found in the USFS document and detailed in the list below.

SELECT KEY DESIGN ELEMENTS (USFS GUIDANCE – TABLE 4.1):

Do not confine or narrow the normal (bankfull) flows.

Align structures perpendicular to the stream channel.

Avoid accelerating the velocity of streamflow, particularly at normal and low flows.

Limit approach road grades into the ford to 10 percent or less if possible.

Use a vertical curve dip through the ford, sufficiently gentle not to catch the bumper or undercarriage of vehicles passing through the ford.

Protect the entire “wetted perimeter” of the ford (the area of the entire high flow), plus freeboard

(typically 2 to 4 feet of additional height). A structure usually needs a maximum capacity adequate to pass the design flow (Q50 to Q100) within its armored cross section.

FEMA REGULATION

In addition to the design elements listed above and recommendations provided by the Enterprise team, the 100‐ year water surface elevations associated with the proposed design will be evaluated against the existing conditions. While the project area is unmapped by FEMA and not a regulated Special Flood Hazard Area (SFHA), the 100‐year water surface elevation will be limited to no more than 1‐ft of rise.

HYDRAULIC ANALYSIS

Existing and proposed hydraulic analysis were conducted for the Tularosa River crossing using a combination of the Channel Analysis calculator in the Hydraulic Toolbox (Federal Highway Administration 2021) and two‐ dimensional hydraulic modeling using SRH‐2D (U.S. Bureau of Reclamation 2017). The SRH‐2D computational mesh generation and model pre‐ and post‐processing was performed using the SMS 13.1.10 interface (Aquaveo

2021). The objective of the analyses was to determine flow depths and velocities during the low flow conditions in order to adequately meet AOP requirements as well as to ensure stability of the crossing through a range of flow conditions. The input data, model development, and results are discussed in the following sections.

TOPOGRAPHIC INFORMATION

As previously discussed, field survey was collected by the Enterprise Team in November 2018 and included points of the road, low water crossing, approximately 2,700‐ft of the Tularosa River, and a portion of the surrounding river valley above the crossing. The survey information included was processed to create a triangular irregular network (TIN) surface to represent the topography of the channel and roadway near the crossing as shown in the figure below. The areas outside of the survey boundary were supplemented using a 4‐meter DEM available through the National Map. All elevations for the study are in units of feet and are referenced to the North

American Vertical Datum of 1988 (NAVD 88).

PRELIMINARY CHANNEL SIZING (HYDRAULIC TOOLBOX)

As a preliminary analysis of flow characteristics within the existing crossing, a model was developed using the

Hydraulic Toolbox Channel Analysis calculator which utilizes the Manning’s equation. For this analysis, a cross section of the channel along the existing road profile was modeled using the low flow rate of 3‐cfs. Using a longitudinal slope of 1.4% (based on survey of the crossing) and a Manning’s roughness value of 0.015 (concrete), the resulting flow depth was 0.14‐ft, flow width was 27.5‐ft, and flow velocity was 1.8‐ft/s. While the existing flow velocity was within the range for Loach minnow passage, the preliminary model indicated that the flow width was too wide to allow for adequate flow depth indicating a barrier to passage of the adult fish. A review of the cross section along the road centerline indicated that there was not a defined low flow channel within the crossing itself. Once the road dropped into the valley, the bottom of the crossing was overly widened (approximately 100‐ ft wide) with very little elevation change from the edge of the crossing to the low point (approximately 6‐in). For this reason, when the base flow hits the crossing, it spreads out such that flow depth is very low.

To determine the proposed low flow crossing characteristics required to meet the previously mentioned design criteria, a similar channel analysis was performed for a variety of crossing layouts. To increase flow depth during low flow conditions, the low water crossing will require a low flow channel instead of the wide and relatively flat crossing that currently exists. Based on Section 4.6 of the USFS low water crossing guidance, maximum allowable traversable flow depth for a low water crossing is 0.5‐ft for traffic safety. Therefore, the target flow depth for the proposed crossing will be the lowest end of the Enterprise Team recommendation or 0.3‐ft. Preliminary models assume a flat cross slope and Manning’s roughness of 0.035 which corresponds to a natural channel bottom and is representative of an articulated concrete block crossing backfilled with natural channel material. Based on the preliminary models, a low flow channel with a top width of 20‐ft, a depth of 0.2‐ft, and approach grades of 1.5% will result in a flow depth of 0.35‐ft and flow velocity of 0.4‐ft/s. While this depth is on the low end for Loach minnow passage, increasing the flow depth during low flow conditions may make the crossing impassable for some vehicles. Hydraulics Toolbox analyses are provided in Appendix A.

TWO‐DIMENSIONAL HYDRAULIC MODELING (SRH‐2D)

To evaluate the preliminary crossing design in relation to the Tularosa River, a two‐dimensional hydraulic model was developed for both the existing and proposed conditions using SRH‐2D and Aquaveo’s SMS. For both models, the computational mesh was developed from the survey information supplemented by the 4‐m DEM. Upstream boundary conditions were specified as a constant discharge using the peak flow values computed by the Enterprise

Team. The downstream boundary conditions were specified as known water surface elevations obtained using

Manning’s equation and an energy grade line slope assumed to equal the streambed slope near the model downstream boundary. Manning’s n values were used to specify roughness and were based on the land use types delineated from the aerial imagery. The computational mesh, land cover type, roughness values, and model results for both the existing and proposed conditions are provided in Appendix A.

The existing model results during the 3‐cfs low flow condition (shown in the figure below) indicate that two flow paths are conveying flow and results in a maximum flow depth of 0.1‐ft and maximum flow velocity of 2.0‐ft/s;

aligning well with the preliminary model developed with the Hydraulic Toolbox. The higher velocity continues along the concrete apron and reaches velocities as high as 7‐ft/s as it spills over the end of the apron contributing to the formation of the incised downstream channel condition. The two flow paths active during low flow are also supported by photos taken by the Enterprise Team in 2018. The eastern most channel visible in the aerial is not active during these conditions but does activate during higher flow events. It should be noted that the low point of the concrete low water crossing does not align well with either active flow path. Instead, the lowest point lies between the two flow paths. This is likely due to the depositional nature of the upstream section noted by the

Enterprise Team and the wide, flat configuration of the existing crossing. Without a dedicated low flow channel to provide a single flow path, the upstream channel likely shifts within the valley over time which has led to braided pattern evident in the aerial. Providing a single low flow channel at the crossing may reduce the lateral migration of the channel as it moves the deposited sediment downstream and stabilizes back to a single thread channel.

For the proposed conditions, a model was developed based on the preliminary design outlined above. This design includes a 20‐ft wide, 0.2‐ft deep articulated concrete block low flow channel with approach roads graded up at

1.5% to tie into the existing road. In addition to the low flow channel, the articulated concrete block should extend at least 20‐ft on either side of the low flow channel to allow for an adequate transition. In addition, as recommended by the USFS low water crossing guidance document, the armored portion of the road should extend to the limits of the high flow boundary. For this reason, a concrete road surface should be provided to the extents of the 100‐year flood boundary. An example section as well as an aerial view of the proposed crossing extents are provided in the figures below.

The proposed conditions were modeled based on the above section as well as the stream restoration design downstream of the crossing. For the stream restoration, the downstream channel was graded to reflect the design that was prepared by the Enterprise Team. In addition to the downstream channel improvements, the proposed low water crossing will require some minor channel realignment upstream to direct flows from the two main flow paths to the low point of the crossing. Approximate channel grading to combine these two flow paths is included in the proposed mesh. Results of the proposed model during the low flow conditions are shown in the figure below.

The proposed model results in a maximum flow depth of 0.3‐ft and maximum flow velocity of 0.9‐ft/s for the low flow condition (3‐cfs) through the crossing which is sufficient for the passage of the adult Loach minnow.

RIPRAP PLACEMENT

It is recommended that riprap be placed both upstream and downstream of the proposed low water crossing. To reduce scour potential on the downstream side of the crossing, it is recommended that riprap be placed at least

10‐ft from the edge of the road for the full length of the armored low water crossing. On the upstream side, riprap is recommended within the portion of the floodplain most susceptible to channel migration. Being that the upstream section of the Tularosa River is braided, the channel(s) will likely shift over time and approach the low water crossing at different angles and directions. In the existing conditions, the eastern most channel runs parallel to the crossing and has resulted in vertical drop from the road surface. Installing riprap on the upslope side will protect the road surface as the upstream segment processes the deposited sediment and stabilizes into a single thread channel. Similar to the downstream side, it is recommended that 10‐ft of riprap be installed from the upstream edge of the road. Based on a channel lining analysis performed using the Hydraulic Toolbox, the required D50 is 12‐in corresponding to Class 3 riprap. Riprap depth should be at least double the D50 or 2‐ft.

Riprap should be placed flush with the road surface and tie into the surrounding grade. The figure below depicts the proposed riprap extents. The proposed channel lining analysis is provided in Appendix A.

ADDITIONAL RECOMMENDATIONS

In addition to the above hydraulics recommendations, the USFS low water crossing guidance provided a few additional recommendations (listed below) that were applicable to the project.

Place object markers along the road at each corner of the structure to define each entrance of the structure.

Install warning signs to identify the approaching ford and warn drivers of flooding and possible traffic delays.

Use marker posts that indicate the depth of flow.

Incorporate construction dewatering into the project. Avoid working in the water.

REFERENCES

Aquaveo. 2021. Surface‐water Modeling System (SMS), version 13.1.10. Provo, UT.

Aquaveo. 2021. Surface‐Water Modeling System, 13.1.10.

Federal Highway Administration. 2021. Hydraulic Toolbox 5.1.

U.S. Bureau of Reclamation. 2017. SRH‐2D, Sedimentation and River Hydraulics ‐ Two‐Dimensional Model.

USFS. 2006. "Low‐Water Crossings: Geomorphic, Biological, and Engineering Design Considerations."

APPENDIX A

HYDRAULIC ANALYSES

Hydraulic Toolbox Analysis Existing Crossing

Proposed Crossing

Riprap Analysis

Selected SRH-2D Information Existing Conditions Surface

Low Water Crossing

Existing Conditions Computational Mesh

Existing Conditions Materials (Manning’s Roughness)

Existing Conditions 1.05YR Water Surface Elevation

Existing Conditions 1.25YR Water Surface Elevation

Existing Conditions 2YR Water Surface Elevation

Existing Conditions 25YR Water Surface Elevation

Existing Conditions 100YR Water Surface Elevation

Existing Conditions 1.05YR Velocities

Existing Conditions 1.25YR Velocities

Existing Conditions 2YR Velocities

Existing Conditions 25YR Velocities

Existing Conditions 100YR Velocities

Proposed Conditions Surface

Proposed Conditions Computational Mesh

Proposed Conditions Materials (Manning’s Roughness)

Proposed Conditions 1.05YR Water Surface Elevation

Proposed Conditions 1.25YR Water Surface Elevation

Proposed Conditions 2YR Water Surface Elevation

Proposed Conditions 25YR Water Surface Elevation

Proposed Conditions 100YR Water Surface Elevation

Proposed Conditions 1.05YR Velocities

Proposed Conditions 1.25YR Velocities

Proposed Conditions 2YR Velocities

Proposed Conditions 25YR Velocities

Proposed Conditions 100YR Velocities

APPENDIX B

USDA ENTERPRISE TEAM REPORT

i

Tularosa River Aquatic Organism Passage and

Stream Channel Rehabilitation

Site Assessment and Conceptual Design Report

Gila National Forest, Reserve Ranger District

The USDA Enterprise Program ii

Prepared by:

Brian Bair Watershed Restoration Project Lead

USDA Forest Service, Enterprise Program

Heidi Klingel Hydrologist/Geologist

USDA Forest Service, Enterprise Program

Corinne Marzullo Civil Engineer

USDA Forest Service, Enterprise Program

Eric Mosier Hydrologist

USDA Forest Service, Enterprise Program

Jamie Stogsdill Civil Engineer

USDA Forest Service, Enterprise Program

February, 2020

In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident.

Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, American Sign Language, etc.) should contact the responsible Agency or USDA’s TARGET Center at (202) 720-2600 (voice and TTY) or contact USDA through the Federal Relay Service at (800) 877-8339. Additionally, program information may be made available in languages other than English.

To file a program discrimination complaint, complete the USDA Program Discrimination Complaint Form, AD-3027, found online at http://www.ascr.usda.gov/complaint_filing_cust.html and at any USDA office or write a letter addressed to USDA and provide in the letter all of the information requested in the form. To request a copy of the complaint form, call (866) 632-9992. Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email:

program.intake@usda.gov.

USDA is an equal opportunity provider, employer and lender.

TABLE OF CONTENTS

TABLE OF CONTENTS

LIST OF FIGURES

LIST OF TABLES

INTRODUCTION

Problem and Objectives

Enterprise Scope of Work

ENTERPRISE DELIVERABLES

Site Assessment

Field Observations

Substrate Assessment

Topographic Survey

Design Assistance

Aquatic Species and their Design Needs

Model Design Flows

HEC-RAS Model Runs

Conceptual Designs

Cost Estimates

REFERENCES

APPENDIX A

APPENDIX B

Bridge and Roadway Design Criteria

LIST OF FIGURES

Figure 1: Project Area Locator Map for the Tularosa River Aquatic Organism Passage and Aquatic Habitat Restoration Project. The project area is located 4 miles northeast of the town of Reserve, New Mexico. 5

Figure 2: Far Upstream of the Crossing; the Reference Reach

Figure 3: Views of large sediment deposits on the valley bottom

Figure 4: The Existing Structure

Figure 5: Downstream of the Crossing

Figure 6. Monumented Survey Control Points, Photos and Descriptions

Figure 7: Topographic site plan of Tularosa River crossing by NSFR-233. North is to the left of figure

Figure 8: HEC RAS output, longitudinal profile of modeled reach, survey stations 775-24+50

Figure 9: Centerline and cross-sections used for the 1D HEC-RAS analysis; north is at the top of the figure. Stations are those by HEC-RAS. Station 772 is just upstream from the crossing; Station 646 is just downstream from the apron

Figure 10: example photo of an articulating concrete block, low water ford

Figure 11. Cross-section view of hardened Ford

Figure 12: Design Profile of Preferred Alternative- Low Water Crossing and Constructed Bed

LIST OF TABLES

Table 1. Monumented Survey Control Points, Surveyed Locations

Table 2: Results of the PeakFQ run for USGS Station #09442740

Table 3: Modeled Velocities and depths for flow 3-33 cfs within the reference reach

Table 4: Cost Comparison of Alternatives Considered

Table 5: Preliminary Cost Estimate for the Preferred Alternative (Road-Stream Crossing and Channel Rehabilitation)

Table 6: Cost Estimates for Enterprise Construction Supervision (COR)

INTRODUCTION

Problem and Objectives The National Forest System Road (NFSR) 233 crossing of the Tularosa River (see Figure 1) has created a migration barrier for fish and amphibians (the federally threatened Loach minnow Tiaroga cobitis and Chiricahua Leopard frog Rana chiricahuensis), as well as degraded aquatic habitat downstream. There is a need to replace or improve the road-stream crossing structure to restore aquatic organism passage (AOP) as well as rehabilitate aquatic habitat and stream channel morphology.

The USDA Enterprise Program was retained by the Forest Service Southwest Region and the Gila National Forest to assist with site assessment and project planning; the specific deliverables associated with the work order are described below. The objectives of this report are 1), to communicate the information gained by our site assessment and 2), to present conceptual design ideas which explore constructing an improved road-stream crossing (for AOP) together with downstream channel rehabilitation.

Figure 1: Project Area Locator Map for the Tularosa River Aquatic Organism Passage and Aquatic Habitat Restoration Project. The project area is located 4 miles northeast of the town of Reserve, New Mexico.

Enterprise Scope of Work The following text can be found in the Enterprise Work Order (WTR-18-0306-001), Attachment 1.

Funding for this work was $30,000 which supported the field and analysis time of a hydrologist and an engineer.

Enterprise shall provide engineering and hydrology assistance on the Tularosa River Crossing Project, in collaboration with Federal Highways. Labor and services may include a site assessment, topographic survey, and design assistance to determine upstream/downstream stabilization features to be designed in combination with a low water crossing.

Deliverables

• Site Assessment

Project assistance will be determined after a site assessment, and may include:

• Surveying

• Hydrology and hydraulic analysis

• Design assistance and/or review

• Drawings, specifications, permit and construction quantities

• Contracting package

Project assistance items verbally agreed to by the client and Enterprise are underlined. Design assistance was to include rough cost estimates.

Dependencies

• Federal Highways will be the lead in developing the crossing design utilizing input provided by USFS/Enterprise staff.

• The Forest will conduct and meet all environmental requirements - permits, SHPO and USFWS consultations, USACE coordination, NEPA, etc.

• Geotechnical services will be provided by the client or the client's partners.

• The client will conduct all AQM services (contract solicitation and award).

• The client will provide logistical support to Enterprise specialists during field visits.

• The client will supply a field appropriate vehicle to Enterprise staff.

• The client is responsible for getting reviews and approvals for designs within a reasonable amount of time after submission for review.

ENTERPRISE DELIVERABLES

Site Assessment Field Observations Photos and photo log can be downloaded from the USFS T drive here:

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\SITE ASSESSMENT\Field_Observations

The objectives of the site assessment were to better understand the processes and dynamics of the stream and floodplain at the site to inform the crossing and channel design. Observations were made along the channel and across the valley bottom for the length of the longitudinal survey, approximately 2,700 feet.

In general, the crossing is located in a depositional area; a wider valley bottom with gentle gradient that tends to periodically aggrade. Significant sediment is contributed to the channel and floodplain throughout the study reach by hillslope raveling; numerous debris fans are evident upstream of the crossing along the valley margins.

The most upstream segment of the study reach is less confined (the channel bed is closer to valley bottom/floodplain elevation) than below the crossing (Figure 2). Because of its apparent floodplain connectivity, this channel segment was used as a reference reach, from which channel dimensions at and below the crossing were developed.

The braided pattern, upstream of the crossing, appears to be a relatively recent development. An historic photo (1964) shows a single channel broadly meandering along the western valley wall. It seems possible that land use, vehicle traffic, and sedimentation from hillslope debris flows caused the channel to short-cut its meander, cutting through the aggraded area with multiple flow paths (Figure 3).

The present crossing may have stabilized the braided reach and the aggraded deposit. The presence of at least two well defined floodplain/terraces on the valley floor above the crossing indicate that there have been multiple occurrences of bed elevation fluctuation.

The aggraded deposit is encroaching on the existing crossing. The braided stream channels flow across the structure, and at the eastern end, are incising into the valley floor against the structure’s edge.

During floods, flow likely accelerates across the downstream structure apron, causing the incision and channel widening present today. The structure’s apron may be at risk of failing as turbulence has scoured most of the supporting soil from beneath it. The elevation change between the upper edge of the apron and the channel bottom is approximately four feet, deeper at channel left where there is a scour hole. A significant effort needs to be made at this location, not only to repair the channel incision, but also to repair the bankfull channel width (now 68 ft. wide here versus 12 ft. at the reference channel); see Figure 4.

As one moves away from the influence of the crossing downstream, the channel gradually narrows, becoming less incised; the channel was affected by the crossing for approximately 300 feet below the structure. At the downstream private boundary fence, the channel appears only slightly incised. The channel has several short, steep, riffles in which larger gravels, medium cobbles, and a few small boulders hold the gradient. No significant pools are present; glides flow between the riffles. Sinuosity is fairly low. (See Figure 5).

Floodplain observations suggest there has been a large volume deposit on the valley floor recent enough to have buried the trunks of live trees 1 to 2 feet deep; deposition occurred before the channel incision evident today. See Figure 5.

Figure 2: Far Upstream of the Crossing; the Reference Reach

Photos of the reference reach (located between long. pro. stations 1423 and 1659). The substrate is notably finer than that specified in the literature for the loach minnow.

Figure 3: Views of large sediment deposits on the valley bottom

Recent floodplain deposit areas.

Looking downstream at the start of braided channel segment, across a sediment deposit

Figure 4: The Existing Structure

Looking downstream, from the eastern-most wetted channel, within the braided segment

Looking west, on the hardened crossing surface

Looking upstream at the crossing apron and incision Looking upstream at the crossing apron and channel incision downstream

Figure 5: Downstream of the Crossing

Valley bottom deposits have buried this tree’s trunk by nearly two feet.

Strata of large volume, valley bottom deposits.

View looking downstream at incised channel. View looking upstream towards crossing. Channel is less incised than at upstream locations.

Riffle segment at far downstream end of study reach. View of private property boundary; downstream end of study reach. Channel is only slightly incised here.

Substrate Assessment Wolman pebble counts were conducted on November 14th, 2018 at 4 locations, all within riffles. This data can be downloaded from the USFS T drive, located here:

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\SITE ASSESSMENT\Substrate

The results found the D50, for all four sites, was fine sand, meaning 50 percent of the sample was this diameter size or smaller. The D84, for all four sites, ranged from coarse sand to small gravel, indicating that most of the stream substrate is less than small gravel in size. The approximate locations for each pebble count are longitudinal profile survey stations (in feet): 3+60 and 17+80 (upstream of crossing), 20+25 and 24+00 (downstream of crossing).

Topographic Survey The crossing vicinity was surveyed November 15-16, 2018, from the private property boundary 850 feet downstream of the crossing, to a point about 1850 feet above the crossing, near a second private property boundary (Figure 7). Through the multi-threaded segment above the crossing, the centerline of the longitudinal profile was taken up the middle channel. See Appendix A for additional survey data.

Survey data (raw and corrected files) as well as Civil-3D drawings and data can be downloaded from the USFS T drive here:

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\DESIGN ASSISTANCE\Topographic_Survey

And here

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\DESIGN ASSISTANCE\Civil_3D_Drawings

Survey equipment used were two Trimble R8S GNSS receivers, 1 Trimble base station with radio for extended range, and two Trimble data collectors. Survey data collected included x,y, and z positions (Accuracy after correction: avg. PDOP 1.9, avg. horizontal 1”, avg. vertical 2”).

Five control points (CP1-CP5) were surveyed and monumented with a ¼’’ rebar pin and pink flagging;

future surveys should use these points to reoccupy our survey. The control points should be locatable with a metal detector, their XYZ surveyed positions, photos, and site descriptions (see Table 1 and Figure 6).

Table 1. Monumented Survey Control Points, Surveyed Locations

Point Y X Z Coordinate System

CP1 996130.7 2459625 5957.761

NM STATE PLANE

ZONE 3

(in feet)

CP2 996201.4 2459715 5961.227

CP3 996496.9 2459539 5963.158

CP4 996046 2459356 5962.28

CP5 995788.6 2459426 5955.991

Some general information revealed by the survey is worth noting (see Figure 8):

• The majority of the channel bed surveyed (2000 feet of 2700 feet total), above and below the crossing, is at a slope between 0.27% and 0.36%.

• Above the crossing, the slope of the centerline channel through the deposit fan (a distance of 130+ feet), is 2.33 percent slope.

• The valley floor (and top of upper banks) has a slope of between 0.8 and 1.1 percent.

The survey resulted in a topographical surface of the channel, valley bottom, road, and stream crossing structure (Figure 7). The hydraulic drop (approximately 4 ft. in height) at the end of the apron is between survey stations 1850 and 1875. The aggraded deposit is the convex section, largely between survey stations 1600 and 1800. The reference reach, assessed by the HEC-RAS model, is located between survey stations 1150 and 775 (feet) (See Figure 2and Appendix A). It is far upstream of the crossing, and upstream of the braided section. It was analyzed by the HEC-RAS model for velocity and depth and compared with values for the loach minnow presented by the literature.

The surveyed longitudinal profile is too long to be displayed in this format, therefore instead, Figure 8 shows the longitudinal profile of the HEC-RAS modeled reach, between survey 775 and 2450.

For the purpose of hydraulic modeling with the HEC-RAS program, the survey included 15 cross-sections which span the valley bottom and are perpendicular to flow (Figure 9). It is important to note they are stationed by HEC-RAS differently than as noted on the longitudinal survey because the modeled reach is shorter than the surveyed reach.

Figure 6. Monumented Survey Control Points, Photos and Descriptions

Control Point Photo Point Description

CP1

on left floodplain downstream of crossing

CP2

at fence line, downstream of cattleguard and road.

CP3

on river right; high point; near juniper line;

upstream of crossing

CP4

on road shoulder; right bank; downstream of crossing at reflector on edge of road

CP5

right bank; downstream of crossing; on floodplain; 50 ft off road; at hot pink rock

Figure 7: Topographic site plan of Tularosa River crossing by NSFR-233. North is to the left of figure.

Figure 8: HEC RAS output, longitudinal profile of modeled reach, survey stations 775-24+50.

Figure 9: Centerline and cross-sections used for the 1D HEC-RAS analysis; north is at the top of the figure. Stations are those by HEC-RAS. Station 772 is just upstream from the crossing; Station 646 is just downstream from the apron.

Design Assistance Aquatic Species and their Design Needs The existing structure at the Tularosa River crossing has an approximate 4 ft. vertical elevation change between the hardened travel surface (low-water ford) and the downstream channel bottom (see Figure 4); this drop is preventing loach minnow (Tiaroga cobitis) from accessing upstream habitat beyond NFS road 233. Habitat below the crossing has been degraded, with few riffles and predominately very fine substrate (see Figure 5). Successful AOP design should mimic conditions (velocity, depth, width, slope) within documented loach minnow habitat for some range of flows. Streams occupied by the loach minnow are typically of gentle gradient (<1%) with riffle habitats in steeper segments (Rinne, 1989;

Propst and Bestgen,1991). Low flow (about 3 cfs) is an appropriate design flow because it maximizes the passable duration; low flow conditions at the site typically exist from October to July.

Loach minnow eggs were observed in water velocities averaging 1 ft/sec, however after hatching larvae moved to riffle margins where the water velocity averaged 0.2 ft/sec. Adult loach minnow were mainly collected in areas with flows averaging 1.9 ft/sec (Paroz et al., 2006). In order to pass adult fish through the crossing, the low-flow water velocity at the structure should therefore be no greater than 1.9 ft/sec.

Significant differences were found among water depths occupied by each loach minnow life stage, however depths by all life stages ranged between 0.3 and 0.9 ft. (Propst and Bestgen, 1991; Paroz et al., 2006) and 0.4 and 0.7 ft (Rinne, 1989). The structure should therefore be narrow enough to maintain a depth between 0.3 and 0.9 ft during low flows.

Loach minnow have been found in gravel-pebble substrates (0.6 inches to 2.5 inches). In faster currents, the fish use cobbles (2.5-10 inches) to shelter them from the flow (Rinne, 1989). Paroz et al. (2006) found loach minnow utilize areas with medium to large cobble. When sand and silt filled the interstitial space among gravel and cobble in riffles, loach minnows were rare or absent (Propst et al., 1988).

Incorporating large cobble into the crossing design and within the downstream channel should be favorable to loach minnow while also providing the bed elevation necessary to reconnect the channel with the floodplain.

The Chiricahua Leopard frog (Lithobates [Rana] chiricahuensis) inhabits a variety of habitats including perennial and intermittent rivers, swamps, perennial and intermittent freshwater lakes, perennial and intermittent freshwater marshes, freshwater springs and ponds. Their lifecycle is complex with eggs and larvae that are entirely aquatic and adults that are primarily aquatic; they need permanent to semi-permanent water. Habitat should include shallow areas with perimeter vegetation for egg deposition and foraging, deeper water areas, root masses, and undercut banks for predator refuge, a variety of flow velocities, and mud substrate areas which supports algae and diatoms (SWESA, 2008). Restoration of the stream channel below the crossing will improve habitat for the Chiricahua Leopard Frog by increasing habitat diversity (i.e., adding large wood, riffles, pool and glides).

Model Design Flows A stream gage was located immediately downstream of the study site (USGS Station #09442740). The (crest) gage had 52 years of record (1956-2016). Since the watershed area of the gage site (428 square miles) was very close to the watershed area at road-stream crossing (406 square miles), the computed peak flow frequency from the gage was used (without an area adjustment) to simulate flows through the surveyed reach. The PeakFQ computer program (USGS 2018), was used to compute frequency flow from the station data, with bulletin 17C guidelines, and without regional skew. Results are show in Table 2 below. Therefore, a reasonable design flow for AOP is at or slightly above 3 cfs; observed flow in November, during our field visit, was estimated at 2 - 3 cfs.

Flow data can be found on the USFS T drive here:

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\SITE ASSESSMENT\Stream_Flow

Table 2: Results of the PeakFQ run for USGS Station #09442740

Exceedance Probability

(percent)

Return Interval (years)

Peak Discharge

(cfs)

Confidence Limits (cfs)

5% 95%

95 1.05 3.0 1.7 27.8

80 1.25 33.1 16.7 73.3

67 1.5 88.9 51.1 139

50 2 214.1 117.2 278

20 5 778.6 426 1119

10 10 1254 806.8 2570

4 25 1836 1538 7820

2 50 2213 2273 19240

1 100 2528 3159 49230

HEC-RAS Model Runs Topographic survey data was manipulated within AutoCad Civil 3D for import to the HEC-RAS hydraulic model. The cross-section array, as shown in Figure 9, utilized about 1,700 feet of the surveyed reach.

The HEC-RAS modeling ends (station 0, downstream end) at about station 2+50 on the topographic survey (therefore, the end of the crossing apron is at about station 8+50 on the topographic map and about 600 in the HEC-RAS model). HEC-RAS Station 772 is just upstream from the crossing; Station 646 is just downstream from the apron.

The HEC-RAS model files can be downloaded from the USFS T drive here:

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\DESIGN

ASSISTANCE\HEC_RAS

A model was developed for the existing condition, using the design flows in Table 2 above; the goals were to assess flow velocity and depth (over a range of flows) within the identified reference reach (between long. pro. Stations 1423 and 1659 (feet; See Figure 2). Additional model inputs define the boundary conditions; an overall stream gradient of about 0.7 percent, a channel Manning’s n value of

0.035 (sand bottom), and overbank n values of 0.05 - 0.10 (grassy vs. wooded).

The 90 to 95 percent exceedance probability of 3-33 cfs is a useful range of flows (design flows) representing near base flow to low stage flooding. Table 3 below shows the HEC-RAS model results;

average depth and velocities in the reference channel, for flow up to 33 cfs would be within the range of the loach minnow, though the present substrate is much finer than the ideal (gravel/pebble). The model results helped to confirm that mimicking the reference reach at the road-stream crossing (e.g., width and slope) should allow loach minnow to pass.

Table 3: Modeled Velocities and depths for flow 3-33 cfs within the reference reach

Return Interval (years)

Flow (cfs)

Average Velocity

(feet/sec.)

Average Depth (feet)

Range of Velocity

(feet/sec)

Range of Depth

(feet)

Top Width of Flow (feet)

Q1.05 3 1.38 0.56 0.37-2.68 0.28-1.53 7.99-8.15

Q1.25 33 2.59 1.42 1.31-5.03 0.36-2.92 28.89-34.42

Conceptual Designs Numerous design alternatives were considered; the list below represents the best options. Their relative merits were assessed for cost and improvement to aquatic organism passage. Due to limited (Enterprise) funding, alternatives were not fully developed (i.e., modelled, drafted), but professional judgement and experience were used to weigh their pros and cons, recommending a best approach.

Alternatives Considered

For every alternative presented, 800 feet of channel rehabilitation downstream of the crossing would be necessary to 1) fill in the existing scour hole at the apron, and 2) aggrade the channel to repair the existing incision. Beyond habitat benefits, aggrading the channel is integral to providing AOP over the crossing because it is necessary to merge the upstream bed elevation with the downstream bed elevation.

The alternative to constructing the proposed riffles and revetments would be to fill in the channel with a large amount of borrowed material; which would likely still require some form of grade control to protect the crossing structure and gradient, especially immediately downstream of the crossing.

1. Add Low Flow Channel to the Existing Crossing Structure Modify the existing structure by 1) reconstructing the existing ford to provide a 12 foot wide by 6 inches deep dip (low flow channel) in the center of the crossing, 2) removing the concrete apron downstream of the crossing, and 3) rehabilitating 800 feet of channel below the crossing with a series of constructed riffles and large wood grade controls. The low flow channel over the ford would improve (over the existing structure) aquatic organism passage during low flow periods (verifiable with HEC-2D velocity modeling).

This option was not carried forward due to providing a minor improvement in aquatic organism passage at the crossing (at best). Modification of the existing structure has construction limiting factors that might prevent full passage. New construction should allow for proper slopes which creates ideal depths and velocities.

2. Bridge Construct a bridge that meets project objectives. Several structure types are available in this alternative including steel modular, cast-in-place slab or pre-stressed, precast, adjacent box beams. Instream channel work would be required to prevent the existing scour hole at the apron from headcutting after the existing structure is removed. A series of grade controls (e.g., constructed riffles) downstream would serve to fill in the scour hole and adjust the stream gradient. Channel width would also need to be adjusted, so as to provide for adequate flow depth.

A full geotechnical report and subsurface drilling investigation would be required to design the bridge foundations. This option was not carried forward due to cost; the lower elevation of the western approach (relative to the eastern approach) significantly increases cost.

3. Articulating concrete block, low-water ford The existing crossing would be removed, including the concrete apron, and replaced with an articulating, open-celled, concrete-block, low-water ford. The concrete block provides texture which would help to slow the flow velocity over the structure, assisting with AOP.

This option was selected as the preferred alternative because it is cost efficient yet also dramatically improves aquatic organism passage at the road-stream crossing.

Preferred Alternative

Civil-3D drawings (.dwg and .pdf) can be downloaded from the USFS T drive here:

T:\FS\BusOps\EnterpriseProgram\Project\R03\Gila\Tularosa_river_rest\DELIVERABLES\DESIGN ASSISTANCE\Civil_3D_Drawings

Road-Stream Crossing

In 2018 Steven Yochum (USFS Stream Team, Rocky Mountain Research Station) was asked to visit the site and provide guidance; his assessment offered a design concept which specifies removing the existing crossing infrastructure, including the apron, replacing it with a shallow and wide conduit structure (with a removable, grated lid). Additionally, downstream channel work to arrest the head-cut below the apron was described.

Our preferred alternative is similar to Yochum’s conceptual design however we recommend installing an articulating, concrete block, low-water ford instead of the shallow conduit structure (see examples, Figure 10 and Figure 11). This is because the Tularosa river has a high sediment, wood and debris load which is certain to cause long-term maintenance issues within any enclosed structure. Integral to the crossing and meeting AOP objectives, constructing a riffle immediately downstream of the crossing (at the present apron location), rather than filling in the existing scour with borrowed material, would protect the structure and help to aggrade the bed to an appropriate gradient (~1%) (see Figure 12).

Looking downstream from the crossing structure design, there are a series of constructed riffles (see the Channel Rehabilitation section below). It is imperative that the first two riffles below the structure are very solidly built as they are key to preventing the channel from headcutting through the crossing.