RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

3.0 BASELINE ASSESSMENT RESULTS

Watershed Conditions Canyon above the 2009). Approximately 4 of the crossing, drains 33,272 acres of 10.8 miles of upper Parleys Size and Land Use wooded mountainous terrain. Creek has been piped to Upper Parleys Creek flows 10.8 accommodate freeway Parleys Creek lies between miles and its two major construction. The majority of the Emigration Creek to the north headwater tributaries, Mountain upper subwatershed is forested, and Mill Creek to the south Dell Canyon and Lambs with less than 10% of the area (Figure 3.1). The upper Canyon, flow for 6.2 miles and developed and an estimated subwatershed, located in Parleys 5.3 miles respectively (SLCO overall impervious cover of

Figure 3.1. Parleys Creek watershed (map from SLCO 2009).

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11.5% (SLCO 2009). Much of Hydrology Flows are not typically released the subwatershed lies within the out of Mountain Dell Dam except Wastach National Forest and is The hydrology of Parleys Creek when the reservoir fills during managed primarily for low- is altered by the water storage spring runoff, and during base impact recreation. The areas and flow regulation operations of flow periods the stream dries up above the Mountain Dell/Parleys Mountain Dell and Little Dell for some distance below the dam Creek confluence receive Reservoirs. Originally completed until gains from groundwater protection as a in 1917, Mountain Dell Dam is a resupply surface flow. Within the water supply watershed. Other 3,000 acre-foot storage facility lower subwatershed, some significant land uses in the upper located at the confluence of additional flow regulation watershed include residential Parleys Creek and Mountain Dell capacity is provided by the 140 cabins in Lambs and Mount Aire Canyon (Figure 3.1, SLCC acre-foot pond in Sugar House Canyons, the City-owned 2010). Little Dell Dam, located Park. Mountain Dell Golf Course, just upstream of Mountain Dell gravel mining, and Reservoir, was constructed in Parleys Creek’s hydrology is transportation. Parleys Creek 1993 and impounds a 20,500 characterized by a distinct parallels throughout acre-foot reservoir designed for springtime peak typical of the study area. flood control, water supply, and snowmelt-driven systems. Based recreation (SLCC 2009). The on analysis of flow data recorded The lower Parleys Creek sub- City’s Parleys Water Treatment at the County gage near Suicide watershed is much smaller, Plant (PWTP) is located just Rock from 1980-2005, mean draining 4,112 acres of primarily downstream of Mountain Dell annual flow is 14.4 cfs, average forested, residential and park Dam, and diverts water from the monthly flow is highest in May areas below the canyon mouth. reservoir to the municipal water (Figure 3.2), and base flows Lower Parleys Creek flows delivery system (SLCO 2009). average about 2 cfs. Peak daily approximately 3.3 miles; of this length about 0.7 miles has been piped to accommodate road crossings. An additional 3.7 miles of lower Parleys Creek west of the RCS study area is conveyed in engineered conduits to the Jordan River (Figure 1.1). Estimated existing impervious cover is 28.9% within the lower sub-watershed; this value is predicted to reach 32.5% by 2030 as a result of additional commercial development (SLCO 2009). More than 60% of the lower Parleys Creek subwatershed lies within the City’s municipal boundaries. Figure 3.2. Monthly flows at Salt Lake County’s gage at Suicide Rock.

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transition to the valley. Within the RCS study area, Parleys Creek flows through areas mapped as primary and secondary groundwater recharge zones, and studies have estimated losses to groundwater to range from about 1.4 to 7 cfs (SLCO 2009).

Urbanization and development throughout the watershed have affected surface water- groundwater patterns. As more of the watershed has been converted to impervious surfaces, a greater proportion of storm water runs off as surface flow rather than infiltrating into the ground, leaving less groundwater available to supply baseflow to the creek during the summer dry period (Figure 3.3). No streamflow gage exists at the downstream end of the study Figure 3.3. Relationship between impervious cover and surface area, so no quantitative data are runoff. Impervious cover in a watershed results available to characterize in increased surface runoff. Diagram and caption text hydrology after the creek flows from FISRWG 1998. through the most urbanized flow occurs on May 12th on subwatershed (SLCO 2009). portion of watershed average (SLCO 2009), and Above the PWTP Parleys Creek downstream from the Suicide average annual high flow is 105 is classified as having perennial Rock gage. However, field cfs based on analysis of the flow; below the PWTP the creek observations during storm events 1980-2005 time period. Since is classified as “perennial- suggest that flows in the lower completion of Little Dell Dam, reduced”, indicating that flows reaches of the creek can be quite however, high flows have been are artificially reduced by the “flashy”, with rapid, brief rises in more substantially regulated, with stream diversions for municipal flow during storms. This is a an average annual high flow water supply. common hydrologic pattern in value of 75 cfs for the urbanized systems (Figure 3.4). 1993–2005 time period. Because of natural alluvial deposition patterns, Wasatch No storage reservoirs are present Average annual precipitation mountain streams including on lower Parleys Creek within ranges from 22 to 42 inches in Parleys Creek also naturally lose the RCS study area, but the the upper subwatershed, and some surface flow to Sugar House Park pond serves from 11 to 22 inches in the lower groundwater where the canyons as an on-line debris basin facility

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that traps the majority of coarse Below: Parleys Creek debris grate. sediment loads. It is estimated that the pond was last dredged in the early 1990s. Since that time, a significant volume of sediment has accumulated in the pond, reducing pond depth and capacity (L. Hemphill 2010, pers. comm.). The County regularly removes debris from the grated culvert inlet at the downstream end of reach LPC_R03 (Figure 2.1) and from a debris grate located about 500 feet upstream from that inlet. A new County debris basin facility is proposed in this area as part of the draft Comprehensive Use and Management Plan for Parleys Historic Nature Park (MGB&A et al. 2010a).

Water Quality

Above Mountain Dell Reservoir, Parleys Creek’s beneficial use classifications as designated by the Division of Water Quality (DWQ) include 1C (high quality drinking water), 2B (secondary contact recreation), and 3A (cold water fishery). In this upper segment, the creek’s water quality is good and fully Figure 3.4. A comparison of hydrographs before and after supports all of its beneficial uses urbanization. The discharge curve is higher and steeper (DWQ 2006). Below Mountain for urban streams than for natural streams. Diagram Dell Reservoir, the designated and caption text from FISRWG 1998. beneficial uses include 2B and 3A; in this segment Parleys Creek standards for any specific water 2007). Within the Sugar House is listed as impaired and only quality constituents at this time. Park pond, outbreaks of avian partially supporting its 3A use However, the creek is subject to botulism and bacteria concerns due to habitat alterations (DWQ a variety of potential have been problems in recent 2006). contamination sources and fish years (L. Hemphill 2010, pers. kills have been documented in comm.). Within Parleys Creek is not currently the stream below Suicide Rock as in the wintertime, UDOT listed by DWQ as exceeding state recently as 2007 (Prettyman regularly salts the six lanes of

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Interstate 80, and these road salts from these newer sites have not and alluvial deposits (Bryant wash directly into Parleys Creek yet gone through quality 1990). Approximately 50 to via storm drains that do not assurance/control procedures 86.2% of the soils in the upper provide any water quality and have not been released to Parleys Creek sub-watershed treatment. The Parleys Canyon the public or comprehensively have severe to very severe soil section of I-80 is a major trucking analyzed. Bacteriological data erosion potential (SLCO 2009). route, and accidents occasionally are also collected independently involve spills that have the by DPU at three sites on Parleys Once it exits the canyon, lower potential to contaminate the Creek; a scatter plot of the DPU Parleys Creek flows through a nearby creek. Sediment inputs E.coli data is provided in Figure series of Pleistocene Lake associated with poorly stabilized 3.5. Results are highly variable, Bonneville deposits ranging from highway fill slopes, and occasional high spikes that finer-grained silt and clay unprotected/broken storm drain exceed the acute state 2B deposits to coarser sand and outlets, and dust tracked out standard (668 CFU/100 mL) gravel deposits (Bryant 1990). from the gravel pit also have have been documented at all Artificial fill material, primarily potential water quality impacts. three monitoring sites. No associated with Interstate 80, also Septic systems for the residential obvious spatial or temporal borders the stream in several of cabins in the upper watershed trends are apparent, and the the lower reaches. In the lower are another potential pollution duration of each observed spike sub-watershed, 20 to 35% of the source, particularly for nutrients is not known. As additional data soils have severe to very severe and bacteria. Within the RCS are collected and analyzed and erosion potential (SLCO 2009). study area, potential nonpoint as DWQ’s new E.coli work group source pollutants include becomes more established, it is After Lake Bonneville receded fertilizers and herbicides from anticipated that a better approximately 16,000 years ago, golf courses and managed parks, understanding of bacteriological it left a series of old shoreline erosion from unprotected slopes contamination sources will deposits that now form and storm drains, urban runoff develop. prominent “benches” along the (e.g., automotive fluids), and edges of . To waste from wildlife (e.g., deer, Geology and Soils reach its modern base level at the ducks, geese) and pets. Jordan River, Parleys Creek had The geology of the upper Parleys to carve through these deposits. Table 3.1 summarizes the Creek subwatershed varies by Evidence of this process is seen existing water quality stations on tributary canyon. Lambs in the tall slopes that extend up Parleys Creek within the RCS Canyon and the lower reaches of to the Bonneville bench levels on study area. To help inform Parleys Canyon flow primarily the south side of the corridor ongoing TMDL studies on the through Twin Creek Limestone, within Parleys Historic Nature Jordan River, several new E.coli Nugget Sandstone, and several Park. Relative to the other monitoring stations (STORET members of the Ankareh smaller creeks in the City, lower numbers 4992235-4992260) formation. Above the Lambs Parleys Creek has carved a have been recently established Canyon confluence, upper relatively broad floodplain and on Parleys Creek by DWQ. Parleys Creek is dominated by shows a lesser degree of geologic Monthly E. coli and flow the Jurassic Pruess Sandstone confinement. However, various measurements have been formation and alluvial material. human-induced alterations to the collected in cooperation with Mountain Dell canyon flows creek—including channel Westminster College. The data through the Kelvin Formation straightening, installation of road

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Table 3.1. Summary of water quality data collection efforts on Parleys Creek within the study area. STORET PARAMETERS SAMPLED SAMPLING SAMPLING OR SITE SITE NAME PERIOD OF RECORD Physical/ ENTITY FREQUENCY Nutrients Metals Bacteria CODE Chemical Parleys Canyon Utah Division 1999—2007 4992230 monthly X X X Creek at mouth of Water Quality (nearly continuous) Parleys: above Utah Division 2007 (partial), 4992235 Parleys historic of Water Quality/ September monthly X a E. coli nature preserve Westminster 2009—present Parleys: below Utah Division 2007 (partial), 4992240 Parleys historic of Water Quality/ September monthly X a E. coli nature preserve Westminster 2009—present Utah Division 2007 (partial), Parleys: top 4992245 of Water Quality/ September monthly X a E. coli of Sugar House Park Westminster 2009—present Utah Division 2007 (partial), Parleys: above Sugar 4992250 of Water Quality/ September monthly X a E. coli House Pond Westminster 2009—present Utah Division 2007 (partial), Parleys: Hidden 4992255 of Water Quality/ September monthly X a E. coli Hollow Westminster 2009—present Parleys: Tanner Park Salt Lake City (at bridge between E. coli, N/A b Department June 2006—present monthly nitrates LPC_R02 T. coliform of Public Utilities and LPC_R03) Salt Lake City Parleys: Sugar E. coli, N/A b Department June 2006—present monthly nitrates House Park T. coliform of Public Utilities Salt Lake City Parleys: Hidden E. coli, N/A b Department June 2006—present monthly nitrates Hollow T. coliform of Public Utilities 1300 South storm Utah Division monthly during E. coli, 4992070 2008—present (partial) XX drain at mouth of Water Quality summer 2009 T. coliform Parleys Creek E. coli, PC4 at canyon mouth Salt Lake County April 2010—present monthly X T. coliform (in UPC_R16A) a Flow data only. b Not applicable. crossing culverts, fill placement, Fish, Birds, and Wildlife designated special status species and bank hardening—have that evolved as the top predator caused increases in channel slope Parleys Creek is a stream of within ancient Lake Bonneville. and entrenchment in some areas. special significance for native The upper portions of Parleys Bonneville cutthroat trout, the Creek and its tributaries within state fish of Utah and a state- the canyon support a core

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Figure 3.5. Scatter plot of Salt Lake City Department of Public Utilities (DPU) E. coli sampling results for Parleys Creek. The acute (single sample) E. coli standard set by the State of Utah for secondary contact recreation is 668 colony-forming units per 100 milliliters. population of Bonneville within the RCS study area are Christmas bird count, a total of cutthroat trout. Core populations limited. Fisheries surveys in 28 different bird species were are of particular significance these lower reaches have observed within the Parley’s because they are believed to documented Bonneville cutthroat Gulch survey area, which represent the pure, pre- trout populations that are the includes reaches LPC_R01, settlement genetic character of offspring of Mountain Dell and LPC_R02, LPC_R03 and several the species (Lentsch et al. 2000). Little Dell brood stock (D. Wiley golf courses (Carr 2009). The Bonneville cutthroat trout from 2010, pers. comm.) During the “eBird” list for this same area lists the Parleys watershed have been RCS field assessments, trout sightings of 65 different species harvested and used as a brood (species unknown) were between 2002 and 2009, stock source to reestablish observed in several study including hawks, owls, populations in other areas and reaches. Rainbow trout and carp woodpeckers, and a wide variety promote statewide recovery of are included in a list of wildlife of songbirds (eBird 2010). Two the species. In addition to sightings within Hidden Hollow of the observed species (green- cutthroat trout, introduced brook (reach LPC_R06) from the 1990s tailed towhee and Virginia trout populations are also present (MGB&A 1998). warbler) are included on the in . 2008 list of birds of conservation The Parleys Creek riparian concern (USFWS 2008). Quantitative data on fish corridor is home to a wide Numerous geese and populations within the lower, variety of bird species. During domesticated ducks frequent the urban portion of Parleys Creek the Audubon Society’s 2005 portions of Parleys Creek within

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the Country Club golf course and that 160 years ago the overall in Sugar House Park. Scientific vegetation density, grass cover, Historical activities surveys of wildlife populations and shrub cover along Parleys that have altered are not available for the Parleys Creek was substantially greater riparian corridor Creek RCS study area. than it is today. Fish, including conditions: However, mammals including native cutthroat trout, were deer, foxes, mice, muskrats, rock initially described as plentiful, but • mining and quarrying for squirrels, and racoons are known the fisheries of the canyon sandstone and gravel to occur within the corridor streams were quickly depleted • logging and timber harvest (MGB&A et al. 2010b, MGB&A due to heavy fishing pressure. 1998). Inmates of the first Utah state • beaver trapping and prison, located in what is now removal Historical Conditions Sugar House Park, were put to and Current Trends work building ponds to raise fish • channel clearing and to resupply the streams (Figure debris removal 3.6). Parleys Creek History • construction of water- Alterations to the Riparian storage reservoirs Parleys Canyon holds a Corridor prominent place in Utah’s • flow diversion for history, as it became an irrigation and drinking Over the last 160 years, the water important travel route shortly various activities associated with after Mormon pioneers entered development and population • railroad and freeway Salt Lake Valley in 1847. The growth in Salt Lake Valley have construction Parleys Canyon travel route, resulted in significant alterations originally known as the Golden • road and stream crossing to the stream channel and Pass Toll Road, was constructed construction riparian conditions of Parleys by Parley P. Pratt, the pioneer for Creek. Among other factors, whom Parleys Creek is named. • residential and systematic programs to clear commercial development Although detailed descriptions, debris from channels and remove drawings, and photos specific to beaver populations have likely • introduction of invasive, the riparian corridor are limited, contributed to the currently nonnative plants available information suggests reduced vegetation density that the riparian corridor at that • piping of the creek in relative to historical conditions. time was vegetated with thick, tall underground conduits When beaver were more grasses and clumps of scrub oak common, their dams increased and willows (Figure 3.6). • channel relocation/ inundated streamside habitat Pioneers also describe having straightening area, elevated the water table, difficulties traversing a broad reduced flood velocities and • bank armoring marsh area with tall grass at the erosion, and trapped sediment convergence of Parleys, and nutrients (Gardner et al. • placement of fill within Emigration, and Red Butte floodplain areas 1999). As beaver populations Creeks (Dixon 1997). decreased, the “checks” on • in-channel pond sediment and water created by Although limited, these available construction beaver dams also decreased, historical descriptions suggest

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resulting in greater flow velocities and bend realignment is evident and sediment supply (Wolman and streambed down-cutting. within the areas now occupied by 1967, Riley 1998, Colosimo and The control and reduction of the Country Club golf course Wilcock 2007). Studies of urban beaver populations throughout (Figures 3.7 and 3.8 ). In channel adjustment generally the west has profoundly altered contrast, the modern channel identify two main stages of stream channel, floodplain, and alignment within the area that is adjustment: an early depositional riparian vegetation conditions now Parleys Historic Nature Park phase and a later, fully urbanized (Wohl 2000). appears similar to the 1938 phase. The early phase occurs alignment. In the 1938 during initial development, when Many of the direct alterations to photograph, the channel in this active construction leads to Parleys Creek have occurred in area appears to already have increased fine sediment supply, order to accommodate been realigned to accommodate increased bar deposits, and transportation development a gravel mining operation in the reduced channel size. The associated with population area now occupied by the BMX late/fully urbanized phase occurs growth. Significant road bike course (Figure 3.7). after construction activities are improvement projects of various Comparison of current channel essentially complete and the types occurred nearly every position with the 1938 alignment watershed has become stable decade along what is now the also illustrates the increase in the with a high percentage of Interstate 80 corridor, requiring length and number of culvert impervious surface area, and numerous creek realignments pipes within the corridor. The runoff magnitudes and volumes and piping projects (Figure 3.6). 1938 photo shows a continuous have correspondingly increased. Within the lower subwatershed, open stream channel between Channels in the “late urbanized” one of the most significant direct 1300 East and 2000 East phase are typically enlarged changes to the creek was the (Bowman and Beisner 2008); relative to their original form due construction of the 1300 South today this stretch of stream is to an oversupply of water relative conduit, which converted the interrupted by five different to sediment supply. These open-channel portions of culvert crossings. The channels have few bar deposits Parleys, Emigration, and Red construction of culvert crossings and are commonly downcut Butte creeks west of 1100 East to and piping of portions of Parleys (incised) with reduced floodplain an underground pipe system. Creek facilitated urban growth access (Figure 3.9). Several of The exact date of conduit but also reduced total channel the reaches of Parleys Creek that construction is not known, but length, resulting in greater were assessed exhibit some housing stock located over the channel slope and higher stream characteristics of the “late conduit system dates to about velocities. The culverts have also urbanized” phase, such as low the late 1920's, suggesting that disrupted the connectivity of the bank erosion/root scour. construction was complete prior riparian corridor by creating to that time. No creek channel barriers to fish and wildlife Other influences such as localized can be seen west of 1100 East in migration. sediment inputs from eroding 1938 air photos of Salt Lake storm drain outfalls or sediment City. Urban Channel deposition within constructed Adjustments ponds modify conditions from In some portions of the RCS this generalized “late urbanized” study area, the channel Urbanized streams have been channel condition. Existing alignment of Parleys Creek has found to undergo a sequence of channel conditions within the changed dramatically since 1938. typical channel adjustments in Parleys Creek corridor reflect a Significant channel straightening response to changes in hydrology complex response to a variety of

SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-9 BIO-WEST, INC. RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

Figure 3.6 Parleys Creek historical timeline.

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historical and ongoing alterations throughout the watershed.

Recent and Anticipated Future Trends

Within the lower Parleys Creek sub-watershed, land use predictions for 2030 indicate a increase in impervious cover from 28.9 to 32.5% and a 6.7% loss of open space. Most of this change is associated with an expected increase in the amount of commercial land use (SLCO 2009). No impervious surface cover increase is predicted for the upper subwatershed.

Figure 3.7. 1938 aerial photo of Parleys Creek east of 2300 East. Climate change is another factor The photo is overlaid with 2006 channel alignment that can be anticipated to affect in red; gaps in the line indicate underground culverts. the Parleys Creek riparian corridor. Climate projections for the southwest region of the United States show increased temperatures, reduced mountain snowpack, a 10–20% decrease in annual runoff volume, reduced springtime precipitation amounts, and anticipated water supply shortages (Karl et al. 2009). The risk of drought, as well as the risk of flooding, are expected to increase. The changes in temperature will likely result in a shift in vegetation communities, and altered precipitation patterns will influence stream hydrology and channel conditions. The timing of snowmelt runoff is expected to occur earlier in the spring, with an anticipated reduction in summertime base flows (Karl et al. 2009). It is Figure 3.8. 1938 aerial photo of Parleys Creek near 1700 East. The photo is overlaid with 2006 channel alignment difficult to predict specific in red; gaps in the line indicate underground culverts. SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-12 BIO-WEST, INC. RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

changes to Parleys Creek with certainty, but recorded annual stream flow volumes on Parleys Creek already show a declining trend between 1970 and 2006 (L. Alserda 2009, pers. comm., Figure 3.10). This trend is anticipated to continue into the future (Karl et al. 2009).

Stream and Vegetation Conditions

Stream Channel Characteristics

Salt Lake County has classified Parleys Creek within the RCS study area as moderately entrenched, meaning the channel is somewhat vertically confined. Figure 3.9. Illustration of streambed lowering (incision) process Composite stream stability common on urbanized streams. Following initial incision ratings for the area were good to (B), the channel may continue to incise and widen fair during County stream until new equilibrium channel/floodplain geometry is reached, posing a potential risk to urban development assessments completed in 2007 on terrace surfaces adjacent to the channel. Diagram and 2008. During these from FISRWG 1998. assessments, the County classified Parleys Creek as Rosgen (1996) stream type B3 in reaches UPC_R16 and LPC_R01; stream type B4 in reaches LPC_R02 and LPC_R03; and stream type F3-4 in the remaining reaches downstream (K. Collins 2009, pers. comm.). County bankfull width estimates for the stream reaches in lower Parleys Creek ranged from 9 feet to 19 feet, with an average value of 14 feet. The estimate for reach UPC_R16 was 16 feet (K. Collins 2009, pers. comm.).

Results of RCS field surveys and Figure 3.10. Plot of temporal trends in annual stream flow at Parleys GIS analyses further illustrate the Creek gage. Plot provided by the Salt Lake City Department of Public Utilities. SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-13 BIO-WEST, INC. RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

Figure 3.11. Cross-section plots extrapolated from digital elevation data. Plots on left (in red) exhibit less vertical confinement and include relatively well-developed active floodplain surfaces. Plots on right (in blue) exhibit a greater degree of vertical confinement between tall, steep side slopes. fact that the Parleys Creek varies, and in some locations the spread out horizontally during channel is moderately channel shape is wider and flood events, dissipating velocity entrenched and in some areas includes broader, flatter bank and reducing erosion potential. inset between tall, steep slopes and floodplain surfaces (Figure (Figure 3.11). However, the 3.11). These areas are important Surveyed channel width values extent of vertical confinement because they allow water to are quite variable, ranging from

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about 5 to 27 feet at low flow, high flow value varies from about Channel slope, as determined for with an average value of 14 feet 13 to 28 feet, with an average of each stream reach from digital (Table 3.2). During the spring 19 feet. In some locations, such elevation data, varies from 1% to runoff period, field surveys were as LPC_R04A, channel width has 3.7% within the RCS study area, conducted at a streamflow of 67 been directly affected by installed with an average value of 1.8% cfs, which is close to the 1993- bank hardening measures. (Figure 3.12, Table 3.2). Parleys 2005 average annual high flow Creek does not show any value of 75 cfs. Width at this obvious consistent spatial trends

Table 3.2. Summary of streambed material, channel geometry, and slope data. MEASURED VALUES AT RIFFLE CROSS SECTION REACH DATA STREAMBED MATERIAL SIZE DATA CHANNEL GEOMETRY REACH NUMBER Low Flow Wetted D16 D50 D84 Percent Local Slope Reach Slope Reach Length Wetted Width Width (ft) b (mm) a (mm) a (mm) a Embedded (ft/ft) d (ft/ft) d (ft) b (ft) b at 67 cfs c UPC_R16A 8 41 124 26 12.5 14.9 0.017 0.017 667 UPC_R16B 5 24 140 36 11.8 15.0 0.021 0.037 832 LPC_R01A 10 36 117 18 16.0 19.6 0.046 0.027 1487 LPC_R01B ------0.020 221 LPC_R02 20 57 135 16 14.9 18.9 0.011 0.019 1659 LPC_R03 12 36 106 11 16.1 20.4 0.007 0.010 815 LPC_R04A 12 54 147 9 9.2 17.6 0.008 0.017 1681 LPC_R04B 8 36 101 21 18.2 22.6 0.007 0.013 1748 LPC_R04C 13 29 56 1 4.9 17.5 0.018 0.012 1285 LPC_R04D - - - - 5.4 13.0 0.015 0.015 1661 LPC_R04E 7 37 115 8 11.2 15.3 0.004 0.016 731 LPC_R05A 10 36 96 18 27.4 28.0 0.014 0.013 619 LPC_R05B 9 32 72 21 15.2 17.7 0.004 0.011 793 LPC_R05C 16 31 64 3 22.0 24.3 0.020 0.015 1147 LPC_R05D 16 66 157 24 14.0 19.0 0.036 0.026 176 LPC_R06 <2 51 135 11 16.1 e 21.1 e 0.037 0.023 803 averages 11 40 112 16 14.2 18.8 0.018 0.018 1020 a The 16th, 50th, and 84th percentile values of the particle size distribution, in millimeters. b Feet. c Cubic feet per second. d Feet per feet. e Estimated wetted width.

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Figure 3.12. Longitudinal profile plot of Parleys Creek streambed based on 2006 digital elevation data. Black cross marks indicate culvert inlets and outlets; red and blue lines indicate open channel stream sections. Data are not shown for reaches LPC_R04C or LPC_R04D because they have been altered by post-2006 channel modifications. in gradient through the study section riffles, medium or fine bank material, and the presence area. Historically, channel gravel comprises the D16 particle or proximity of artificial rip rap or gradient would have shifted to a size, and cobble-sized material boulder material. flatter, less confined, more comprises the D84 particle size sinuous channel type in the (Table 3.2). Embeddedness Vegetation Characteristics flatter valley area west of 1100 values are highly variable. In East; however, this portion of the flatter-gradient portions of the Table 3.3 lists all plant species creek is now piped underground channel such as run and pool noted on the data forms during in the 1300 South conduit. areas, particle sizes are smaller, the study area mapping effort. with sand and silt often Species are identified by their Median (D50) streambed particle dominant. No consistent common and scientific names, size at the measured cross upstream-to-downstream trends mapping code, wetland indicator sections ranges from 24 to 66 are evident in the pebble count status (USFWS 1988), and millimeters (mm), indicating that results; rather, bed material size whether the species is native to medium- and large-sized gravel and embeddedness appear to be Utah or introduced (NRCS are the dominant substrate sizes largely a function of local factors 2009). A total of 86 different in riffle areas of Parleys Creek such as sediment inputs from species were noted during the (Table 3.2). At most of the cross erosion areas, composition of Parleys Creek mapping work,

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Table 3.3. Plant species noted during Parleys Creek mapping work. SCIENTIFIC NAME COMMON NAME WETLAND INDICATOR STATUS NATIVE TO UTAH OR INTRODUCED Acer grandidentatum bigtooth maple not listed native Achillea millefolium common yarrow facultative upland native Acer negundo boxelder facultative wetland native Aegilops cylindrica jointed goatgrass not listed introduced Agropyron cristatum crested wheatgrass not listed introduced Agrostis gigantea redtop no indicator introduced Ailanthus altissima tree of heaven no indicator introduced Ambrosia artemisiifolia annual ragweed facultative upland native Artemisia ludoviciana white sagebrush facultative upland native Arctium minus lesser burdock not listed introduced Artemisia tridentata big sagebrush not listed native Carduus nutans nodding plumeless thistle not listed introduced Cirsium arvense Canada thistle facultative upland introduced Conium maculatum poison hemlock facultative wetland introduced Centaurea solstitialis yellow star-thistle not listed introduced Cirsium vulgare bull thistle facultative introduced Convolvulus arvensis field bindweed not listed introduced Chrysanthemum leucanthemum oxeye daisy not listed introduced Betula occidentalis water birch facultative wetland native Bromus arvensis field brome not listed introduced Bromus inermis smooth brome not listed native Bromus tectorum cheatgrass not listed introduced Catabrosa aquatica water whorlgrass obligate wetland native Cardaria draba whitetop no indicator introduced Cercocarpus ledifolius curl-leaf mountain mahogany not listed introduced Chenopodium album lambsquarters facultative upland native Chrysothamnus viscidiflorus yellow rabbitbrush not listed native Cichorium intybus chicory not listed introduced Cornus sericea redosier dogwood facultative wetland native Cynoglossum officinale gypsyflower (houndstongue) not designated introduced Dactylis glomerata orchardgrass facultative upland introduced Elaeagnus angustifolia Russian olive facultative introduced Elymus repens quackgrass facultative upland introduced Equisetum arvense field horsetail facultative upland native Ericameria nauseosa rubber rabbitbrush not listed native Euphorbia myrsinites myrtle spurge not listed introduced Fraxinus pennsylvanica green ash facultative wetland native Gleditsia triacanthos honeylocust facultative native Grindelia squarrosa qurlycup gumweed facultative upland native Gutierrezia sarothrae broom snakeweed not listed native Helianthus annuus common sunflower facultative upland native Hedera helix English ivy not listed introduced Hordeum jubatum foxtail barley facultative native

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Table 3.3. Plant species noted during Parleys Creek mapping work (cont.). SCIENTIFIC NAME COMMON NAME WETLAND INDICATOR STATUS NATIVE TO UTAH OR INTRODUCED Juniperus osteosperma Utah juniper not listed native Lactuca serriola prickly lettuce facultative upland introduced Lonicera involucrata twinberry honeysuckle facultative native Lonicera tatarica tatarian honeysuckle no occurrence introduced Mahonia repens creeping barberry not listed native Mentha arvensis wild mint facultative wetland native Melilotus officinalis yellow sweetclover facultative upland introduced Medicago sativa alfalfa not listed introduced Melica spectabilis purple oniongrass obligate upland native Onopordum acanthium scotch cottonthistle not listed introduced Parthenocissus quinquefolia Virginia creeper no occurrence native Phalaris arundinacea reed canarygrass obligate wetland native Phragmites australis common reed facultative wetland native Pinus nigra Austrian pine not listed introduced Pinus ponderosa ponderosa pine facultative upland native Populus angustifolia narrowleaf cottonwood facultative native Poa bulbosa bulbous bluegrass not listed introduced Populus deltoides eastern cottonwood facultative wetland native Poa pratensis Kentucky bluegrass facultative upland introduced Poa secunda sandberg bluegrass not listed native Prunus virgniana chokecherry facultative upland native Pseudoroegneria spicata bluebunch wheatgrass obligate upland native Quercus gambelii Gambel oak not listed native Rhus glabra smooth sumac not listed native Rhus trilobata skunkbush sumac no indicator native Rosa woodsii Woods' rose facultative native Rumex crispis curly dock facultative wetland introduced Salix exigua narrowleaf willow obligate wetland native Salix fragilis crack willow facultative introduced Schoenoplectus acutus hardstem bulrush obligate wetland native Secal cereale cereale rye not listed introduced Sisymbrium altissimum tall tumblemustard facultative upland introduced Solanum dulcamara climbing nightshade facultative introduced Solidago missouriensis Missouri goldenrod not listed native Symphyotrichum eatonii Eaton's aster facultative native Symphoricarpos occidentalis western snowberry no occurrence native Tamarix ramosissima saltcedar facultative wetland introduced Tetradymia canescens spineless horsebrush not listed native Thinopyrum intermedium intermediate wheatgrass not listed introduced Toxicodendron rydbergii western poison ivy facultative upland native Typha cattail not listed no status Ulmus pumila Siberian elm not listed introduced Vinca major bigleaf periwinkle not listed introduced

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with about half of the species cheatgrass (Bromus tectorum) being native to Utah. As seen in (Table 3.4). Dominant canopy species/ vegetation types Table 3.4, most of the nonnative in the study area: species within the corridor occur Canopy (tree) cover is generally in the canopy and understory high throughout the study area • box elder vegetation layers, while the shrub (Table 3.5) although near-stream layer is dominated almost tree cover is limited in portions of • cottonwood entirely by native species. Box the Country Club golf course. elder (Acer negundo) and Because of the generally high- •Gambel oak cottonwood (Populus sp.) are the quality tree cover within the • introduced/native tree mix most common native trees along Parleys Creek riparian corridor, the stream-side areas of Parleys the riparian functions of shading • other native trees or Creek, with Gambel oak and water-temperature control shrubs common on upper slope areas. are met to a high degree. Thirty- Siberian elm (Ulmus pumila), an seven percent of the overall • Russian olive introduced invasive tree, is also mapped area has greater than • Siberian elm very common in the study area 25% cover in all three vegetation and comprises the dominant layers (canopy, shrub, • understory canopy species in some reaches understory); these areas are (Table 3.4). Common shrub particularly effective at providing species include narrowleaf willow the riparian functions of nutrient (Salix exigua) and redosier filtration and sediment trapping. dogwood, (Cornus sericea) with Invasive weeds are a significant Woods’ rose (Rosa woodsii) and problem in all study reaches and skunkbush sumac (Rhus in 66% of the overall mapped trilobata) common on upper area (Table 3.5). portions of slopes. The understory vegetation layer Issues Affecting locations. Common types of trash include miscellaneous small shows the greatest species Riparian Functions variety. Virginia creeper items such as bottles, cans, food (Parthenocissus quinquefolia) is wrappers, ropes, tarps, etc. During the baseline assessment the most common native These items are common in the work, several common issues understory species in stream-side more accessible stream reaches were observed to be affecting areas, with intermediate that are used for recreation. and limiting riparian functions in wheatgrass and ragweed Another common category of the Parleys Creek corridor. (Ambrosia sp.) common on trash is remnant/obsolete pieces These issues are discussed by upper slopes. Introduced of infrastructure such as pieces of function below. orchardgrass and Kentucky concrete and asphalt, old pipes bluegrass dominate the and barrels, broken fencing, understory cover in a number of Aesthetics obsolete erosion control devices the stream reaches within the such as failing silt fence, etc. In Country Club and Sugar House Although many visually some instances the concrete and Park. Common invasive appealing portions of Parleys asphalt pieces are associated with understory species include lesser Creek exist, the presence of trash poorly designed bank burdock (Arctium minus) and and debris degrades corridor stabilization efforts. A total of 78 aesthetics in a number of individual litter areas were

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Table 3.4. List of mapped canopy, shrub, and understory plant species found in each assessed stream reach. PLANT SPECIES

Common Name Scientific Name LPC_R02 LPC_R03 LPC_R06 LPC_R01B LPC_R01A UPC_R16B UPC_R16A LPC_R04C LPC_R05C LPC_R04E LPC_R04D LPC_R05D LPC_R04B LPC_R05B LPC_R04A LPC_R05A Bigtooth maple Acer grandidentatum XX XXXX X X Boxelder Acer negundo XXXXXXXXXXXXXXXX Water birch Betula occidentalis XX XXXX Curl-leaf mountain Cercocarpus ledifolius X mahogany Green ash Fraxinus pennsylvanica X XXXX Honeylocust Gleditsia triacanthos XX Utah juniper Juniperus osteosperma X Austrian pine a Pinus nigra a X Ponderosa pine Pinus ponderosa XXX CANOPY Narrowleaf cottonwood Populus angustifolia XXX XXXX XXXXXXX Eastern cottonwood Populus deltoides XXXXXXXXXXXXXXXX Gambel oak Quercus gambelii XXXXXXXXX X X X Smooth sumac Rhus glabra XXX X X Siberian elm b Ulmus pumila b XXX XXXXXXXXXXXX Saltcedar b Tamarix Ramosissima b X Tree of heaven c Ailanthus altissima c XXX X X Russian olive b Elaeagnus angustifolia b XX X X XXXX XX White sagebrush Artemisia ludoviciana X Big sagebrush Artemisia tridentata XXXXX X Chrysothamnus Yellow rabbitbrush XX X X X viscidiflorus Redosier dogwood Cornus sericea XXXXX XXX XXX X Rubber rabbitbrush Ericameria nauseosa XXX Twinberry honeysuckle Lonicera involucrata XX Tatarian honeysuckle a Lonicera tatarica a XXXXX Chokecherry Prunus virgniana XXX XX XX X SHRUB Skunkbush sumac Rhus trilobata X XXXXXXX XX X X Woods' rose Rosa woodsii XXXXX XXXXXXX XX Narrowleaf willow Salix exigua XXX XXX XXXXXXXX Crack willow a Salix fragilis a XXX XXX Symphoricarpos Western snowberry X occidentalis Cattail Typha XX

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Table 3.4. List of mapped canopy, shrub, and understory plant species found in each assessed stream reach (cont.). PLANT SPECIES

Common Name Scientific Name LPC_R02 LPC_R03 LPC_R06 LPC_R01B LPC_R01A UPC_R16B UPC_R16A LPC_R04C LPC_R05C LPC_R04E LPC_R04D LPC_R05D LPC_R04B LPC_R05B LPC_R04A LPC_R05A Common yarrow Achillea millefolium X Crested wheatgrass a Agropyron cristatum a XX X XX Redtop a Agrostis gigantea a XXXXX Annual ragweed Ambrosia artemisiifolia XXXXX X XX X Field brome a Bromus arvensis a XX Smooth brome Bromus inermis X Water whorlgrass Catabrosa aquatica XX XXX Lambsquarters a Chenopodium album a X Chicory a Cichorium intybus a XXX Orchardgrass a Dactylis glomerata a XXXXXXXXX Field horsetail Equisetum arvense X Curlycup gumweed Grindelia squarrosa XX X Broom snakeweed Gutierrezia sarothrae XX Common sunflower Helianthus annuus XX Foxtail barley Hordeum jubatum XX Prickly lettuce a Lactuca serriola a XX X Creeping barberry Mahonia repens X Alfalfa a Medicago sativa a XXX Purple oniongrass Melica spectabilis X UNDERSTORY Yellow sweetclover a Melilotus officinalis a XXXXXXX X Wild mint Mentha arvensis XXXX X Parthenocissus Virginia creeper XXXXX XXXX XXX X quinquefolia Reed canarygrass Phalaris arundinacea XXX Common reed Phragmites australis XX X Sandberg bluegrass Poa secunda X Bulbous bluegrass a Poa bulbosa a XX X Kentucky bluegrass a Poa pratensis a XXXX XX X Bluebunch wheatgrass Pseudoroegneria spicata XX Curly dock a Rumex crispis a X Hardstem bulrush Schoenoplectus acutus X Cereale rye a Secal cereale a XXX Tall tumblemustard a Sisymbrium altissimum a X Climbing nightshade a Solanum dulcamara a X XXXX Missouri goldenrod Solidago missouriensis XX

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Table 3.4. List of mapped canopy, shrub, and understory plant species found in each assessed stream reach (cont.). PLANT SPECIES

Common Name Scientific Name LPC_R02 LPC_R03 LPC_R06 LPC_R01B LPC_R01A UPC_R16B UPC_R16A LPC_R04C LPC_R05C LPC_R04E LPC_R04D LPC_R05D LPC_R04B LPC_R05B LPC_R04A LPC_R05A Eaton's aster Symphyotrichum eatonii XX Spineless horsebrush Tetradymia canescens X Intermediate Thinopyrum intermedium X X XXXXX X wheatgrass Western poison ivy Toxicodendron rydbergii XXXXX X X Jointed goatgrass b Aegilops cylindrica b XXXX Scotch cottonthistle b Onopordum acanthium b XXXX XXX Myrtle spurge b Euphorbia myrsinites b XXX Quackgrass b Elymus repens b XX X Lesser burdock b Arctium minus b XX XXXXXXXXXXXX Cheatgrass b Bromus tectorum b XXX X XXXXX Whitetop b Cardaria draba b XX XXX X X Houndstongue Cynoglossum officinale b XX XXXX X (Gypsyflower) b

UNDERSTORY Bigleaf periwinkle c Vinca major c XX English ivy c Hedera helix c XX X Musk thistle b Cardus nutans b XX Canada thistle b Cirsium arvense b XXXX X X Poison hemlock b Conium maculatum b X Yellow star-thistle b Centaurea solstitialis b XX Bull thistle b Cirsium vulgare b X Convovulus ssp. b Field bindweed b X Chrysanthemum Chrysanthemum Oxeye daisy b X leucanthemum b a Species not native to Utah. b State- or city-listed, nonnative, noxious weed species. c Nonnative, invasive species. mapped in the study area during Wildlife Habitat a food source. Therefore, the RCS baseline assessment and Connectivity healthy native plant communities work. Road noise associated are necessary for a riparian with the proximity of Interstate A wide range of native bird and corridor to function to its 80 also impacts the aesthetics of mammal species rely on native maximum potential in terms of the Parleys Creek corridor. insects as a key food source wildlife habitat. As discussed Graffiti is also common in (Tallamy 2009). These insects above, invasive nonnative plant reaches that have concrete must share an evolutionary species are a concern in all of the headwalls at culvert inlets or history with plants in order to study reaches within the Parleys outlets. recognize them and use them as

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Table 3.5. Percent cover and invasive species class for mapped vegetation polygons. POLYGON PERCENT CANOPY PERCENT SHRUB PERCENT INVASIVE SPECIES REACH NUMBER COVER a COVER a UNDERSTORY COVER a CLASS LPC_R01A 1 N/A N/A N/A none LPC_R01A 2 6—25 26—50 76—100+ high LPC_R01A 3 76—100+ 76—100+ 0 low LPC_R01A 4 76—100+ 51—75 0 none LPC_R01A 5 6—25 6—25 76—100+ low LPC_R01A/R01B/R02 6 76—100+ 51—75 0 none LPC_R01A 7 0 76—100+ 0 none LPC_R01A 8 6—25 26—50 51—75 low LPC_R01A 9 0 6—25 76—100+ majority LPC_R01A 10 26—50 51—75 26—50 low LPC_R01A 11 0 6—25 76—100+ moderate LPC_R01A 12 0 0 76—100+ high LPC_R01A 13 76—100+ 76—100+ 0 low LPC_R01A 14 76—100+ 6—25 0 none LPC_R01A 15 76—100+ 26—50 6—25 moderate LPC_R01A 16 76—100+ 51—75 26—50 moderate LPC_R01A 17 76—100+ 26—50 0 low LPC_R01A/R01B 18 26—50 26—50 76—100+ high LPC_R01B/R02 19 51—75 26—50 76—100+ majority LPC_R01B/R02 20 76—100+ 51—75 1—5 none LPC_R02 21 76—100+ 6—25 51—75 high LPC_R02 22 76—100+ 6—25 26—50 high LPC_R02 23 51—75 26—50 26—50 moderate LPC_R02 24 76—100+ 76—100+ 6—25 none LPC_R02 25 76—100+ 51—75 1—5 moderate LPC_R02/R03 26 6—25 6—25 76—100+ majority LPC_R02 27 76—100+ 26—50 0 none LPC_R02 28 51—75 51—75 76—100+ majority LPC_R02 29 76—100+ 76—100+ 6—25 moderate LPC_R02 30 76—100+ 26—50 26—50 high LPC_R02 31 6—25 26—50 76—100+ none LPC_R03 32 76—100+ 6—25 6—25 moderate LPC_R03 33 76—100+ 26—50 26—50 high LPC_R03 34 76—100+ 0 0 none LPC_R04A 35 26—50 0 76—100+ none LPC_R04A 36 6—25 51—75 1—5 moderate LPC_R04A 37 76—100+ 26—50 51—75 high LPC_R04A 38 76—100+ 51—75 51—75 high

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Table 3.5. Percent cover and invasive species class for mapped vegetation polygons (cont.). POLYGON PERCENT CANOPY PERCENT SHRUB PERCENT INVASIVE SPECIES REACH NUMBER COVER a COVER a UNDERSTORY COVER a CLASS LPC_R04A 39 76—100+ 51—75 51—75 high LPC_R04A 40 51—75 6—25 51—75 high LPC_R04A 41 76—100+ 26—50 26—50 moderate LPC_R04A 42 6—25 51—75 51—75 low LPC_R04A 43 76—100+ 51—75 26—50 none LPC_R04A 44 76—100+ 26—50 0 moderate LPC_R04A 45 26—50 6—25 76—100+ majority LPC_R04A 46 76—100+ 26—50 26—50 high LPC_R04A 47 51—75 26—50 6—25 moderate LPC_R04A 48 76—100+ 26—50 51—75 high LPC_R04A 49 1—5 0 76—100+ none LPC_R04B 50 51—75 26—50 51—75 moderate LPC_R04B 51 6—25 0 6—25 none LPC_R04B 52 26—50 6—25 1—5 moderate LPC_R04B 53 76—100+ 26—50 51—75 high LPC_R04B 54 51—75 26—50 76—100+ high LPC_R04B 55 26—50 6—25 51—75 high LPC_R04B 56 0 1—5 76—100+ none LPC_R04B/R04C 57 26—50 6—25 76—100+ high LPC_R04C 58 26—50 26—50 51—75 high LPC_R04B 59 0 0 76—100+ none LPC_R04B 60 0 0 76—100+ none LPC_R04C 61 26—50 6—25 51—75 moderate LPC_R04C 62 0 6—25 51—75 moderate LPC_R04C 63 26—50 6—25 76—100+ majority LPC_R04C 64 0 6—25 51—75 moderate LPC_R04C 65 6—25 6—25 76—100+ none LPC_R04C 66 51—75 26—50 26—50 majority LPC_R04C 67 51—75 26—50 51—75 majority LPC_R04C 68 51—75 51—75 51—75 high LPC_R04C 69 26—50 26—50 51—75 high LPC_R04C 70 0 0 51—75 none LPC_R04D 71 51—75 51—75 76—100+ high LPC_R04D 72 6—25 0 76—100+ none LPC_R04D 73 6—25 1—5 76—100+ high LPC_R04D 74 1—5 1—5 51—75 moderate LPC_R04D 75 0 6—25 76—100+ low LPC_R04D 76 76—100+ 51—75 26—50 moderate LPC_R04D 77 26—50 6—25 51—75 moderate

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Table 3.5. Percent cover and invasive species class for mapped vegetation polygons (cont.). POLYGON PERCENT CANOPY PERCENT SHRUB PERCENT INVASIVE SPECIES REACH NUMBER COVER a COVER a UNDERSTORY COVER a CLASS LPC_R04D 78 26—50 26—50 51—75 moderate LPC_R04D 79 0 6—25 51—75 moderate LPC_R04E 80 0 6—25 51—75 moderate LPC_R04E 81 26—50 6—25 76—100+ high LPC_R04E 82 6—25 0 76—100+ high LPC_R04E 83 51—75 51—75 26—50 high LPC_R04E 84 51—75 51—75 76—100+ high LPC_R04E 85 26—50 26—50 76—100+ majority LPC_R04A 86 51—75 26—50 51—75 high LPC_R05A 87 76—100+ 26—50 26—50 high LPC_R05A 88 51—75 26—50 26—50 high LPC_R05A/R05B 89 26—50 51—75 26—50 moderate LPC_R05B 90 76—100+ 51—75 26—50 high LPC_R05B 91 51—75 51—75 6—25 moderate LPC_R05B 92 26—50 51—75 51—75 moderate LPC_R05D 93 76—100+ 51—75 26—50 high UPC_R16A 94 51—75 51—75 6—25 moderate UPC_R16A 95 26—50 76—100+ 6—25 none UPC_R16A 96 51—75 26—50 26—50 none UPC_R16A 97 51—75 51—75 26—50 moderate UPC_R16A 98 51—75 26—50 26—50 high UPC_R16A 99 26—50 51—75 6—25 moderate UPC_R16A/R16B 100 51—75 51—75 6—25 moderate UPC_R16B 101 6—25 51—75 26—50 moderate UPC_R16B 102 1—5 6—25 26—50 moderate UPC_R16B 103 26—50 51—75 26—50 low UPC_R16B 104 26—50 26—50 26—50 high UPC_R16B 105 6—25 26—50 51—75 high UPC_R16B 106 26—50 51—75 26—50 moderate UPC_R16B 107 26—50 26—50 26—50 moderate LPC_R05C 108 51—75 6—25 76—100+ moderate LPC_R05C 109 51—75 51—75 51—75 moderate LPC_R05C 110 51—75 26—50 51—75 moderate LPC_R06 111 76—100+ 26—50 26—50 high LPC_R06 112 51—75 51—75 51—75 high LPC_R06 113 26—50 6—25 76—100+ moderate LPC_R06 114 51—75 26—50 6—25 moderate LPC_R06 115 26—50 26—50 76—100+ low LPC_R06 116 26—50 26—50 51—75 none a N/A = not applicable.

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Creek corridor, and significantly Invasive plants affect the composition of the Factors limiting shrub of concern in the study understory and canopy and understory cover: area: vegetation layers. In some areas invasive species comprise the • oversteepened slopes • oxeye daisy majority plant cover within a vegetative layer, limiting the • inadequate revegetation • yellow star-thistle ability of native plants to thrive efforts following construction or fill and support native insects, birds, placement • musk thistle and wildlife. A lack of understory and shrub cover in some reaches • whitetop • soil compaction from also limits habitat quality in terms heavy foot traffic of structural diversity, which is • poison hemlock particularly important for bird • poorly controlled runoff from upland areas • Canada thistle populations.

• houndstongue Another issue that affects wildlife habitat in terms of riparian Nutrient Filtration • saltcedar connectivity is the presence of and Sediment Trapping stream crossing culverts. A total •quackgrass of nine major road crossing Several areas within the Parleys culvert pipes are present within Creek corridor lack the dense • myrtle spurge the study area (Figure 3.12, near-stream understory cover Table 3.6). Several of these that is needed to maximize the • Scotch thistle culverts impede or block fish ability of the riparian corridor to passage due to their long length filter sediment, nutrients, and • bull thistle and high flow velocities. This pollutants from storm runoff. In limits the ability of fish • common burdock some areas, understory cover is populations to use Parleys Creek high but the community is as a continuous travel corridor. • Russian olive dominated by invasive weeds or Within the RCS study area, a mowed turf. These types of • Siberian elm total length of 0.75 mile of cover do not serve the filtration stream is contained in culvert function as well as tall, dense, • tree of heaven pipes, limiting the overall length deep-rooted native grass of open-channel stream channel communities would. Another • jointed goatgrass available as aquatic habitat. The factor limiting the filtration longest continuous segments of function in portions of Parleys • field bindweed stream in the study area include Creek is the design of storm drain the 4,200-foot-long segment outfalls. In many areas, pipes •English ivy within Parleys Historic Nature discharge directly into the main Park and a 3,000-foot-long flow of the stream, eliminating • periwinkle vine segment encompassing study the opportunity for runoff to be reaches LPC_R04B and filtered by riparian vegetation. • cheatgrass LPC_R04C within the Country Club golf course.

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Table 3.6. Size and condition of stream crossing culverts in the study area. VERTICAL ESTIMATED CROSSING CROSSING DROP FROM CROSSING REACH CROSSING INLET OUTLET LOCATION AND LENGTH INLET TO SIZE OR PIPE NUMBER(S) TYPE CONDITION CONDITION DESCRIPTION (feet) OUTLET a DIAMETER b (feet) (feet) concrete bridge Flume and bottom of --over concrete 9 H x 25 L fair good pedestrian bridge UPC_R16A walls/floor round corrugated between UPC_R16B metal pipe good; tailwater Interstate 215 625 33 8 good and LPC_R01A with concrete pool present on bottom Wood footbridge in wooden full-span LPC_R02 - - -N/A c N/A c Parleys Park bridge Parleys Park - between LPC_R02 concrete box -- 6 H x 16 L good good main bridge and LPC_R03 culvert fair - grated between LPC_R03 with metal; good; deep plunge Interstate 80 1359 33 round pipe 6 and LPC_R04A evidence of pool at outlet periodic clogging fair; deep Country Club - between LPC_R04A tailwater pool access road and 264 9 round pipe 7.5 fair and LPC_R04B present; bare bank tee area areas concrete Country Club - 25 L x 4.5 H LPC_R04B - - footbridge fair fair trail crossing x 6.5 W and wingwalls Country Club - concrete bridge good; piers 30 L x 6 H utility pipe/golf LPC_R04B - - with concrete in channel good x 12.5 W cart crossing piers at banks side arches: stone bridge with Country Club - golf 1.5 H x 5 W LPC_R04B - - three arch good good cart crossing center arch: openings 5 H x 8 W metal/wood plank Country Club - golf between LPC_R04B 28 L x 5 H --bridge with good good cart crossing and LPC_R04C x 12 W concrete wingwalls fair/poor - concrete is Country Club - concrete box 35 L x 5 H fair- concrete is LPC_R04C - - cracked/ access road culvert x 33 W cracked/degraded degraded; scour at footing steel beam bridge Country Club - 25 L x 5.5 H LPC_R04C - - with concrete good good obsolete bridge x 8 W wingwalls

SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-27 BIO-WEST, INC. RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

Table 3.6. Size and condition of stream crossing culverts in the study area (cont.). VERTICAL ESTIMATED CROSSING CROSSING DROP FROM CROSSING REACH CROSSING INLET OUTLET LOCATION AND LENGTH INLET TO SIZE OR PIPE NUMBER(S) TYPE CONDITION CONDITION DESCRIPTION (feet) OUTLET a DIAMETER b (feet) (feet) metal pipe fair; minor erosion between LPC_R04C (squashed) behind headwall 2000 East 103 3 7 H x 8 W good and LPC_R04D with concrete and minor scour headwalls and sill below sill wood planks good; concrete Country Club - golf 35 L x 4.5 H LPC_R04D - - on top of concrete supports good cart crossing x 14 W supports in floodplain poor; partly Country Club - round metal pipe between LPC_R04D blocked fair; no scour piped section near 134 6 with gabion 7.5 and LPC_R04E by sediment evident Interstate 80 headwall and debris Country Club - round metal pipe good; gabion good; gabion walls recently piped with gabion in LPC_R04E 262 6 7 walls limit bank limit bank section near headwalls vegetation vegetation Interstate 80 and concrete sill good; minor between LPC_R04E round metal pipe good; graffiti art erosion left bank; 1700 East 322 6 7 and LPC_R05A in concrete on headwall graffiti on headwall Sugar House Park full-span steel 54 L x 4.4 H LPC_R05A - - good good - blue footbridge pedestrian bridge x 8 W Sugar House Park round concrete fair - some scour between LPC_R05B - eastern road 85 3 pipe with concrete 4fairand undercutting and LPC_R05C crossing headwalls of armored banks concrete bridge fair; wingwalls Sugar House Park 16 L x 12 W LPC_R05C - - across stone confine channel fair - footbridge x 7 H block wingwalls to 10-foot width Sugar House Park round concrete between pond underwater fair; deep scour - western road 80 3 pipe with concrete 5.5 and LPC_R05D in pond pool present crossing headwall good; deep between LPC_R05D concrete box multiple metal 1300 East 682 12 8 H x 8 W tailwater pool and LPC_R06 culvert grates present full-span steel 40 L x 12 H Hidden Hollow LPC_R06 - - good good pedestrian bridge x 8 'W full-span steel 100 L x 25 H Hidden Hollow LPC_R06 - - good good pedestrian bridge x 8 W ponded; requires Downstream end concrete box frequent removal LPC_R06 - - 5 H x 8 W N/A c of Hidden Hollow culvert of debris from metal grates a Estimated streambed elevation change between inlet and outlet based on digital elevation data. b H = height, L = length, W = width. c Not applicable.

SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-28 BIO-WEST, INC. RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

Stream Stability

A number of different issues were noted as affecting stream stability within the Parleys Creek riparian corridor. Specific issues are discussed in the subsections below.

Fill Encroachment Poorly vegetated fill slopes associated with freeway and trail construction, commercial development, flood control dredging, and historic land uses affect stability in various parts of the riparian corridor. Because these slopes lack vegetation and the associated resistive strength it provides, they are vulnerable to erosion during flood events. Fill Top left: Soil compaction from heavy foot traffic in Parleys Park. Top slopes also restrict floodplain right: Unprotected fill slope in Hidden Hollow. Bottom left: Bank width and laterally confine high scalloping from lack of woody riparian vegetation in Sugar House Park. flows, causing increased flow Bottom right: Low bank/root zone erosion in Sugar House Park. velocities and shear stress on streambanks. Fill encroachment Parleys Creek channel, and creation and maintenance of also limits the ability of floodplain evidence of rill erosion in these important habitat features such surfaces to act as sponges to areas is common. In some cases as scour pools, undercut banks, absorb flood water. pipes protrude into the bed of the and spawning gravels. channel, creating flow Deposition of sediment on Storm Drain Outfalls obstructions that have hydraulic floodplain areas is also Erosion was observed at various and potential stability effects. Of important, as it provides fresh storm drain pipe outfalls within a total of 38 mapped outfall substrate for the growth of willow the study area. These outfalls locations within the study area, and cottonwood seedlings that deliver storm water runoff to the 22 are recommended for are needed to maintain native creek from streets, freeways, improvements to resolve erosion riparian forests. However, gutters, and rooftops. The problems or improve filtration of excessive amounts of erosion or outfalls often lack adequate runoff. deposition can degrade habitat outlet protection to dissipate and water quality and threaten runoff velocities and protect Bank Erosion infrastructure and homes. against erosion. In cases where Lateral erosion of streambanks is outlet protection is provided, a natural process in stream Several types of bank erosion stabilized conveyance channels channels, which are dynamic were observed in the study area. are often lacking between the systems. Erosion and sediment Low bank erosion/root zone protected outlet and the main transport are necessary for the scour is particularly evident in the

SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-29 BIO-WEST, INC. RIPARIAN CORRIDOR STUDY FINAL PARLEYS CREEK MANAGEMENT PLAN

downstream half of the study area below reach LPC_R04B. This type of erosion is associated with high impervious cover and the resulting flashy urban hydrology that produces frequent, erosive runoff events during storms. In some areas, it appears that streambed lowering may also be contributing to low bank erosion by causing the toe of the slope to become undermined. In some reaches, tall, vertical bare banks are present where the creek has migrated laterally into historic or more recent fill material. Bank “scalloping” is another type of erosion observed in the Parleys Creek corridor; this type of erosion involves the development of widened sections of bank where woody shrubs or trees are lacking, and is common in park areas where grass is mowed to the edge of the streambank.

SALT LAKE CITY OCTOBER 2010 DEPARTMENT OF PUBLIC UTILITIES3-30 BIO-WEST, INC.