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RIPARIAN CORRIDOR STUDYFINAL CITY CREEK MANAGEMENT PLAN

SALT LAKE CITY OCTOBER 2010

DEPARTMENT OF PUBLIC UTILITIES BIO-WEST, INC.1-1

1.0 INTRODUCTION

Salt Lake City’s urban creeks andtheir associated riparian corridorsare unique and important naturalresources. To recognize theimportance of these resources,Salt Lake City (the City) passed aRiparian Corridor Overlay Zone(RCO) ordinance on July 22,2008. The RCO ordinanceestablishes restrictions andprovisions for land uses occurringwithin 25, 50, and 100 feet ofany above-ground city streamchannel. In conjunction withpassage of the ordinance, theCity Council authorized the SaltLake City Department of PublicUtilities (DPU) to conduct streamcorridor studies to assess baselineconditions on the above-groundportions of City, Emigration,Parleys, and Red Butte Creekswithin City boundaries. ThisRiparian Corridor Study (RCS)Management Plan documentpresents the results of the

baseline assessment of the CityCreek riparian corridor, describesthe desired future condition ofthe corridor as determined frompublic and stakeholder input, andidentifies opportunities forimprovement projects within thecorridor.

Riparian CorridorStudy and Management Plan Goals

The City has identified fourprimary objectives of the CityCreek RCS as follows:

• to assess existing streamand riparian vegetationconditions;

• to determine desiredfuture conditions;

• to identify opportunitiesfor restoration andremediation of the CityCreek corridor; and

• to use the information,data, and mapsdeveloped during thestudy to inform planning,permitting, andadministrative processesof the RCO ordinance.

In addition to these objectives,specific purposes of the RCSpublic outreach process includethe following:

• to elicit community andstakeholder participation,

• to identify public valuesand concerns, and

• to communicate results ofthe study for publicawareness, education,and support.

The City Creek RCS and publicoutreach process is separate frombut related to the previouslycompleted RCO ordinance publicoutreach process. The RCS isintended to provide criticalinformation that will guide theimplementation and permittingaspects of the ordinance but isnot intended to result in changesor revisions to the ordinance.




Figure 1.1. Emigration, Red Butte, Parleys, and City Creeks study areas.

Study Area

In addition to the City Creekriparian corridor described indetail in this document, thecomplete DPU study alsoincludes assessment of theabove-ground portions of theRed Butte Creek, Parleys Creek,and Emigration Creek ripariancorridors within City boundaries(Figure 1.1). The overall study isbeing completed in two phases. The studies on Emigration andRed Butte Creeks werecompleted as the first phase ofthe project, from fall 2008

through winter 2010; studies onParleys and City Creeks arebeing completed as the secondphase of the project, from spring2009 through summer 2010. More detailed information on allfour of the riparian corridorstudies can be found byaccessing the DPU website atwww.slch2o.com.

Importance and Functions of Riparian Corridors

Streams and riparian areas areunique, rare, sensitive, and

highly important elements of thelandscape. Riparian corridors,which encompass in-stream,riparian, and adjacent terrestrialhabitats, function as complexinterdependent ecosystems(Figure 1.2). The size, shape,flow regime, and bed materialcharacteristics of the streamchannel influence the amount,type, and distribution ofvegetation on the streambanks. In turn, the condition, density,and composition of streambankvegetation communities influencethe size, shape, and stability ofthe stream channel (Simon et al.2004). These reciprocal




Figure 1.2. Schematic illustration of major interactions amongriparian corridor resources and processes.

influences operate through avariety of mechanisms includingstreambank shear strength, soilmoisture content, flow resistance,bank steepness, floodingdynamics, erosion, anddeposition.

Because of the complexity of riparian systems, alterations toany single component of thesystem can have positive ornegative effects on multiple othercomponents of the system. Inhealthy riparian corridors, streamchannel processes such asflooding, meandering, erosion,and deposition providecolonization surfaces andmoisture to support diverse,

healthy riparian vegetationcommunities. In turn, healthyriparian vegetation communitiesprovide streambank stability,shading, and woody debrisinputs to support diverse, healthyaquatic communities.

Riparian areas occupy only asmall proportion (less than 3%)of the land area of Utah (USU2003) and comprise about 1.2%of the land area of Salt LakeCity. Despite their small size,riparian corridors serve a varietyof important functions within thelandscape, as discussed below.

Riparian CorridorDefinition

There is no universally agreed uponscientific definition of the term“riparian;” however, the term istypically used in modern scientificliterature to describe the transitionalarea located between aquatic (in-stream) and uplandhabitats. Riparian plants thatoccupy this transitional area aretypically adapted to conditions thatare periodically wet andperiodically disturbed by floodevents.

Within the legal framework of theCity’s RCO ordinance, the term“riparian corridor” is defined as thearea within 100 feet horizontally oneither side of the annual high waterlevel (AHWL) of above-groundstreams (Figure 1.3). Dependingon the stream channel andstreambank conditions at a specificlocation, the legally defined ripariancorridor often includes uplandfringe and developed stream-sideareas in addition to those areas thatwould be considered “riparian”based on the scientific definition. Within the City’s RCO ordinance,the term “stream corridor” isdefined as including the activestream channel as well as the100-foot riparian corridor on eachside of the channel. Therefore, thetotal stream corridor width equals200 feet plus the width of thestream at high water, which variesdepending on the specific locationalong the stream channel. The CityCreek RCS addresses conditionswithin the City Creek streamcorridor according to this definition.




Figure 1.3. One hundred-foot Riparian Corridor Overlay Zoneordinance riparian corridor.

Habitat for Mammals,Birds, and Fish

The ecological role of riparianzones is disproportionate to theirsmall size. In Utahapproximately 75% of the state’sbird species rely on riparianhabitat (USU 2003), and in thewestern United States up to 80%of all mammal and bird speciesrely on riparian zones for somepart of their life cycle (Krueper1993). The habitat importanceof City Creek and the otherabove-ground stream corridors inSalt Lake City is enhancedbecause these streams lie close tothe Great Salt Lake, anecosystem of hemisphericsignificance in terms of providingresting, staging, and nestinghabitat for migratory birdpopulations. Much of the valueof riparian zones can be

attributed to the fact thatmoisture and nutrientsaccumulate in these low-lyingareas, leading to a greaterdiversity and density of plantcommunities. Healthy ripariancorridors also support multiplestructural layers of vegetation,including understory, shrub, andcanopy layers that furthercontribute to habitat complexity(USU 2003).

Shading and Water-Temperature Control

Healthy stream-side vegetationprovides a canopy that insulatesthe stream from the potentiallyharmful effects of excessive solarradiation. When water gets toowarm, its oxygen-carryingcapacity is reduced, which canharm fish and aquatic insectpopulations. Therefore, intacttree and shrub cover alongstreams, such as City Creek, isimportant for water quality. Shaded riparian areas alsoprovide a cool, pleasantenvironment for City residents

seeking refuge from summertimeheat. Depending on how steepthe streambanks are in aparticular location, the shadingfunction may be provided bymoisture-dependent plants aloneor by a combination of theseplants plus the plants growing inadjacent, drier locations higherup on the banks. Therefore,even in areas where streambanksare steep and active floodplainsurfaces are limited, thecondition of the broader “streamcorridor” (as defined in the RCOordinance) is relevant to theshading and water-temperaturecontrol function.

Aesthetics

In arid Salt Lake City, therelatively lush, green, tallvegetation within ripariancorridors is visually distinct fromthe remainder of the landscapeand has a unique aesthetic value. The sound of flowing water isalso pleasing and calming. Because riparian corridors havethese aesthetic qualities, people




gravitate to these areas to havepicnics, go for walks, and findquiet respite from the urbanlandscape.

Recreation and OpenSpace

Many of Salt Lake City’s parksand open-space areas arelocated along riparian corridors. These areas function asimportant pockets of green spacewithin an otherwise urbanizedcity environment. They provideopportunities for residents toexperience and learn about theunique, natural processes andecology of riparian corridors, aswell as opportunities for bothactive and passive recreation.

Floodplain Storage and Flood DamageReduction

Well-vegetated, perviousstreambanks and low-lying

floodplain surfaces act assponges that absorb snowmeltand flood water and can reducedownstream flooding. Intactriparian vegetation also slowsflood-water velocities anddissipates erosive energy. Floodplain and perviousstreambed areas enable rechargeof springtime runoff water intothe ground, providing a source ofstreamflow later in the yearduring the dry summer months(Montgomery 1996). Becausemuch of City Creek within SaltLake City has a naturally steepand entrenched shape, the extentof flat, hydrologically connectedfloodplain surfaces is limitedrelative to flatter-gradient alluvialrivers. Nevertheless, somefloodplain surfaces are present,particularly in areas where thechannel width has not beenconfined by road fill, trails, orbank-hardening measures. These areas of the ripariancorridor provide some level of

flood storage and groundwaterrecharge, while these functionsare missing in areas where thecreek has been piped or linedwith impervious concrete.

Travel Corridorsand Connectivity

The linear nature of ripariancorridors makes them naturaltravel routes for fish, birds,mammals, and other aquatic andterrestrial species. In Salt LakeCity, the corridors provide alongitudinal connection between




habitats in the mountains andhabitats in the valley.

Organic Matter Inputs

Well-vegetated riparian corridorsprovide a supply of leaf litter andwoody debris to the streamchannel and aquaticenvironment. In small streamswhere photosynthesis is typicallyless significant, these organicmatter inputs supply the primarysource of energy and nutrientsfor aquatic insects and fish (USU2003). Snags, branches, and leaflitter provide important cavityhabitat and cover for birds andother terrestrial animals that usestreambank areas, while woodydebris jams within the streamchannel add to aquatic habitatcomplexity and provide cover forfish.

Filtration of Sediment and Pollutants

Where a buffer of vegetation,especially tall grass or denseshrubs, is present alongstreambanks, the vegetation isable to physically trap sedimentand associated pollutantsconveyed in runoff from uplandareas (Montgomery 1996). Vegetation communities withhigh stem and root densities areespecially effective in thisfunction. Well-vegetatedfloodplain surfaces serve a similarfiltration and trapping functionwhen they are inundated duringflood events and can reduce theamount of sediment and

pollutants entering downstreamreceiving waters. Vegetation canalso reduce pollutant loads viabiological uptake of nutrients andother chemicals attached torunoff.

In portions of the City’s ripariancorridors, this filtration function is“bypassed” to some extentbecause much of the stormrunoff enters the creeks in aconcentrated fashion throughstorm drain pipes. However, asignificant amount of runoff stillenters via the streambanks, andwater that exits storm drainoutfalls often flows alongstreambank areas for somedistance before reaching themain stream channel. Therefore,healthy streambank vegetationpositively influences water qualityeven in an urban storm waterrunoff setting.

Streambank Stability

Healthy vegetation communitiesadd significantly to the strengthand stability of streambanks. Vegetation protects theunderlying soil from erosion dueto raindrop impact orconcentrated runoff. Roots addtensile strength to the soil andcan anchor the soil to moreresistant underlying soil or rocklayers. Woody stems and trunksimpart resistive strength thatprotects against lateral bankscour during high-flow events. Streambank vegetation alsoincreases surface roughness,which helps dissipate energy andreduce flow velocities (Gray andSotir 1996). Woody plants andplants with dense, deep rootnetworks are especially valuablein terms of streambank stability.




Storm Water Conveyance

Within the developed portions ofSalt Lake City, most of the runoffgenerated from rooftops, roads,and other impervious surfacesduring storm events is conveyedfirst into curbside gutters, theninto storm drains andunderground pipes, then into theCity’s streams, including CityCreek. The City relies on thesenatural steam channels to conveystorm water to downstreamconduit and detention facilities ina safe manner that minimizes therisk of damage to infrastructurefrom flooding.

Public Outreachand Involvement

The preparation of the CityCreek RCS Management Planhas required extensive public andagency involvement activitiesthroughout the planning process. The planning process included abroad outreach element thatemphasized public and agencyinvolvement in identifyingdesired future conditions for thecreek. The overall goal of thepublic outreach element was toelicit community and stakeholderparticipation and identify publicvalues and concerns associatedwith the riparian corridor,including environmental issues,aesthetic values, recreationaccess, water quality, wildlifehabitat, and flood control. Inaddition, it is the intent toeffectively convey in this plan theresults of the study for public

awareness, education, andsupport.

Several methods of public andagency involvement were used togain insight into the concerns ofthose potentially affected by thisplan. These methods includedfacilitation of public workshops,formation of a riparian corridor

subcommittee, and developmentof an interactive web page todisseminate information. Eachmethod is described in moredetail below.

Public Workshops

A series of two public workshopswere conducted during the




planning process to solicit andobtain public input and to sharethe results of project activities.These public workshopsconsisted of both a “formal”presentation and question-answer period and an “informal,open-house” period wherebyindividuals could freelyparticipate. Each workshop washeld at a convenient locationnear the study area, and bothCity and consultant staff wereon-hand to answer questions andrecord input. Each workshopwas advertised on the City’s webpage for the RCS projects and atlocal media outlets. Workshopflyers were posted around theCity at public locations and attrailheads throughout the studyarea.

The first public workshop washeld on April 27, 2010, at theSweet Branch Library. The firstworkshop allowed public and

agency participants theopportunity to identify the issues,concerns, and opportunities thatexist relative to the project studyarea. Maps and photographs ofthe study area were available toorient participants and elicit theirsite-specific input. An overviewof the planning process waspresented, including specificpublic outreach and baselinecondition assessment activities,and participants were educatedabout important riparian corridorfunctions. In addition, asummary of results from thebaseline stream and vegetationassessment work was reviewed,along with detailed handouts ofthe information being presented. Participants were encouraged tofill out a workshop response formand return it to the project teamwith their input. Approximately14 individuals attended the firstworkshop.

The second public workshop washeld on June 15, 2010, at BryantMiddle School. The secondworkshop served to present anddiscuss the range of viableriparian corridor improvementprojects, the draft visionstatement, and the Draft RCSManagement Plan document. An overview of the plandocument was presented andopportunities for providingcomments were discussed. Maps, photos, and schematicdrawings were used to presentthe proposed types of projectsand to provide guidanceregarding the appropriate scaleand locations for the projects.

“Our goal is that this studywill use a collaborativeapproach to informationexchange, joint informationgathering, consultation, andconsensus in a way that willpromote legitimacy andtransparency, encouragecreative problem-solving, andsupport a timelyimplementation.”

–Mayor Ralph Becker’s goalfor community involvement

in the Riparian Corridor Study Management Plan projects




Summaries of the proposedprojects were provided inworkshop handouts and anupdate of the planning processtimeline was presented. Participants were asked to helpprioritize projects for specificstudy reaches, and werespecifically asked to comment onthe draft vision statementprovided on the workshopresponse form. Approximately14 individuals attended thesecond workshop.

Riparian Corridor StudySubcommittee Meetings

The RCS Subcommittee wasformed to provide guidance toDPU throughout the studies andbroadly represent the variousstakeholders who have aninterest in the planning process. The Subcommittee helpedidentify issues, evaluate data and data collectionmethods, develop the visionstatement, recommend andcritique restoration projects, andreview chapters of the plandocument. Subcommitteemembers were solicited by theCity to participate in the project.

Members of the RCSSubcommittee included thefollowing:

• City Creek Residents

• Red Butte CreekResidents

• Hogle Zoo

• Red Butte Garden and Arboretum

• Salt Lake City PublicUtilities AdvisoryCommittee

• Salt Lake City Parks

• Salt Lake City OpenSpace Lands Program

• Salt Lake County

• Salt Lake Valley HealthDepartment

• Trout Unlimited

• University of Utah

• Utah Open Lands

• Utah Rivers Council

• Utah Departmentof Environmental Quality

• United States VeteransAdministration MedicalCenter

• Utah Division of WildlifeResources

• Salt Lake City CouncilStaff

• U.S. Fish and WildlifeService

The RCS Subcommitteeconvened a total of seven timesduring the 2008–2010 planningprocess for the four creeks.

Interactive Web Page

Salt Lake City DPU dedicated apage on their web site specificallyfor the RCS projects(www.slcgov.com/utilities/ud_riparian_corridor_stream_study.htm). A history of the RCSproject was provided on the webpage, along with informationrelated to the RCO ordinance. Amap of study area streams couldbe downloaded by web sitevisitors, as could all informationdisseminated at each of thepublic workshops includingpresentations, handouts,comment forms, and meetingannouncements. Web-basedpublic comment forms were alsomade available on this web page.

Management PlanApproach

The planning process for the CityCreek RCS Management Planinvolved the coordination andcooperation of members of thepublic, state and localgovernment agency staff, andconsultant team planners andresource scientists workingtogether throughout the planningprocess to complete thisdocument. Those involvedhelped perform key activitiesduring the planning processincluding public and agencyinvolvement, baseline resourceinventories and analyses, visionstatement formulation, andimprovement projectidentification. Figures 1.4 and




Figure 1.4. Organizational Chart for the Salt Lake City RiparianCorridor Management Plans.

Figure 1.5. Timeline of Salt Lake City Riparian Corridor Studiesand Management Plans.

1.5 provide an overview of theCity Creek RCS planning processorganization and timeline.

Initial steps during the planningprocess focused on compilingrelevant and available resourcedata, topography, mappinglayers, and aerial photography. A reconnaissance-level fieldassessment was performed earlyin the planning process to helpdetermine appropriate datacollection efforts and divide thecreek into specific study reaches. Once preliminary reaches weredefined and data collectionprotocols established, field workwas conducted to characterizestream channel, streambank, andriparian vegetation conditionsthroughout each reach. Relevantdata for both the streamcondition and vegetationcondition assessments werecollected and assembled in aGeographic Information System(GIS) format.

Desired future conditions foreach study stream weredetermined primarily throughpublic outreach and stakeholder participation efforts. Historicaldata and trend assessment resultswere used to help define realistic,reach-appropriate riparianvegetation and stream conditiontargets. Targets are focusedtoward achieving the specificriparian corridor functionsidentified as priorities during theoutreach process. Desired futureconditions were compared withexisting conditions determined

through the baseline assessmentprocess to assess how wellriparian functions are beingachieved in the different reaches. Appropriate types ofimprovement projects wereidentified for each reach, andcosts for the different types ofprojects were estimated. Specific

projects were then prioritized andranked based on costs, benefits,and public input.

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