LITTLE CONESTOGA CREEK WATERSHEDASSESSMENT, LANCASTER, PA.

FACULTYAndy deWet, Franklin & Marshall College

Jeff Marshall, Franklin & Marshall College

Dorothy Merritts, Franklin & Marshall College

Steve Weaver, Colorado College

Jesse Yoburn, TA, Franklin & Marshall College

STUDENTSGarrett Bayrd, Whitman College

Abby Bowers, The College of Wooster

Kyle Cavanaugh Trinity Univesrity

Aaron Davis, Colorado College

Jennifer Fallon, Washington and LeeUnivbersity

Nancy Harris, Carleton College

Ashley Hawes, Smith College

James Orsher, Amherst College

Lauren Manion, Frankln & Marshall College

Jaime Tomlinson , Frankln & Marshall College

Bowers, Fallon, and Hawes, figure 3 Longitudinal profile for the east branch of Bachman Run is closer to theexpected exponential curve.

LITTLE CONESTOGA CREEK WATERSHED ASSESSMENT,LANCASTER, PA.

ANDREW P. DE WET, Franklin & Marshall College

JEFF MARSHALL, Franklin & Marshall College

DOROTHY MERRITTS, Franklin & Marshall College

STEVE WEAVER, Colorado College

INTRODUCTIONRiver systems have been dramatically impactedby dams, reservoirs, channelization and land-usechanges. Impacts include loss of water qualityand biodiversity and changes in the functionalcharacteristics of streams (Petts & Calow,1996). At the same time there are increasingdemands being placed on river systems. Overthe last few decades numerous attempts havebeen made to restore damaged streamecosystems. Given the complexity of riversystems there is an increasing efforts to applyscientific principles to the development ofenvironmentally sensitive approaches formanaging rivers.

In Pennsylvania numerous individuals andorganizations, including the state government,have recognized the urgency of the situation andare encouraging restoration efforts throughlegislative initiatives and funding opportunities.

Most streams in Lancaster County, southeasternPennsylvania, have been heavily impacted byhuman activities. Land-use change hasdramatically accelerated over the last fewdecades and concern over stream health hasresulted in numerous stream restoration projects.Local watershed groups have been formed andstream restoration projects are being initiated orproposed in numerous locations in the county.

Unfortunately many of these initiatives areoccurring without significant scientific input.There is a need to provide this information to

Figure 1. The Little Conestoga Creek Watershed inLancaster County, PA including project locations (1 =Bachman Run, 2 = Swarr Run, 3 = Long’s Park Creek).

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these efforts in order to maximize the potentialfor success.

BACKGROUNDPrior to 1700, the area of Lancaster County wasinhabited by Native Americans, particularly theSusquehannock group (Kent, 1984; Wallace,1989). In the early 1700's the area was settledand rapidly cleared by Europeans. LancasterCounty was founded in 1729 and Lancaster Cityin 1730. By 1999 the County's population was460,000 (US Census Bureau, 2000). Since the1950's the population has increased by between9 and 15% per decade and it is projected thataround 110,000 people will be added to thecounty population over the next 20 years.Lancaster County also ranks as one of the mostagriculturally productive areas in the US. Itsupports large Amish and Mennonitecommunities and is a top tourist destination inPennsylvania.

The steady increase in population has resulted ingradual conversion of woodlands to fertileagricultural land and increasingly theconversion of agricultural land to urban andsuburban development. Between 1970 and1990 the proportion of county land defined asurban more than doubled, from 44 square milesto 105 square miles, out of a total of 946 squaremiles (Lancaster County Water Resources TaskForce, 1996). At present, only about 11% of aonce fully forested county consists of woodland.Most of these wooded areas occur as narrowstrips along the Conestoga and Susquehannarivers where the banks are steep and unsuitablefor farming, as small woodlots, or on elevatedridges beyond the border of Lancaster City.

The Conestoga Creek, the main drainage inLancaster County, flows into the SusquehannaRiver and then into the Chesapeake Bay. Mostof the rivers in the county are highly impactedby agricultural and urban land use. Forexample, the Conestoga Creek has the highestnutrient yields entering the Susquehanna River(Ott et al., 1991). Concern about local andregional environmental issues has led to adramatic rise in interest in stream restoration inthe county. Interest has come from numerous

groups including trout fishermen, conservationorganizations and local governments. At least 6stream restoration projects have been completedor are in progress in the County.

The Little Conestoga CreekThe Little Conestoga Creek is one of the maintributaries of the Conestoga Creek and is locatedcompletely within Lancaster County (Figure 1).The watershed covers an area of 65.6 mi2 and is68% agricultural, 22% urban and 10% forested(Loper & Davis, 1998). Much of the watershedis within the Urban Growth Boundary ofLancaster City and is undergoing rapid changefrom agriculture to suburban and urban land use.About 90% of the watershed is underlain byfractured carbonate bedrock particularly of theConestoga Formation. The thick residual soilsproduced from the carbonate produce richagricultural topsoil and as a result agriculture isstill the leading land-use in most of the sub-basins of the watershed. However, at least onesub-basin is 82% urban.

Stream water in the basin is used for irrigation,livestock, and commercial operations but is notused for public supply. Residents in the basinobtain their water from municipal water systems(83%) which obtain their water from theConestoga River and the Susquehanna River, orfrom private wells. Discharges into the basininclude industries with National PollutionDischarge Elimination System (NPDES)permits, storm-water, and sewage treatmentplants (Loper & Davis, 1998).

Nutrient levels in the basin are high with thelower part of the West Branch of the LittleConestoga frequently having nitrateconcentrations above 10mg/L. As expectednutrients are highest in sub-basins with thehighest agricultural land use. Urban/suburbandevelopment produces other impacts such asincreased sediment loads and bioassessmentstudies have shown that almost the wholewatershed is impaired (Loper & Davis, 1998).

Recently a grassroots watershed alliance hasbeen formed for the Little Conestoga Creek(The Little Conestoga Watershed Alliance -

LCWA). Several stream restoration projectshave been proposed but little is known aboutwhere the main problems exist in the watershed.To some extent projects are determined byopportunity - developers that are prepared tomodify plans to accommodate environmentalfriendly stream development or land ownersprepared to allow a stream restoration project ontheir land. However, there is a need to study thedynamics of the stream system in order tounderstand how the system is responding to thechanges that are occurring in the watershed.

Figure 2. The Little Conestoga Watershed Assessmentparticipants on a field trip to the Chesapeake Bay.

PROJECTSFrom the beginning it became clear that wecould not study the whole watershed in detail.We decided to divide into 3 groups and eachgroup would study a sub-basin of the LCW thatrepresented a different land-use history.

Project 1: Bachman RunStudents: Ashley Hawes, Jennifer Fallon, andAbby Bowers.

This sub-basin is experiencing rapid sub-urbanization. Conversion of agricultural landsto suburban developments and improved erosioncontrols during construction appear to bereducing the sediment flow into this stream.Reduced sediment loads and increaseddischarge is resulting in the remobilization ofthe floodplain and channel sediments. The result

is bank erosion, channel incision, and channelwidening. Many landowners are respondingwith hard engineering ‘solutions’.

Project 2: Swarr RunStudents: Garrett Bayrd, Aaron Davis, andNancy Harris.

This sub-basin includes agricultural land-use aswell as suburban developments. Many of thesuburban areas were developed before theimplementation of storm water managementregulations in Pennsylvania. The resultingdramatic increase in discharge, combined with areduced sediment load, has resulted in channelincision. Where bedrock, or armored channelbeds occur, lateral erosion and channelwidening is evident. Straightening of many ofthe stream channels during the 1940’s and1950’s has exacerbated the problems byincreasing the stream gradients. Uncontrolledaccess to the streams by livestock has resulted inwide, shallow channels in many areas.

Project 3: Long’s Park CreekStudents: Kyle Cavanaugh, Lauren Manion,James Orsher, and Jaime Tomlinson.

The urban development in this small sub-basindistinguishes it from the other tributaries of theLCW. The channel is highly modified bychannelization, hard engineering of the banks,and floodplain destruction. The nutrient andsediment content of the creek is generally lowerthat the other tributaries of the LCW, while themetal content of the sediment is much higher.

CONCLUSIONSDuring this study it became abundantly clearthat streams are complex systems. Streams,particularly in areas undergoing rapid land-usechanges, are often out of equilibrium. In theLCW, deforestation since the 1700’s probablyresulted in a dramatic increase in the sedimentflux to the floodplain system. Improvements inagricultural practices and sub-urbanization havereduced this sediment influx, while rapid run-off

has increased. Floodplain and channelsediments are now being remobilized. Locallythis results in complex, and frequentlyunwelcome changes in the channel morphology.Perhaps more importantly increased sediment inthe streams is negatively impacting ecosystemsdownstream such as the Chesapeake Bay.

ACKNOWLEDGEMENTSWe thank the KECK Geology Consortium andNSF for supporting this project. Jesse Yoburnhelped with logistics and technical problems andwas funded through the Franklin & MarshallCollege Hackman fellowship program. JanieWissing helped in countless ways.

REFERENCES CITEDKent, B. C., 1984, Susquehanna’s Indians.

Anthropological Series n.6, ThePennsylvania Historical and MuseumCommission, Harrisburg, PA, 438 p.

Lancaster County Water Resources Task Force,1996, Lancaster County Water ResourcesPlan: Water Supply Plan and WellheadProtection Program. Lancaster CountyPlanning Commission, Lancaster, PA. 245p.

Loper, Connie A. and Davis, Ryan C., 1998, ASnapshot Evaluation of StreamEnvironmental Quality in the LittleConestoga Creek Basin, Lancaster County,Pa. USGS Water Resources InvestigationsReport 98-4173.

Ott, Arthur N., 1991, Nutrient Loading Status ofthe Conestoga River Basin - 1985-1989,Susquehanna River Basin Commission,Publication No. 133, 14p.

Petts, Geoffrey and Calow, Peter (Editors),1997, River Restoration. Blackwell Science,231p.

Wallace, P. A.W., 1989, Indians inPennsylvania. Anthropological Series n.5,The Pennsylvania Historical and MuseumCommission, Harrisburg, PA, 200 pp.

A GEOMORPHIC INTERPERATION OF THESWARR RUN WATERSHED OF

LANCASTER COUNTY, PENNSYLVANIA

GARRETT B. BAYRDDepartment of Geology, Whitman College

Sponsor: Pat Spencer, Whitman College

AARON G. DAVISDepartment of Geology, Colorado College

Sponsor: Christine Siddoway, Colorado College

NANCY J. HARRISDepartment of Geology, Carleton College

Sponsor: Mary Savina, Carleton College

INTRODUCTIONThe Little Conestoga Waters drains directlyinto the Conestoga River which, in turn, drainsinto the Susquehanna River, the largesttributary of the Chesapeake Bay. Thiswatershed is of particular concern becauserecent studies have shown that increasedamounts of sediment in the Chesapeake Baytributaries result in lower light levels in theshallow and sensitive Chesapeake Bay. Thisstems from areas such as the Little Conestoga,where current land practices encourageerosion through impervious land cover, poorlivestock management, and the deteriorationand confinement of riparian zones. In ourwatershed we looked at three differentlocations in order to examine how the river'sphysical parameters change in areas ofdifferent land use. We examined a smalltributary of Swarr Run called Miller's Runwhich is representative of the upper reaches ofthe watershed. Miller's Run gives us a pictureof how suburban sprawl can affect rivergeomorphology. We also studied a stretch of

the Swarr Run along the Mann farm to seehow the presence of cows can affect thechannel's geomorphology. This area is alsointeresting because the channel wasstraightened between 1947 and 1958 in orderto create more usable farmland(Carlson,2001). Our final study location is immediatelyupstream in the Snavely Farm, whichhistorically has had similar land use to theMann Farm but stopped allowing cows in theriver fifteen years ago. In each location weobserved differences in channelgeomorphology which reflects differences inland use, local geology, and temporal changein the river to maintain a state of equilibrium.

Swarr Run WatershedSwarr Run has a drainage area of 7.2 mi2

which represents a significant portion of theLittle Conestoga watershed. (Lopar, Davis,1998) Historically, agriculture has been theprimary land use and 68% of the landcontinues to be used by agriculture. Manyfarms continue to use poor livestock andfarming practices such as allowing cows to

graze freely in the stream channel, clearing ofriparian vegetation, and straitening channels tomaximize useable farmland. Within the lasttwenty years urban sprawl from the city ofLancaster has prompted significantdevelopment in the Swarr Run watershed.Currently, 19% of the land is characterized asurbanized. This development increasesimpervious cover that tends to make streamsprone to flash floods. Development adjacentto the stream tends to confine and straightenthe channel through the use of riprap. Also,many homeowners mow riparian vegetationthat is important for maintaining stable banks.Presently, only 12% of the watershed remainforested resulting in a huge change in run-offfrom precolonial pristine conditions. As aresult, the natural equilibrium the streamsestablished is no longer balanced with thisland use changes.

METHODSOur work revolved around gathering data thataccurately reflects the channel morphology ofour specific site locations. For both theSnavely and Mann Farm locations we used thetotal station to establish the water level width,depth, and elevation. The Total Station wasnecessary because a considerable degree ofaccuracy was needed to establish the subtleelevation changes over a long distance. Aconsiderably more concentrated number ofdata points were taken in the Snavely stretchof Swarr Run because the stream was muchmore complicated. Generally, we tried toestablish a set of data points at the beginningand end of each riffle and in the middle ofmost pools. In order to place this highlyaccurate, dense data in a larger context weconstructed a stream profile for the entirelength of Swarr Run using Pennsylvania StateTOPO maps with five foot intervals. Inaddition to the total station, we constructed 18cross sections over the Snavely and MannFarms using a mounted level to determineelevation and a tape measure to establishdistance. These cross sections give us arepresentation how the channel shape varies inthe two farms. Finally, we analyzed soilsamples from cut banks and a core sample weobtained using a vibracore. We analyzed the

grain size distribution for each sample using aseries of sieves in a Rototap for fourteenminutes. This gives us clues to establishinghow the sediment record preserves majorregional land use changes. When analyzingMiller’s run we used a hand level and hipchainto create fairly accurate longitudinal profilefor an 800m stretch of the run. We were ableto use this method because the elevationchanges in Miller’s Run are far greater than inthe Snavely and Mann Farms. We then fit thisdata into the context of the entire Miller’s Runlongitudinal profile based on TOPO map.

RESULTS AND DISCUSSIONOur data suggests there is a significantdifference in channel morphology between theSnavely and Mann Farms. The Snavelysection of Swarr Run exhibits a more naturalstream pattern while the Mann Farm stretchshows a significant need for future streamrestoration. The Snavely stretch shows amuch tighter meandering pool riffle pattern asopposed to longer and deeper pools in theMann property with a lower sinuosity. (Seefigures 1 and 2) The channel shape alsochanges from a confined "V" shape with avery well defined thalweg in the Snavely Farmto a broad "U" shape with a less definedthalweg in the Mann Farm. (See figure 3)Further comparison shows that the averagestream width is nearly twice as wide in theMann Farm as well as being deeper, whichfurther suggests abnormally large pools

creating slow moving water. Slowing waterdown over large pools is problematic to water

Mann and Snavely Cross Sections

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Fig 1. Cross sections of the Mann and Snavely Farms,showing the change from v-shaped profiles to lesshealthy, u-shaped profiles.

quality because it reduces the dissolvedoxygen. Also, the large width of poolsincreases water temperature, particularly inthis location because there are virtually notrees for shade. Finally, these large poolsforce the stream to deposit much of itssuspended and bed load creating the muckysilty bottom we observed. These conditionsdo not promote a natural diverse streamecosystem and suggest that the Mann Farmstretch of Swarr Run be not in a natural stateof equilibrium. We believe that the presenceof cows in the stream is the primary cause ofthis change in channel morphology. Cowsexert a tremendous amount of pressure andcause considerable bank erosion that tends towiden the channel. (Trimble, 1993) Also,cows destroy riparian vegetation that isimportant for bank stabilization. This furtherillustrates the importance of simple livestockmanagement practices such as fencing offcows from the stream. Over a period of 15years the Snavely Farm stretch of Swarr Runappears to have recovered significantly fromthe presence of cows. However, there is asignificant drop in channel slope from theSnavely Farm to the Mann Farm that couldcause some of the observed difference. Morework needs to be done to understand the causeand effect of this change in slope.

MILLERS RUNMiller’s run is an excellent example of a smalltributary that has been thrown out ofequilibrium by excessive development. Ourlongitudinal data suggests upper reaches of thestream are degrading, while lower sections areaggrading. (See figure 4) A bedrock

outcropping marks the hinge point of thistransition. We observed extensive, extremecutbanks upstream of the bedrock were thestream incised into the ancient alluvial fan.The ideal alluvial fan plane is represented asthe line on the figure four. (Knighton, 98)Below the outcrop we observed aggregatingpiles of gravel. This is consistent withincreased discharge in the stream caused bygreater impervious cover after development.(Trimble, 1997) The stream appears to bemore sinuous in historical aerial photography,implying development resulted instraightening that could also be a major factorin the degradation. The upper stream appearsto be reestablishing meanders to further reduceits slope because it is easier to cut away thesofter side banks than continue to incise the

gravel bed.

Longitudinal Profile of Swarr Run

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Fig 2. Longitudinal profile of the larger area,including that of the Snavely farm.

Longitudinal Profile of Snavely Farm

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Fig. 3. Longitudinal profile of Snavely farm, showingthe more healthy, tighter pool-riffle system.

Degradation AggradationIdealalluvialfanlongitudinalProfile

Fig 4. Longitudinal Profile of Millers Run, Showingthe Areas of agradation and degration.

REFERENCESTrimble, S., 1993, Erosion effects of cattle on

streambanks in Tennessee, U.S.A.. Earthsurface processes and landforms, vol. 19,451-464 (1994)

Trimble, S., 1997, Contribution of streamchannel erosion to sediment yield from anurbanizing watershed, Science vol. 278,1442-1444

Knighton, David,1998, Fluvial forms andprocesses: a new perspective, Oxforduniversity press Inc, New York, 242-322

Carlson, Erin, 2001, Comprehensive streamassessment in the Little Conestoga CreekWatershed, Franklin and Marshall College

Lancaster County GIS Department, 2001

Loper, C.A. and Davis, R.C., 1998: Asnapshot evaluation of streamenvironmental quality in the LittleConestoga Creek Basin, Lancaster County,P,A, U.S. Geological Survey, WaterResources Investigations Report. 98-4173:September, 1998.

GEOMORPHIC ASSESSMENT OF BACHMAN RUN WITHIN THE LITTLE CONESTOGA CREEK WATERSHED

ABBY L. BOWERS Department of Geology, The College of Wooster

Greg Wiles, The College of Wooster

JENNIFER FALLON Department of Geology, Washington and Lee University

Sponsor: Elizabeth Knapp, Washington and Lee University

ASHLEY G. HAWES Department of Geology, Smith College

Sponsor: Robert Newton, Smith College

INTRODUCTION A recent study by the U. S. Geological Survey(USGS) found that the Conestoga River and its tributary subbasins contribute the highest nutrient yields to the Susquehanna River (Loper and Davis, 1998). As the largest river emptying into the Chesapeake Bay, the Susquehanna is the focal point of restoration efforts to improve the Chesapeake’s water quality. Recent point source pollution regulations by the EPA are effectively controlling the amount of industrial waste that enters the Bay, but the water quality of the Chesapeake Bay Watershed remains poor. Although the next step in the process of restoring the Chesapeake Bay must be to improve the water quality of its tributaries, many of the streams and rivers that empty into the Bay, such as the Conestoga River, do not have significant point source pollution. These tributaries pick up contaminants as they flow through agricultural areas and receive runoff from city streets and highly fertilized backyards. Ordinarily, streams and rivers have mechanisms that help them reduce the amount of runoff and contaminants that enter

the stream, but urbanization greatly reduces these capabilities. One of the impacts urbanization has had on the watershed is the increase in the amount of impervious surfaces in the form of city streets, buildings, parking lots, and even residential lawns, which inhibit rainwater infiltration. Rather than soaking in, the water pours off streets, carrying pollutants picked up along the way and running into drainage pipes that often empty directly into a stream or river. Thus, impervious surfaces not only contribute to higher levels of contaminants, but they also are responsible for flash flood behavior and increased erosion (Simon and Downs, 1994). Increased erosion is often a sign of an unstable stream, which develops when the scouring process leads to degradation or when sediment deposition leads to aggradation. Degradation results from a fall in base level, a decrease in sediment supply, or an increase in discharge. Aggradation occurs with a rise in base level, an increase in sediment supply, or a decrease in discharge (Knighton, 1998). To remain in its natural stable state, a stream needs to carry a consistent sediment load to prevent aggradation and degradation. A stream may

remain in equilibrium, even as it laterally migrates, as long as the stream’s bankfull width and width/depth ratio remain constant (Rosgen, 1996). Stable streams are desirable because they exhibit low erosion rates and less flashy flood behavior. Bachman Run, a small subbasin of the Little Conestoga Creek Watershed, is experiencing rapid development that is affecting the stability of the stream and both erosion and more frequent flash floods have been observed (Figures 1 and 2).

PROJECT AREA The headwaters of Bachman Run are located in the northeast corner of the Little Conestoga Creek Watershed in Manheim and Warwick townships. The stream’s two branches drain an area of 9.9 km2 with an average discharge of 0.15 m3/sec. The area land use is primarily agricultural, but farmland is being converted to residential areas. A recent survey by the USGS using 1994 Landsat data, found the land use of Bachman Run Watershed to be 10% urban, 85% agricultural, and 4% forest land (Loper and Davis, 1998). The underlying geology of the watershed includes the Cocalico Shale, Eplar Limestone and Dolomite, Stonehenge Limestone, Buffalo Springs Dolomite, Zooks Corner Dolomite, and Ledger Dolomite. The stream channel consists of cut banks, point bars, mid-channel bars, and gravel bars. The streambed is also characterized by multiple outcrops of bedrock and has been altered by human additions of dams and bridges. The channel banks and flood plains include sandy/silty loam deposits, and the meanders range from gentle to tortuous and irregular. The confluence occurs in a recently developed neighborhood, providing an easily accessible study site to observe the morphological changes a stream undergoes in response to development.

METHODS Cross-sections of various stream reaches were obtained using an automatic level. Longitudinal profiles of the confluence area of

the west and east branches were created by digitizing information from Lancaster County Geographic Information System (GIS) database (2001) and ArcView GIS. A detailed longitudinal profile showing thalweg depth, water level, channel bank, and flood plain locations was created by using a total station (TS). The depth to bedrock was found by driving a six-foot iron rod into the stream bottom sediments at the thalwag depth, and measuring the depth relative to the channel bottom and the water level. The location of the points where the bedrock was measured was established with Global Positioning System (GPS). This data was then added to the data collected with the total station to create a longitudinal profile that included bedrock depth. Aerial photographs from 1947 to 1988 and color infrared photographs from 2000 were studied to compare the morphologic changes of the stream that accompanied the land use transition from entirely agricultural to significantly urbanized.

RESULTS AND DISCUSSION Cross-sectional data from several reaches

Figure 1 The sinuosity and low width-depth ratio of the west branch contrast with the straightened and more shallow channels of the east branch and main trunk.

Figure 2 Longitudinal profile for the West Branch Bachman Run deviates from an expected exponential curve.

along Bachman Run show that channels in the west branch have a lower width/depth ratio than those located in either the east branch or the main trunk (Figure 1). Streams with low width/depth ratios generally tend to be less impacted and more sinuous. In addition to the lower width-to depth ratio, the west branch also had more meanders than the east branch or the main trunk, resulting in higher sinuosity values. When sinuosity was calculated using valley lengths and thalweg lengths measured in ArcView from the Lancaster County GIS database, the values for the west branch ranged from 1.18 at the headwaters to1.03 in the mid-valley to 1.29 at the confluence. The east branch sinuosity values ranged from 1.0 to 1.18 and the value for the main trunk was 1.05. In the short duration of the project, active erosion was observed. Many residents owning property along the banks of Bachman Run mow their lawns to the edge of the stream, a practice that destabilizes the banks and limits the infiltration capacity for rainwater. Banks where riparian vegetation is allowed to remain tend to be more stable and resist erosion. A small rainfall event resulted in multiple slumps in which portions of residents’ lawns fell into the stream. Large scale bank erosion and meander migration was observed from comparing old aerial photos and 35 mm snapshots taken by residents. As erosion allows for sediment transport, it is expected that the longitudinal profiles will

reveal a sediment wedge advancing through the watershed. Longitudinal profiles generated from the Lancaster GIS database did not provide enough detail to ascertain whether or not the wedge was present (Figures 2 and

3). However, the GIS profiles approximate an exponential curve, characteristic of a profile of a stream in its natural state. The closer the curve is to exponential, the closer that stream is to its stable state. While constructing the cross sections, bedrock

outcrops of Buffalo Springs Dolomite were observed in west branch of the stream. Core samples taken downstream of the confluence revealed bedrock of the same formation buried half a meter below the channel bed. This data combined with a longitudinal profile allowed us to compare the bedrock depth along the length of the stream, indicating the presence of a Colonial deforestation sediment wedge that is slowly being transported downstream (Figure 4).

CONCLUSIONS With increasing population pressures, suburban sprawl will continue as more land is converted from farms to housing developments. The amount of impervious surface in Bachman Run watershed will parallel the increase in development, resulting in larger volumes of runoff entering the stream. An increase in discharge causes several changes in stream dynamics that can already be observed in Bachman Run. One of these is flashier flood behavior due to the lower rainwater infiltration rates. Flash floods not only pose a problem for the residents who must deal with the high waters but also contribute large-scale erosion events. Another change resulting from an increase in discharge is channel incision; incision is an indicator of a stream’s instability, and a stream will continue to incise until it reaches a new

Figure 3 Longitudinal profile for the east branch of Bachman Run is closer to the expected exponential curve.

Figure 4 Longitudinal profile of the West Branch of Bachman

Run created from Total Station data.

state of equilibrium. Bachman Run is degrading, and is not in equilibrium. The depth to which the stream may incise is limited by the presence of bedrock near the surface. Once the post-Colonial sediment wedge overlying the bedrock is removed, the stream will most likely erode its banks and widen its channel. Although some bank erosion has already occurred, it will become much more severe once the bedrock base level is reached. Bachman Run appears to be one of the least impacted streams in the Little Conestoga Creek Watershed, but the increase in development could easily change this. Any changes in the morphology and carrying capacity of Bachman Run directly impact the Little Conestoga Creek, Conestoga River, and the Chesapeake Bay. Thus, measures that can be implemented now in order to prevent further impact to Bachman Run should be considered so that this watershed does not become a future restoration project or contribute to the water quality problems plaguing the Chesapeake Bay.

REFERENCES CITED Knighton, D, 1998, Fluvial forms

andprocesses: a new perspective. OxfordUniversity Press Inc., New York, NY, USA.

Lancaster County GIS Department, 2001. Loper, C. A. and Davis, R. C., 1998: A

snapshot evaluation of stream environmental quality in the Little Conestoga Creek Basin, Lancaster County, PA. U. S. Geological Survey, Water Resources Investigations Report, 98-4173: September, 1998.

Rosgen, D., 1996, Applied river morphology. Wildland hydrology, Pagosa Springs, CO, USA.

Simon, A. and Downs, P. W., 1995: An interdisciplinary approach to evaluation of potential instability in alluvial channels. Geomorphology 12, 215-232.

LAND USE ASSESSMENT OF LONG’S PARK

CREEK WATERSHED

KYLE CAVANAUGHGeosciences Dept., Trinity University

Sponsor: Diane Smith, Trinity University

LAUREN MANIONDept. of Geosciences, Franklin & Marshall College

Sponsor: Andy de Wet, F&M College

JAMES ORSHERGeology Dept., Amherst College

Sponsor: Jack Cheney, Amherst College

JAIME TOMLINSONGeosciences Dept., Franklin & Marshall College

Sponsor: Dorothy Merritts, F&M College

INTRODUCTIONThe Little Conestoga Creek Watershed,covering 65.5 mi2 in the south centralPennsylvania county of Lancaster is a key partof the drainage basin of the Conestoga River.This watershed lies in the Susquehanna RiverWatershed, which is the largest tributary of theChesapeake Bay. This estuary is the largest inthe United States and has been plagued withenvironmental problems for decades. Sincethe 1980s many restoration efforts have beenmade to reduce some of the effects ofpollution in the Chesapeake Bay Watershed.In order for large-scale restoration projects tobe successful, efforts must begin at headwatersites such as the Little Conestoga Creek andits tributaries.

Long's Park Creek (LPC) is one of thetributaries that is a possible candidate for asmall-scale restoration project. This 2.05 mi2

watershed contains highly impacted urbanareas, a stretch of woodlands, a number ofhighways and a small farm. Because of this

varied setting, the creek exemplifies many ofthe issues of Lancaster County streams. Eachof these land types affects the health of thestream differently. The urban developmentalong LPC distinguishes it from othertributaries of the Little Conestoga Creek,which flow mainly through suburbandevelopments and agricultural lands. Changesin land use in LPC Watershed are reflected inboth the stream channel geometry and thechemistry of the water and sediment. Througha study of these aspects one can gain a betterunderstanding of the condition of this streamand the possibility for restoring equilibrium.

METHODS

Field WorkNineteen sites along LPC were chosen tosurvey in order to provide examples of bothimpacted and more natural reaches of thestream and thereby determine the affects ofurbanization on channel morphology. At eachsite, the cross-section was performed using an

automatic level and a stadia rod. A separategroup of sites was chosen as water andsediment testing locations, again for theirrepresentation of differing levels ofdevelopment. On site, the water was tested fortemperature, dissolved oxygen, pH, and totaldissolved solids, and in the lab, the watersamples were tested for nitrate and phosphatelevels. A sediment sample was collected at thesame locations to determine heavy metalconcentrations. In order to provide abackground with which LPC data could becompared, sixteen USGS sites were alsosampled (Lopar and Davis, 1998).

Lab WorkAll the water samples were tested for bothnitrate and phosphate levels using a Spectronic20D spectrometer. The sediment sampleswere tested for concentrations of cadmium,magnesium, lead, barium, zinc and iron in anInductively Coupled Plasma AtomicEmissions Spectrometer (ICP-AES). Thesamples were put through EPA acid digestionprocess 3050 and then run through the ICP-AES. All of the sampled sites were enteredinto an ArcView GIS Database, along with thelocation of all out fall pipes along LPC.Building cover for 1947, 1971, and 2000 wascalculated on the database by digitizingbuildings from aerial photographs for thoseyears.

RESULTSThe physical characteristics of LPC proved tobe highly variable. Three cross-sections werechosen to represent the characteristics ofdiffering land-uses. Cross-section “A” wastaken in a wooded area near the confluence ofLPC and the Little Conestoga Creek, andcross-section “G” was taken approximately 15meters upstream. Both show a healthyriparian zone and a well-developed floodplain.“A” is a good example of a more naturalstream. “G” is located just downstream of anartificially straightened stretch of the stream,which was altered to protect a sewage linefrom erosion. Upstream of cross-section “G”,where cross-section “Q” was taken,development is more prevalent. “Q” has acharacteristic V shape.

All geochemical and nutrient data for LPC canbe found on Table 1 and their correspondinglocations are in Figure 1. On 6/19/01 nitratelevels varied from 5.0 mg/L to 9.2 mg/L. On7/3/01 levels ranged from 1.9 mg/L to 6.2mg/L. Additional sites tested on 7/3 were alsorelatively low. Phosphate levels on 6/19averaged 0.34 mg/L; on 7/3 they averaged0.27 mg/L. The average of the additional siteswas 0.26 mg/L.

Plotting amounts of cadmium, zinc, and leadin stream sediment samples collected on7/3/01 against a ratio with respect to a meanvalue of metal concentration found inuncontaminated soils (data from Bowen,1979), the trends of metals throughout thewatershed can be seen. Cadmiumconcentrations stay relatively constantthroughout the watershed except for sites 18and 23. Lead and zinc, however, show adistinct change upstream of site 10, whereconcentrations surpass the mean. Also there isa distinct drop below the mean, for lead,upstream of site 22. The zinc concentrationdrops below the mean upstream of site 23.

Re-sampling of multiple sites on differentdates revealed consistently proportionalrelations in concentration of metals at eachsite. When overlapping sites were comparedfor two different dates (6/27/01 and 7/3/01),trend lines for cadmium, zinc and lead all hada slope of 1±0.2. This shows that the dataremained relatively consistent between the twosample dates.

DISCUSSIONThe shape of Cross-section “Q” is most likelycaused by developing the land along thestream banks, straightening the stream, andreinforcing it with riprap to protect the

Fig. 2 Sample sites along Long’s Park Creek

surrounding areas from erosion. These actionsincrease runoff and therefore discharge,increasing sediment load, which leads toincising and steepening of banks. Cross-sections “G” and “A” are located in a lessanthropogenically impacted area. These crosssections exhibit a more natural shape. Cross-section “G” shows a traditional meanderprofile, with the deposition bank on the leftand the cut-bank on the right. Cross-section“A” shows a traditional pool profile. Thedramatic difference between the channelgeomorphology of the urban area and that ofthe forested area is an example of how landuse practices have affected the physicalproperties of the stream.

When viewed against the backdrop of the restof the Little Conestoga Creek Watershed, thenitrate and phosphate levels of LPC are lowerthan average. All of the nutrientconcentrations fall below the safe limit of 10mg/L of nitrates for drinking water(Commonwealth of Pennsylvania, 1994).

Table 1 shows both nitrate and phosphate datafor the 22 samples collected from LPC and the16 USGS sites that were re-sampled. LPCnutrient levels were lower than the USGS sitesbecause the land usearound LPC is primarily commercial. Over80% of the land in the Little Conestoga CreekBasin is used for agriculture, and most of theUSGS sites are located on streams that flowthrough farmland. As suspected, the runofffrom fertilized fields is a major contributor ofnutrients.

When compared to sediment samples from theUSGS sites, the LPC is elevated in zinc,cadmium, and lead (Fig. 2). Between sites 10and 11 there is a dam on the LPC. Upstreamof this dam, concentrations of lead and zincare higher than the rest of the stream. Thedam may be acting as a trap for sedimentladen with heavy metals, keeping them in theupper reaches of the stream. The upper sites,24 and 25, lie in the Dillerville swamp, whichis upstream of major industries. Site 26 is

Tabel 1. Water sampling results for Long’s Park Creek sites on 6/19 and 7/3*

Site TºC6/19

TºC7/3

pH6/19

pH7/3

TDS6/19

TDS7/3

DO6/19

DO7/3

Nit6/19

Nit7/3

Phos6/19

Phos7/3

1 21.3 19 7.8 8 380 244 6.50 9.28 8.5 5.7 0.45 0.172 21.6 19 7.6 8.1 369 334 7.74 8.75 9.2 6.2 0.35 0.263 21.0 18 7.7 8.3 395 390 7.41 9.51 5.4 2.4 0.57 0.124 21.3 19 7.7 8.4 393 392 7.43 9.39 5.0 2.9 0.11 0.045 16.1 16 6.7 7.2 461 453 NT 5.95 5.9 3.2 0.44 0.166 NT 20 NT 8.4 NT 395 NT 9.02 NT 2.5 NT 0.057 19.5 18 7.5 8.2 417 415 6.44 8.52 6.8 3.1 0.13 0.158 NT 20 NT 8 NT 422 NT 7.71 NT 3.3 NT 0.299 NT 20 NT 8 NT 424 NT 7.8 NT 3.4 NT 0.2410 NT 19 NT 7.9 NT 391 NT 8.75 NT 2.9 NT 0.211 NT 20 NT 8 NT 389 NT 11.1 NT 3.5 NT 0.2212 NT 18 NT 8.1 NT 426 NT 8.58 NT 3.2 NT 0.0813 NT 18 NT 7.9 NT 428 NT 9.1 NT 3.1 NT 0.2514 17.5 18 7.6 8 426 430 7.33 9.12 5.5 3.3 0.33 0.2115 NT 17 NT 8.1 NT 426 NT 8.62 NT 2.9 NT 0.1316 NT 16 NT 8.1 NT 427 NT 9.08 NT 3.3 NT 0.1822 NT 21 NT 7.6 NT 419 NT 5.86 NT 2.6 NT 0.2724 NT 29 NT 7.9 NT 356 NT 8.98 NT 1.9 NT 0.6125 NT 28 NT 7.7 NT 362 NT 15 NT 1.9 NT 0.726 23.1 24 7.1 8 385 385 5.46 9.41 5.3 1.7 0.37 0.0127 25.8 27 8.3 9.2 294 300 10.22 14.6 8.1 1.9 0.33 0.7828 NT 26 NT 9.1 NT 286 NT 13.5 NT 1.9 NT 0.66

*(TDS-Total Dissolved Solids (ppm), DO- Dissolved Oxygen (mg/L), Nit-Nitrates (mg/L), Phos-Phosphates (mg/L),NT-Not Tested

Long's Park Pond and is therefore not subjectto industry.

The most probable sources for zinc and leadare industries in the northern area of the city ofLancaster. In this area there are companieswith a history of metal pollution (EPA ToxicRelease Inventory, 2001), including the metalprocessing plant, Alcoa, a Superfund site.Additionally, the watershed is underlain by theLedger Formation, a limestone-dolomite unitthat contains some layers of zinc ore(Freedman, 1972). Runoff from road surfaces(motor oil, tire tracks, gasoline) or fly ash(Page et al., 1979) from smokestacks couldalso be sources of metal pollution.

Cadmium levels are relatively consistentthroughout the Little Conestoga Creekwatershed, with the exception of the two LPCsites, which are high due most likely to pointsource pollution. Still the Little ConestogaWatershed concentrations are very high(between 4 and 22 times the mean value ofuncontaminated soils (data from Bowen,1979)). The consistency of cadmium levelssuggests a background source for the metal,perhaps in the bedrock or from long termdischarge of fly ash. Further research isrequired to determine the exact source.

CONCLUSIONSThis study has attempted to indicate some theeffects of urbanization on a stream. LPC is aunique section of the Little ConestogaWatershed and while development clearly hashad many negative effects, the stream doeshave some positive characteristics as well.Negative aspects include radically alteredphysical characteristics such as the artificiallysteepened and straightened stream channel,and lack of a natural flood plain. All of theseproblems contribute to frequent flash floodsand overall degradation. Positivecharacteristics include the lack of farmland,which has resulted in lower nutrient pollution,and a fairly healthy riparian zone in somestretches that helps reduce erosion and keepstemperatures lower.

The high metal concentrations are also a causeof concern. The concentrations of zinc andlead are up to ten times the uncontaminatedmean (Bowen, 1979) and cadmiumconcentrations exceed one hundred times theuncontaminated mean (Bowen, 1979) in someareas. If the dam between sites 10 and 11were removed, large amounts of suspendedsediment would increase metal concentrationsdownstream. Organisms lower on the foodchain, such as bottom feeders, could takegreater concentrations of heavy metals intotheir tissues. In turn, higher organisms that eatthe lower organisms would accumulate evenhigher concentrations of these toxic metals inthe process of biomagnification.

Due to the time constraints of the project, thenumber of sampling locations had to belimited. For better results, many moresediment and water samples would have to betaken in a more systematic way and averagedtogether. Rather than collecting the sedimentfrom the same part of the stream channel eachtime, the samples were selected on the basis ofwhere the finest grains could be gathered. Inthe future, the tests should be conductedseveral times throughout the year in order torule out seasonal variations. Finally, a more indepth look at the sediments trapped behind thedam in LPC could possibly provide a record ofindustrialization through metal concentration.

Fig. 2. Levels of Zn, Pb, and Cd in LPC sedimentsare much higher than those found in USGS sites.

REFERENCES CITEDBowen, H.J.M. (1979). "Environmental

Chemistry of the Elements". AcademicPress, London and New York.

Commonwealth of Pennsylvania. (1994)Pennsylvania Code, Title 25,Environmental Resources, Department ofEnvironmental Resources, Chapter 93,Water Quality Standards, Paragraph 93.7,Section C.

EPA Toxic Release Inventory:http://www.epa.gov/enviro/html/toxic_releases.html

Freedman, Jacob (1972) "GeochemicalProspecting for Zinc, Lead, Copper, andSilver, Lancaster Valley, SoutheasternPennsylvania". Geological SurveyBulletin 1314-C. United StatesGovernment Printing Office, WashingtonD.C.

Lancaster County GIS Information Database

Lopar, Connie A. and Davis, Ryan C. (1998)A Snapshot Evaluation of StreamEnvironmental Quality in the LittleConestoga Creek Basin, Lancaster County,Pennsylvania. In "Water-ResourcesInvestigations Report 98-4173". USDepartment of the Interior.

ACKNOWLEDGEMENTSWe would like to thank our Keck Sponsorsand Advisors, the Keck Consortium, F&MCollege and the department of Geosciences,our fellow project colleagues, Jesse Yoburn,and Janie Wissing for their invaluable helpand guidance.