Prepared in cooperation with the Pennsylvania Department of Environmental Protection, and in 

collaboration with Franklin and Marshall College and the U.S. Environmental Protection Agency

Effects of Legacy Sediment Removal on Nutrients 

and Sediment in Big Spring Run, Lancaster County, 

Pennsylvania, 2009–15

Scientific Investigations Report 2020–5031

U.S. Department of the Interior

U.S. Geological Survey

Effects of Legacy Sediment Removal on 

Nutrients and Sediment in Big Spring Run, 

Lancaster County, Pennsylvania, 2009–15

By Michael J. Langland, Joseph W. Duris, Tammy M. Zimmerman, and 

Jeffrey J. Chaplin

Prepared in cooperation with the 

Pennsylvania Department of Environmental Protection, and in collaboration with 

Franklin and Marshall College and the U.S. Environmental Protection Agency

Scientific Investigations Report 2020–5031

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Langland, M.J., Duris, J.W., Zimmerman, T.M., and Chaplin, J.J., 2020, Effects of legacy sediment removal and effects 

on nutrients and sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15: U.S. Geological Survey Scientific Investigations Report 2020-5031, 28 p., https://doi.org/10.3133/sir20205031. 

Associated data for this publication:

Langland, M.J., 2019a, Archival data sets for regressions to estimate continuous streamflow, turbidity, and suspended 

sediment in support of study evaluating effects of removal of legacy sediment at Big Spring Run, Lancaster County, 

Pennsylvania, 2009–2015: U.S. Geological Survey data release, https://doi.org/10.5066/F747495R. 

Langland, M.J., 2019b, Data collected and sediment loads estimated in support of study evaluating effects of removal 

of legacy sediment at Big Spring Run, Lancaster County, Pennsylvania, 2009–2015: U.S. Geological Survey data 

release, https://doi.org/10.5066/F7ZK5FZ0.

Langland, M.J., 2019c, Data in support of study evaluating effects of legacy-sediment removal on nutrients and 

sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15: U.S. Geological Survey data release, 

https://doi.org/10.5066/F7GH9G5K.

ISSN 2328-0328 (online)
iii

Acknowledgments

The authors wish to thank Jeffrey Hartranft (Pennsylvania Department of Environmental Protection), Dr. Dorothy Merritts (Franklin and Marshall College), and Dr. Robert Walter (Franklin and 

Marshall College) for their cooperation and partnership during all phases of the study. The 

authors thank Laura Medalie (U.S. Geological Survey [USGS] New England Water Science 

Center [WSC]) and Joseph Bell (USGS Maryland-Delaware-District of Columbia WSC) for the 

technical reviews, which resulted in substantial improvement to this report. The authors also 

thank Daniel Galeone (USGS Pennsylvania WSC) and the USGS New Jersey WSC for their input 

on how to evaluate the continuous turbidity data collected for use in estimating continuous 

suspended-sediment concentrations.

v

Contents

Acknowledgments........................................................................................................................................iii

Conversion Factors......................................................................................................................................vii

Abstract...........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Study Area.......................................................................................................................................................2

Methods...........................................................................................................................................................4

Nutrients.................................................................................................................................................4

Streamflow ............................................................................................................................................5

Turbidity ..................................................................................................................................................6

Sediment.................................................................................................................................................6

Data Management and Statistical Evaluation .................................................................................6

Data Handling...............................................................................................................................6

Continuous Data...........................................................................................................................7

Statistical Tests of Discrete Data..............................................................................................9

Data Limitations.....................................................................................................................................9

Quality Control Samples..............................................................................................................................10

Effects of Legacy Sediment Removal ......................................................................................................10

Nutrients ..............................................................................................................................................12

Streamflow...........................................................................................................................................12

Turbidity ................................................................................................................................................12

Suspended Sediment .........................................................................................................................18

Summary........................................................................................................................................................25

References Cited..........................................................................................................................................26

Figures

1. Location of Big Spring Run study area and vicinity, Lancaster County, Pennsylvania.....3

2. Aerial photograph in the prerestoration period at Big Spring Run, Lancaster

County, Pennsylvania.................................................................................................................11

3. Sample collection and streamflow conditions for downstream site 015765195

during the prerestoration period and postrestoration period.............................................13

4. Comparison of pre- and postrestoration nutrient and suspended-sediment

concentrations in Big Spring Run, Lancaster County, Pennsylvania.................................14

5. Time sequence for a storm at Big Spring Run, Lancaster County, Pennsylvania,

September 18, 2012.....................................................................................................................15

6. Exceedance probability of streamflow for site 015765195, Big Spring Run, Lancaster

County, Pennsylvania. ...............................................................................................................16

7. Turbidity in relation to streamflow at site 015765195, Big Spring Run, Lancaster

County, Pennsylvania, during a storm event from December 22 to 23, 2011.....................17

8. Sediment concentration in relation to turbidity at three sites in Big Spring Run,

Lancaster County, Pennsylvania..............................................................................................19
vi

9. Photograph showing example of mass wasting in the streambank below the

downstream site in Big Spring Run near Mylin Corners, Pennsylvania............................20

10. Comparison of suspended-sediment concentrations at site 015765195, Big Spring

Run, Lancaster County, Pennsylvania, to two sites in an adjacent watershed from

Galeone and others (2006).........................................................................................................21

11. Daily suspended-sediment loads at site 015765195, Big Spring Run, Lancaster

County, Pennsylvania.................................................................................................................24

12. A comparison of suspended-sediment loads in the postrestoration period using the

Weighted Regressions on Time, Discharge, and Season method and the continuous

method..........................................................................................................................................25

Tables

1. Precipitation totals by water year at Lancaster Filtration Plant #2 (LCRP1) rain gage

near Big Spring Run, Lancaster County, Pennsylvania. The end of the

prerestoration period and beginning of the postrestoration period occurred

between 2011 and 2012................................................................................................................4

2. Description of three U.S. Geological Survey surface-water monitoring sites, Big

Spring Run, Lancaster County, Pennsylvania ..........................................................................5

3. Description of turbidity sondes and sensors used at three sites on Big Spring Run,

Lancaster County, Pennsylvania................................................................................................6

4. Summary of missing and censored 15-minute unit-value data for streamflow and

turbidity at three sites, Big Spring Run, Lancaster County, Pennsylvania, water

years 2009–15 ................................................................................................................................8

5. Streamflow statistics for storms at Big Spring Run near Mylin Corners,

Pennsylvania, water years 2009–15.........................................................................................16

6. Summary of daily, monthly, and annual suspended-sediment loads at three sites in

Big Spring Run, Lancaster County, Pennsylvania, water years 2009–15...........................22
vii

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

Acre 4,047 square meter (m2)

Acre 0.4047 hectare (ha)

square mile (mi2) 259.0 hectare (ha)

Volume

cubic feet (ft3/s) 7.48 gallon (gal)

gallon (gal) 0.13368 cubic feet (ft3/s)

million gallons (Mgal) 3,785 cubic meter (m3)

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

million gallons per day (Mgal/d) 1.85814 cubic foot per second (ft3/s)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

ton, short (2,000 lb) 0.9072 megagram (Mg) 

ton per day (ton/d) 0.9072 metric ton per day

ton per day (ton/d) 0.9072 megagram per day (Mg/d)

ton per day per square mile [(ton/d)/mi2] 0.3503 megagram per day per square kilometer 

[(Mg/d)/km2]

ton per year (ton/yr) 0.9072 metric ton per year

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: 

 °C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Elevation, as used in this report, refers to the distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm 

at 25 °C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L)
viii

Abbreviations

ASTM American Society for Testing and Materials

BMP best management practice

BOL Bureau of Laboratories

MRL method reporting limit

NWQL National Water Quality Laboratory

PaDEP Pennsylvania Department of Environmental Protection

SSC suspended-sediment concentration

USGS U.S. Geological Survey

WRTDS Weighted Regressions based on Time, Discharge, and Season

WY water year
Effects of Legacy Sediment Removal on Nutrients 

and Sediment in Big Spring Run, Lancaster County, 

Pennsylvania, 2009–15

By Michael J. Langland, Joseph W. Duris, Tammy M. Zimmerman, and Jeffrey J. Chaplin

Abstract

Big Spring Run is a 1.68-square mile watershed underlain 

by mostly carbonate rock in a mixed land-use setting (part 

agricultural and part developed) in Lancaster County, Pennsylvania. Big Spring Run is a subwatershed of Mill Creek, a 

tributary to the Conestoga River. These watersheds are known 

contributors of nutrient and sediment loads to the Chesapeake 

Bay and several stream reaches are on the Pennsylvania 

impaired waters list. Big Spring Run is listed as impaired and 

was selected by the Pennsylvania Department of Environmental Protection to evaluate a novel best management practice to 

restore natural aquatic ecosystems by removing legacy sediment. The study was designed to quantify sediment and nutrient contributions in pre- and postrestoration periods (water 

years 2009–11 and 2012–15, respectively) using an intensive 

monitoring approach at three surface-water sites within the 

watershed. Instrumentation at each site continuously measured 

(15-minute intervals) streamflow, water temperature, and turbidity. Water-quality samples were collected routinely (generally monthly and during selected storms); sampling frequency 

varied by site and constituent at the three monitoring sites. 

Effects of legacy sediment removal and restoration 

on nutrient concentrations varied in surface water samples 

depending on the form (particulate, dissolved, organic, inorganic). For example, total phosphorus concentrations at the 

downstream site decreased from a median of 0.19 milligram 

per liter (mg/L) to 0.04 mg/L, pre- and postrestoration periods, 

respectively. Concentrations of orthophosphate, the dissolved 

form of phosphorus, were not significantly different pre- to 

postrestoration at the downstream site. Similarly, nitrate concentrations, the dominant form of nitrogen in Big Spring Run 

surface-water samples (92.3 percent of total nitrogen) were not 

significantly different in the pre- compared to the postrestoration periods. 

Legacy sediment removal and restoration had significant effects on suspended-sediment concentrations and loads. 

Median suspended-sediment concentrations at the downstream 

site decreased from 556 mg/L prerestoration to 74 mg/L 

postrestoration even though streamflow hydrographs during 

the two periods were similar. In the postrestoration period, 

the mean annual suspended-sediment load conveyed to the 

restoration area from the upstream sites was 839 tons, whereas 

mean annual suspended-sediment load at the downstream site 

was reduced to 242 tons.

Streamflow during storms transports a large proportion of 

the suspended-sediment load; there were a total of 320 storms 

over the study period. In Big Spring Run, a single storm event 

can transport more than 25 percent of the annual suspendedsediment load. The greatest single-storm contribution to 

suspended-sediment load was 38 percent in water year 2015 at 

the downstream site. Although streamflow magnitudes during 

storms varied greatly over the study period, median streamflow was 17.5 cubic feet per second and median duration was 

about 3 hours and 24 minutes. 

Results observed for this study using the newly proposed best management practice were compared with other 

best management practices intended to reduce sediment. 

For example, during a previous study, statistically significant reductions in suspended-sediment concentration were 

observed when streambank fencing was implemented in an 

adjacent watershed; however, suspended-sediment reductions 

were an order of magnitude less than the reductions observed 

in the current study. Median suspended-sediment concentration at the downstream site was reduced by 482 mg/L in the 

current study compared to only 30 to 46 mg/L as a result of 

streambank fencing.

Introduction 

Identification and quantification of the relative contribution of nutrient and sediment sources from watersheds in the 

Chesapeake Bay are needed to assist resource managers in 

developing and implementing strategies to reduce nutrient and 

sediment loads to the bay. These reductions are necessary to 

meet nutrient and sediment allocation goals to help remove the 

Chesapeake Bay from the impaired waters list. Recognition 

of large amounts of historical sediment with relatively high 

nutrient concentrations that are stored along valley-bottom 
2 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

corridors, also known as legacy sediment (Walter and Merritts, 2008), has led the Commonwealth of Pennsylvania 

to evaluate a best management practice (BMP) that targets 

legacy sediment-impaired aquatic ecosystems for restoration 

(Hartranft and others, 2011). The valley morphology changes 

resulting from legacy sediment storage alter natural aquatic 

ecosystem functions and processes that maintain healthy water 

quality and habitat (Hartranft and others, 2011). Aquatic ecosystem restoration resulting from removal of legacy sediment 

is proposed to substantially reduce sediment and nutrient loads 

to streams. Sediment storage historically increased in valley 

bottoms and stream channels as a result of timbering, land 

clearing, deposition of sediment behind thousands of small 

mill dams, and marginal and ineffective soil retention methods. The proposed BMP involves legacy sediment removal to 

restore natural valley morphologies, biogeochemical processes, and biological components of natural aquatic ecosystems (Hartranft and others, 2011). 

The landscape around Big Spring Run has been greatly 

altered since the arrival of European settlers in the early to 

mid-1700s; dark rich soils containing plant macrofossils characteristic of wetland vegetation indicate a wetland-dominated 

paleoenvironment (Merritts and others, 2010). Land-clearing 

activities led to migration of soil down the gentle slopes to the 

valley bottom. In addition, a grain mill dam about 8-feet (ft) 

high was built on the lower reach of Big Spring Run in the 

mid-1700s. The eroded sediment filled the valley bottom over 

time and the amount of stored sediment in the Big Spring Run 

corridor increased. At some point in time (between 1890 and 

early 1900), dam breaching caused stream incision into the 

legacy sediment. 

Big Spring Run was selected by the Pennsylvania Department of Environmental Protection (PaDEP) to evaluate the 

proposed restoration BMP approach to determine the effects of 

legacy sediment removal on nutrients and sediment because of 

previous studies done in the basin and the historical evidence 

of a small mill dam. Galeone and others (2006) monitored surface water, nutrient and sediment loads, and groundwater quality from 1993–2001. Gutshall (2004) and Walter and Merritts 

(2008) determined that streambank erosion in the Big Spring 

Run headwaters during a 1.5-year period (2003–04) occurred 

at a rate of approximately 0.2 ton of sediment per linear foot 

of stream channel per year. Prior to restoration in October 

2011, as much as 35 and 54 percent of the sediment originated 

from two tributaries upstream from the restoration area (U.S. 

Geological Survey [USGS] 015765185 and USGS 01576516, 

respectively), and as much as 70 percent originated within 

the sediment restoration area (Merritts and others, 2010). 

Additional studies by Franklin and Marshall College (Walter 

and others, 2007; Weitzman, 2008; Merritts and others, 2010, 

2013) present information on nutrient and sediment sources 

and identify the large volume of legacy sediment in the valley 

bottom as a major contributor of nutrients and sediment in 

watersheds such as Big Spring, and that much of the sediment 

originates from streambank erosion. 

Long-term BMP efficiency studies to assess and document sediment and nutrient reductions with components 

consisting of (1) identification of sources and loads, (2) 

prerestoration monitoring, (3) remediation, and (4) postrestoration monitoring are costly and rarely applied in management 

strategies in a quantifiable fashion. This study was designed 

to document changes in water quality (specifically, sediment 

transport) after restoration. An upstream-downstream approach 

was utilized to quantify the sediment mass transported into 

and out of the restoration area by comparing streamflow and 

surface-water-quality data in the pre- and postrestoration 

periods. 

Purpose and Scope

This report presents the results of nutrient and sediment 

contributions from Big Spring Run prior to, during, and after 

the removal of legacy sediment and restoration of natural 

aquatic ecosystem forms and processes. Nutrient and sediment 

concentrations and loads were determined for a prerestoration 

period (water years 2009–11) and compared to nutrient and 

sediment concentrations and loads for a 4-year postrestoration 

period (water years 2012–15). Water year is defined as the 

12-month period from October 1 through September 30 of the 

following year and is designated by the calendar year in which 

it ends. The comparison presented here documents the effects 

of removing legacy sediment in Big Spring Run. 

Study Area

The 1.68-square mile (mi2) Big Spring Run watershed 

is near the town of Willow Street, which is approximately 

4 miles (mi) south and southeast of the city of Lancaster in 

Lancaster County, Pennsylvania. The study reach includes 

the main stem of Big Spring Run and an unnamed headwater tributary (fig. 1). Big Spring Run flows north and joins 

Mill Creek, which is a tributary to the Conestoga River. The 

Conestoga River and Mill Creek watersheds have been identified as important contributors of nutrient and sediment loads 

to Chesapeake Bay (Koerkle, 2000; Gellis and others, 2004). 

Many stream reaches in the Conestoga River and Mill Creek 

watersheds are impaired, including Big Spring Run, which is 

listed for aquatic life, construction, siltation, habitat modification, and unknown toxicity (Pennsylvania Department of 

Environmental Protection, 2014).

The Big Spring Run watershed is underlain by CambrianOrdovician age carbonate and siliciclastic rocks covered by 

a variable layer of soil less than 5 ft thick. Approximately 

90 percent of the watershed is underlain by limestone (Conestoga Formation); with the remaining area underlain by 

dolomite (Vintage Formation) and quartzite, schist, or phyllite (Antietam and Harpers Formations, undivided) (Berg 

and others, 1980; Galeone and others, 2006). The Conestoga 
Study Area 3

015765195 Big Spring Run near Mylin Corners, PA

015765185 Unnamed tributary to Big Spring Run near Willow Street, PA 01576516 Big Spring Run near Willow Street, PA

76°16'30" 76°16' 76°15'30" 76°15'

39°59'30"

39°59'

39°58'30"

Stream gages

Major streams

EXPLANATION

Big Spring Run watershed 

Sediment removal site excavation limit

LANCASTER COUNTY

Lancaster

Filtration

Plant 2

Muddy Run-Mill

Creek watershed 

PENNSYLVANIA

0 0.25 0.5 MILE

0 0.25 0.5 KILOMETER

Major streams and watersheds from U.S. Geological Survey, 2019

2008 imagery from PAMAP Program, 2009

County boundary base from U.S. Census Bureau digital data, 2000

1:100,000 Albers Equal-Area Conic projection: Standard Parallels 40° N and 42° N,

Central Meridian 78° W, Latitude of Origin 39°

Figure 1. Location of Big Spring Run study area and vicinity, Lancaster County, Pennsylvania. Figure modified from Merritts and 

others (2013).
4 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

Formation has characteristics of karst, including sinkholes, 

surface depressions, springs, pinnacles, swales (Galeone and 

others, 2006), and typically higher recharge rates compared 

to nearby geologic formations (Gerhart and Lazorchick, 

1988). The soils along the ridges and adjacent side slopes 

are predominantly classified as the Conestoga (fine-loamy), 

Penlaw (fine-silty), and Pequea (course-loamy) series. Along 

the middle and lower slopes, soils are classified as the Lehigh 

(fine-loamy) series and along the streams as the Clarksburg 

(fine-loamy) series (Custer, 1975). 

Based on the 2011 National Land Cover Database (U.S. 

Geological Survey, 2014), land use in the Big Spring Run 

watershed is approximately

• 50 percent agricultural (pasture/hay and 

cultivated crops), 

• 46 percent developed (open space, low, medium, 

and high intensity development, and barren land 

including rock/sand/clay), and 

• 4 percent forested (deciduous and evergreen forests, shrub/scrub, and emergent herbaceous and 

woody wetlands). 

From 2001 to 2011, land classified as developed 

increased by 10 percent and forested land increased by 

1 percent, with agricultural lands decreasing by 11 percent 

(LaMotte, 2008; U.S. Geological Survey, 2014). The increase 

in developed land and decrease in agricultural land mostly 

occurred in the western part of the watershed near the town of 

Willow Street. The mean basin elevation is 409 ft above the 

North American Vertical Datum of 1988 (NAVD 88).

Limited local precipitation data were available within 

the study area; therefore, rainfall patterns were characterized 

using data from the Pennsylvania State Climatologist LCRP1 

site (Lancaster Filtration Plant #2) operated by the Lancaster 

Water Company 4.1 mi to the northeast of the study area (fig. 

1). The average yearly precipitation and temperature at the 

LCRP1 site are 41 inches and 60 °F, respectively (Pennsylvania State Climatologist, 2016). Daily precipitation data from 

the Pennsylvania State Climatologist (2016) from October 1, 

2008, to September 30, 2015, used in data analysis described 

in this report are available in Langland (2019b). A summary of 

the rainfall data by water year is provided in table 1.

For this study, three U.S. Geological Survey streamgages 

were installed—two upstream of the restoration area (referred 

to hereafter as the east and west sites for USGS 01576516 and 

USGS 015765185, respectively) and one downstream of the 

restoration area (hereafter referred to as the downstream site 

for USGS 015765195) (fig. 1). Each streamgage was equipped 

with a transducer to measure water-level change, a water-quality sonde, satellite telemetry equipment, and automatic samplers. The locations of the three streamgages were based on 

the original restoration removal plans and were to have been 

placed directly upstream or downstream from the removal 

area. By the time of construction, increased costs necessitated 

changes to the original plan. The downstream site (USGS 

Table 1. Precipitation totals by water year at Lancaster Filtration 

Plant #2 (LCRP1) rain gage near Big Spring Run, Lancaster County, 

Pennsylvania. The end of the prerestoration period and beginning 

of the postrestoration period occurred between 2011 and 2012.

Water year1 Precipitation at LCRP1 (in 

inches)

2009 41.19

2010 39.95

2011 51.42

2012 37.67

2013 39.02

2014 55.4

2015 40.52

Average, prerestoration period 44.19

Average, postrestoration period 43.15

1

Water year is defined as the 12-month period from October 1 through September 30 of the following year. The water year is designated by the calendar 

year in which it ends. 

015765195) is approximately 400 ft downstream and outside 

of the final sediment removal area. The upstream east and west 

site locations (USGS 01576516 and 015765185) were located 

approximately 130 and 175 ft, respectively, upstream and 

outside of the restoration area. In 2015, the west site (USGS 

015765185) was moved approximately 195 ft downstream and 

inside the restoration area. 

Methods

In this section, sample-collection and data-analysis 

methods for nutrient, streamflow, turbidity, and suspendedsediment concentration (SSC) data are described. The analytical and statistical methods for estimating missing continuous 

streamflow and turbidity records and additional modifications 

to the data are discussed, and statistical approaches to data 

analysis are described.

Nutrients

From water year (WY) 2009 through WY2011, nutrient 

samples were collected using a Teledyne ISCO® automated 

sampler that was programmed to collect a sample based on 

in-stream conditions. Nutrient samples were collected concurrently with suspended sediment samples. If the automated 

sampler was triggered while field personnel were on site, 

measurements of instream specific conductance, pH, dissolved 

oxygen, and temperature were made using a calibrated field 

meter as described in the USGS National Field Manual (U.S. 

Geological Survey, variously dated). The automated samplers 

were programmed to collect a sample every 15 minutes for 

the first 3 hours (12 samples) and then programmed to collect 
Methods 5

samples every 30 minutes for the next 6 hours (12 samples) 

for a total of 24 samples collected over a sampling event (total 

of 9 hours). The sampling event trigger for the automated 

sampler was when stream stage increased by 0.5 ft over a preset stage or when instream turbidity exceeded 100 Formazin 

nephelometric units (FNU). From WY2009 through WY2011, 

when the 24 samples were recovered from the automated 

sampler, bottles for nutrient analysis were selected from the 

rising limb, peak, and falling limb of the hydrograph. The 

samples were then processed according to the sample processing guidelines described in the USGS National Field Manual 

(U.S. Geological Survey, variously dated). Once processed, 

the samples were shipped on ice to the USGS National Water 

Quality Laboratory (NWQL, Lakewood, Colorado). Nutrient analysis at the NWQL included filtered nitrate, filtered 

ammonia, total nitrogen, filtered total nitrogen, total phosphorus, filtered total phosphorus, filtered nitrate plus nitrite, and 

filtered orthophosphate.

From WY2012 through WY2015, nutrient samples were 

collected concurrently with SSC samples using a multiplevertical channel-integrated sampling approach (a nonisokinetic 

equal width integrated sample) as described in the USGS 

National Field Manual (U.S. Geological Survey, variously 

dated). During sample collection, field properties (specific 

conductance, pH, dissolved oxygen, and temperature) were 

determined using a calibrated field meter as described in the 

USGS National Field Manual (U.S. Geological Survey, variously dated). Field properties were measured in each of three 

sections at each site and the median value was reported. After 

collection, samples were split using a 7-liter (L) polyethylene 

churn splitter and processed according to sample processing 

methods described in the USGS National Field Manual (U.S. 

Geological Survey, variously dated). Nutrient samples were 

analyzed by the Pennsylvania Department of Environmental 

Protection Bureau of Laboratories (PaDEP BOL) for filtered 

and unfiltered nitrate plus nitrite, filtered and unfiltered total 

phosphorus, filtered and unfiltered ammonia, filtered and unfiltered total nitrogen, and filtered and unfiltered orthophosphate. 

All discrete nutrient, total suspended solids, and 

suspended-sediment concentration data are available in the 

companion data release (Langland, 2019b). Laboratory reporting standards vary between analytical laboratories and as a 

result, nomenclature is often different between laboratories. In 

our study, the terms “dissolved” and “filtered” and the terms 

“total” and “unfiltered” are used interchangeably throughout 

this report.

Streamflow 

Three continuous streamflow streamgages were established on Big Spring Run (table 2). Two of the sites were 

upstream of the restoration area, the easternmost upstream 

tributary in the study area was USGS 01576516, and the 

westernmost upstream tributary in the study area was USGS 

015765185. The third site, which was downstream of the 

restoration area, was USGS 015765195. Streamflow was measured at these three sites according to standard USGS protocols and methods (Turnipseed and Sauer, 2010). Briefly, every 

15-minutes a stream stage (gage height) measurement was 

made with a pressure transducer. Periodic (every 4–6 weeks) 

instantaneous streamflow measurements were made adjacent 

to the stream stage sensor using a Sontek Flowtracker handheld Acoustic Doppler Velocimeter (ADV®). Over time, a 

relational rating was established between stream stage and 

instantaneous discharge so that instantaneous discharge could 

be predicted. Streamflow measured at 15-minute increments is 

described as continuous streamflow throughout this report. All 

streamflow data from this site are available in the companion 

data release (Langland, 2019b).

Table 2. Description of three U.S. Geological Survey surface-water monitoring sites, Big Spring Run, Lancaster County, Pennsylvania.

 [USGS, U.S. Geological Survey; Pa., Pennsylvania; mi2, square miles] 

USGS site number USGS site name Local name Latitude1 Longitude1 Drainage area 

(decimal degrees) (decimal degrees) (mi2

)

01576516 Big Spring Run above East site (east) 39.99154444 76.2609306 0.36

Tributary near 

Willow Street, Pa.

015765185 Unnamed Tributary to West site (west) 39.99119167 76.26395278 1.05

Big Spring Run near 

Willow Street, Pa.

015765195 Big Spring Run near Downstream site 39.9959361 76.26403889 1.68

Mylin Corners, Pa.

1

Latitude/longitude coordinate datum is North American Datum of 1983 (NAD 83).
6 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

Turbidity

At each of the three USGS sites (east, west, downstream), 

a YSI or ANALITE turbidity probe and sonde were deployed 

according to standard USGS protocols (Wagner and others, 

2006). Turbidity sondes were programmed to measure, record, 

and transmit data every 15 minutes. Turbidity measured in 

15-minute increments is described as continuous turbidity 

data throughout this report. Throughout the 7-year course of 

data collection for this study, the make and model of turbidity probes used at each site was changed. The timing of these 

changes and specifications for each instrument is documented 

in table 3. 

Sediment

Suspended-sediment samples were collected concurrently with nutrient samples as described in the Nutrients 

section. From WY2009 through WY2011, all SSC samples 

were analyzed at the USGS Pennsylvania Water Science 

Center (New Cumberland, Pennsylvania) using the American 

Society for Testing and Materials (ASTM) D3977-97: Test 

Method A-Evaporation (American Society for Testing and 

Materials, 2006). From WY2012 through WY2015, suspended 

sediment samples were analyzed by the USGS sediment 

laboratory in Louisville, Kentucky, using ASTM D3977-97: 

Test Method B-Filtration (American Society for Testing and 

Materials, 2006). 

Data Management and Statistical Evaluation

This section describes the methods of data handling, 

including pairing continuous streamflow and turbidity datasets, censoring of data, regression models used to predict missing continuous data, and regression models used to predict 

continuous suspended-sediment concentration. In addition, 

methods used to analyze continuous streamflow, turbidity, 

sediment, and discrete nutrients and physical stream characteristics in the pre- and postrestoration periods are described. 

Note, all times in all datasets presented in this report and in the 

companion data releases (Langland, 2019a,b,c) are in Eastern 

Standard Time (Coordinated Universal Time minus 5 hours). 

Data Handling

Raw continuous streamflow and turbidity data were 

retrieved internally from the USGS Aquarius Timeseries 

database for sites 01576516 (east), 015765185 (west), and 

015765195 (downstream). Data were loaded into R-stats (R 

ver. 3.5.0) using R-studio (ver. 1.1.453). Data were handled 

with the R statistical computing software (combination of 

tidyr and base R packages; R Core Team, 2017). All continuous data values were paired with a date-time value from 

a complete time series from October 1, 2008, at 00:00:00 

through September 30, 2015, at 23:45:00, creating a dataset of 245,280 datapoints for date-time, streamflow, and 

turbidity measurements.

Streamflow data were censored at the 10-year recurrence 

base-flow interval as determined using USGS Streamstats (ver. 

4.2.1) available at https://streamstats.usgs.gov/ss/. Streamflow 

at the east site was censored at or below 0.29 cubic feet per 

second (ft3/s), streamflow at the west site was censored at or 

below 0.63 ft3/s, and streamflow at the downstream site was 

censored at or below 0.97 ft3/s. All turbidity values below 

0.1 FNU were censored, as variation below this range is 

outside of the operational limits of the sensors. Missing data 

from the data import and data censoring were indicated with 

NA values.

Discrete suspended sediment data were loaded into R 

using the USGS dataRetrieval package (De Cicco and others, 

2018). Discrete samples were paired with the proper sites and 

appended to the 15-minute time point that fell closest to the 

date and time of the discrete sample collection. 

Table 3. Description of turbidity sondes and sensors used at three sites on Big Spring Run, Lancaster County, Pennsylvania.

 [LED, light emitting diode; USGS, U.S. Geological Survey; nm, nanometers]

USGS site number Make and 

model

Light source Range Reported units Date installed Date removed

01576516 

(East site)

ANALITE NEP395 Broad brand, 

400–680 nm 1–1,500 Formazin nephelometric units 9/15/2008 8/30/2011

YSI 6136 Near infrared LED, 

780–900 nm 1–1,000 Formazin nephelometric units 8/30/2011 11/1/2017

015765185 

(West site)

ANALITE NEP395 Broad brand, 

400–680 nm 1–1,500 Formazin nephelometric units 9/30/2008 8/30/2011

YSI 6136 Near infrared LED, 

780–900 nm 1–1,000 Formazin nephelometric units 8/30/2011 11/1/2017

015765195 

(Downstream site)

YSI 6026 Near infrared LED, 

780–900 nm 1–1,000 Formazin nephelometric units 10/7/2008 8/30/2011

YSI 6136 Near infrared LED, 

780–900 nm 1–1,000 Formazin nephelometric units 10/7/2008 Current
Methods 7

Once regression models were computed to predict missing continuous streamflow and turbidity values, the surrogate regressions were computed to predict continuous SSC. 

Complete time-series record for streamflow and turbidity at 

each site using regression models to fill missing values was 

not possible. Rather, regressions were used to fill in as much 

data as possible at each site based on streamflow and turbidity at the other two adjacent study sites. If the two adjacent 

sites had gaps in streamflow or turbidity in their measured 

record, then a regression model could not be used to predict 

the missing data. Finally, all possible predicted and measured 

streamflow and turbidity data at each site was merged to create 

a blended time series. The methods used are covered in detail 

in Langland (2019a). Continuous suspended-sediment load 

was computed using base R and tidyr packages. Continuous 

SSC is the quantity of suspended sediment passing a point in 

a stream over a specific period of time. The regression model 

selected to predict continuous SSC was based on continuous 

turbidity. All continuous turbidity measurements were made 

(or missing/censored values predicted) at 15-minute intervals. 

When 15-minute SSC concentration data are converted to load 

and expressed as tons per day, suspended sediment load per 

day is computed with the following formula,

SSLday = ∑1→96SSCCi × Qi × k

where

SSLday is the suspended-sediment load for the ith 

values, in tons per day; 

SSCCi is suspended-sediment concentration for the 

ith value in milligrams per liter (mg/L);

Q is streamflow for the ith value in ft3/s; and

k is a conversion factor equal to 

0.0027 seconds × L × short tons

day × ft3 × mg

The value for the constant k is derived from other common 

conversions (86,400 seconds/day × 28.32 L/ft3 × 1.102 /109

tons/mg) (Norton and others, 2019). To convert the daily load 

to a 15-minute load, the SSLday must be divided by 96 (the 

number of 15-minute intervals in 1 day):

SSL15-minute = SSLday/96 

where

SSL15-minute is the suspended-sediment load, in tons, 

per 15-minute interval; and

96 is the number of 15-minute intervals in 1 day.

Daily, monthly, and annual suspended sediment loads 

were computed by summing all available continuous values. 

Annual suspended sediment loads were computed on the 

basis of water year, not calendar year. For the purposes of our 

report, missing values were treated as zero load, so the values 

presented here, although accurate for measured and predicted 

data, may underrepresent the total load at larger time intervals (days, months, years) with large proportions of missing 

values (table 4).

Continuous Data

Once the data were prepared as described above, six 

regression models were developed and compared for each site. 

For streamflow regression models, a subset of data was created 

for instances when all three sites had concurrently measured 

streamflow values (no missing values between the three 

sites) for the prerestoration period (WY2009–WY2011) and 

postrestoration period (WY2012–WY2015). A similar process 

was also used to subset the data for which all three sites had 

concurrently measured turbidity values from pre- and postrestoration periods. Regressions were then built in base R relating 

the variable of interest (either turbidity or streamflow) at one 

site with concurrent measures at one other site or both of the 

other sites. These regressions were computed both in linear 

and log10 space. Comparisons of the diagnostic statistics of the 

regression models were made for the six models (three linear 

models, three log10 models) at each location for two conditions 

(pre- and postrestoration periods) for both streamflow and turbidity. We expected that there would be large difference in the 

relation between streamflow and turbidity at the downstream 

site after restoration. Therefore, we built models for all sites to 

represent pre- and postrestoration conditions. To consistently 

analyze and select the best regression model for each site and 

constituent, the six regression models for streamflow and the 

six regression models for turbidity were evaluated using (1) 

summary statistics for all dependent and independent variables; (2) boxplots of all variables; (3) exploratory correlation 

plots of all variables; and (4) basic model statistics including 

the number of observations, the root mean square error, the 

adjusted coefficient of determination (adjusted R2), the model 

standard percent error, the predicted residual error sum of 

squares statistic, and a bias correction factor for log normalized data. The input data that were used to create each regression model, a description of the model selection process, and 

an archive of each model are available in Langland (2019a). 

Output from the selected models that was used in subsequent 

analysis for this report is provided in Langland (2019b). The 

number of censored and missing continuous values for each 

site are reported in table 4. 

Next, six regression models were developed and compared to relate streamflow and (or) turbidity to SSC. It should 

be noted, that although we did estimate as much of the missing 

turbidity and streamflow record as possible with the models 

described above, there were still some gaps in data that could 

not be filled. The datasets were used in a similar workflow 

to model the relation between streamflow and (or) turbidity 

and measured discrete SSC. Models were created only for 

data from the site where sediment was being predicted and 

were created for the prerestoration (WY2009–WY2011) and 

postrestoration (WY2012–WY2015) periods. The data subsets 

that were used to create all regression models, a description 

of the model selection process, and an archive of the models 

are available in Langland (2019a). The SSC output from the 

selected models that was used in all subsequent analysis for 

this report is provided in the companion data release (Langland, 2019b).
8 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15 Table 4. Summary of missing and censored 15-minute unit-value data for streamflow and turbidity at three sites, Big Spring Run, Lancaster County, Pennsylvania, water years 2009–15. [Streamflow is censored at and below the 10-year recurrence base-flow interval for each site. The 10-year recurrence base-flows for East Branch, West Branch, and Downstream are 0.29 cubic feet per second (ft3/s), 0.63 ft3/s, and 0.97 ft3/s, respectively. Turbidity is censored at 0.1 Formazin nephelometric units (FNU) at all three sites. Only missing 15-minute unit-values for streamflow and turbidity above prescribed censoring levels are presented] Water 01576516 East site 015765185 West site 015765195 Downstream site year1 Censored Missing Censored Missing Censored Missing Censored Missing Censored Missing Censored Missing streamflow streamflow turbidity turbidity streamflow streamflow turbidity turbidity streamflow streamflow turbidity turbidity unit-values unit-values unit-values unit-values unit-values unit-values unit-values unit-values unit-values unit-values unit-values unit-values (percent) above (percent) above (percent) above (percent) above (percent) above (percent) above censor censor censor censor censor censor level level level level level level (percent) (percent) (percent) (percent) (percent) (percent) 2009 0.00 24 0.00 18 50 36 0 12 3 5 1 16 2010 6.19 0 0.00 5 42 20 0 18 13 6 0 16 2011 0.04 17 0.00 27 48 28 0 59 0 5 0 60 2012 0.01 0 0.00 14 48 2 0 31 4 16 0 47 2013 0.00 24 0.00 31 66 47 21 39 1 5 34 41 2014 7.63 0 1.72 3 43 0 16 3 3 0 2 15 2015 3.77 0 2.01 5 60 1 35 15 10 0 11 12 Prerestoration 2.40 14 0.00 17 46.86 17 0.02 30 5.45 5 0.26 31 period (2009–11) Postrestoration 3.03 6 1.03 13 53.30 6 19.04 19 4.84 5 11.81 26 period (2012–15) Study period 2.78 9 0.60 15 50.73 11 11.54 24 5.10 5 7.04 28 (2009–15)

1Water year is defined as the 12-month period from October 1 through September 30 of the following year. The water year is designated by the calendar year in which it ends.
Methods 9

In computing daily, monthly, and annual summaries of 

data, there was still an issue with a significant number of missing data (table 4). We compared a summing method, where all 

data for each available period were summed, then averaged 

over that period, and the average values were substituted for 

missing values. The summing method is the more conservative 

method and biases the suspended-sediment load values low, 

when contrasted with the less conservative averaging method 

that biases the suspended-sediment load values high. All subsequent data evaluations presented in this report and the daily, 

monthly, and annual outputs presented in the companion data 

release (Langland, 2019b) are based on the summing method. 

Flow-duration curves were used to define the storm 

event streamflow value. A flow-duration curve is a statistical cumulative frequency curve that shows the percent of 

time for which specific discharges are equaled or exceeded 

(exceedance frequency distribution) during a given period of 

time. In a single plot and related table, the flow characteristics of a stream throughout the range of observed discharges 

are combined without regard to the sequence in which those 

discharges were observed. If the period of observation is 

long enough, the curve can be used to evaluate the differences in the distribution of flows (Searcy, 1959). In this study, 

flow-duration curves were compiled using the methods of 

Granato (2009) for 3 years prior to restoration and 4 years 

after restoration.

The compiled flow-duration curves were used to compare 

streamflow distribution in the pre- and postrestoration periods 

at the downstream site. The flow-duration curve of the downstream site in the prerestoration period was used to assign a 

value for the 5-percent exceedance probability. The 5-percent exceedance probability corresponded to a streamflow of 

7.84 ft3/s. Any streamflow at the downstream site greater than 

or equal to 7.84 ft3/s lasting at least 15 minutes was considered 

a storm event throughout the study area. 

Statistical Tests of Discrete Data

All statistical comparisons between groups of data (nutrients and sediment) were conducted using the nonparametric 

Wilcoxon (Mann-Whitney) rank-sum test as described in 

Helsel and Hirsch (2002). This test can be conducted with no 

assumptions about the distribution of the data and rejecting the 

null hypothesis (p-value <0.05) indicates that the median (and 

other percentiles of the data) are different. All Wilcoxon tests 

were done in TIBCO® S-PLUS, version 8.1.

In many figures, data are presented as boxplots. A boxplot 

is a way to compare the statistical distribution of one set of 

data with another. The box consists of a median line, with 

the upper part of the box representing the 75th percentile of 

the data and the lower part of the box representing the 25th 

percentile of data. Upper and lower adjacent lines that extend 

from the box represent 1.5 times the interquartile range, that 

is 1.5 times the range of the median to the 75th percentile, 

and 1.5 times the median to the 25th percentile, respectively. 

The upper and lower detached “x” symbols represent any 

observation that is 1–2 times the 75th percentile and the 25th 

percentile, respectively. The upper and lower detached “o” 

values represent values that are greater than 2 times the 75th 

and 25th percentiles, respectively (Helsel and Hirsch, 2002). 

Data Limitations

Throughout this 7-year study, there were several factors 

that could limit data interpretability. Here, we describe the 

sources of study uncertainty so that we can reliably interpret 

the data provided. 

One factor that could affect interpretation of the data was 

the change of equipment used to measure turbidity in the pre- 

(WY2009–WY2011) and postrestoration (WY2012–WY2015) 

periods (table 3). The maximum value that could be accurately 

reported on the turbidity probes decreased between these 

periods at the east and west sites. However, at the downstream 

site, even though the sonde was changed from a YSI 6026 to a 

YSI 6136, the maximum detectable value stayed the same. The 

change of equipment at the east and west sites was unlikely 

to affect the predicted SSC at the downstream site, although it 

could have affected the predicted SSC values at both the east 

and west sites.

In the prerestoration period, suspended-sediment concentrations were measured at the USGS Pennsylvania Water 

Science Center laboratory, and in the postrestoration period 

they were measured at the USGS Kentucky sediment laboratory. Although the laboratories and methods used to quantify 

suspended sediment were different, both laboratories used one 

of the approved methods (ASTM D3977-97) for suspendedsediment analysis (Federal Interagency Sedimentation 

Project, 2007).

In the prerestoration period, discrete sediment and nutrient samples were collected using an automatic sampler. This 

sampler uses a tube to collect a single, discrete sample from 

the water column at a defined place in the channel. In the 

postrestoration period, discrete sediment and nutrient samples 

were collected using a USGS equal-width increment multiple-vertical method, which is a depth- and width-integrated 

sample. Many studies have shown that discrete samples tend 

to bias sediment values low when compared to integrated samples. If this bias was present in this study, we would expect 

that a comparison of pre- and postrestoration suspendedsediment concentrations at the downstream site would show 

lower concentrations in the prerestoration period and higher 

concentrations post restoration; however, this was the opposite 

of the treatment effect observed. Therefore, we do not consider 

this to be an important source of bias in this study. 

Additionally, there was a change in sampling protocol 

concurrent with changes in sampling method. In the prerestoration period, storm samples were collected by automated 

samplers that could be triggered 24 hours a day to catch sampling events. However, in the postrestoration period when the 

switch to manual sampling was made, there was a bias toward 

sampling during daylight hours and the maximum number of 
10 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

storm sampling events was set at eight samples per year. Both 

of these factors could exclude the collection of samples from 

some storm events each year. It was noted in our data analysis that discrete suspended-sediment concentrations in the 

postrestoration period were lower than in the prerestoration 

period. However, both pre- and postrestoration sampling was 

conducted over a representative range of flows and the surrogate regression used to predict continuous suspended-sediment 

concentration from continuous turbidity was analyzed on all 

available turbidity measurements/predictions (24 hours a day, 

7 days a week). Therefore, the pre- to postrestoration difference in sampling protocol should not influence the results of 

the study. 

The nutrient laboratories used to analyze water samples 

in the pre- and postrestoration periods were also different. 

The average method reporting limit (MRL) for the USGS 

NWQL nutrient method was 0.04 mg/L (used in the prerestoration period), whereas the average reporting limit for the 

PaDEP BOL nutrient method was 0.008 mg/L (used in the 

postrestoration period), a difference of 168 percent. Although 

there is a large percent difference between the MRLs, the 

values observed in this study for all nutrients, except nitrite 

and ammonium, were more than 10 times the reporting limits 

discussed here. This indicates that the difference in laboratory 

reporting methods caused little, if any, bias in our analysis of 

nutrient data between the pre- and postrestoration periods. 

From WY2009 to WY2015 the west site (USGS 

015765185) was located approximately 175 ft outside of 

the restoration area. In the spring of 2015, the west site was 

moved 190 ft downstream, to about 15 ft inside of the restoration area as a result of the landowner installing a new sediment management practice upstream of, and adjacent to, the 

original site. The sediment management upstream of the west 

site could have affected the pre- to postrestoration outcome at 

the west site at that time. We hypothesize that this move had 

minimal impact on streamflow and turbidity measurements, 

but a change in location could induce positive or negative 

bias into the analysis of data from the west site in the pre- and 

postrestoration periods. 

Quality Control Samples

During WY2014, there were two field-blank samples and 

four field-replicate samples collected for nutrients analysis. 

All field blanks and field replicates were collected at the 

downstream site. The two blank samples were negative for all 

nutrients (filtered and unfiltered nitrate plus nitrite, filtered and 

unfiltered total phosphorus, filtered and unfiltered ammonia, 

filtered and unfiltered total nitrogen, filtered and unfiltered 

orthophosphate, and total suspended solids). Although the 

number of blanks was limited, and no blanks were run at the 

NWQL, the two field blanks that were collected demonstrated 

that the sampling methodology used during the postrestoration period did not create any bias near the reporting level 

for any nutrients. These results lend confidence in any value 

at or near the method reporting level for samples in the 

postrestoration period.

The replicate data, which is only available for the PaDEP 

BOL from the postrestoration period, indicates that the field 

variability, expressed as percent difference, for the nutrients analyzed were as follows: filtered nitrate plus nitrite, 

0.9 percent; unfiltered nitrate plus nitrite, 1.5 percent; filtered 

total phosphorus, 16.4 percent; unfiltered total phosphorus, 

10 percent; filtered ammonia, 0.0 percent; unfiltered ammonia, 

4.5 percent; filtered total nitrogen, 0.8 percent; unfiltered total 

nitrogen, 3.2 percent; filtered orthophosphate, 3.3 percent; 

and unfiltered orthophosphate, 4.0 percent. All nutrients had 

low field variability (less than 5 percent difference between 

field replicates) except filtered and unfiltered total phosphorus, 

which had a 10–16 percent different between field replicates. 

This higher variability is likely because total phosphorus has 

a higher affinity for the sediment in the water column; thus, 

any variation in sample splitting from the churn would be seen 

most prominently in total phosphorus data. We did observe a 

decrease in median phosphorus concentration from 0.19 mg/L 

in the prerestoration period to 0.04 mg/L in the postrestoration 

period. This decrease represents a difference of 160 percent, 

nearly 10 times greater than the variability owing to field 

sampling (16.4 percent), indicating that observed variability as 

a result of sampling was not a source of bias in our interpretations of the current study’s data. 

Effects of Legacy Sediment Removal 

Changes in nutrient concentration and sediment transport 

occurred as a result of the restoration. From September 2011 

through mid-December 2011, approximately 21,704 cubic 

yards (22,955 tons) of streambank and floodplain sediment 

was removed from the restoration area in the Big Spring Run 

watershed (fig. 2; Merritts and others, 2013). The stored sediment was moved offsite in 2012. In some regions of the restoration area, stream sinuosity was increased, and off-stream 

features were designed to restore 4.7 acres of a stream and 

wetlands complex that could affect the timing and delivery of 

water and sediment downstream. Sediment removal restored 

a potential maximum increase in storage of approximately 

13.3 acre-ft (converted from cubic yards removed; Michael 

Rahnis, Franklin and Marshall College, written commun., 

2016) or 4.3 million gallons (Mgal) of water. Total nitrogen 

and total phosphorus in the removed legacy sediment had concentrations of 2.9 and 1.5 pounds per ton, respectively (Merritts and others, 2013); that equates to about 63,670 pounds 

of total nitrogen and 26,346 pounds of total phosphorous 

permanently removed from the restoration area. 
Effects of Legacy Sediment Removal 11

015765195

015765185

01576516

76°15'50" 76°15'40"

39°59'40"

39°59'30"

Stream gages

EXPLANATION

Sediment removal site

excavation limit

Direction of stream flow

Post-restoration stream

channel placement

2008 imagery base from PAMAP Program, 2009

1:100,000 Albers Equal-Area Conic projection: Standard Parallels 40° N and 42° N,

Central Meridian 78° W, Latitude of Origin 39°

0 0.05 0.1 MILE

0 0.05 0.1 KILOMETER

Figure 2. Aerial photograph in the prerestoration period at Big Spring Run, Lancaster County, Pennsylvania. Parallel blue lines 

represent the final stream channel placement (postrestoration) and red boundary line represents sediment removal site excavation 

limit (Michael Rahnis, Franklin and Marshall College, written commun., November 16, 2008).
12 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

Nutrients 

Nutrient samples were collected over a wide range of 

streamflows (fig. 3), providing good representation of nutrient 

concentrations during baseflow and storms especially at the 

downstream site. Nitrogen and phosphorus can be present in 

many forms (particulate, dissolved, organic, inorganic) that 

are acted upon by various physical and chemical processes. 

Phosphorus more readily adsorbs to sediment particles than 

nitrogen, allowing for removal of phosphorous from the water 

column as sediment settles. Important processes for nitrogen 

reduction are plant uptake and denitrification, which involves 

mediation by microbes under anaerobic conditions to convert 

oxidized forms like nitrate to nitrogen gas. 

Excavation of legacy sediment from the restoration area 

allowed water that was channelized before restoration to 

access the floodplain during storms, which decreased streamflow velocities and promoted deposition in the floodplain 

(Merritts and others, 2013). As a result, suspended-sediment 

concentrations at the downstream site decreased significantly 

after upstream banks were pared back and legacy sediments were removed (p-value < 0.0001; fig. 4A). Phosphorus 

adsorbed onto those sediment particles was also removed 

from the water column. Total phosphorus concentrations at the 

downstream site decreased from a median concentration of 

0.19 mg/L to 0.04 mg/L (p-value = 0.0036; fig. 4B) during the 

pre- to postrestoration period even though streamflow hydrographs during the two periods were similar. Orthophosphate, 

also called dissolved inorganic phosphate, is a dissolved form 

of phosphorus available to aquatic plants and is more likely to 

be removed by plant uptake rather than sediment deposition. 

Orthophosphate at the downstream site was not significantly 

different in the postrestoration period (p-value = 0.4584; 

fig. 4C).

The decrease in suspended-sediment concentration 

demonstrated in figure 4A did not result in a corresponding 

decrease in nitrogen concentrations (fig. 4D). Nitrate is the 

dominant form of nitrogen in Big Spring Run (92.3 percent of 

total nitrogen), but it does not readily adsorb onto suspendedsediment particles like phosphorus does. The primary means 

of nitrogen removal are uptake by plants or denitrification and, 

over the timeframe of this study, neither of these processes 

seemed to be effective at producing a significant change in 

nitrate concentration (p-value = 0.1151; fig. 4D). As a result 

of legacy sediment removal, the plant community in the 

restoration area shifted from dominance by nonnative species 

preferring upland settings to native wetland species (Merritts 

and others, 2013). These species are more suited for nutrient 

uptake, thus nitrate concentrations in Big Spring Run may 

decline over time as the plant community matures.

Streamflow

 Streamflow during storms transports a large proportion 

of the sediment load; in Big Spring Run a single storm event 

can transport more than 25 percent of the annual sediment 

load. For the purposes of this report, a storm is defined as 

streamflow with an exceedance probability of 5 percent or less 

and a duration of at least 15 minutes. All storms were defined 

on the basis of streamflow at the downstream site in the 

prerestoration data. By using these criteria, storms that move 

relatively small amounts of sediment, but cumulatively shape 

channel morphology over time (Rosgen, 1996) are included 

along with large storms that occur infrequently but can be 

responsible for transporting large percentages (greater than 25 

percent) of the annual sediment load.

For the downstream site, any streamflow greater than 

7.84 ft3

/s (5-percent exceedance probability) lasting at least 

15 minutes was considered a storm. A total of 320 storms 

occurred over the study period, resulting in streamflows that 

ranged in magnitude from 7.95 ft3/s to 417 ft3/s, with durations 

from 15 minutes to more than 43 hours. Although streamflow 

magnitudes during storms varied greatly over the study period, 

the median streamflow was 17.5 ft3/s and the median duration 

was about 3 hours and 24 minutes (table 5). 

The effect of the restoration can be observed in photographs (fig. 5). In the restoration area, streambanks were pared 

back by excavation, allowing water that would otherwise be 

confined to the channel (fig. 5A) access to the floodplain. As 

water exits the channel and spreads out onto the floodplain 

(fig. 5B–D), velocity decreases along with the ability to sheer 

sediment particles and transport them downstream. Within a 

few hours of the peak streamflow, water recedes (fig. 5E,F) 

and eventually returns to the baseflow condition depicted 

in figure 5A. Although the floodplain of the restoration area 

temporarily stores stormwater, measurable attenuation of 

streamflow peaks was not observed downstream. Exceedance probabilities in the pre- and postrestoration periods at 

the downstream site were nearly identical (fig. 6), indicating 

any streamflow attenuation resulting from legacy sediment 

removal was not apparent in the streamflow record at the 

downstream site. Selected streamflow hydrographs upstream 

of restoration were also compared to hydrographs at the downstream site. Hydrograph shape was identical indicating no 

detectable attenuation of storm runoff, however, the timing of 

hydrograph rise and peak differed because of the upstream to 

downstream positions of the sites on the landscape. Attenuation of streamflow peaks may not have been observed because 

the area of restoration was small relative to the area draining 

to the downstream site; however, water velocities were likely 

lower in the restoration area, which provided for sediment 

removal from the water column. 

Turbidity

Increases and decreases in turbidity are strongly related 

to changes in streamflow in most non-point source-dominated 

watersheds, such as Big Spring Run. The turbidity-streamflow 

relation is affected by streamflow velocity; high streamflow velocities are needed to entrain, suspend, and transport 
Effects of Legacy Sediment Removal 13

0 20 40 60 80 100

Exceedance probability, in percent

1

10

100

Streamflow, in cubic feet per second

0.3

A

1

10

100

0.3

0 20 40 60 80 100

Exceedance probability, in percent

Streamflow, in cubic feet per second

B

Prerestoration

(October 1, 2008-

September 30, 2011)

Postrestoration

(October 1, 2011-

September 30, 2015)

EXPLANATION

Sample collected during

prerestoration period

Sample collected during

postrestoration period

Figure 3. Sample collection and streamflow conditions for downstream site 015765195 during the A, 

prerestoration period (water years 2009–11) and B, postrestoration period (water years 2012–15).
14 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

10

100

1,000

10,000

100,000

Suspended-sediment concentration, in milligrams per liter Unfiltered total phosphorous, in micrograms per liter

0.01

0.05

0.10

0.50

1.00

0.005

0.050

0.500

Filtered orthophosphorous, in micrograms per liter

p-value < 0.0001

A

170 26

p-value = 0.0036

B

35 73

p-value=0.4584

C

35 72

p-value=0.1151

D

35 73

1

5

10

Filtered nitrate plus nitrite, in milligrams per liter

Number of values

EXPLANATION 

75th percentile plus 1.5 times the interquartile range or largest value, whichever is smaller

75th percentile

Median

25th percentile

25th percentile minus 1.5 times the interquartile range, or lowest value, whichever is greater 

Outier that is 1–2 times less than 25th percentile 

Far outlier that is at least 2 times lower than the 25th percentile

Far outlier that is more than 2 times the 75th percentile

Outlier that is 1–2 times greater than the 75th percentile

30

x

x

o

o

Prerestoration

Postrestoration

Figure 4. Comparison of pre- and postrestoration nutrient and suspended-sediment concentrations in Big Spring Run, Lancaster 

County, Pennsylvania. Data for unfiltered total phosphorous and for filtered orthophosphorous were censored at 0.02 and 0.008 

micrograms per liter, respectively.
Effects of Legacy Sediment Removal 15

Streamflow, in cubic

feet per second

0

50

200150

100

Streamflow, in cubic

feet per second

0

50

200150

100

Streamflow, in cubic

feet per second

0

50

200150

100

03:00 06:00 09:00 12:00 15:00 18:00 21:00 24:00

Time on September 18, 2012

A. 09:00 1.7 cubic feet per second B. 16:30 35 cubic feet per second

B

A

C. 16:45 169 cubic feet per second D. 17:15 201 cubic feet per second

C

D

E. 18:00 93 cubic feet per second F. 19:15 39 cubic feet per second

E

F

All times are in Eastern Standard Time

StreamflowHydrograph position

EXPLANATION

, Inc., . Photographs are from a webcam operated by Telemonitor

on at the time of the picture is presented on 

, Pennsylvania, September 18, 2012 Time sequence for a storm at Big Spring Run, Lancaster County Figure 5.

approximately 150 yards upstream from downstream site 015765195, looking upstream and to the south-southwest. Hydrograph positithe right. All times are Eastern Standard Time.
16 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

Table 5. Streamflow statistics for storms at Big Spring Run near Mylin Corners, Pennsylvania, water years 2009 –15.

[For Big Spring Run near Mylin Corners, Pennsylvania (015765195), a storm is defined as streamflow exceeding 7.84 cubic feet per second with a duration of 

at least 15 minutes. Streamflow of 7.84 cubic feet per second has an exceedance probability of 5 percent. ft3/s, cubic feet per second; hrs:min:sec, 

hours minutes seconds]

Water year1/ 

Period of 

record

Number of 

storms

Median peak 

streamflow (ft3

/s)

Median duration 

(hrs:min:sec)

Date and time 

of storm 

with largest 

streamflow 

(hrs:min:sec)

Largest 

streamflow 

 (ft3

/s)

Date and time 

of storm with 

longest duration 

(hrs:min:sec)

Longest 

duration 

(hrs:min:sec)

2009 53 13.5 2:47:04 8/28/09 22:30 223 12/11/08 23:00 20:34:22

2010 41 18.5 3:49:27 6/3/10 20:30 289 10/17/09 8:15 38:46:58

2011 53 18.8 3:01:41 9/7/11 20:00 417 9/7/11 20:00 43:17:30

2012 62 11.3 1:49:19 9/18/12 16:15 201 12/7/11 22:30 18:02:10

2013 32 24.8 3:52:41 1/31/13 0:30 222 10/29/12 18:00 38:22:11

2014 40 20.4 5:20:14 10/11/13 8:37 261 4/30/14 13:30 38:25:11

2015 39 18.7 3:24:01 10/15/14 13:35 221 3/10/15 22:15 17:32:31

Period of record 320 17.5 3:23:53 9/7/11 20:00 417 9/7/11 20:00 43:17:30

1

Water year is defined as the 12-month period from October 1 through September 30 of the following year. 

in which it ends.

The water year is designated by the calendar year 

0 20 40 60 80 100

Exceedence probability, in percent

1

10

100 Streamflow, in cubic feet per second

7.84

5 percent

Prerestoration (October 1, 2008–

September 30, 2011)

Postrestoration (October 1, 2011–

September 30, 2015)

EXPLANATION

Figure 6. Exceedance probability of streamflow for site 

015765195, Big Spring Run, Lancaster County, Pennsylvania. For 

the purposes of this report, a storm is defined as streamflow with 

a probability of exceedance of 5 percent or less and a duration of 

at least 15 minutes.

sediment in the water column. Examining graphs of turbidity 

and streamflow over time can provide an improved understanding of in-stream processes affecting sediment. A typical 

turbidity-streamflow response, in this case for a storm that 

occurred from December 22 to December 23, 2011, at the 

downstream site (USGS 015765195) is shown in figure 7A. 

Peak turbidity may occur before or after storm peaks, 

depending on the sediment source and velocity of water acting 

on the stream bed and banks. This results in a time-shifted 

relation between turbidity and streamflow where equivalent instantaneous flows on the rising and falling limb of a 

storm hydrograph are characterized by dramatically different 

turbidity values (fig. 7B). This phenomenon is referred to as 

hysteresis and can influence the results of the daily suspendedsediment load derived from continuous measurements of 

turbidity, as shown for the same December 2011 storm at the 

downstream site (USGS 015765195) (fig. 7B). For a given 

streamflow of about 22 ft3/s on the rising limb of the hydrograph, the turbidity is approximately 600 FNU, whereas on 

the falling limb of the hydrograph for the same streamflow of 

22 ft3/s, the turbidity is approximately 200 FNU. 

The hysteresis shape and duration are a function of 

streamflow velocity (travel time) and the sediment sources 

in the basin. Analysis of the streamflow-turbidity shape can 

provide information on sediment sources in small watersheds 

(Oxley, 1974; Klein, 1984; Landers and Sturm, 2013). Sediment originating from the stream channel typically causes 

higher turbidity values as streamflow increases, and sediment originating from more distant basin sources may cause 

higher turbidity values as streamflow decreases because of 

the timing of the tributary inflows (Asselman, 1999). The 

hydrographs for storms producing flows greater than 7.84 ft3

/s 
Effects of Legacy Sediment Removal 17

0

10

20

30

40

50

60

70

Streamflow, in cubic feet per second

0

200

400

600

800

1,000

1,200

1,400

Turbidity, in formazin nephelometric units 

19:30 22:30 01:30 04:30 07:30 10:30 12:30

December 22, 2011 December 23, 2011

0 10 20 30 40 50 60 70

Streamflow, in cubic feet per second

0

200

400

600

800

1,000

1,200

1,400

Turbidity, in formazin nephelometric units 

A 

Rising limb 

Falling limb 

B 

Turbidity 

Streamflow

EXPLANATION

Peak turbidity 

Peak streamflow

EXPLANATION

Figure 7. Turbidity in relation to streamflow at site 015765195, Big Spring Run, Lancaster County, Pennsylvania, during a 

storm event from December 22 to 23, 2011.
18 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

(5-percent exceedance probability) at the downstream site 

(USGS 015765195) suggest that suspended sediment is 

predominately from the stream channel in the Big Spring 

Run watershed. Merritts and others (2013) have estimated 

that streambanks in the Big Spring Run study area supply 

30–65 percent of the overall load. 

Decreases in average turbidity observed in the postrestoration period likely are due to surface water being reconnected 

to the floodplain, resulting in increased storage of sediment in 

the restoration area and a reduction in sediments originating 

from within the restoration area.

Continuous measurements of turbidity were used to 

provide a continuous time series of suspended-sediment concentrations and loads in the pre- and postrestoration periods in 

the Big Spring Run watershed. Continuous turbidity measurements have been shown to provide reliable estimates of suspended-sediment concentration with a quantifiable uncertainty 

(Gray and others, 2000). A simple linear regression model 

relating turbidity to suspended-sediment concentration is often 

sufficient for reliable computations of suspended-sediment 

concentration (Rasmussen and others, 2009). A linear relation 

between turbidity and sediment concentration can be difficult 

because of site-specific interferences such as water clarity, 

presence of organics and biota, and sediment particle size. 

In the current study, regression models were used to predict 

missing values to create a more complete record of continuous suspended-sediment concentrations over the 7-year study 

period for each of the three sites (Langland, 2019b). 

Suspended Sediment

The model input data and regressions used to predict the continuous suspended-sediment record at each 

site in the pre- and postrestoration periods are presented in 

figure 8; additional regression diagnostics are presented in 

Langland (2019a). 

Streambanks erode primarily by (1) freeze-thaw, where 

the soils expand upon freezing and loosen upon thawing; 

(2) fluvial erosion, where streambank and bed sediments are 

entrained and eroded by water; and (3) mass wasting, where 

part of the streambank slumps into the stream (fig. 9). Sediment concentrations at the three sites in Big Spring Run were 

greatly affected by mass wasting especially during the prerestoration period (2009–11). When streambanks were excavated 

and pared back during restoration, mass wasting decreased 

and the restoration area changed from a sediment source to a 

sediment sink, an area where sediment settled from the water 

column and was stored. 

At the downstream site, median suspended-sediment 

concentration decreased from 556 mg/L before restoration 

to 74 mg/L after restoration (p-value < 0.0001; fig. 10). This 

change in sediment concentration is consistent with the large 

reduction in sediment loading that can be attributed to the restoration. The mean annual sediment load conveyed to the restoration area from the two upstream sites in the postrestoration 

period was 839 tons. More than 70 percent (597 tons) of this 

sediment load was removed as the stream traversed through 

the wetland environment and suspended sediment settled out 

of the water column; therefore, the mean annual suspendedsediment load downstream of the restoration was only 242 

tons (table 6). 

The restoration BMP was compared with other BMPs 

intended to reduce sediment in streams (fig. 10). Galeone and 

others (2006) compared suspended-sediment concentrations 

measured at two sites in a 1.42-mi2

 watershed, adjacent to Big 

Spring Run, where streambank fencing was installed along 

a 2-mi reach approximately 5–12 ft landward of the streambank. The intent of the fencing was to prohibit livestock from 

accessing the stream and to promote streambank stability. 

Samples for suspended-sediment concentration were collected 

before and after the fencing was installed. Although statistically significant reductions in suspended-sediment concentration were realized from the fencing, they were an order of 

magnitude less than the reductions observed in the current 

study. The median suspended-sediment concentration was 

reduced by 482 mg/L in the current study compared to only 

30–46 mg/L as a result of streambank fencing (fig. 10). 

Summary statistics for suspended-sediment loads for the 

three Big Spring Run sites on a daily, monthly, and annual 

basis are presented in table 6. The data used to compute the 

summary statistics are available in Langland (2019b). It 

should be noted the turbidity record that was missing (because 

data to fill the missing record were also missing from the sites 

used for predictions), could impact before-and-after implementation comparisons, especially at the west and east sites. 

However, the downstream record was much more complete 

and conclusions at the downstream site are well supported. 

Daily suspended-sediment loads at the downstream site varied 

greatly during the study (fig. 11), ranging from <0.005 ton 

on multiple days to 201 tons on January 25, 2010 (table 6). 

The largest proportion of annual sediment load was supplied 

during storms that occurred on September 7, 2011 (29.5 percent), January 31, 2013 (35.1 percent), and October 15, 2014 

(38.1 percent) (table 6). Median daily suspended-sediment 

load after restoration was about one-tenth of the load prior 

to restoration (0.892 ton compared to only 0.087 ton in the 

postrestoration period; fig. 11). These decreases were statistically significant (p-value <0.0001) for daily and monthly time 

steps (table 6). 

Implementing the restoration BMP greatly reduced the 

sediment load moving from the upstream sampling sites to 

the downstream sampling site. Prerestoration sediment loads 

increased by a mean of 106 percent between upstream sites 

and the downstream site, indicating sediment was added from 

the upstream sites and the unrestored reach. As part of the 

restoration process, sediment supply was greatly reduced or 

eliminated by mechanically removing streambanks to restore a 

natural stream and wetland complex. Postrestoration sediment 

loads decreased by a mean of 69.3 percent, indicating that 

sediment from the upstream area was trapped in the restoration area. Potential explanations for the observed reductions 
Effects of Legacy Sediment Removal 19

0

1

2

3

4

5

Log10 suspended-sediment

concentration, in milligrams per liter

0

1

2

3

4

5

Log10 suspended-sediment

concentration, in milligrams per liter

0

1

2

3

4

5

Log10 suspended-sediment

concentration, in milligrams per liter

0 1 2 3

Log10 turbidity, in formazin nephelometric units

0 1 2 3

Log10 turbidity, in formazin nephelometric units

USGS 01576516 (East) site prerestoration

logSSC_east= +0.521* logTurb_east+1.69

R2=0.288 

USGS 01576516 (East) site postrestoration

logSSC_east= +1.17* logTurb_east+0.253

R2=0.739 

USGS 015765185 (West) site prerestoration

logSSC_west= +0.555* logTurb_west+1.38

R2=0.348 

USGS 015765185 (West) site postrestoration

logSSC_west= +1.37* logTurb_west−0.157

R2=0.724 

USGS 015765195 (Downstream) site prerestoration

logSSC_ds= +0.859* logTurb_ds+0.694

R2=0.515 

USGS 015765195 (Downstream) site postrestoration

logSSC_ds= +1.1* logTurb_ds+0.0353

R2=0.729 

 

A B

C D

E F

Figure 8. Sediment concentration in relation to turbidity at three sites in Big Spring Run, Lancaster County, Pennsylvania. All date 

ranges are in water years. A, Site 01576516 (east), 2009–11; B, site 01576516 (east), 2012–15; C, site 015765185 (west), 2009–11; D, site 

015765185 (west), 2012–15; E, site 015765195 (downstream), 2009–11; and F, site 015765195 (downstream), 2012–15
20 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

Figure 9. Photograph showing example of mass wasting in the streambank below the downstream site in Big Spring Run 

near Mylin Corners, Pennsylvania. Photograph taken by U.S. Geological Survey on October 16, 2014. 

are (1) removal of streambanks and (2) restoration of a natural 

stream and wetland complex that trapped sediment supplied 

by upstream sources. 

The continuous suspended-sediment regression method 

of computing annual loads was compared to a commonly 

used load-calculation method. The method, Weighted Regressions on Time, Discharge, and Season (WRTDS; Hirsch and 

others, 2010) is currently used to compute annual loads in the 

Chesapeake Bay watershed. Loads from WRTDS were not 

available in the prerestoration period of the study but were 

available for comparison in the postrestoration period of the 

study (WY2012–WY2015). The loads computed by the continuous suspended-sediment regression method and WRTDS 

are similar (fig. 12), with little variation observed between the 

predicted loads of each method. Precise comparisons of statistical significance between the two methods were not quantified 

because there were no reliable measures of error associated 

with either method and there were only four comparisons possible (WY2012–WY2015). Longer-term comparisons (greater 

than 10 years) integrating measurement error should be made 

for more effective statistical comparison of these methods 

of load computation. The continuous suspended-sediment 

regression method used in this study effectively quantified 

the prerestoration to postrestoration suspended-sediment load 

reduction observed from implementation of the restoration 

BMP at the downstream site. 
Effects of Legacy Sediment Removal 21

USGS 015765195

(Current study downstream site)

USGS 01576529 USGS 01576527

(Sites from Galeone and others [2006])

100,000

100

10

10,000

1,000

1

0.1

Suspended-sediment concentration, in milligrams per liter

170 26 203 217 166 190

p-value < 0.0001 p-value < 0.0001 p-value=0.002

Number of values

EXPLANATION 

75th percentile plus 1.5 times the interquartile range or largest value, whichever is smaller

75th percentile

Median

25th percentile

25th percentile minus 1.5 times the interquartile range, or lowest value, whichever is greater 

Outier that is 1–2 times less than 25th percentile 

Far outlier that is at least 2 times lower than the 25th percentile

Far outlier that is more than 2 times the 75th percentile

Outlier that is 1–2 times greater than the 75th percentile

30

x

x

o

o

Prerestoration

Postrestoration

Figure 10. Comparison of suspended-sediment concentrations at site 015765195 (downstream), Big Spring Run, Lancaster 

County, Pennsylvania, to two sites in an adjacent watershed from Galeone and others (2006).
22 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15 Table 6. Summary of daily, monthly, and annual suspended-sediment loads at three sites in Big Spring Run, Lancaster County, Pennsylvania, water years 2009–15. [Max, maximum; Min, minimum; USGS, U.S. Geological Survey] Water year1 Daily suspended-sediment load (tons) Monthly suspended-sediment load (tons) Annual Ratio of max daily Ratio of max monthly suspended suspended- suspended- sediment sediment load sediment load to load to annual (tons) annual suspended- suspended- sediment sediment load load (percent) Max Median Mean Min Max Median Mean Min (percent) USGS site number 01576516 (East) 2009 25.5 0.58 1.25 0.005 67 26.4 29.6 2.73 325 7.85 20.7 2010 37.1 0.39 1.00 0.003 76 23.3 29.2 3.14 347 10.69 21.9 2011 36.0 0.60 1.64 0.003 82.9 33.3 37.4 1.05 377 9.55 22.0 2012 56.0 0.14 1.10 0.002 108 14.8 31.5 4.9 378 14.81 28.5 2013 44.1 0.041 0.58 0.0004 56 9.7 14.7 0.337 147 30.0 37.9 2014 46.5 0.060 0.61 0.0002 68 8.0 18.2 1.2 219 21.2 31.1 2015 43.6 0.028 0.38 0.001 62 2.0 11.0 0.28 133 32.78 46.4 Prerestoration 37.1 0.53 1.25 0.003 82.9 29.0 31.8 1.05 350 (mean) 9.4 (mean) 21.5 (mean) period Postrestoration 56.0 0.061 0.671 0.0002 108 8.4 19.1 0.278 219 (mean) 24.7 (mean) 36 (mean) period USGS site number 015765185 (West) 2009 31 0.19 1.45 0.00237 64 26 24 3.15 264 11.7 24.2 2010 35 0.33 1.86 0.0011 78 33 33 0.40 365 9.6 21.3 2011 42 0.26 2.62 0.0017 82 18 26 2.29 180 23.4 45.6 2012 55 0.142 1.57 0.001 103 16 28 0.014 331 16.6 31.3 2013 250 0.046 8.4 0.000014 423 25 97 0.008 967 25.9 43.8 2014 125 0.040 3.53 0.000004 159 60 65 0.304 774 16.1 20.5 2015 150 0.024 2.77 0.000004 151 2 34 0.79 413 36.3 36.6 Prerestoration 42 0.26 2.0 0.001 82 26 28 0.40 270 (mean) 14.9 (mean) 30.3 (mean) period Postrestoration 250.0 0.043 4.07 0.000004 423 20.5 55.8 0.008 620 (mean) 23.7 (mean) 33 (mean) period USGS site number 015765195 (Downstream) 2009 103 0.67 3.68 0.018 241 78 95 10.9 1,140 9.04 21.1 2010 201 1.50 7.5 0.005 376 280 201 4.24 2,210 9.10 17.0 2011 190 0.78 4.17 0.009 359 32.6 80 12.4 643 29.5 55.9 2012 43.3 0.138 1.09 0.002 95 13.8 23.3 0.10 279 15.5 34.1
Effects of Legacy Sediment Removal 23

Table 6. Summary of daily, monthly, and annual suspended-sediment loads at three sites in Big Spring Run, Lancaster County, Pennsylvania, water years 2009–15.–Continued

[Max, maximum; Min, minimum; USGS, U.S. Geological Survey] 

Water year1 Daily suspended-sediment load (tons) Monthly suspended-sediment load (tons) Annual Ratio of max daily Ratio of max monthly 

suspended suspended- suspended- sedisediment load sediment load to ment load to annual 

(tons) annual suspended- suspended- sediment 

sediment load load (percent)

Max Median Mean Min Max Median Mean Min (percent)

2013 89 0.042 1.10 0.00002 130 3.30 21.1 0.36 253 35.1 51.62014 42.7 0.111 0.74 0.003 48.9 17.1 19.3 1.29 232 18.4 21.1

2015 78 0.058 0.67 0.000005 80 3.86 17.0 0.50 204 38.1 39.4Prerestoration 201 0.892 5.26 0.005 376 48.8 129 4.24 1,331 (mean) 15.9 (mean) 31.3 (mean)

period

Postrestoration 89 0.087 0.88 0.000005 130 7.0 20.2 0.096 242 (mean) 26.8 (mean) 36.5 (mean)

period

1Water year is defined as the 12-month period from October 1 through September 30 of the following year. The water year is designated by the calendar year in which it ends.
24 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

0.001

0.01

0.1

1

10

100

1,000

Daily suspended-sediment load, in tons per day

October 10, 2008 July 1, 2009 April 1, 2010 December 30, 2010 September 30, 2011

October 1, 2011 September 30, 2012 September 30, 2013 September 30, 2014 September 30, 2015

0.001

0.01

0.1

10

100

1,000

Daily suspended-sediment load, in tons per day

1

Median=0.892 tons per day

A

Median=0.087 tons per day

B

Figure 11. Daily suspended-sediment loads at site 015765195 (downstream), Big Spring Run, Lancaster County, Pennsylvania. A, Water 

years 2009–11 (prerestoration period), and B, water years 2012–15 (postrestoration period).
Summary 25

Water year

2009 2010 2011 2012 2013 2014 2015

0.1

1

10

100

1,000

10,000

Suspended-sediment load, in tons

1,140

2,210

643

279 253 232 204

102

321

515

207

NA NA NA

WRTDS method

Continuous method (Current study)

102 Number of samples

EXPLANATION

Figure 12. A comparison of suspended-sediment loads in the 

postrestoration period (water years 2012–15) using the Weighted 

Regressions on Time, Discharge, and Season (WRTDS) method 

and the continuous method. NA, not applicable.

Summary

This report presents the results of a study of a restoration 

area within the Big Spring Run watershed, with a 1.68-mi2

drainage area near the town of Willow Street, approximately 

4 miles south and southeast of the city of Lancaster in Lancaster County, Pennsylvania. The study evaluated the effects 

of a restoration best management practice (BMP) that removes 

legacy sediment to restore natural aquatic resources within Big 

Spring Run. There were three USGS streamgages installed—

two upstream of the restoration area (referred to as the east 

and west sites for USGS 01576516 and USGS 015765185, 

respectively) and one downstream of the restoration area 

(referred to as the downstream site for USGS 015765195).

Samples were collected over a wide range of streamflows at the downstream site, providing good representation 

of nutrient and sediment concentrations during baseflow and 

storms in the pre- and postrestoration periods. As a result of 

implementing the restoration BMP, suspended-sediment concentrations in surface water at the downstream site decreased 

significantly; phosphorus that had adsorbed onto sediment 

particles was also removed from the water column (0.19 mg/L 

prerestoration period compared to 0.04 mg/L postrestoration 

period). There was no concurrent reduction in orthophosphate and nitrate, which are typically soluble in water and not 

adsorbed to sediment particles. There was also no concurrent 

decrease in total nitrogen in the postrestoration period when 

compared to the prerestoration period because 92.3 percent 

of the total nitrogen in the study area was present as soluble 

nitrate-nitrogen. Owing to nitrate’s solubility, it is unlikely 

to be affected by management practices that primarily affect 

groundwater and not the full range of surface-water samples 

analyzed in this study. 

All storms, at all sites, during the study period were 

defined on the basis of streamflow at the downstream site in 

the prerestoration data. A storm in Big Spring Run was defined 

as an event with a probability exceedance of 5 percent or less 

and a duration of at least 15 minutes, which corresponded 

to a streamflow value of 7.84 ft3

/s at the downstream site 

(USGS 015765195). Streamflow exceedance probabilities in 

pre- and postrestoration periods at the downstream site were 

nearly identical, indicating that streamflow attenuation resulting from the restoration was not apparent in the streamflow 

record at the downstream site.

During the study period, increases and decreases in 

turbidity were strongly related to changes in streamflow, as is 

true in most non-point source-dominated watersheds. Peak turbidity in Big Spring Run typically occurred before streamflow 

peaks. The hysteresis observed for storms at the downstream 

site (USGS 015765195) indicate that sediment in Big Spring 

Run is predominately from the stream channel. This finding 

supports previously published results that indicate streambanks are a major source of sediment in Big Spring Run. 

At the downstream site, median suspended-sediment 

concentration decreased from 556 mg/L in the prerestoration 

period to 74 mg/L in the postrestoration period. During the 

prerestoration period, suspended-sediment concentrations at 

the three sites in Big Spring Run were greatly affected by mass 

wasting. When streambanks were excavated and pared back 

during restoration, mass wasting decreased and the restoration 

area changed from a sediment source to a sediment sink, an 

area where sediment settled from the water column and was 

stored. Mean annual sediment load conveyed to the restoration 

area from the east and west sites, in the postrestoration period 

was 839 tons. This load was reduced between the east and 

west sites and the downstream sites by 597 tons, as indicated 

by the mean annual load at the downstream site in the same 

period of 242 tons. Single storms were found to account for 

a large proportion of the load throughout the study period. 

The largest single-storm contributions to the annual sediment 

loads were supplied during storms that occurred on September 7, 2011 (29.5 percent of the annual load), January 31, 

2013 (35.1 percent of the annual load), and October 15, 2014 

(38.1 percent of the annual load). 

Implementing the restoration BMP reduced the concentration of suspended sediment 10 times more than a 

streambank-fencing BMP described in a previous study in a 

small adjacent watershed in the Mill Creek drainage basin. 

In this study, median suspended-sediment concentration was 

reduced by 482 mg/L at the downstream site when compared 

to the prerestoration period. In contrast, the streambankfencing BMP reduced median suspended-sediment concentrations by 30 and 46 mg/L (site 01576527 and site 01576529, 

respectively) when compared to paired watersheds that did not 

have fences.
26 Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15

Implementing the restoration BMP greatly reduced the 

suspended-sediment load delivered to the site downstream of 

the restoration area. During the prerestoration period, suspended-sediment load increased by 106 percent as the stream 

traversed the unrestored area. In contrast, there was a decrease 

of 69.3 percent as the stream traversed the restored area in the 

postrestoration period. This finding supports the conclusion 

that the BMP restored the stream reach of Big Spring Run 

from a sediment source, driven by non-point sources and mass 

streambank wasting, to a sediment trap that reconnected the 

stream to a naturalized wetland in the floodplain. Suspendedsediment concentration, phosphorus concentration, and mean 

annual suspended-sediment load were all reduced after implementation of the BMP.

References Cited

American Society for Testing and Materials, 2006, D3977-97, 

Standard test methods for determining sediment concentration in water samples: ASTM International, Annual 

Book of Standards, Water and Environmental Technology, 

v. 11.02, 7 p.

Asselman, N.E.M., 1999, Suspended sediment dynamics in 

a large drainage basin: the River Rhine: Hydrological Processes v. 13, p. 1437–1450. 

Berg, T.M., Edmunds, W.E., Geyer, A.R., Glover, A.D., 

Hoskins, D.M., MacLachlan, D.B., Root, S.I., Sevon, W.D., 

and Socolow, A.A., comps., 1980, Geologic map of Pennsylvania: Pennsylvania Geological Survey, 4th ser., Map 1, 

scale 1:250,000, 3 sheets.

Custer, B.H., 1975, Soil survey of Lancaster County, Pennsylvania: U.S. Department of Agriculture, Soil Conservation 

Service, 152 p.

De Cicco, L.A., Hirsch, R.M., Lorenz, D., and Watkins, W.D., 

2018, dataRetrieval: U.S. Geological Survey code GitLab 

database, accessed October 2019 at https://code.usgs.gov/

water/dataRetrieval.

Federal Interagency Sedimentation Project, 2007, Collection and use of total suspended solids (TSS) data: Federal 

Interagency Sedimentation Project Technical Committee 

Memorandum 2007.01, 4 p., accessed October 2017 at 

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For more information about this report, contact:

Director, Pennsylvania Water Science Center

U.S. Geological Survey

215 Limekiln Road

New Cumberland, PA 17070

Publishing support provided by the Pembroke and West 

Trenton Publishing Service Centers
ISSN 2328-0328 (online)

http://doi.org/10.3133/sir20205031

Langland—Effects of Legacy Sediment Removal on Nutrients and Sediment in Big Spring Run, Lancaster County, Pennsylvania, 2009–15—SIR 2020–5031