The Efficacy of Constructed StreamminusWetland Complexes at Reducingthe Flux of Suspended Solids to Chesapeake BaySolange Filosodagger Sean M C SmithDagger Michael R Williamsdagger and Margaret A Palmerdaggersect

daggerUniversity of Maryland Center for Environmental Science Chesapeake Biological Laboratory Solomons Maryland 20688 UnitedStatesDaggerUniversity of Maine School of Earth and Climate Sciences Bryand Global Sciences Center Orono Maine 04469 United StatessectNational Socio-Environmental Synthesis Center (SESYNC) 1 Park Place Suite 300 Annapolis Maryland 21401 United States

S Supporting Information

ABSTRACT Studies documenting the capacity of restored streams to reducepollutant loads indicate that they are relatively ineffective when principal watershedstressors remain intact Novel restorations are being designed to increase the hydraulicconnectivity between stream channels and floodplains to enhance pollutant removaland their popularity has increased the need for measurements of potential loadreductions Herein we summarize input-output budgets of total suspended solids(TSS) in two Coastal Plain lowland valleys modified to create streamminuswetlandcomplexes located above the head-of-tide on the western shore of Chesapeake BayLoads entering (input) and exiting (output) the reconfigured valleys over three yearswere 103 plusmn 26 and 85 plusmn 21 tons respectively and 41 plusmn 10 and 46 plusmn 9 tonsrespectively In both cases changes in loads within the reconfigured valleys wereinsignificant relative to cumulative errors High variability of TSS retention among stormflow events suggests that the capacity ofthese systems to trap and retain solids and their sustainability depend on the magnitude of TSS loads originating upstreamdesign characteristics and the frequency and magnitude of large storms Constructed streamminuswetland complexes receivingrelatively high TSS loads may experience progressive physical and chemical changes that limit their sustainability

INTRODUCTION

Streams are considered sentinels and integrators of watershedimpacts because of their sensitivity to direct and indirectwatershed disturbances1minus4 Landscape alterations from humanactivities usually lead to the degradation of stream ecosystemsand the loss of ecosystem services5minus7 Therefore as more of theEarthrsquos surface is transformed from natural to anthropogenicland-cover states stream restoration initiatives are increasinglyimportant especially when based on an ecosystem servicesframework8

The specific mechanisms that lead to the degradation ofstreams and the loss of ecosystems services are unclear as theyvary according to landscape settings and types of stressors910

Yet it is well established that human actions at the landscapescale that disrupt processes controlling water and sedimentsupply to stream channels tend to deteriorate the physical habitatconditions ecological processes and ecosystem functions ofstreams11minus13 Accordingly practices that seek to restore waterand sediment regimes in streams are commonly prioritized bywatershed managers as potential methods to improve waterquality habitat biodiversity14 and the overall functioning of loticecosystems Stream restoration to improve water quality is nowcommon in the United States Australia Canada China JapanKorea15minus19 and particularly Europe due to the recent legislationreferred to as the ldquoWater Framework Directiverdquo20 In the USstream restoration is also increasingly used to mitigate impacts ofland use and cover changes on the water quality of degraded

coastal water bodies such as the Gulf of Mexico and SanFrancisco and Chesapeake baysChesapeake Bay (hereafter the Bay) has the highest land-to-

water ratio of any coastal water body in the world21 Hence theBay is particularly sensitive to the extensive land use and coverchanges that have occurred in the region since colonization22

The degradation of thousands of miles of headwater streamsfrom watershed transformations has induced large fluxes offluvial sediment to subestuarine tributaries propelling a four- to5-fold increase in sedimentation rates observed in the Bay inrecent years23minus26 Higher sediment loads have been linked toincreased turbidity in the Bay over the last quarter century27 anddecreased water clarity is considered one of the most seriousimpediments to Bay health and restoration efforts28 Thereforestream restoration focused on reducing sediment export fromwaterways to the estuary is part of an evolving strategy to meettotal maximum daily load (TMDL) requirements to restore theBay2930 The Chesapeake Bay TMDL for total suspended solids(TSS) is based mostly on mineral sediment but also includesbiologically derived materials that can affect ecological processesin both nontidal and tidal waters31

Received January 8 2015Revised June 24 2015Accepted June 26 2015

Article

pubsacsorgest

copy XXXX American Chemical Society A DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

Approaches commonly used to reduce sediment export fromwaterways to the Bay include traditional in-stream interventionsintended to modify hydraulic conditions stabilize streamchannels and prevent bank erosion and sediment exportdownstream However improving water quality and reducingsediment transport using these restoration approaches hasproven especially difficult832 Watershed managers and thestream restoration community in the Chesapeake Bay regionhave responded to the problem by implementing novel streamcorridor restoration designs including the conversion of erodedchannels to streamminuswetland complexes that enhance a channelrsquoscapacity to trap and retain suspended materials being deliveredfrom upstream sources while reducing erosion33

Nontidal Bay tributaries within the Coastal Plain physio-graphic province comprise a substantial portion of the watersheddrainage network These fluvial systems are particularlyvulnerable to erosion due to limited structural control frombedrock combined with a surficial lithology dominated by highlyerodible materials3435 Low-gradient channels within widevalleys at the interface of the tidal zone are sedimentldquobottlenecksrdquo that have the potential to regulate the transportof sediment to tidal estuaries36 The position of the lowlandCoastal Plain channels adjacent to the Bayrsquos tidal headwatersmay therefore help mitigate the turbidity problem in estuarinewaters relatively quickly if they reduce the transport efficiency ofsuspended solids supplied from the catchmentLowland Coastal Plain valley channels targeted for the

implementation of streamminuswetland complexes may augmentstorage and reduce the export of suspended solids to tidaltributaries of Chesapeake Bay These novel restoration projectsintended to reduce pollutant loads to the Bay are costly and theirTSS reduction capabilities relatively unknown thereby calling forquantitative assessments of their performance and sustain-ability3738 Completing such assessments is difficult because theyrequire simultaneous stream discharge and TSS data obtained onmultiple dates in every season over several years that span a rangeof hydrological conditions39 Thus load estimates are rarely doneto evaluate water quality changes associated with streamrestoration practices For example that we are aware there arecurrently no documented studies estimating changes in TSSloads resulting from a reconfigured valley reach in the Mid-Atlantic Coastal PlainIn this paper we monitored lowland valley Coastal Plain

streams of Chesapeake Bay to provide a quantitative assessmentof changes in TSS loads within reconfigured stream reachesimmediately upstream of the tidal boundary Monitoring datawere used to determine if suspended solids are reduced throughtrapping and retention within the reconfigured valleys Morespecifically our study goals were to (a) quantify the magnitude ofTSS retention in these modified stream corridors (b) evaluatevariability in loading patterns and retention rates and identifyfactors that explain the variability and (c) determine how loadsentering and exiting the reconfigured valleys compare with loadsfrom other streams in the region that have not been deliberatelyreconfigured into streamminuswetland complexes We discuss theimplications of our findings with respect to the potential forstream corridor restoration to help meet nonpoint sourcepollution goals the impacts on nutrient dynamics and primaryproduction and expected future land-use and climate-inducedchanges in precipitation patterns expected for the region

MATERIALS AND METHODS

Study Watersheds Our study was conducted withinMarylandrsquos Coastal Plain (Figure S1 Supporting Information)in nontidal lowland valley reaches containing second- and third-order streams draining the western shore of Chesapeake BayStream channels in the region have modest 5minus10 longitudinalgradients in their headwater reaches but transition to nearly flatgradients near the tidal boundary The higher order lowlandstream valleys have side-slopes that exceed 30 in some locationsand commonly contain sediment deposits derived from manyforms of disturbance since European colonization The particularstudy valleys also have sediment deposits from damming orponding of the stream channel in recent decadesLowland valleys with degraded stream channels in Maryland

are increasingly targeted for reconfiguration to streamminuswetlandcomplexes833 to mimic habitat conditions associated with standsof Atlantic white cedar (Chamaecyparis thyoides) swampsHowever funding for these projects is usually provided withthe intent of reducing pollutant loads to meet Chesapeake BayTMDL targets2940

The streams we investigated herein called Howardrsquos Branch(HBR) andWilelinor Tributary (WIL) are located within valleys10 or more times as wide as their active channels (Figure S2Supporting Information) WIL drains a developed watershed ofabout 78 ha (Table S1 Supporting Information) with a mix ofcommercial industrial high-density residential and trans-portation land covers directly connected to the channel bydrainage pipes HBR drains about 98 ha of mostly low-densityresidential transportation and forest areas (Table S1 Support-ing Information) but the impervious areas are also directlyconnected to the stream channel through stormwater drainagepipes The valley reaches studied at HBR and WIL werereconfigured in 2002 and 2004 respectively through massgrading and placement of structural controls to guide water flowsThe reconfiguration design objectives were channel stabilizationwetland creation stream-floodplain reconnection and creation oftopographic conditions conducive to Atlantic white cedarpropagation41 (See Supporting Information for project designschematics)Prior to reconfiguration the HBR valley reach had been

dammed for the purpose of water supply in the 1960s and 1970sThe dam had breached exposing a layer of fine sediment that hadaccumulated at the bottom of the pond that was capped with alayer of sand as part of the project design TheWIL project valleywas previously impounded by two in-stream ponds that capturedsurface runoff from an adjacent highway and upstreamdevelopment The pond dams were reconfigured to create twobypass ponds connected to the mainstem channel at their upperends Neither of the ponds has an outlet structure exchangingflows with the mainstem channel through the connection at theirupper ends or by overtopping their sand berms

Study Design and Sampling Strategy Both restorationprojects were constructed several years prior to our monitoringwork therefore we assessed their effectiveness at trapping andretaining TSS transported from upstream by using a massbalance approach where inputs upstream of the reconfiguredstream reaches were compared with outputs downstream Todetermine loads upstream and downstream we installedsampling stations at the top and bottom of each restored streamreach to measure streamflow and TSS concentrationsWe assessed the performance of the reconfigured reaches over

a period of three water years fromOctober 1 2008 to September

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

B

30 2011 when water samples were collected once every 2 weeksduring baseflow conditions and at least once per season duringstormflows Baseflow occurs when there is no direct precipitationrunoff contribution to stream discharge Hence baseflowsamples were collected two or more days after the end of arainfall runoff event Stormflow samples were collected overentire hydrographs (ie during the rising and falling limbs of astorm event) Stormflow is defined herein as any period whenstreamflow was above the average baseflow levelBaseflow and stormflow samples were collected using 1 L acid-

washed polyethylene bottles Baseflow samples were collectedmanually using a protocol for wadable streams adapted from theUSGS42 whereas stormflow samples were collected usingautomated samplers (ISCO model 6712) The ISCO samplerswere configured to collect up to 24 samples per event at 5minus15min intervalsThe automated samplers were initiated by actuators when

stream stage was near 2 cm above baseflow levels and samplingcontinued until a return to baseflow levels was achieved Forlong-duration events full ISCO bottles were replaced sosampling could continue throughout the entire storm hydro-graph During warm months the ISCO samplers were filled withice to limit biological activity in the water samplesOnce retrieved from the field the water samples were

transported to the laboratory in a dark cooler and stored at 4degCprior to being processed All water samples were filtered in thelab within 24 h and concentrations of TSS were determinedusing the EPA Gravimetry Method 1602 and Standard Method208 E (httpnaslcblumcesedu) the Method Detection Limit(MDL) was 24 mg Lminus1 TSS and the quantitation limit was set at00005 mg Lminus1 TSSThe method to determine TSS concentrations involved

filtering a known volume of water through preweighed 47 mmglass-fiber filters (GFF Whatman 07 μm nominal pore size) inincrements of 100 mL using vacuum pressure no greater than 10in Hg When the filter was saturated it was folded in half storedin a labeled glassine envelope and frozen Prior to analysis thefilters were dried at 105 degC and then placed in a desiccator Oncesamples reached room temperature they were individuallyweighed Total suspended solids concentrations (mg Lminus1) werecalculated as the weight of the filter after collection of the sampledivided by the volume of water filteredTo determine stream discharge water depth (stage height)

was recorded continuously at 5minus15 min intervals at the up- anddownstream sampling stations of each stream using pressuresensors with data loggers The sensors were placed inside a 2 in(1 in = 254mm) inner diameter PVC stilling well installed in thechannel The well had holes drilled near the sensor to increaseresponse time and reduce possible stage artifacts associated withhigher stream velocities The water pressure sensors were pairedwith a barometric pressure sensor that recorded data at 5 minintervals to correct for atmospheric pressure effects on the stagemeasurementsInstantaneous streamflow was measured near the monitoring

stations immediately after collection of baseflow samples andalso during a wide range of stage depths during storm eventsWater depth and streamflow velocity were determined using ameasuring rod and an electromagnetic flow meter (MarshMcBirney Flo-Mate 2000) respectivelyAt the HBR reach and upstream of WIL instantaneous stream

discharge was determined using the cross-sectional method43 AtHBR discharge was measured in the open channel while at WILdischarge was measured in a 1-m concrete culvert using a

velocity-area method44 The downstream station of WIL had acompound weir with a 120deg V-notch capable of conveying up to034 m3 sminus1 and a 244 m rectangle section above it capable ofconveying flows up to 067 m3 sminus1 flows 12 in above thecompound structure could convey 298 m3 sminus1 In the last year ofthe study instantaneous flow downstream of HBR was measuredusing a 9 in Parshall flume

Data Computation The instantaneous discharge and stagedata collected at each sampling station were used to developstage-discharge relationships43 by plotting instantaneous dis-charge against log-transformed stage data recorded in continuoustime intervals to produce a linear function Power functions arecommonly used to build rating curves based on the asymptotictrends as stage goes to zero Logarithms of the power functionproduce a linear relation that can be used to convertinstantaneous readings of stream stage into discharge valuesOnce the continuously recorded stage data were converted intodischarge time series we calculated annual discharge and totaldischarge for individual storm events for each hydrometricstation by adding discharge values for each 5minus15 min intervalover the desired time period Storm events were determined bythe period when discharge was above the average baseflow valueLoads were calculated for individual time intervals as the

product of TSS concentrations and discharge For the timeintervals when flow was at or below the maximum level measuredduring baseflow we calculated loads using flow-weighted meanconcentrations (FWMC) (eq 1) of water samples collectedduring baseflow (ie during the biweekly samplings) as

= sum ΣC Q QFWMC ( )i i i (1)

where Ci is the concentration (mg Lminus1) Qi is the discharge (Lsminus1) for the interval i when a water sample was collected and thedenominator is the sum of observed discharges (sumQi)For the intervals when discharge values were above the

maximum observed during baseflow we calculated loads using alogminuslog regression curve from the relation between dischargeand TSS loads measured in samples collected during stormflowIn order to reduce bias and account for the hysteresis betweensediment loads and discharge commonly observed over theduration of a single runoff event we used separate discharge-loadregression curves for the rising and falling limbs of thehydrographs45

After TSS load time-series were estimated for each samplingstation we determined loads (kg yrminus1) over the three-yearperiod separately for each water year (OctoberminusSeptember) andeach storm event sampled (kg eventminus1) The difference (Δ)between loads entering (INPUT) and exiting (OUTPUT) astudy reach was used to determine net sediment storage or export(eq 2) Net storage was assumed to have occurred when the loadbelow the reconfigured reach (OUTPUT) was significantlylower than that above it (INPUT) In such instances Δ LOADwas negative

Δ = minusLOAD OUTPUT INPUT (2)

Uncertainty Analysis Uncertainties inherent to waterquality data collected in small watersheds can be substantial46

These uncertainties typically derive from common proceduresused for water quality data collection such as dischargemeasurements and sample collection46 We used the DataUncertainty Estimation Tool for Hydrology and Water Quality(DUET-HWQ) model to determine the cumulative probableuncertainties associated with TSS load estimates for each study

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

C

site47 The foundational mathematical component is the root-mean-square error propagation method48

RESULTS

Potential TSS Load Reductions (Storage vs Export) Atotal of 132 samples were collected at HBR during baseflowconditions and 960 individual samples during stormflow (gt17storm events at both stations) over the 3-year sampling periodAt WIL 110 baseflow and 860 stormflow samples (gt14 stormevents at both stations) were collected around the same periodThe total TSS loads entering (input) HBR andWIL over the 3-yrperiod was 103 plusmn 26 tons and 41 plusmn 10 tons respectively Theamount of TSS exported from the HBR reach downstream(output) was about 15 lower than the load upstream (input)while the export from WIL increased (Figure 1) Howeverdifferences were not significant for either reach because theywere within the range of cumulative errors from load estimatesFor HBR uncertainties in load estimates were on the order of

28 and 25 for inputs and outputs respectively ForWIL theseuncertainties were 26 for inputs and 20 for outputs

Variability in TSS Loads and Retention Rates Over thestudy period TSS loads in the reconfigured reaches wereoverwhelmingly dominated by stormflow inputs (Figure S6Supporting Information) whereas baseflow loads contributedless than 15 of the total loads entering the reaches There wassubstantial variability in the amounts of TSS entering (input) andexiting (output) each reconfigured reach during the differentstormflow events sampled (Figure 2) At HBR TSS inputsduring individual storm events ranged between 02 and 33 kghrminus1 whereas outputs ranged between 01 and 40 kg hrminus1 AtWIL inputs and outputs during storm events ranged between 02and 31 kg hrminus1 and 04 and 83 kg hrminus1 respectively The largestloads were observed during stormflow events in the late summerand early fall During these events TSS output was always higherthan input

Figure 1Total load of TSS entering (IN) and exiting (OUT) the reconfigured stream reach at Howardrsquos Branch (HBR) andWilelinor Tributary (WIL)during the study period (3 years) The uncertainty values associated with load estimates are indicated by error bars

Figure 2 Comparison of TSS loads upstream (IN) and downstream (OUT) of the reconfigured reaches at Howardrsquos Branch (HBR) and WilelinorTributary (WIL) during individual storm events sampled over the study period The stormflow sampling events are grouped by season regardless of thesampling year

Figure 3 Balance of TSS from input and output along the reconfigured reaches at Howardrsquos Branch (HBR) and Wilelinor Tributary (WIL) for stormevents sampled versus storm size The black circles indicate net export of TSS during a storm event and the red circles represent net retention The blackarrow indicates the point where all stormflow sampling events resulted in TSS export rather than retention

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

D

As TSS inputs and outputs varied among storm events themass balances per storm event varied as well from approximately07minus7 kg hrminus1 for HBR and 09minus5 kg hrminus1 for WIL (Figure 3)The magnitude of loads during storm events was clearlyassociated with storm size In both streams only storms smallerthan 1 in resulted in TSS net retention The larger stormsresulted in the net export of TSS and themagnitude of the exportwas significantly related to storm sizeThe relative contribution of stormflow to annual discharge

upstream of the HBR and WIL reconfigured reaches was about40 and 80 respectively (data not shown) Therefore whileannual discharge at HBR had a larger proportion of baseflow thanstormflow that of WIL was the oppositeAt HBR concentrations of TSS in baseflow decreased from

upstream to downstream from about 9 mg Lminus1 to 75 mg Lminus1Concentrations in stormflow (FWMC) also decreased fromabout 120 mg Lminus1 upstream to 60 mg Lminus1 downstream At WILaverage baseflow concentrations decreased along the reconfig-ured reach from about 6mg Lminus1 to 4mg Lminus1 but increased duringstormflow events from 26 mg Lminus1 upstream to 53 mg Lminus1

downstreamLoad Comparison We recognize that the lack of

prereconfiguration data prevents us from quantifying theeffectiveness of these projects at reducing preconfigurationloads Nevertheless inputminusoutput load reduction estimates fromthis study indicate that our stream reaches did not export lowerquantities of TSS compared to those observed in several nearbyCoastal Plain streams (Figure 4) The comparison indicates that

although the valley reconfigurations may reduce loads they donot drive the TSS export rate below the range of contemporarystream valleys in the region that have not been reconfigured Onthe other hand the reconfigurations likely helped stabilize TSSexcess loads from the breached dam at HBR and from an erodingpond at WIL prior to project implementation

DISCUSSIONStream restoration represents a growing public investment fornonpoint source pollution mitigation and is viewed as a potentialoption for reducing sediment loads to aquatic ecosystems385051

Consequently there is a demand for scientifically defensibleassessments of how these systems perform and whether they areeffective at reducing pollutant loads transported downstreamNot only are quantitative assessments important to verify that

water quality goals and objectives are achieved and sustained butalso to provide feedback to restoration practitioners and waterresources managers about the appropriateness of designs andimplementation plansIn this study we show that the two reconfigured lowland

Coastal Plain stream valleys transformed into streamminuswetlandcomplexes had TSS loads similar to those of other degradedstreams nearby in the study region Moreover loads exported outof the reaches (output) did not differ significantly from loadsentering the reaches (inputs) so any changes in TSS loadsobserved during the study period were too small in relation to themagnitude of cumulative errors of load estimates to besignificant However while these results may make it difficultto conclusively evaluate the performance of these reconfiguredstreams at retaining TSS transported from upstream in thewatershed and reducing loads downstream they provide valuableinformationMost importantly our results indicate that any TSS retention

that occurred in these greatly modified reaches is relatively smallin comparison to reductions needed to considerably lessen TSSloadings into tidal waters They also show that accuratelyquantifying TSS retention for stream restoration projects can bedifficult because of the cumulative errors commonly associatedwith load estimates in small order streams46 Monitoringprograms designed to estimate pollutant load reductions inrestored streams must therefore use methods to minimizecumulative errors including flow-rated structures (such as theweir and flume used at WIL and HBR respectively) andautomated concentration sampling equipment that is capable ofmeasuring over the entire duration of runoff events46 At bestuncertainties in runoff and water quality measurements inmonitoring studies should be carefully estimated4752 in order toguarantee that load reductions associated with stream restorationprojects are scientifically defensible47

At HBR low banks and a broad flat floodplain adjacent to thestream channel upstream of the reconfigured reach complicatedthe measurement of high flows and created uncertainties in loadestimates However not accounting for these potentialuncertainties our calculations indicate that this system retainedmore TSS than it exported (although the amount retainedannually was only about 17 of the upstream load) By contrastload calculations for WIL indicate that the channel eitherexported or retained TSS entering the reconfigured reach whilenot accounting for potential measurement uncertainties indicatesthat the channel exported more TSS than it retained for theduration of the study periodWe calculated uncertainties in our load estimates because of

the potential for underperformance in relation to expectation andcost of pollutant reduction efficiency associated with streamrestoration and the importance of considering this in decisionmaking However it is important to recognize that cumulativeerrors result in a worst-case scenario and that the actual errors arelikely considerable smaller due the tendency for positive andnegative errors to cancel one another particularly whenaggregating multimetric and multiyear data sets53 As analternative and for comparison using the more traditionalstatistic of standard deviation in place of cumulative errorsconsiderably constrains the uncertainty in our load estimates(ie 61 and 142 tons for HBR and WIL respectively)Substituting the cumulative errors in Figure 1 with these standarddeviation values (not shown) indicates that the input-outputcomparison for HBR is marginally significant whereas that ofWIL remains insignificant (p gt 005)

Figure 4 Total suspended solids (TSS) loads (denoted by ) calculatedat the upstream and downstream ends of the WIL and HBR valley sitesafter project construction and suspended sediment loads from severalnearby locations49 The TSS load for Dividing Creek was estimated fromunpublished data (2012minus2013) Error bars show 50 error relative tothe trend line

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

E

An analysis of TSS loads during individual stormflow eventsrevealed that the capacity of these reconfigured stream valleys totrap and retain TSS can vary considerably This variabilitydepends in part on the season and size of the storm event In thereconfigured reaches storms that were 1 in or smaller in sizeresulted in both the net retention and export of TSS Howeverwhen storms were larger than 1 in no net retention wasobserved among the storm events sampled suggesting that largerstorms usually result in the net export of TSS An increase inloads during the larger storms was more pronounced atWIL thanat HBRDespite the moderate number of storms sampled for

stormflow in our study they included a wide range of sizesrepresenting the distribution of rain events common in theregion For example our study included two tropical storms anda hurricane which tend to occur in the summer and beginning offall in the region Therefore the importance of storm size as afactor influencing TSS retention in the reconfigured reaches isnot an artifact of our sample sizeOther factors controlling estimated retention of TSS in these

reaches include the relative importance of stormflow versusbaseflow in annual discharge and to a lesser extent TSSconcentrations in stormflow and baseflow and whether or notthey increased or decreased downstream of the reconfiguredreaches For example at HBR baseflow accounted for about 60of the annual discharge in the reconfigured reach whereasFWMC in baseflow were slightly lower downstream thanupstream (probably because of TSS retention during smallerstorms) By contrast at WIL annual discharge was dominated bystormflow while the FWMC in stormflow practically doubledfrom upstream to downstream of the reconfigured reach As aresult TSS loads downstream of the reach increased substantiallyduring storm events especially those gt1-inWe expected WIL to have a better capacity to accumulate

sediment for longer periods of time than HBR because the largerand deeper ponds likely create a more steady system for TSSretention However impounding nutrient-rich stormwater inlarge ponds can affect nutrient and decomposition dynam-ics54minus57 and enhance primary production For example nutrientscan be transformed from dissolved inorganic into organic formsnot only changing ecosystem metabolism5859 but also theamount of particulate material in suspension Most of thismaterial would be transported downstream during large stormevents increasing TSS and organic matter loads to tidal waters Ifthe organic material produced within these ponds is more labilethan the natural material transported in streams from thewatershed oxygen consumption in water downstream mayincrease55 thereby impacting ecological processes in the BayRates of organic matter and nutrient processing can be used as

functional indicators for assessing stream ecosystem health58

Therefore even if including large ponds in stream restorationshelp retain nutrients in organic matter and reduce loadstransported downstream changes in organic matter and nutrientprocessing in stream ecosystems can cause a shift in ecosystemfunctioning59 and possibly the loss of ecosystem servicesFurthermore long-term impoundment of nutrient-rich stream-water in ponds can cause anoxia in bottom waters and enhancehyporheic denitrification60 although the effective zone ofsignificant denitrification in streams often differs from the sizeof the hyporheic zone61 Thus increasing whole-streamdenitrification can only be achieved if a higher proportion ofstream discharge passes through reactive areas of the hyporheiczone61 and in large deep ponds this is unlikely to happen

The contact of anoxic water with sediment can also enhancethe release of orthophosphate to the water column and increaseprimary productivity Furthermore anoxia in the bottom layersof ponds and lakes can lead to the accumulation of ammonium byboth organic matter mineralization and limited nitrification Ifhigher loads of orthophosphate and ammonium are exportedinto the Bay they can aggravate eutrophication especiallybecause ammonium is the preferred form of N utilized byphytoplankton62

The reconfigured reach at HBR has a series of shallow poolsand wetland areas that may augment TSS retention during stormrunoff events especially when they are small However whilethese pools and wetland areas may create conditions under whichsediment retention can occur the long-term efficiency ofmodified channels may ultimately be determined by naturaland anthropogenic factors controlling yields of suspended solidsin the headwaters63 or above the reconfigured reach64

Loads of TSS entering the reconfigured HBR reach wererelatively high in comparison to loads at WIL The catchmentdrained by HBR has fairly steep slopes and easily erodible soilmaterials in the headwater region Therefore processesoccurring in the catchment such as severe erosion at the top ofheadwater channels connected to stormwater drainage pipescommon in the study area8 probably contributed sediment to thereconfigured reachIn addition flocculates generated by iron (Fe) oxidizing

bacteria (FOB) observed at HBR during the study period are apotential source of TSS within the restored reaches Ironoxidizing bacteria flourish in environments with steady fluxes ofreduced Fe (II) from groundwater seeps and O2 supplied fromoxygenated water6566 such as at the interface of stream andwetland features that compose wetlandminusstream complexesWhile the natural formation of flocculate and mats from FOB areubiquitous in the study region these are prone to resuspensionduring stormflow events and can considerably increase TSSconcentrations in reconfigured streams Therefore whilestreamminuswetland complexes may reduce the transport ofsuspended sediments to downstream waters they mayconcomitantly enhance the export of other types of suspendedsolid materials such as from FOB flocculateThe most important drivers regulating the net export or

retention of TSS in both stream reaches are rain size andintensity Accordingly climate change that results in an increasein the frequency of large storms may ultimately determine theirsustainability and effectiveness at reducing TSS loads todownstream waters For example if the frequency of large andintense storm events in the Chesapeake Bay region increases withclimate change67 the effectiveness of these engineered systems attrapping and retaining TSS will likely decrease in the futureTherefore increased stormwater runoff in a wetter climate inaddition to other factors that influence TSS dynamics inreconfigured streams such as the supply of TSS upstream ofthe targeted reach FOB and primary production fromimpounded water should be carefully evaluated in streamrestoration projects in order to bolster their potential resiliencyand long-term sustainabilityIn conclusion the modification of lowland valleys into

streamminuswetland complexes is currently perceived by manywatershed managers as a viable and effective re-engineeringtechnique that can be used to augment the retention of TSStransported from upstream runoff and erosion in developedcatchments While our data provide some evidence that at leastone of these systems can reduce TSS loads to downstream

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

F

waters the capacity of these systems to store suspended solids islimited It is however possible that the reconfigured streams areexporting less TSS than they were prerestoration if sedimenterosion from within the channel or TSS inputs to the channelwere significantly higher than they are today We believe that thisis unlikely since comparisons with other nearby streams indicatethat both the upstream and downstream stations at our studysites were within the range of sediment loading variability in theregion However the breached dams that existed at each of ourstudy locations prior to reconfiguration may have createdunusual conditions and produced locally elevated sources ofsuspended solidsFurther estimating TSS loads in streams from concentration

measurements can underestimate the transport of mineralsuspended sediment USGS data collected from a Coastal Plainstream in the region shows concentrations of TSS to beapproximately 44minus81 of suspended sediment concentrationsin flows ranging from 10minus10 000 Ls as shown using datacollected from a nearby Coastal Plain USGS gaging station atWestern Branch68 Large sized sand and gravels transported asbedload were also not sampled but may account for up to 20 ofthe total load in small streams69 As a result more coarse mineralsediment may have been transported into the valley reaches thanmeasured using TSS sample analysis and the coarse sedimentsizes would have been more susceptible to trapping in the lowgradient systems and require higher flow rates to beremobilized70 However increasing the residence time ofsediment loads within the restored reaches may decrease thecapacity of these systems to store sediment and compromise thelongevity of projects if sources from the channel upstream orfrom the catchment are not effectively managedRegardless of how these reconfigured reaches perform the

ecological implications of modifying lowland channels to addressproblems of excess sediment and nutrients originating fromupstream locations in the watershed are complex (8) and mayresult in undesirable outcomes Therefore other measures suchas the implementation of stormwater best management practices(BMPs) in the watershed should be part of the solution forreducing pollutant loads to Chesapeake Bay either alone or intandem with stream restoration projects since such practices willlikely improve the effectiveness and long-term sustainability ofstream restorations

ASSOCIATED CONTENT

S Supporting InformationSection S1 Figures S1minusS6 Table S1 The SupportingInformation is available free of charge on the ACS Publicationswebsite at DOI 101021acsest5b00063

AUTHOR INFORMATION

Corresponding AuthorPhone 410-326-7348 fax 410-326-7264 e-mail filosoumcesedu

Author ContributionsThe manuscript was written through contributions of all authorsAll authors have given approval to the final version of themanuscript

NotesThe authors declare no competing financial interest

ACKNOWLEDGMENTS

We thank Eric Dunman Kristin Politano Rosemary Ury and JenLi for lab and field assistance the Maryland Department ofNatural Resources for field assistance and Alynne Bayard for GISanalysis This work was supported by grants from the MarylandDepartment of the Environment Anne Arundel County (GrantNo 8 0 6 2 D406 9 48 ) a n d NOAA (G r a n t No NA10OAR4310221)

ABBREVIATIONS

FOB iron (Fe) oxidizing bacteriaFWMC flow-weighted mean concentrationsHBR Howardrsquos BranchMDL method detection limitTMDL total maximum daily loadTSS total suspended solidsWIL Wilelinor Tributary

REFERENCES(1) Allan J D Landscapes and riverscapes the influence of land use onstream ecosystems Annu Rev Ecol Syst 2004 35 257minus284(2) Lowe W H Likens G E Moving headwater streams to the headof the class BioScience 2005 55 (3) 196minus197(3) Paul M J Meyer J L Streams in the urban landscape Annu RevEcol Syst 2001 32 333minus365(4)Williamson C E DoddsW Kratz T K Palmer M A Lakes andstreams as sentinels of environmental change in terrestrial andatmospheric processes Frontiers in Ecology and the Environment 20086 (5) 247minus254(5) Grimm N B Sheibley R W Crenshaw C L Dahm C NRoach W J Zeglin L H N retention and transformation in urbanstreams Journal of the North American Benthological Society 2005 24626minus642(6) Meyer J L Paul M J Taulbee W K Stream ecosystem functionin urbanizing landscapes Journal of the North American BenthologicalSociety 2005 24 (3) 602minus612(7) Sweeney B W Bott T L Jackson J K Kaplan L A NewboldJ D Standley L J Horwitz R J Riparian deforestation streamnarrowing and loss of stream ecosystem services Proc Natl Acad Sci US A 2004 101 (39) 14132minus14137(8) Palmer M A Filoso S Fanelli R M From ecosystems toecosystem services stream restoration as ecological engineeringEcological Engineering 2014 65 62minus70(9) Walsh C J Roy A H Feminella J W Cottingham P DGroffman P M Morgan R P The urban stream syndrome currentknowledge and the search for a cure Journal of the North AmericanBenthological Society 2005 24 (3) 706minus723(10) Wenger S J Roy A H Jackson C R Bernhardt E S CarterT L Filoso S Gibson C A Hession W C Kaushal S S Marti EMeyer J L Palmer M A Paul M J Purcell A H Ramirez ARosemond A D Schofield K A Sudduth E B Walsh C J Twenty-six key research questions in urban stream ecology an assessment of thestate of the science Journal of the North American Benthological Society2009 28 (4) 1080minus1098(11) Doyle M W Harbor J M Rich C F Spacie A Examining theeffects of urbanization on streams using indicators of geomorphicstability Physical Geography 2000 21 (2) 155minus181(12) Poff N L Zimmerman J K Ecological responses to altered flowregimes a literature review to inform the science and management ofenvironmental flows Freshwater Biol 2010 55 (1) 194minus205(13) Vietz G Stewardson M Walsh C Fletcher T Another reasonurban streams are stuffed geomorphic history challenges andopportunities In Proceedings of the 6th Australian Stream ManagementConference Managing for Extremes 6minus8 Grove J R Rutherford IDEds River Basin Management Society Canberra Australia 2012 pp1minus7

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

G

(14) FISRWG Stream Corridor Restoration Principles Processes andPractices GPO Item No 0120-A SuDocs No A 5762EN3PT653Federal Interagency Stream RestorationWorking Group 1998 ISBN 0-934213minus59-3(15) Amirault H Stream restoration in Canada In Proceedings of theStream Restoration Conference NC State University WilmingtonOctober 6 2012(16) Brooks S S Lake P S River restoration in Victoria Australiachange is in the wind and none too soon Restoration Ecology 2007 15(3) 584minus591(17) del TanagoM G de Jalon D G Roman M River restoration inSpain theoretical and practical approach in the context of the EuropeanWater Framework Directive Environ Manage 2012 50 (1) 123minus139(18) Morandi B Piegay H Lamouroux N Vaudor L How issuccess or failure in river restoration projects evaluated feedback fromFrench restoration projects J Environ Manage 2014 137 178minus188(19) Lu Y Fu B Feng X Zeng Y Liu Y Chang R Wu B Apolicy-driven large scale ecological restoration quantifying ecosystemservices changes in the Loess Plateau of China PLoS One 2012 7 (2)e31782(20) Haase P Hering D Jahnig S C Lorenz A W SundermannA The impact of hydromorphological restoration on river ecologicalstatus a comparison of fish benthic invertebrates and macrophytesHydrobiologia 2013 704 (1) 475minus488(21) Smith S Chesapeake Bay In Encyclopedia of Water ScienceTrimble S Ed Taylor and Francis Reference Group LLC New York2006(22) CBP Bay history Chesapeake Bay Program website httpwwwchesapeakebaynethistory (accessed September 2014)(23) Brakebill J W Ator S W Schwarz G E Sources of Suspended-Sediment Flux in Streams of the Chesapeake BayWatershed A RegionalApplication of the SPARROWModel J Am Water Resour Assoc 201046 (4) 757minus776(24) Brush G S Patterns of recent sediment accumulation inChesapeake Bay (VirginiaMaryland USA) tributaries Chem Geol1984 44 (1) 227minus242(25) Colman S M Bratton J F Anthropogenically induced changesin sediment and biogenic silica fluxes in Chesapeake Bay Geology 200331 (1) 71minus74(26) Pasternack G B Brush G S Hilgartner W B Impact ofhistoric land-use change on sediment delivery to a Chesapeake Bay sub-estuarine delta Earth Surf Processes Landforms 2001 26 (4) 409minus427(27)Williams M R Filoso S Longstaff B J Dennison W C Long-term trends of water quality and biotic metrics in Chesapeake Bay 1986to 2008 Estuaries Coasts 2010 33 1279minus1299(28) Tango P J Batiuk R A Deriving Chesapeake BayWater QualityStandards J Am Water Resour Assoc 2013 49 (5) 1007minus1024(29) Schueler T Stack B Recommendations of the Expert Panel toDefine Removal Rates for Individual Stream Restoration Project Preparedby the Chesapeake Stormwater Center and Center for WatershedProtection for the Urban Stormwater Work Group Chesapeake BayProgram 2013 pp 1minus131(30) USEPA US Environmental Protection Agency on behalf of theChesapeake Bay Program 2013 Chesapeake Bay Program websitehttpwwwchesapeakebaynetdocumentscbp_rtc_2013pdf(31) Gray J R Glysson G D Turcios L M Schwarz G EComparability of suspended sediment concentration and totalsuspended solids data In US Geological Survey Water ResourcesInvestigations Report 2000 p 4191(32) Selvakumar A OConnor T P Struck S D Role of streamrestoration on improving benthic macroinvertebrates and in-streamwater quality in an urban watershed case study J Environ Eng 2010136 (1) 127minus139(33) Brown K Urban stream restoration practices an initial assessmentThe Center for Watershed Protection Ellicott City MD 2000(34) Reger J Cleaves E T Physiographic Map of Maryland MarylandGeological Survey Baltimore MD 2008

(35) Smith S Gutierrez L Gagnon A Maryland Streams minus Take aCloser Look Watershed Services Maryland Department of NaturalResources Annapolis MD 2009(36) Phillips J D Slattery M C Sediment storage sea level andsediment delivery to the ocean by coastal plain rivers Progress in PhysicalGeography 2006 30 (4) 513minus530(37) Boomer K BWeller D E Jordan T E Empirical models basedon the universal soil loss equation fail to predict sediment dischargesfromChesapeake Bay catchments J Environ Qual 2008 37 (1) 79minus89(38) Smith S M C Belmont P Wilcock P Closing the gap betweenwatershed modeling sediment budgeting and stream restoration InStream Restoration in Dynamic Fluvial Systems Scientific ApproachesAnalyses and Tools Geophyical Monograph 194 Simon A Bennett SJCastro J M Eds American Geophysical Union Washington DC2010(39) Filoso S Palmer M A Assessing stream restorationeffectiveness at reducing nitrogen export to downstream watersEcological Applications 2011 21 (6) 1989minus2006(40) Shenk G W Linker L C Development and application of the2010 Chesapeake Bay watershed total maximum daily load model J AmWater Resour Assoc 2013 49 (5) 1042minus1056(41) Laderman A D The Ecology of the Atlantic White Cedar WetlandsA Community Profile US Fish and Wildlife Service Report 85(721)1989(42) Edwards T K Glysson G D Field Methods for Measurement ofFluvial Sediment Techniques of Water-Resources Investigations Book 3Chapter C2 US Geological Survey Reston VA 1999(43) Rantz S EMeasurement and Computation of Streamflow Volume1 Measurement of Stage and Discharge Volume 2 Computation ofDischarge US Geological Survey Water-Supply Paper 1982 p 2175(44) US Department of the Interior Bureau of Reclamation WaterResources Research Laboratory Water Measurement Manual Wash-ington DC 2001(45) Sedimentation Engineering Vanoni V Ed Prepared by the TaskCommittee for the Preparation of the Manual on Sedimentation of theSedimentation Committee of the Hydraulics Division AmericanSociety of Civil Engineers 1975(46) Harmel R D Cooper R J Slade R M Haney R L Arnold JG Cumulative uncertainty in measured streamflow and water qualitydata for small watersheds Transactions-American Society of AgriculturalEngineers 2006 49 (3) 689(47) Harmel R D Smith D R King K W Slade R M Estimatingstorm discharge and water quality data uncertainty A software tool formonitoring and modeling applications Environmental Modelling ampSoftware 2009 24 (7) 832minus842(48) Topping J Errors of Observation and Their Treatment 4th edChapman and Hall London UK 1972(49) Marcus W A Kearney M S Upland and coastal sedimentsources in a Chesapeake Bay estuary Annals of the Association ofAmerican Geographers 1991 81 (3) 408minus424(50) Bernhardt E S Palmer M Allan J D Alexander G BarnasK Brooks S Sudduth E Synthesizing U S river restoration effortsScience (Washington DC U S) 2005 308 (5722) 636minus637(51) Kenney M A Wilcock P R Hobbs B F Flores N EMartiacutenez D C Is Urban Stream Restoration Worth It J Am WaterResour Assoc 2012 48 603minus615(52) Jordan T E Pierce J W Correll D L Flux of particulate matterin the tidal marshes and subtidal shallows of the Rhode River estuaryEstuaries 1986 9 (4) 310minus319(53) Williams M R Fisher T R Eshleman K N Boynton W CKemp M W Cerco C F An integrated modeling system formanagement of the Patuxent River basin in the mid-Atlantic region ofthe USA Int J Remote Sensing 2006 27 3705minus3726(54) Johnston C A Beaver pond effects on carbon storage in soilsGeoderma 2014 213 371minus378(55) Naiman R J Johnston C A Kelley J C Alteration of NorthAmerican streams by beaver BioScience 1988 38 (11) 753minus762

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

H

(56) Pinay G Clement J C Naiman R J Basic principles andecological consequences of changing water regimes on nitrogen cyclingin fluvial systems Environ Manage 2002 30 (4) 481minus491(57)Maynard J J Dahlgren R A OrsquoGeen A T Autochthonous andAllochthonous Carbon Cycling in a Eutrophic Flow-Through WetlandWetlands 2014 34 (2) 285minus296(58) Young R G Matthaei C D Townsend C R Organic matterbreakdown and ecosystem metabolism functional indicators forassessing river ecosystem health Journal of the North AmericanBenthological Society 2008 27 (3) 605minus625(59) Marcarelli A M Baxter C V Mineau M M Hall R O JrQuantity and quality unifying food web and ecosystem perspectives onthe role of resource subsidies in freshwaters Ecology 2011 92 (6)1215minus1225(60) Seitzinger S Harrison J A Bohlke J K Bouwman A FLowrance R Peterson B Drecht G V Denitrification acrosslandscapes and waterscapes a synthesis Ecological Applications 200616 (6) 2064minus2090(61) Harvey J W Bohlke J K Voytek M A Scott D Tobias C RHyporheic zone denitrification Controls on effective reaction depthand contribution to whole-streammass balanceWater Resour Res 201349 (10) 6298minus6316(62) Carpenter E J Dunham S Nitrogenous nutrient uptakeprimary production and species composition of phytoplankton in theCarmans River estuary Long Island New York Limnol Oceanogr 198530 (3) 513minus526(63) Houser J N Mulholland P J Maloney K O Uplanddisturbance affects headwater stream nutrients and suspended sedi-ments during baseflow and stormflow J Environ Qual 2006 35 (1)352minus365(64) A Summary Report of Sediment Processes in Chesapeake Bay andWatershed Langland M J Cronin T M Eds US Department of theInterior US Geological Survey 2003(65) Prestegaard K L Gilbert L Phemister K Effects of concretechannels on stream biogeochemistry Maryland Coastal Plain In AGUSpring Meeting Abstracts 2005 Vol 1 p 02(66) Emerson D Fleming E J McBeth J M Iron-oxidizing bacteriaan environmental and genomic perspective Annu Rev Microbiol 201064 561minus583(67) Najjar R G Pyke C R Adams M B Breitburg D HershnerC Kemp M Wood R Potential climate-change impacts on theChesapeake Bay Estuarine Coastal Shelf Sci 2010 86 (1) 1minus20(68) Gray J R Glysson G D Turcios L M Schwarz G EComparability of suspended sediment concentration and totalsuspended solids data In USGS Water Resources Investigations Report2000 p 4191(69) Yorke T H Herb W J Effects of Urbanization on Stream Flowand Sediment Transport in the Rock Creek and Anacostia River BasinsMontgomery County Maryland 1962 74 USGS Professional Paper 10031978(70) Wilcock P Pitlick J Cui Y Sediment Transport PrimerEstimating Bed-Material Transport in Gravel-Bed Rivers Gen Tech RepRMRS-GTR-226 Fort Collins CO US Department of AgricultureForest Service Rocky Mountain Research Station 2009

Environmental Science amp Technology Article

DOI 101021acsest5b00063Environ Sci Technol XXXX XXX XXXminusXXX

I