sampling techniques for suspended sediment

SAMPLING TECHNIQUES SAMPLING TECHNIQUES FORFOR

SUSPENDED SEDIMENTSUSPENDED SEDIMENTIntroduction to Sediment SamplingIntroduction to Sediment Sampling

USGS Technical training in Support of Native USGS Technical training in Support of Native American Relations (TESNAR) 2013American Relations (TESNAR) 2013

Siletz, Coquille, Umatilla, and Cowlitz TribesSiletz, Coquille, Umatilla, and Cowlitz Tribes

Siletz, OR May 20-23, 2013Siletz, OR May 20-23, 2013

SAMPLING TECHNIQUESSAMPLING TECHNIQUES

Why a suspended-sediment sampler?Why a suspended-sediment sampler?

– Standardization of instrumentation among Standardization of instrumentation among investigatorsinvestigators

– Tool for obtaining a Tool for obtaining a representative samplerepresentative sample

http://www.flickr.com/photos/cougars/3805314887/

The The Colorado Colorado

River River SamplerSampler

Used until Used until the mid-the mid-1940’s1940’s

SAMPLING TECHNIQUESSAMPLING TECHNIQUESStandardizationStandardization

Jaukowsky Suspended-Sediment Sampler (FISP, 1940, p. 131)

Deploying the JaukowskySuspended-Sediment Sampler from a boat

in the Yellow River

near Zhengzhou, ChinaMay 17, 2002

(FISP, 1940, p. 131)

Deploying the Jaukowsky Suspended-Sediment Sampler (FISP, 1940, p. 131)

in the Yellow River near Zhengzhou, ChinaZhang L. dumping sample


Standardized instrumentsStandardized instruments

– Isokinetic sample collectionIsokinetic sample collection

– Velocity- or discharge-weighted samplesVelocity- or discharge-weighted samples


Representative sampleRepresentative sample

– Site selection -- characteristic of reach?Site selection -- characteristic of reach?

– Temporal variabilityTemporal variability

– Spatial variabilitySpatial variability

– Sampling frequencySampling frequency

Streamflow ConstrictionsStreamflow Constrictions


Site selectionSite selection

– Uniform flow in x-sectoinUniform flow in x-sectoin

– Well-mixed flowWell-mixed flow

– Ability to sample range of flows, most importantly Ability to sample range of flows, most importantly medium-and-high flowsmedium-and-high flows

– Availability of historical dataAvailability of historical data


Temporal variabilityTemporal variability– Sediment transport variability over timeSediment transport variability over time

Event hydrographEvent hydrograph

Seasonal hydrographSeasonal hydrograph

Annual hydrographAnnual hydrograph


Spatial variabilitySpatial variability– Site specificSite specific

Variability over the width of the channel cross sectionVariability over the width of the channel cross section Variability in each sampled verticalVariability in each sampled vertical

– Basin characteristicBasin characteristic Higher versus lower elevation sitesHigher versus lower elevation sites Northern versus southern exposures Northern versus southern exposures


Sampling frequencySampling frequency

– Generally dictated by the study approach and Generally dictated by the study approach and level of fundinglevel of funding

– Less critical to collection of a discrete Less critical to collection of a discrete representative sample than site selection, and representative sample than site selection, and temporal and spatial variabilitytemporal and spatial variability


Sample collection methodsSample collection methods

– Depth-integrated samplingDepth-integrated sampling– Point-integrated samplingPoint-integrated sampling– Point samplingPoint sampling– Grab or dip samplingGrab or dip sampling– Pumped samples *Pumped samples *– Single-stage samples *Single-stage samples *

*will be covered in separate lecture*will be covered in separate lecture


Depth-integration techniquesDepth-integration techniques

– Equal-width increment (EWI) methodEqual-width increment (EWI) method

– Equal-discharge increment (EDI) methodEqual-discharge increment (EDI) method

– Single-vertical sample (Box sample)Single-vertical sample (Box sample)

Max depth

9 (ft) 15 (ft) 35 (ft) 72 (ft) 110 (ft) 180 (ft) 220

Vel. ft/sec

1.5 1,2,3,4,7,8,13,14,15 2,3,5,7,8,13,14,15 13,14,15 13,14,15 13,14 13,14

1.7 1,2,3,4,5,7,8,9,13,14,15 2,3,5,7,8,9,13,14,15 13,14,15 13,14,15 13,14 13,14

2 1,2,3,4,5,6,7,8,9,10,11,13,14,15 2,3,5,6,7,8,9,10,11,13,14,15 6,10,11,13,14,15 10,11,13,14,15 10,11,13,14 13,14

3 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 2,3,5,6,7,8,9,10,11,12,13,14,15 6,10,11,12,13,14,15 10,11,12,13,14,15 10,11,12,13,14 12,13,14 12

5 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 2,3,5,6,7,8,9,10,11,12,13,14,15 6,10,11,12,13,14,15 10,11,12,13,14,15 10,11,12,13,14 12,13,14 12

5.3 1,3,4,5,6,7,8,9,10,11,12,13,14,15 1,3,5,6,7,8,9,10,11,12,13,14,15 6,10,11,12,13,14,15 10,11,12,13,14,15 10,11,12,13,14 12,13,14 12

5.9 1,3,4,5,6,7,8,9,10,11,12,13,14 1,3,5,6,7,8,9,10,11,12,13,14 6,10,11,12,13,14 10,11,12,13,14 10,11,12,13,14 12,13,14 12

6 1,3,4,5,6,7,9,10,11,12,13,14 1,3,5,6,7,9,10,11,12,13,14 6,10,11,12,13,14 10,11,12,13,14 10,11,12,13,14 12,13,14 12

6.6 1,3,4,5,9,10,12,13,14 1,3,5,9,10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 12,13,14 12

6.7 1,4,5,9,10,12,13,14 5,9,10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 12,13,14 12

7.4 1,4,5,10,12,13,14 5,10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 12,13,14 12

7.6 1,4,10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 12,13,14 12

8.9 1,10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 12,13,14 12

10 10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 10,12,13,14 12,13,14 12

12.5 10,12,14 10,12,14 10,12,14 10,12,14 10,12,14 12,14 12

15 12,14 12,14 12,14 12,14 12,14 12,14 12

Key for Previous ChartKey for Previous Chart

1) US DH-48 2) US DH-59 3) US DH-76 4) US DH-81 5) US DH-95 6) US DH-2 7) US D-74 8) US D-74AL 9) US D-95 10) US D-9611) US D-96A1 12) US D-9913) US P-61A1 14) US P-6315) US P-72


Equal-width increment (EWI) methodEqual-width increment (EWI) method– Cross section divided into (~8-20) equal-width Cross section divided into (~8-20) equal-width

incrementsincrements– Sampling transit rate for all sample verticals Sampling transit rate for all sample verticals

determined at the deepest/fastest verticaldetermined at the deepest/fastest vertical– Collect velocity-weighted sub-samples from the Collect velocity-weighted sub-samples from the

mid-point vertical in each width incrementmid-point vertical in each width increment– Composite all sub-samples for analysisComposite all sub-samples for analysis

Transit Rate Ratios for Transit Rate Ratios for Nozzle/Bottle CombinationsNozzle/Bottle Combinations


Equal-discharge increment (EDI) methodEqual-discharge increment (EDI) method– Stream discharge divided into (4-9) equal Stream discharge divided into (4-9) equal

increments of dischargeincrements of discharge– Collect velocity- and discharge-weighted Collect velocity- and discharge-weighted

samples from the centroid vertical of each samples from the centroid vertical of each discharge incrementdischarge increment

– Vary the transit rate among verticals to obtain Vary the transit rate among verticals to obtain equal sample volumesequal sample volumes

– Analyze samples individually or compositedAnalyze samples individually or composited

EDI CentroidsEDI Centroids

Why the different number of Why the different number of verticalsverticals

Why sometimes 5 verticalsWhy sometimes 5 verticals Why sometimes 20 verticalsWhy sometimes 20 verticals Assumption madeAssumption made

– Sample collected at the center of the centroid Sample collected at the center of the centroid represents the mean concentration for that represents the mean concentration for that centroidcentroid

– If, not, must increase number of verticalsIf, not, must increase number of verticals


Single-vertical sampleSingle-vertical sample– Use EDI method to determine sample vertical locationUse EDI method to determine sample vertical location– Sample vertical should be at the point in the cross Sample vertical should be at the point in the cross

section where the mean sediment concentration occurs section where the mean sediment concentration occurs over the largest range in stageover the largest range in stage

– Use the slowest transit rate possible without overfilling Use the slowest transit rate possible without overfilling the sample bottlethe sample bottle

– Duplicate samples are typically collected Duplicate samples are typically collected


Point-integration techniquePoint-integration technique– Necessary in depths >15 feet (total sampler traverse Necessary in depths >15 feet (total sampler traverse

>30 feet)>30 feet)– A point-integrating sampler is necessaryA point-integrating sampler is necessary– Used in conjunction with EWI or EDI methodUsed in conjunction with EWI or EDI method– Transit rates determined by EWI or EDI methodTransit rates determined by EWI or EDI method– Descending traverse matched by ascending traverseDescending traverse matched by ascending traverse– Single-vertical sub-samples composited for analysisSingle-vertical sub-samples composited for analysis


Point samplingPoint sampling– Use a point-integrating samplerUse a point-integrating sampler– Samples represent discrete points in the sampled cross Samples represent discrete points in the sampled cross

section and/or verticalssection and/or verticals– Samples may be velocity-weighted over an interval Samples may be velocity-weighted over an interval

equal to the fill time for the nozzle/bottle combinationequal to the fill time for the nozzle/bottle combination– Samples may be instantaneous snap shots of sediment Samples may be instantaneous snap shots of sediment

transport at a point without consideration for velocitytransport at a point without consideration for velocity


Grab or dip samplingGrab or dip sampling– Flow conditions or other unusual circumstances Flow conditions or other unusual circumstances

generally render standard samplers unusable generally render standard samplers unusable – Sediment is well mixed spaciallySediment is well mixed spacially– Samples are not integratedSamples are not integrated– Samples are seldom representative Samples are seldom representative

Grab or Dip SamplingGrab or Dip Sampling

Technique Points to RememberTechnique Points to Remember• Site selection- characteristic of reach, uniform Site selection- characteristic of reach, uniform

flow, well mixed, sample full range of flows, flow, well mixed, sample full range of flows, H/L elev, N/S exposure, any historical data H/L elev, N/S exposure, any historical data

• Temporal variability- event, seasonal, annualTemporal variability- event, seasonal, annual• Variations in X-sec and w/i sampling vertical, Variations in X-sec and w/i sampling vertical,

sediment sizes (coarse,sand,silt,clay) will varysediment sizes (coarse,sand,silt,clay) will vary• How frequent sample- depends on objectivesHow frequent sample- depends on objectives• EWIEWI- equal width & transit rate, volume not - equal width & transit rate, volume not

equal, first set transit rate at thalwegequal, first set transit rate at thalweg• EDIEDI- volume equal, width and transit rate not - volume equal, width and transit rate not

equal; need Q meas, equal; need Q meas, divide by 10,30,50,70,90 %divide by 10,30,50,70,90 %

A Good ReferenceA Good Reference

Field Methods for the Measurement Field Methods for the Measurement of Fluvial Sedimentof Fluvial Sediment

http://pubs.usgs.gov/twri/twri3-c2/http://pubs.usgs.gov/twri/twri3-c2/

sampling techniques for suspended sediment

Documents

sediment sampler fisp

yellow river

discrete representative

sample range of flows

sampling techniqueswhy

dip samplingpumped samples

singlestage samples

lower elevation sitesnorthern