SEDIMENT DATA- COLLECTION TECHNIQUES

SEDIMENT DATA-COLLECTION TECHNIQUESSW1091TCCASTLE ROCK AND VANCOUVER,WASHINGTONSediment Records DataOrganizationLarry Freemanlfreeman@usgs.gov

DATA ORGANIZATION FOR ADAILY SEDIMENT RECORDSTARTS IN THE FIELD

TechnicianField Note

Observer Sampling Instructions.• Frequency ofsampling.• Bottle labeling.• Field Office contactinformation.• Bottle fill range.

Observer Sample Log Sheet.

GET YOUR SAMPLES TO THELAB AS SOON AS POSSIBLE• AVOIDS PROBLEMS WITH SAMPLESCAUSED BY:– FREEZING– EVAPORATION– BIOLOGICAL GROWTH

MEANWHILE, BACK AT THEOFFICE………

GATHER TOGETHER ALL FIELD NOTES(TECH AND OBSERVER) AND CHECKAGAINST LAB RESULTS.• ACCOUNT FOR ALL TECHNICIANAND OBSERVER SAMPLES.• LOOK FOR INFORMATIONDISCREPANCIES BETWEEN FIELDNOTES AND LAB RESULTS,I.E., DATE/TIME, TECH/OBS,EWI/EDI/BOX.

LAB DATA REVIEW• LOOK FOR UNEXPECTED andUNEXPLAINABLE DIFFERENCES BETWEENSAMPLE SETS.– Do the concentration results compare well?– Do the size analysis results compare well?• SCAN THE LAB RESULTS FOR "OUTLIERS"TO ADJACENT SAMPLE VALUES ANDEXPECTED CONCENTRATION TREND.

SLEDS sample report.

SURFACE WATER DISCHARGERECORD MUST BE FINALIZED.• SURFACE WATER RECORD NEEDS TOHAVE BEEN REVIEWED ANDAPPROVED FOR PUBLICATION ANDRECORD SHOULD BE FLAGGED AS“FINAL”.• OTHERWISE YOU COULD BEWASTING TIME!!

FOLLOW A RECORDCOMPUTATION CHECKLIST.• THERE ARE MANY STEPS,• BUT THE FOLLOWING ARE THEPRINCIPAL STEPS

Example ofa SedimentRecordsChecklist

TABULATE SAMPLE CONCENTRATION DATA

EVALUATE THE LAB DATA

MORE STEPS• DETERMINE CROSS-SECTIONCOEFFICIENTS– An involved topic of it’s own (See John Gray).

PLOT SAMPLES ON TIME-SERIESSTAGE OR DISCHARGE RECORD• Manually, using plotting package, or using USGS computational software.

DEVELOP TRANSPORT CURVES.• Plotsampleconcentrationvs. waterdischargeonlog/logpaper.

TRANSPORT CURVE• Draw a best fitline or linesthat balance thesamples.• Line may havemultiplesegments.

Example Transport Curve Set.• Label samplepoints with date orseason.• Often there aremultiplerelationships.• It is very easy toapply curvesincorrectly.

DEVELOP TEMPORAL CONCENTRATIONCURVES.

LOOK TO THE PAST FOR HELP• LOOK AT RECORDS FOR PREVIOUS YEARS.– How were storm peaks estimated?– What is the typical slope of sedigraph for the rising and fallinglimbs?– How much variation in samples? Is it within normal limits for thesite?– What is the expected variation in loads from season to season, orfor different types of runoff events?– Were coefficients previously used? If so, what were they and havethey changed?• REFER TO LAST YEAR’S STATION ANALYSIS.– Any special calculations needed?– Other considerations?

COMPUTE DAILY VALUESOF CONCENTRATION ANDSEDIMENT DISCHARGE.• There are a variety of methods:– By manually subdividing (good luck!)– Spreadsheets (be careful of these).–*GCLAS (USGS approvedsoftware).

EVALUATE DAILY VALUES– PLOT DAILY SEDIMENT LOAD ANDWATER DISCHARGE, OR– CONCENTRATION AND WATERDISCHARGE AND COMPARE WITHPREVIOUS YEARS.• See the next few slides.

Plot mean Daily Concentration mg/Lvs. Water Discharge cfs

COMPARE SEDIMENT and WATERHYDROGRAPH

STILL MORE STEPS• COMPARE WITH UPSTREAM ORDOWNSTREAM SITES.– Can differences in loads and concentrations beexplained?• WRITE STATION ANALYSIS.

Comparison with station in the same basin.

STATION ANAYLSIS– DESCRIBE THE SAMPLING PROGRAM– PROVIDE A SAMPLE DATA SUMMARY.• WHAT TYPE OF SAMPLES AND HOW MANY.• FLOW RANGE SAMPLED BY TECHNICIAN ANDOBSERVER OR POINT SAMPLER.– DESCRIBE THE SEDIMENT DISCHARGEMEASUREMENTS THAT WERE MADE.– DISCUSS APPLICATION OF CROSS-SECTIONCOEFFICIENTS.

MORE ABOUT THE STATIONANALYSIS• DESCRIBE HOW THE RECORD WAS COMPUTED, i.e.WHAT SOFTWARE WAS USED.– DISCUSS SAMPLES THAT WERE NOT USED.– DISCUSS ANY ESTIMATED PERIODS.– DISCUSS ANY SPECIAL METHODS USED DURINGRECORD COMPUTATION OR DURING FIELD SAMPLING.• SUMMARIZE PARTICLE SIZE ANALYSES.• DISCUSS BED MATERIAL SAMPLING.• DISCUSS BEDLOAD MEASUREMENTS ANDCOMPUTATIONS.• REMARK ON RECORD QUALITY.• INDICATE WHO PROCESSED THE RECORD.

ANY QUESTIONS??