StreamStats Web Application - Illinois Water Conference - · PDF filevalues used in the last...
Transcript of StreamStats Web Application - Illinois Water Conference - · PDF filevalues used in the last...
StreamStats Web StreamStats Web ApplicationApplication
streamstats.usgs.govstreamstats.usgs.govAudrey Ishii, P.E.
Illinois Water Science Center
Overview—Streamflow Statistics
• What—Estimate of streamflow under some condition, such as the 100-year flood flow, flow durations, etc.
• Used in engineering design flows for bridges, culverts, mapping floodplains, setting water allocations, determining allowable waste discharges.
• How Computed—At stream gages--statistical analysis of historic flows, the flood-frequency or flow duration curveUngaged sites: Regression equations relating the characteristics of the curve to basin characteristics.
Q100 = a(TDA)b(MCS)c(PermAvg)d(Rf)
Selected discharge gages with more than 25 years of record for analysis.
Streamflow gaging stations are not distributed evenly.The density impacts the quality of regional analyses.
Percentage changes in the 100-year peak flow estimate between 1987 and 2004
1Max. = 35Avg. = 6
Max. = 50Avg. = 27
Max. = 29Avg. = 4
Max. = 81Avg. = 9
Max. = 24Avg. = 7
Max. = 95Avg. = 15
Max. = - 2Avg. = - 8
Traditional Methods for Measuring Basin Characteristics
• Very labor intensive and costly• Not completely reproducible• Error-prone• Often not documented well in reports• Users need source materials and expertise• Some BC not easily reproduced by GIS methods
GIS Methods for Basin Characteristics
• Several custom software packages developed, GIS Weasel, BasinSoft, BASINS, WMS, mostly developed for watershed modeling, often ESRI.
• Needed GIS datasets not always readily available • No documented national standard methods• Several methods used for some characteristics• Users need source data and expertise• Often not documented well in reports• Some measurements are scale-dependent
StreamStats GIS computations
• Create hydro networks of rivers and streams
• Process DEM and stream network for watershed analysis
• Delineate drainage basins and measure basin characteristics
• Represent channel shape using three-dimensional models
• Connect geospatial features to time series measurements recorded at gaging sites
• Runs within ESRI Arc 8/9 software• Public domain utilities developed
jointly by U. Texas at Austin and ESRI
StreamStats Web Application
• Provides published streamflow statistics and basin characteristics for gages
• Computes basin characteristics for ungaged sites
• Provides regression-based estimates of streamflow statistics for ungaged sites
User InterfaceArcIMS
Streamflow Statistics Database
NSS Calculation
Program
GIS DatabaseArcHydro
At astreamgage
At an ungaged location
StreamStats Benefits
• Cost—Time to delineate and compute basin characteristics reduced from hours to minutes
• Accuracy—As good or better than manual methods• Consistency—Important for statistical validity• Accessibility—User does not need GIS expertise or
software
National StreamStats Status
• 14 states up and running• National gages web site• 14 additional states underway• Data upgrades on 3
states (PA, ID, WA)• Each state is developed
(and funded) separately
http://streamstats.usgs.gov
•Read the user guidance provided in the links at the left of the main page.
•Access the Illinois application from the main StreamStats page at http://streamstats.usgs.gov
Obtaining the basin characteristics and flood quantiles—select the site using the latititude and longitude Zoom To
Delineate the watershed using the BasinDelineation tool
Generate a streamflow statistics report at any site.
Evaluation of Illinois StreamStats
• Basin characteristics at 283 USGS rural gaging stations
• Sensitivity of basin characteristics to estimated flood quantiles
• Flood quantiles at 169 USGS rural gaging stations (random sampling)
• Reliability testing
Basin Characteristics Differencesin the Illinois Studies
• Digitized watersheds• 30-m DEM• NHD (1:100K)• Manually extended main
channel to saddle point for slope computation
• Automated basin delineation• 30-m DEM (newer)• Hydro-corrected NHD (1:100K)• Longest flow path method to
determine main channel and intersection point with upper boundary
Published (BasinSoft) StreamStats
Evaluation of Basin CharacteristicsDRAINAGE AREA
n=283
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STREAMSTATS
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MEAN CHANNEL SLOPE CORRECTION LOG EQUATIONn=283
y = 1.0767x0.9486
R2 = 0.9529
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StreamStats_SL
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ats_
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StreamStats values of drainage area, mean channel slope, basin length, average permeability, percent open water were compared with the published values used in the last flood frequency update. The results for drainage area and mean channel slope are shown on the left. The relation between drainage area and slope is shown below.
Distribution of relative differences between StreamStats (SS) and the published values (BS) for DA
ERROR INTERVAL (BS-SS)/BS-0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6
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Mean = 0.0, STD = 0.10The range of ± 1 STD is shown n=283
ERROR INTERVAL, (BS-SS)/BS-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
PE
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-0.6
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Sensitivity of flood quantiles to differences in DA: Errors associated with one standard deviation
-7.3%
7.5%
1 STD
Errors are for Q100 from Regions 1,3,5
Summary of Basin Characteristics Evaluation
• Automatically delineated drainage area generally agrees well with manually delineated (differences are not statistically significant).
• Discrepancy appears to occur more frequently in small watersheds (DA < 0.5 mi2).
• It appears that controls on flow such as roads and culverts has a larger effect for small watersheds. Judgment (the EditBasin tool) can be used to ensure the correct delineation.
• Slope definition differs, but sample differences by region were not significant after adjustment.
Q100 Estimates
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100-year peak estimates using BasinSoft and manual drainage basin delineation against StreamStats for all regions, n = 164, without manual corrections or user judgment.
Arithmetic Scale
The differences are not statistically significant by paired t-test and Wilcoxon Signed Rank test (p-value < 0.05) whether by region or total, except for Region 1. No region had statistically significant differences in SL, DA, or any other basin characteristic.
PROVISIONAL RESULTPROVISIONAL RESULT
Reliability Testing
• Eight new users tested StreamStats at 28 typical structure sites over state (8 repeated values).
• One structure site was eliminated from the study because of identification uncertainty.
• Five structure sites were misidentified or misread by single testers, so those results were omitted, leaving 7 repeated tests for 5 sites, 8 repeated tests for 22 sites.
• The average absolute maximum deviation from the mode of responses was 1.34 percent for the 27 structures tested by 7-8 users.
• Conclusion: Extremely reliable results provided that the site is correctly identified.
Average absolute maximum deviation from the mode = 1.31 percent
Reliability Testing
1.390.092.5400.710.20000.40.892.940
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1.185.501.130.450.69000.160.2300.560.490.15
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Q100 = 1760Q100 = 6110
Q5 Estimates--Repeats and OptionalN = 30
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StreamStats
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Comparison of IDOT manual determinations with StreamStats.
New IDOT Structure Information Management (SIMS) Layer
• As a result of the reliability test results, a new layer was added to the application to provide identification for the IDOT structures.
• Other layers can be added upon request.
• The next slide illustrates the features of the new layer.
Use the i button to get the structure number.
Check the IDOT structure layer and refresh
StreamStats Enhancements
• Porting to ArcGIS Server/Web Services– Batch jobs, multi-user, transparent remote
access, stability• NHD Navigation/Reach indexing
– Drainage-area ratio for ungaged sites– Stream tracing for dams, point Q’s, etc.
• Weighted estimates for ungaged basins that cross state lines
• IDOT Structure Inventory Management System (SIMS) shapefile
Future Illinois refinement:1:24K NHD, 10-m DEM
24K (Hi-res) NHD recently completed, 10-m DEM is being completed now.hio has already incorporated this data into their StreamStats application.
Estimate of QTs in Ungaged AreasEstimate of QTs in Ungaged Areas
Design storms
Frequency analysis
Event model
Regionalequations
streamstats.usgs.gov
Synthetic frequency curves Continuous
simulation model
Event model