U.S. Geological Survey Iowa Water Science Center Iowa City, IA 52240 319-358-3615 [email protected] by David Eash Iowa StreamStats Implementation of Design – Peak-Flow Determination Presented at the ASCE Environmental and Water Resources Conference Ames, IA April 3, 2014
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U.S. Geological Survey
Iowa Water Science Center
Iowa City, IA 52240
319-358-3615
by David Eash
Iowa StreamStats Implementation of Design –
Peak-Flow Determination
Presented at the ASCE Environmental and
Water Resources ConferenceAmes, IA
April 3, 2014
What is StreamStats?
A map-based Web application that provides
information that can be used by engineers,
managers, and planners to make informed
decisions on water-related activities
Primary products are basin delineations, basin-
characteristic measurements, and estimates of
streamflow statistics
Program allows for the analysis of upstream and
downstream relations along streams
How is StreamStats Information Used?
Engineering Design—Bridges, culverts, roads, levees, dams, and other structures along streams; flood-plain mapping
Water and Land Management—Water rights adjudication, in-stream flows, fish passage/habitat studies
Water Quality Regulation—Low flows, perennial vs. intermittent streams (TMDL’s, NPDES Permits)
Sampling Network Design—Cover a range of desired flows
StreamStats Site Capabilities
Provides published streamflow statistics and basin characteristics for USGS streamgages
For user-selected ungaged sites:
• Delineates drainage basin boundaries
• Allows editing of basin boundaries, if necessary
• Computes basin characteristics
• Provides estimates of streamflow statistics based on regression equations
• Allows for download of basin boundary shapefiles
• Allows the printing of maps shown in user interface
StreamStats Implementation for Iowa
74 regression equations from 3 USGS streamflow-
estimation reports will be implemented in StreamStats
StreamStats will allow users to click on any ungaged
or gaged stream site in Iowa and obtain estimates of
30 streamflow statistics
7 low-flow statistics that include 4 annual and 2
seasonal low-flow probabilities and the harmonic
mean
15 flow-duration statistics that include 1% - 99%
exceedance probabilities
StreamStats Implementation for Iowa
8 peak-flow statistics that include 2- to 500-year
recurrence-interval floods
90-percent prediction intervals will be computed for
an ungaged site (for low-flow & peak-flow regression
estimates)
Peak-flow equations were implemented in June 2013
Low-flow and flow duration equations will be
implemented in near future
IA StreamStats app uses peak-flow regional-
regression equations published in SIR 2013-5086
New Iowa Flood Regions
3
3
1
2
2
518 streamgages used for defining six
flood regions
1
3
2
Northwest
Northeast
Southern
Iowa Low-Flow Regions
IA StreamStats app will use low-flow regional-
regression equations published in SIR 2012-5171
Flood Region 1 Regression Equation
Regression equations take the form:
Q1%=DRNAREA0.56610(0.917+0.567 I24H10Y-0.742
CCM^0.55)
where:
DRNAREA is drainage area, in square miles
I24H10Y is maximum 24-hour precipitation that
occurs on average once in 10 years, in inches
CCM is constant of channel maintenance (DRNAREA/
total length of all streams in basin), in mi2/mi
Flood Region 1 Drainage-Area Only
Regression Equation
Regression equations take the form:
Q1%= 102.67 DRNAREA0.524
where:
DRNAREA is drainage area, in square miles
Flood Region 2 Regression Equation
Regression equations take the form:
Q1% = 10(11.1 - 7.92 x DRNAREA^-0.031 -0.002 x DESMOIN
-0.025 x BSHAPE)
where:
DRNAREA is drainage area, in square miles
DESMOIN is percent area of basin within Des
Moines Lobe landform region (percent area)
BSHAPE is a shape factor measure of basin
shape computed as BASLEN2/DRNAREA
Flood Region 3 Regression Equation
Regression equations take the form:
Q1% = 10(6.41 – 3.06 x DRNAREA^-0.097 – 0.009 x KSATSSUR
– 0.035 x BSHAPE)
where:
DRNAREA is drainage area, in square miles
KSATSSUR is the average saturated hydraulic
conductivity of soil (micrometers per second)
BSHAPE is a shape factor measure of basin shape
computed as BASLEN2/DRNAREA
Watershed Delineation from a Point
1. User selects point on stream
2. Point is transferred to a cell in a flow-direction grid derived from a DEM
3. GIS determines boundary from flow-direction grid up to points at which the boundary for the new site intersects boundaries in boundary map layer
4. GIS accumulates all upstream areas and dissolves internal boundaries
National
Hydrography
Dataset (NHD)
Watershed
Boundary
Dataset (WBD)
National
Elevation
Dataset (NED)
StreamStats Integrates NHD Streams, WBD
Boundaries and NED Elevation in ArcHydro
Burning and Walling of DEM
Forces DEM to agree with stream
network and WBD or locally
digitized drainage boundaries
12-digit HUCs Watershed Boundary Dataset
1
2
3
StreamStats Similar Gages tool estimates
flows at ungaged sites based on flows at
at nearby streamgages for drainage-area
ratios between 0.5 and 1.5
Regional exponents table 15
New Statistical Methodologies included in
the Iowa Peak-Flow Estimation Study
Flood-probability analyses include results of new
statewide regional skew analysis (Bayesian
GLS/WLS regression analysis – constant value -0.4)
New flood-probability analysis method used - EMA
(expected moments algorithm) with new MGB
(multiple Grubbs-Beck) test for detecting low-outliers
New optimization test used for selecting best
transformation for drainage area for the regression
analyses - either a log 10 or a power transformation
QUESTIONS
Iowa Regional Skew Study
Bayesian WLS/GLS Regression
1982 (MSE = 0.302) 2010 (MSE = 0.160)ERL = 17 yrs ERL = 50 yrs
Constant
Regional
Skew Value
for Iowa =
-0.400
240 gages
Effects of including or censoring low
outliers
Figure 5
West Branch Floyd River near Struble
Flood Region 3 transformations of
drainage area for Q1%
Figure 8
Log-10
transformation
of DA
Power
transformation
of DA
DA-0.097
Relative % change between EMA/MGB &
B17B/GB using new skew for Q1%
283 Iowa streamgages – Q1%
Figure 11
RPchange = 100(Qnew-Qold/Qold)Mean 11.8 %
Median 2.0 %
Figure 12
283 Iowa streamgages
Relative % change between EMA/MGB new
skew & B17B/GB old skew for Q1%
Mean 5.0 %
Median -2.1 %
Relative % change between Q1% using
RREs from 2013 and 2001 reports
Figure 13
185 Iowa streamgages
Mean 7.9
Median 6.4
Iowa StreamStats Introductory Page
Lists statistics
estimated
Gives report
referenceLink to Iowa StreamStats
application
Other issues,
cooperative
statement
National Station Statistics Site
Base Layers
Street MapWorld TopoUSA TopoImagery
Streamgage Reports
State Applications
Iowa User Interface
Toolbar
Console
Panel
Banners
Working With Panels
Click on plus (+) sign to
expand list
Display Streamgages
Check box beside layer
name (Stream Gages)
Navigation Panel
Click on points of
compass to move map
center
Overview Map
User Interface at Iowa StreamStats
Startup 1:4,500,000
Zoom-in to Ames area to 1:80,000
Zoom-in to Ames area to 1:10,000
Example Point Selection (1:2,000)
Select Ungaged Site
Scale must indicate
1:24,000 or greater
Click on Watershed
Delineation from a
Point
Watershed Delineation from a Point
1. User selects point on stream
2. Point is transferred to a cell in a flow-direction grid derived from a DEM
3. GIS determines boundary from flow-direction grid up to points at which the boundary for the new site intersects boundaries in boundary map layer
4. GIS accumulates all upstream areas and dissolves internal boundaries
National
Hydrography
Dataset (NHD)
Watershed
Boundary
Dataset (WBD)
National
Elevation
Dataset (NED)
StreamStats Integrates NHD Streams, WBD
Boundaries and NED Elevation in ArcHydro
Burning and Walling of DEM
Forces DEM to agree with stream
network and WBD or locally
digitized drainage boundaries
Example Basin Delineation
Flow Statistics from Regression Equations
Click on Estimate Flows
Using Regression Equations
• Regression equation
estimates assume natural
flow conditions at the
selected site
StreamStats Ungaged Site Report
Multi-Region Basin Calculation
Multi-Region Basin Calculation
Multi-Region Basin Calculation
Multi-Region Basin Calculation
Multi-Region Basin Calculation
Edit a Delineated Basin Tool
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