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TRANSCRIPT
Use of Continuous Simulation Watershed Models
for Estimating Stormwater Detention Volumes in an
Uncertain Future
Dennis Dreher, Rishab Mahajan and Tom Price and | February 27, 2020
Outline
• Ramifications of Climate Change
• Tools for Stormwater Design
• How Does HSPF work?
• Previous Stormwater Design Applications of HSPF
• Related Ongoing Applications of HSPF
• Looking Forward
Ramifications of Climate Change
Source : Peterson et al. 2013
Example of
Flooding
due to to
Extreme
Precipitation
Event
NASA Earth Observatory, 2019
Updated Rainfall Data
Bulletin 70 Updated Bulletin 70
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Return Period
Bulletin 70 and Updated Bulletin 70 Comparison
RaInfall B70 Rainfall UB70
~13%
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Bulletin 70 vs Updated Bulletin 70 Comparison
Rainfall Runoff (CN=85) Detention (CN=85)
Increased Runoff and Detention Requirements
Tools for Stormwater Design
What is a Design Storm Model
• Uses predicted rainfall distributions such as 100-year,
24-hour event (e.g., Bulletin 70)
• Predicts peak runoff for selected design storm of a
given duration and frequency
• Traditional method used for designing detention
basins and storm sewers basins and storm sewers
Design Storms Don’t Reflect Full Hydrologic Cycle
What is Continuous Simulation Model
• Uses actual precipitation and related meteorological data
• Captures the effects of antecedent moisture on runoff volumes and peaks
• Simulates the entire hydrological cycle
• Calibrated to observed flow at stream gages
• Model output is continuous time history of the quantity and/or quality of runoff from a watershed
• Allows evaluation of small and large storm events as well as drought conditions.
HSPF
• HSPF (Hydrologic Simulation Program – Fortran) was
developed in the 1970s and has been
applied relatively widely in NE Illinois
• First application for water quality simulation in
the Areawide Water Quality Management Plan (1979)
• Used for stormwater/flood modeling in DuPage
County for 30 years
• Used in Seattle, western Washington, SE Wisconsin
How Does HSPF Work
HSPF: Hydrologic Simulation Program - Fortran
• Continuous simulation, lumped parameter watershed model
• 1D Surface and subsurface hydrology and hydraulics
• Sediment, water quality, temperature modeling on surface and in-stream
• Sponsored and continually updated by US EPA (through Aqua Terra) and USGS over 20 years
15
Watershed Characterization
• Watershed delineated
into sub basins
incorporating
variability in
– Land Use
– Soil Cover
– Topography
HSPF Model Components
IMPLND
✓Snow
✓Water
• Solids
•Quality
RCHRES
✓Hydraulics
•Temperature
• Sediment
•BOD/DO
•Nitrogen
•Phosphorus
•Carbon
•Plankton
Point Sources
✓Flow
• Constituents
✓ Hydrology component
✓ Water quality component
PERLND
✓Snow
✓Water
• Sediment
•Quality
•Pesticide
•Nitrogen
•Phosphorus
•Tracer
Land segments
Stream segment
Outlet (Flow, Constituents)
Hydrology Process – Land Segments
Vegetation/Surface Storage
Lower Zone Soil Storage
Upper Zone Soil Storage
Stre
am S
egm
ent
SnowSolar radiation, air temp, cloud cover, wind speed
Melt
Melt
Infiltration to deep groundwater
Precip
Variable Irrigation and Vegetation growth
Evapotranspiration
Surface Runoff
Interflow
Infiltration
Canopy interception
Active groundwater
Melt Storage
Hydrology Process-Stream Segments
Stream
Based on volume-discharge relationship (F-tables)
Point sources
1D Flow from upstream segment
Bed
1D Flow to downstream segment (or reservoir/flow split)
Evaporation Precipitation Inflow from land segment
Model Calibration
• Process of adjusting model parameters to match
measured data (flow)
Annual & Monthly Water Balance Calibration
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MONTH (1 = JANUARY, 12 = DECEMBER)
MONTHLY S/R RATIO BY MONTH
SALT CREEK AT WESTERN SPRINGS
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MONTHLY RECORDED FLOW (cfs)
SIMULATED VS RECORDED MONTHLY FLOWS
SALT CREEK AT WESTERN SPRINGS
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RECORDED MONTHLY AVERAGE FLOW (cfs)
MONTHLY S/R RATIO VS MONTHLY FLOW
SALT CREEK AT WESTERN SPRINGS
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MONTHLY S/R VS TIME
SALT CREEK AT WESTERN SPRINGS
MONTHLY S/R VALUES ANNUAL S/R VALUES
Event Calibration
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MONTH (1 = JANUARY, 12 = DECEMBER)
EVENT SIMULATED/RECORDED RATIO BY MONTH
SALT CREEK AT WESTERN SPRINGS
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TIME (event number)
EVENT SIMULATED/RECORDED RATIO VS TIME
SALT CREEK AT WESTERN SPRINGS
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cfs)
EVENT RECORDED PEAK (cfs)
SIMULATED VS RECORDED EVENT PEAK FLOWS
SALT CREEK AT WESTERN SPRINGS
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-2 -1 0 1 2E
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PE
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OW
S (
cfs)
NORMAL DEVIATIONS
SIMULATED & RECORDED EVENT PROBABILITY
SALT CREEK AT WESTERN SPRINGS
RECORDED SIMULATED
Regional Applications of HSPF
for Stormwater Management
Regional HSPF-based Stormwater Design Studies
• Led by the Northeastern Illinois Planning Commission
with IDOT/DWR Support
– Evaluation of Stormwater Detention Effectiveness in
Northeastern Illinois, 1989
– Investigation of Hydrologic Design Methods for Urban
Development in Northeastern Illinois, 1991
• Guidance provided by a Regional Stormwater Advisory
Committee
Evaluation of Stormwater Detention
Effectiveness in Northeastern Illinois, 1989
Background and Methodology
• 100-year floods in 1986 and 1987 raised concerns about flood damage
• IDOT/DWR hired NIPC to assess the effectiveness of existing detention policies
• A sophisticated HSPF model was set up for Salt Creek
• Tested the effectiveness of existing and proposed detention policies in preventing increases in downstream flooding
Key Findings
• Common detention standards were not adequate to prevent increases in downstream flooding
• Many detention basins overflowed for events smaller than 100-year
• Detention release rates of 0.15 cfs/acre and 0.04 cfs/acre were effective in preventing increases in downstream flooding for the 100-year and 2-year events, respectively
Model Stormwater Drainage and Detention Ordinance
• A new model ordinance adopted by NIPC included the
following key recommendations:
– 100-year release rate of 0.15 cfs/acre
– 2-year release of 0.04 cfs/acre
• To minimize increases in bankfull flow conditions
• To provide extended detention times to
enhance pollutant removal for small to moderate storms
– Detention storage should be calculated based on the new
Bulletin 70 design rainfall totals using hydrograph methods
like NRCS and HEC methods
Model Stormwater Drainage and Detention Ordinance
• Most county stormwater agencies subsequently
adopted these recommendations
• Some adopted more stringent standards for the
100-year release rate: e.g., 0.10 cfs/acre
• These standards were (and still are) some of
the most stringent in the country
Investigation of Hydrologic Design Methods
for Urban Development in NE Illinois, 1991
Investigation of Hydrologic Design Methods for Urban
Development in NE Illinois
• Comparison of Hydrologic Design Methods
– Existing event models vs regionally calibrated HSPF
• Unit Area Detention Volume Chart
– Utilize continuous simulation HSPF to account for
antecedent conditions and seasonal variability
Comparison of Hydrologic Design Methods
• Compared existing design storm models with
each other
– Runoff volumes and detention volumes
• Then compared them to a regionally calibrated
HSPF model
Comparison of Hydrologic Design Methods for Urban3
.04
4.4
7
7.5
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4.1
12-YEAR 10-YEAR 100-YEAR
RUNOFF VOLUME - RESIDENTIAL
Rainfall Rational Formula NRCS CN HSPF Design Storm
3.4
0
7.4
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3.0
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11
.20
1.6
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7.8
0
2-YEAR 100-YEAR
DETENTION STORAGE
Rational Formula
NRCS CN Method
HSPF DesignStorm
Unit Area Detention Volume Chart
• Purpose was to provide a simpler, more accurate alternative to design storm methods for detention design
• Utilized locally calibrated HSPF model to account for antecedent moisture conditions and seasonal variability
• Based on 40 years of continuous simulation
• Done for NIPC dual release rates (0.04 and 0.15 cfs/acre)
• Also for DuPage County for single release rate (0.10 cfs/acre)
Unit Area Detention Chart based on continuous simulation
Detention Storage Requirements3
.40
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3.0
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.20
1.6
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7.8
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2.1
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8.0
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2-YEAR 100-YEAR
RES DETENTION STORAGE
Rational Formula NRCS CN Method
HSPF Design Storm HSPF Continuous
RESIDENTIAL DETENTION STORAGE
5.8
0
13
.00
7.3
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17
.80
6.0
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15
.80
6.8
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18
.00
2-YEAR 100-YEAR
COM DETENTION STORAGE
Rational Formula NRCS CN Method
HSPF Design Storm HSPF Continuous
COMMERCIAL DETENTION STORAGE
Related Ongoing Applications of HSPF
Current Application of HSPF
• DuPage County
• Fox River Study Group
• Chicago Metropolitan Agency for Planning
DuPage County
HSPF Application in DuPage County
• HSPF and FEQ are used for floodplain mapping and project evaluation within DuPage County
• HSPF
– Countywide calibration of parameters for four different land covers, two soil types, and three slope ranges.
– Calibrated to USGS streamflow gages in Salt Creek, East Branch DuPage River, and West Branch DuPage River watersheds.
• Annual and monthly water balance
• Current calibration of ~ 20 events during ~ 10 year calibration period
HSPF in DuPage County
– Used to produce 60+ year time series of runoff and
flow using two “design” precipitation gages
– Conduct frequency analysis on simulated flows and
stages for
• Floodplain mapping
• Evaluate flood control projects
• Better representation of variable floodplain, wetland, and
detention storage conditions
Fox River Study Group
Fox River Watershed Model
• 33 sub-watershed HSPF models
• Continuous Simulation
– Flows
– Concentration
• Used as input into instream model for
simulating impacts on water quality
from non-point sources
• Plan to use the model for other
applications such as flood control
43
Watershed Management Scenarios
• Model would be used to evaluate impact of
management actions on Fox River Water Quality
– Non Point and Point Source Reductions
– Dam Removal
Chicago Metropolitan Agency for Planning
Watershed Planning
• Traditional watershed planning have used simple
spreadsheets model for pollutant load estimation
• CMAP and Geosyntec applied the HSPF to predict
pollutant loads in Mill Creek, a tributary of Fox River
• Provides a more accurate assessment of loading
for watershed planning purposes
Mill Creek Watershed Planning Support
• Simulate loads for
– Total Nitrogen
– Total Phosphorus
– Sediment and E.coli
Importance of calibrated continuous simulated model
Simulated load match the measured loads well
Looking Forward
Update Unit Detention Charts
• Existing charts are outdated
• Develop and calibrate continuous simulation HSPF models using recent rainfall data
• Update unit area detention volume charts based on HSPF models
Update Watershed Specific Release Rates
• Develop basin-specific detention release rates
based on HSPF simulation
• Currently being done for Cook County and being
considered in Lake County
• Important to look at 2-year and 100-year release
rates
Assess Volume Control
• Model volume control benefits of green
infrastructure
• Supplements the focus on detention release rates
only
Expanding Water Quality Applications
• DuPage County looking into using HSPF for water
quality applications
• CMAP will be applying the HSPF model for Indian
Creek Watershed–Based Plan
Opportunities for Regional Collaboration
• CMAP
• County stormwater agencies
– Several have expressed interest in update detention design nomographs
• State and federal agencies: ISWS, IDNR, USGS
• Geosyntec and ECT as technical advisors
Questions ?