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REAL TIME FLOOD FORECASTING WITH PCSWMM, NEXRAD, ENVIRONMENT CANADA AND SWMM5
Rob James and Karen Finney Computational Hydraulics International (CHI)Guelph, Ontario, Canada
Presenters
Rob James P.Eng. CEO Karen Finney M.Sc. P.Eng.
About CHI
• Developer of PCSWMM
• Spatial decision support for the US EPA SWMM5 hydrology & hydraulics engine
• Provide education and engineering services for water management modeling
Outline
1. Flood forecasting modeling time line2. SWMM enhancements for rural areas3. Incorporation of remote sensing RADAR4. TRCA Nexflood setup5. Model development and validation
Improve the accuracy of flood forecasting through:• More detailed, higher‐resolution hydrological and hydraulic modelling
• High resolution radar‐rainfall acquisition and processing• Real‐time forecasting and flood analysis tools• An accessible spatial decision support environment
Radar acquisition, processing and forecasting
• Leverages the spatial resolution and remote sensing capabilities of radar
• Produces rain gauge‐calibrated radar rainfall• Determines storm speed and direction• Forecasts and area‐weights rainfall up to 3 hours ahead
2008, TRCA Etobicoke Creek
(200 km2)
2010, CVC Cooksville Creek
(36 km2)
2011, TRCA Don RiverNexflood(360 km2)
2013, Brazil Sao Paulo(Six priority basins total area 270 km2)
2013, Halifax Water
Environment Canada Precip.
format radar support
2013, Support for Environment
Canada GRIB2 format
2014, LSCA Tannery Creek
(39 km2)
2014, City of Montreal
McGill Radar support
2015, TRCA Etobicoke Creek update
(200 km2)
Flood forecasting modelling time line
Toronto Flooding, July 2013
(National Post)
Toronto Union Station, July 15, 2012
Key technologies
NEXRAD WSR‐88D
US EPA SWMM 5HTML5
GoogleEarth
Environment Canada Precip.
PCSWMM Real‐Time
• Official US EPA SWMM5 engine• GIS engine• Open standards• No data migration• Stand‐alone product • Proven
– 25 years– 70 countries– 10,000 project
• Efficient solution of complex models
2. SWMM enhancements for rural modeling
Courtesy viewingnaturewitheileen.blogspot.com
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Courtesy truedakotan.com
Courtesy eastmetrowater.areavoices.com
Seasonal parameters
• Parameters that could vary in a similar way every year• Subcatchment pervious area parameters• Surface roughness• Surface storage and interception• Infiltration
– Capillary action of the soil– Hydraulic conductivity– Retained soil moisture
• Adjusted on a monthly basis• Time patterns repeated every year• Spatially variable
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Enhancements: tile drainage
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Courtesy pubs.usgs.gov
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Approximation for base flow
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Approximation for tile drainage
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
VALIDATION OF SWMM ENHANCEMENTS
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
RSWMM engine validation
• Add new functionalities– Architect/structure new code – Minimize changes to SWMM5 source code– Minimize changes to the input file
• Generate same results as official EPA SWMM5• Model comparison tool
– Run model using the first engine– Run model using the second engine– Compare computed output
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Compare output filesDifference found between OldsCollege‐testSWMM5_0_022.out and OldsCollege‐testSWMM5_0_902.out:
Time step Index SWMM5_0_022 SWMM5_0_902 Difference10631 100 0.00216678414 0.00216673082 5.33182174E‐08
...17553 155 33.774044 33.77559 0.00154495239Max difference: 0.010505217553 126 0.8495136 0.8600188 0.0105051994
Object statistics:Differences found for 12 objects (total 157 objects).
Object Index & Name Number of Diff32 Subcatchment 'S4A' Losses 6...126 Link 'C3' Froude Number 3155 System Storage 2
Time step statistics:Differences found for 9 time steps (total 21816 time steps).
TS Index & Time Number of Diff2417 1992‐04‐17 6:50:00 PM 2
...3036 1992‐04‐22 2:00:00 AM 2
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
164 projects compared
• Modifications were required to our initial code changes• End result: no measurable change to computed results
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
US RADAR Installations
www.hrwc.ca 27
Canadian RADAR Installations
www.hrwc.ca 29
Radar fills in the blanks between rain gauges
Nexflood
“Nexflood provides information at a granular level that is not easily replicated by other forecasting systems such as those using advance‐warning gauges, empirical relationships, or model‐derived relationships between rainfall and runoff at a location of interest”
TRCA office setup
• Database and web server• Handles data transactions and reporting
• 2 machines running 4 RAP and 4 SWMM5 RT models
• DHR and DHSR products processed with and without the real‐time raingagenetwork
TRCA office setup
Flood vulnerable asset analysis
TRCA flood roles
Advisory role
• Estimate flood threat using Nexfloodmodel
• Provide information to municipalities and flood emergency and response departments
• Appropriate response are taken and include road closures and messaging media, school boards, and first responders
TRCA flood roles
Operational role
• Operate flood control reservoirs to provide moderation of flood during a large event
G.Ross Lord Dam
Model development: hydraulics
• 42 HEC‐RAS models• ~3000 transects• ~270 bridges• ~60 reaches• ~225 km of natural channels• 1 dam: 4 operational gates• Solution method
– SWMM5 dynamic wave routing– Full St. Venant equations
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Bridge representation
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Custom bridge shapes
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Model development: hydrology
• 70 subcatchments• land‐use layer• soil‐type layer• pond storage &
discharge curves• Solution method
– SWMM5 non‐linear reservoir routing– Green & Ampt infiltration
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Subcritical steady flow analysis
• Previously created HEC‐RAS model imported into PCSWMM
• Model represents section of Don River, Toronto, Ontario
• Model consists of about 4 km of river and has three bridge structures
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
100y water surface elevation profile
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
100y W.S. elev. profile at bridges
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
100y W.S. elev. profile: adjusted
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
SWMM5 vs. HEC‐RAS – 100y
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Model verification
• 3 flow gages• 9 rain gages• 7 radar‐rainfall products
– BR radar only– BR rain gage rainfall– BR watershed rain gage rainfall– DHSR radar only– DHSR rain gage rainfall– DHSR watershed rain gage rainfall– DPA radar (NEXRAD PPS)
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Model verification
• 3 flow gages• 9 rain gages• 7 radar‐rainfall products
– BR radar only– BR rain gage rainfall– BR watershed rain gage rainfall– DHSR radar only– DHSR rain gage rainfall– DHSR watershed rain gage rainfall– DPA radar (NEXRAD PPS)
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Event 6 – November 13, 2008 (49.3 mm)
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Event 6 – November 13, 2008 (49.3 mm)
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Computed vs. Observed maximum flow at Todmorden
C O M P U T A T I O N A L H Y D R A U L I C S I N T E R N A T I O N A L
Thank you