Advanced Floodplain Modeling TechniquesStorm Drain Master Planning and Flood Reduction Analysis
North Bay Watershed AssociationMay 6th, 2011
Rick Jorgensen, Winzler & KellyCarlos Diaz, Winzler & Kelly
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Introduction to 2 Case Studies
Discussion of Status Quo
Value Added by New Modeling Approach
Salvador Creek Case Study
City of Sonoma Case Study
Open Forum for Questions
Presentation Overview
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Flood Reduction Analysis, Salvador Creek, City of Napa
Alternatives Analysis aimed at identifying flood reduction solutions for the City
Storm Drain Master Plan, City of Sonoma
Master Plan and CIP Development
Both applications represent first time this modeling approach has been used in North America!
Two Case Study Applications
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Flood Reduction Analysis Typically restricted to 1-D channel hydraulics (HEC-RAS)
Maybe 1-D channel coupled to 2-D floodplain
SD system not considered
Storm Drain Master PlanningTypically 1-D storm drain model only (StormCAD) or hydraulic calculations
Downstream tailwater conditions taken from design storm and/or 100-year FEMA models
Historic Modeling Approaches
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisThe New Approach
MIKE URBAN
(urban hydrology and
hydraulics)
MIKE 11 (1D channel hydraulics)
MIKE 21 (2D floodplain
hydraulics)
MIKE FLOOD
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Flood Reduction Analysis Storm drain system provides detention and attenuation
Storm drain system can cause as much flooding as channel in some cases
Improved representation of flooding extent, timing and duration of flooding
Ability to visualize flooding and flood reduction due to improvements
Ability to quantify benefits and costs of alternatives
Value Added by New Approach
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Storm Drain Master PlanningIf it pops, where does it go?
Ability to visualize extent of flooding, identify priorities, and impacts of improvements
Ability to visualize transfer opportunities and benefits/drawbacks
Ability to better represent flooding of structures
Potential for savings on CIP projects - using a constant DS boundary condition can be conservative and doesn’t consider timing of peaks
Value Added by New Approach
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Big PictureClients get 2 significant products – channel and SD system models
Dynamically linked – able to analyze impacts to other systems from changes in one system
Ability to visualize – a picture’s worth a thousand words
Value Added by New Approach
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Highly urbanized watershed (~5,000 acres) with historical flooding
Modeling has evolved over the years
Initially tasked by FCWCD to analyze 4 alternatives Detention basins
Floodwalls
Bypass channel
Flapgates
Next steps include additional pipes <30” diameter and additional bypass alternatives
Flood Reduction Analysis, Salvador Creek
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis2005/2006 Napa River Flooding
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisRecent Salvador Creek Flooding
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
The players Napa County Resources Conservation District City of Napa Napa County Flood Control and Water Conservation District
Modeling has evolved over the years on Salvador Creek
Original HEC models since 1999 Unsteady MIKE 11 modeling started in 2001 MIKE FLOOD in 2005/2006
W&K inherited MIKE FLOOD model in 2008 and updated hydrology and added storm drain system
Historical Modeling
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
New MIKE Model – Salvador Movie
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisModel Development - MIKE URBAN
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisMIKE URBAN
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisMIKE URBAN
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisMIKE URBAN
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Biale Bridge
Jefferson BridgeTrower Bridge
HSB1HSB2
HSB3
Garfield Bridge
Zerba Bridge
7
9
11
13
15
17
19
21
23
0 500 1000 1500 2000 2500 3000 3500 4000
Max
. Wat
er S
urfa
ce E
leva
tion
(m)
Chainage (m)
2005 HWM Data
Previous MF Results (100 yr, 24 hr Precip)
MU/MF Model Results (100 yr, 24 hr Precip)
Final Calibration
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisMU/MF Baseline Flood
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisAlternative 1 – Upland Detention
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Biale Bridge
Jefferson BridgeTrower BridgeHSB1
HSB2HSB3
Garfield Bridge
Zerba Bridge
7
9
11
13
15
17
19
21
23
0 500 1000 1500 2000 2500 3000 3500 4000
Max
. Wat
er S
urfa
ce E
leva
tion
(m)
Chainage (m)
2005 HWM Data
Calibrated Baseline (100 Yr, 24 Hr Precip)
Alternative 1 (100 Yr, 24 Hr Precip)
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisAlternative 3 – Floodwalls With Flapgates
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Biale Bridge
Jefferson BridgeTrower BridgeHSB1
HSB2HSB3
Garfield Bridge
Zerba Bridge
7
9
11
13
15
17
19
21
23
0 500 1000 1500 2000 2500 3000 3500 4000
Max
. Wat
er S
urfa
ce E
leva
tion
(m)
Chainage (m)
2005 HWM Data
Calibrated Basline (100 Yr, 24 Hr Precip)
Alternative 3 (100 Yr, 24 Hr Precip)
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisNext Phase – Bypass Options
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Considers pipes larger than 24-in diameter
~11.3 miles of pipe
Four watersheds – Nathanson Creek,
Fryer Creek,
Sonoma Creek, and
Schell Creek,
1st application of all three MIKE models for SDMP purposes and CIP project development
Storm Drain Master Plan, City of Sonoma
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
New MIKE Model – Sonoma Movie
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis Sonoma Watershed Map
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Aerial/LIDAR
Channel Cross Section Field Surveys
City GIS and Manhole Dipping
Old FEMA models
SDMP Model Development
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Baseline for Assessment - SCWA Flood Control Design Criteria
Analyzing model results for compliance with criteria
Identifying channel improvements
Identifying storm drain system improvements
CIP Development Process
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Storm Drain System with drainage < 1 sq. mile – minor waterway
1 foot freeboard requirement at 10 year design storm
Surface routes shall be available to handle 100-year flows with no inundation of structures
Fryer Creek ~ 2 sq. miles – secondary waterway25-year event with 1.5 feet of freeboard
100-year event with no inundation of structures
Nathanson Creek > 4 sq. miles – major waterway100-year event within channel banks
SCWA FCDC Criteria
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction AnalysisSonoma Baseline Model Results
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
Channel Improvement Model Results
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
CIP Project Model Results
Advanced Floodplain Modeling Techniques Storm Drain Master Planning and Flood Reduction Analysis
2 case study applications of MIKE model
Improved representation of flooding extent, timing and duration of flooding from dynamic model
Ability to visualize flooding and flood reduction due to improvements
Ability to quantify benefits and costs of alternatives
Potential for savings on CIP projects - using a constant DS boundary condition can be conservative and doesn’t consider timing of peaks
Summary
Advanced Floodplain Modeling TechniquesStorm Drain Master Planning and Flood Reduction Analysis
Questions?