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?