HEC-RAS 1D+2D Modeling in the

Santa Clara River Watershed in

Ventura Co, CA

• Is 2D modeling a better alternative

to 1D modeling in some cases of

riverine hydraulics?

• Have we seen 2D modeling be a

common request from communities

during Risk MAP?

• Is it possible with HEC-RAS 5.0 that

more communities will be open to

or eager for 2D modeling?

Introductions

• Ed Curtis, PE, CFM – Senior Engineer

with FEMA Region IX

FEMA project manager for the Ventura

County, CA project highlighted in this

presentation

• Joe Thomas, PE, CFM – Project

Manager with AECOM as part of the

BakerAECOM JV

Presentation Objectives

First, a Brief Project History

• Phase 1 – MapMod Project

47 miles

Preliminary September 2014

• Phase 2 – Risk MAP Project

70 miles

Preliminary December 2015

Santa Clara River Valley

Santa Clara River Valley

First, a Brief Project History

• FEMA proposed mixed scopeStream Reach Length 2D Flow Area Stream Reach Length 2D Flow Area

Adams Barranca 7.0 1.0 Harmon Barranca 3.8 N/A

Balcom Canyon* 2.0 0.5 O’Leary Creek 2.0 N/A

Bear Creek 2.0 0.5 Peck Drain 2.0 1.0

Briggs Drain 2.0 1.0 Piru Creek 4.0 N/A

Brown Barranca 3.8 0.5 Real Canyon 3.0 1.0

Clark Barranca 2.8 0.5 Reimer Ditch 3.0 1.0

Ellsworth Barranca

7.5 1.0 Santa Paula Creek*

10.0 0.5

Fagan Canyon 5.0 1.0 Sudden Barranca 2.7 2.0

Fairview Canyon 1.0 0.3 Timber Canyon* 4.0 0.5

Franklin Barranca 3.2 1.0 Todd Barranca 8.1 2.0

Haines Barranca 3.0 0.5 Wiley Canyon 1.0 N/A

Totals 82.9 15.8

MODEL BUILD

Model Build/Conversion

Model Build/Conversion

Model Build/Conversion

USACE Feasibility Study FEMA Physical Map Revision Study

HEC-RAS v4.1.0 HEC-RAS 5.0 October 2015 BETA(June Beta initially)

Steady state hydrology Unsteady flow hydrographs

2005 LiDAR 2005 LiDAR

Calibrated ‘n’ values USACE ‘n’ values (channel)

Detailed channel crossing structure data Detailed channel crossing structure data

~250 – 500’ cross spacing <200’ cross section spacing (most ~50’)

Lateral Structures + Split flows + OBReaches

Lateral structures + 2D flow areas

1% & 0.2% ACF events 10%-, 2%-, 1%-, & 0.2%- ACF events

N/A 10 – 20’ cell sizes

~2.6/3.0 Weir coefficients 0.5 Weir coefficients

RESULTS

Did it work???

• Several weeks for initial build

• Level of detail for ‘n’ values

• Hydraulic structures in 2D Mesh

• Levees

• Weirs (1D/2D connections)

• Conversion from June to October Beta

Sharing the Results

• Webinar with stakeholders

• General concurrence

• Local consultant recreation issues

• Preliminary Issuance 12/23/2015

• Official RAS 5.0 was released February

2016…

PROJECT STATUS /

PATH FORWARD

Current Project Status/Path Forward

• Re-run in HEC-RAS 5.0

• Slight change in results

• Pending Revised Preliminary

• Unknown comments/appeals future

Caveats, Considerations, Thoughts

• Revised Zone A to Zone AE

• More refined analysis of flooding in the

valley

• NOT calibrated to high water marks

• Future revisions/additions to HEC-RAS

• Flow path assumptions

• Downstream tie-in

RAS 5.0 vs. effective

Questions?Ed Curtisedward.curtis@fema.dhs.gov

Joe Thomasjoseph.thomas@aecom.com