Boise River, Idaho: Many Agencies Working

Towards One Version of the Truth

Ellen Berggren, USACE Walla Walla DistrictIdaho Silver Jackets

USACE Flood Risk Management & Silver Jackets Workshop

August 23, 2012

Idaho Silver Jackets

Core Team Agencies

• Boise River General Investigation• Idaho Risk Map Coordination• Boise River Inundation Mapping• Flood Response Training• Flood Response After Action Review• Tabletop Exercises• Gaging Station Web Camera • Whole Community Approach to

Floodplain Mgmt Conference• Joint USACE/FEMA Levee Briefings• Boise River Flood Risk Community

Meeting

• Boise River General Investigation• Idaho Risk Map Coordination• Boise River Inundation Mapping

Boise River Inundation Mapping Study Agency Resources and Studies Leveraged

• Ada City-County Emergency Management (funding and technical review)

• Boise City (GIS, technical review)• Garden City (technical review)• Idaho Water Resource Board / Idaho Department of Water

Resources (funding, technical review)• USGS (river gage data)• FEMA (digital flood insurance rate maps)• USACE (funding, project mgt, modeling)• National Weather Service (technical review; AHPS funding,

development and implementation)

Flow Rate (cfs)

Comments

4,900 50-Percent Chance Flow

6,500 Bankfull Flow

7,000 Flood Stage at Glenwood Gage

7,200 10-Percent Chance Flow

7,440 2006 Flow Event, Used for Calibration

8,310 1998 Flow Event, Used for Calibration

9,500 New Flow

11,000 2-Percent Chance Flow

13,000 New Flow

15,000 New Flow

16,600 1-Percent Chance Flow

20,000 New Flow

23,900 0.5-Percent Chance Flow

29,000 New Flow

34,800 0.2-Percent Chance Flow

• HEC-RAS model• Model originally

prepared for Lower Boise Feasibility Study (General Investigation)

• 15.9 mile reach of river through Boise and Garden City

• Shaded depth maps for 15 flows

Interactive Flood Maps now PublicNational Weather Service

AHPS - Advanced Hydrologic Prediction Service Web Page http://water.weather.gov/ahps2/inundation/inundation_google.php?g_datatype=depth&wfo=boi&gage=bigi1

Outreach• Meetings

­ Floodplain managers­ Elected officials­ Community

• Press releases• Media interview• Webpage• Watershed Conference

Google Earth Fly-Through the 500 Year Flood Inundation

Questions

Photo provided by Larry Ridenhour